CIBSE Journal April 2025

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Journal

Performance monitoring

Scotland’s Passivhaus push for new schools

High achievers

Following last month’s CIBSE Building Performance Awards, where the Entopia Building was crowned overall champion (page 20), it is encouraging to see more design teams prioritising the optimisation of operational building performance.

Woodmill High School and St Columba’s RC High School are two new schools on the Dunfermline Learning Campus in Fife, Scotland, that, together, form the largest Passivhaus education building in the UK (page 30).

Their performance is exceptional, with an operational energy use of 45kWh·m-² per year for the combined schools. The design team, led by architect AHR, was incentivised to minimise energy use by the schools being partly financed by a Scottish grant scheme that offers more funding the lower the operational energy use; the schools beat the target and was awarded the full amount available.

Another Passivhaus-accredited school in Scotland – Riverside Primary School –is featured in an article on point-of-use water heaters on page 41. The design team managed to reduce energy consumption by calculating actual hot-water use per appliance, rather than basing a specification on a worst-case scenario.

The schools system within England sits under the Department for Education (DfE), and it has the task of decarbonising around 67,000 educational buildings across 23,000 primary and secondary schools. The DfE has the advantage of having a modelling platform for schools (MPS), developed by UCL, which can simulate the performance of every education facility under a range of retrofit scenarios.

UCL’s Professor Dejan Mumovic is the DfE’s scientific adviser for climate change, and says the MPS can help existing schools plot a route to net zero. The MPS also features CIBSE’s Weather Files, which means schools and retrofits can be assessed for overheating risks. Mumovic is also keen that net zero strategies take indoor environmental quality and cognitive performance into account, and is factoring these considerations in ongoing research (page 34).

The rise in AI means data centres arguably have the biggest sustainability challenge of any sector. On page 26, we speak to leading designers in the field to find out how they are addressing concerns over surging energy requirements and Grid constraints, and on page 44 we feature a project that aims to capture 17MW of waste heat from data centres in West London.

l Alex Smith, editor asmith@cibsejournal.com

Contributors

Anastasia Mylona How CIBSE and US counterparts continue to work together on key decarbonisation projects

Asad Kwaja A look at Aecom’s plans to reuse 17MW of waste heat from data centres in West London

Editorial

Editor: Alex Smith

Tel: +44 (0)1223 378034

Email: asmith@cibsejournal.com

Technical editor: Tim Dwyer

Reporter: Molly Tooher-Rudd

Designer: Kevin Reed

Chief sub-editor: Jo Halpin

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Simon Foxell How the new Competence Framework for Sustainability in the Built Environment will work

The opinions expressed in editorial material do not necessarily represent the views of the Chartered Institution of Building Services Engineers (CIBSE). Unless specifically stated, goods or services mentioned in editorial or advertisements are not formally endorsed by CIBSE, which does not guarantee or endorse or accept any liability for any goods and/or services featured in this publication.

We remind all readers that it is their responsibility to verify advertisers’ products claims.

Tim Dwyer

This month’s CPD module is on efficient heat pump application for heating and domestic hot water

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www.cibsejournal.com The

Events & Training

Voices

14 The ties that bind

Anastasia Mylona on how CIBSE and ASHRAE will continue collaborating on key decarbonisation projects, despite uncertainty over America’s international ties

17 Unintended consequences of fire safety reform

The impact that new fire safety rules are having on design, stalling delivery of high-rise flats

54 Q&A: Climate standards

A new competency framework sets industry-wide standards to integrate sustainability into professional roles. Simon Foxell explains

20 Rewriting the rules of retrofit

The Entopia Building sets a new benchmark for sustainable retrofits. Andy Pearson explores how CIBSE’s 2025 Building Performance Champion cut whole life carbon by 84%

24 Model homes

The transformative potential of the new Home Energy Model , by Sustenic’s John Henderson and Jose Ortiz FCIBSE

26 Power struggle

AI’s boom is fuelling data centre demand, straining energy, cooling and

the Grid. Molly Tooher-Rudd explores engineers’ sustainable solutions

30 Class act

The UK’s largest Passivhaus school has energy use of 45kWh·m-² per year. Andy Pearson explores its design and performance-based funding method

34 Race to net zero schools

UK schools emit 2% of national carbon, but retrofits fall behind. Professor Dejan Mumovic explores models to speed up decarbonisation and prevent overheating. Alex Smith reports

Technical

Heating, water heaters and data centres

37 In demand

Demand-response strategies dominated topics at the DESNZ/ IEA Heat Pump Research Seminar. Molly Tooher-Rudd and Alex Smith summarise the event, which is gaining in popularity

41 Tapping into efficiency

At Passivhaus-certified Riverside Primary School, in Perth, water heaters shape the hot-water strategy. Baxi’s Andy Green outlines the solution

44 Turning waste into warmth

Aecom’s West London energy centre will pipe data centre waste heat to 25,500 homes and businesses. Asad Kwaja explains the design

For cibse

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COVER Keith Hunter Photography

P08 iStock.com / CC BY-NC-ND 2.0: MHCLG

P10 iStock.com / kckate16

P11 iStock.com / Benjamin Robinson

P17 iStock.com / goncharovaia

P37 iStock.com / Laurence Dutton

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P20-23 Soren Kristensen / Jack Hobhouse

P24 iStock.com / Andrii Yalanskyi

P26 iStock.com / tiero

P30-33 Keith Hunter Photography

Half of homes must be fitted with heat pumps by 2040 News

Annual installations need to hit 450,000 by 2030, says climate committee

More than half of UK homes will have to be fitted with heat pumps by 2040 to keep the country on track to meet its net zero emissions targets, the Climate Change Committee (CCC) has told the government.

The body has published its advice for how the UK can reach its 7th carbon budget, which is set to run from 2038 to 2042, and stipulates that UK emissions should fall by 87% of 1990 levels by 2040.

In the report, the CCC states that 52% of homes must be heated using a heat pump by 2040, up from just 1% now.

To meet this target, the committee says the annual rate of heat pump installations in existing residential properties must rise from 60,000 last year to nearly 450,000 by 2030, and

then increase again, to around 1.5 million, by 2035. The anticipated rate of increase for heat pump deployment outlined in the report is in line with that seen in Ireland and the Netherlands, says the CCC.

Its report also reaffirms the committee’s view that hydrogen should not play a role in home heating.

The CCC estimates that the total cost to the UK economy of achieving net zero by 2050 will be, on average, around 0.2% of gross domestic product (GDP) per year until 2050, lower than the previous figure of 0.6% of GDP contained in the 6th carbon budget five years ago.

CIBSE, in its response to the CCC’s latest carbon budget advice, said it showed that ‘rapid’ decarbonisation of the built environment is essential to meeting net zero targets.

Don’t rule out hydrogen for heating, say Scottish leaders

Hydrogen should not be ruled out as a home heating option, according to the Scottish government’s acting Cabinet Secretary for Net Zero and Energy.

Gillian Martin told the Scottish parliament that while the Climate Change Committee has ruled out hydrogen for home heating (see above), others have advocated for the role it could have in decarbonising existing gas infrastructure. She said: ‘I do not think we should rule anything out. We do not know what will happen in the future with regard to technologies.’

The Scotsman newspaper has reported that the Scottish government is reviving the idea of using hydrogen in home heating. In an interview

with the newspaper, First Minister John Swinney said he is ‘very keen’ on the prospect that hydrogen home heating offers, describing it as ‘a really exciting opportunity’.

Swinney hailed Scotland’s first hydrogenheated homes at Scottish Gas Networks’ H100 programme in Fife – currently the UK’s biggest trial project for the technology – as a ‘shining example’ of how the country is leading the way in solutions to tackle climate change.

But Gillian Campbell, co-director of The Existing Homes Alliance, urged the Scottish government to ‘stop being distracted by the prospect of hydrogen for heating and focus on tried and tested solutions’.

Scotland drops home heat decarbonisation bill

The Scottish government has shelved its groundbreaking home heat decarbonisation legislation.

Gillian Martin, acting Cabinet Secretary for Net Zero and Energy, said in a recent Scottish parliament cost-of-living debate that the

Heat in Buildings Bill will not be published until she ‘can be satisfied that the interventions in it will decrease fuel poverty at the same time as they decarbonise houses’.

The bill was designed to implement proposals for all homes and businesses in

Scotland to have clean heating systems by 2045. It also included controversial moves to require anyone buying a home or business premises to rip out their fossil fuel heating systems within two years of completing the sale.

Framework launched to tackle competence in sustainability

The Construction Industry Council and environmental thinktank The Edge have published a Competence Framework for Sustainability in the Built Environment

The document is designed to create an underpinning framework for developing discipline-specific sustainability competence requirements across the built and natural environment sector. It sets core criteria for achieving sustainability, facilitating the development of sector-specific competence frameworks, and supporting a ‘consistent’ approach to competence frameworks. The framework has been drafted as a ‘seed document’ for a British Standard in the BSI’s Competence in the Built Environment series. (See Q&A on page 54.)

Conservatives abandon 2050 net zero target

Kemi Badenoch drops policy introduced by Theresa May

Leader of the Conservatives Kemi Badenoch has abandoned the party’s commitment to the UK’s 2050 net zero emissions target, ending cross-party agreement to tackle climate change.

In a recent speech, kick-starting a wider review of Tory policies, the Leader of the Opposition said: ‘Net zero by 2050 is impossible.’

Existing plans for hitting the target were not realistic and ‘it doesn’t look like we are going to get remotely close to net zero by 2050’, she said. ‘Anyone who has done any serious analysis knows it cannot be achieved without a significant drop in our living standards or, worse, by bankrupting us.’

The 2050 net zero target was introduced by Theresa May’s

Conservative government in 2019.

Badenoch said that, based on last year’s installation rate of heat pumps, it would take 340 years to reach the Climate Change Committee’s target for half of all homes to be heated with the devices by 2040. ‘There is no way we can do this quickly enough on that timescale,’ she added.

The speech was criticised by. Charlotte Lee, chief executive of the Heat Pump Association, who said backtracking on the 2050 target without another plan risked undermining market confidence.

‘Business confidence rests not just on what the current government says, but on the consensus across all major parties on climate action,’ she said.

Work starts on mining County Durham heat

Construction has begun on a largescale mine water heat project to harness geothermal heat from disused coal mines in coastal County Durham. A new energy centre will use mine water pumped to the surface and treated by the Mining Remediation Authority at Dawdon. The heat will be used in a district heat network being developed to serve the new 1,500-home Seaham Garden Village, which is due to be delivered over the next decade. The project has benefited from a grant from the government’s Heat Networks Investment Project.

Net zero job sector grows 10%

The UK’s net zero economy generated £83.1bn in gross value added and has grown 10% in the past year, according to a new report. Commissioned by the Energy and Climate Intelligence Unit, and using analysis by CBI Economics, the report shows that UK employment within the net zero sector has grown 10.2% over the past year, supporting the equivalent of 951,000 full-time jobs. Employees in net zero businesses earned an average of £43,076 per year, higher than median gross annual earnings for full-time employees across the UK of £37,430 in April 2024. Each full-time net zero job also generated £105,500 in economic value, 38% above the UK average.

Gemserv wins heat network contract

Gemserv has been reappointed to deliver the government’s Heat Network Efficiency Scheme (HNES) for a further four years. Following a successful tender process, Gemserv, supported by Ramboll and Gleeds Consultancy, will continue to manage overall delivery, as well as pre-application engagement and support, application management, and monitoring and reporting processes for HNES. The scheme is designed to improve the efficiency and carbon intensiveness of older heat network infrastructure.

Government accepts Grenfell recommendations

The government has announced a sweeping review of the construction products safety regime as part of its response to last year’s concluding report into the Grenfell Tower disaster.

Deputy Prime Minister Angela Rayner announced in February that all of retired-High Court judge Sir Martin Moore-Bick’s recommendations have been accepted.

In a green paper published alongside the response, the government sets out proposals for ‘system-wide’ reform of the construction products sector, the regulatory regime that governs it and the institutions responsible for assuring that products can be used safely. It has promised ‘tougher’ oversight of those responsible for testing and certifying, manufacturing and using construction products, with ‘serious consequences’ for those who break the rules.

The government has also accepted the recommendation to create a single construction industry regulator, but this new body will not undertake testing and certification of construction products, or issue certificates of compliance. Instead, oversight of Conformity Assessment

Bodies will be strengthened via reform of the products regime.

The government and the Building Safety Regulator will set out plans for ongoing review of the definition of higher-risk buildings in the summer. In addition, the regulator will launch a consultation on further changes to Approved Document B by the autumn.

The government will use new powers to investigate whether the organisations criticised in the Grenfell report should be debarred from being awarded new contracts. The seven are Arconic Architectural Products, Exova, Harley Façades, Kingspan, Rydon, and SAS Saint-Gobain, then owner of insulation firm Celotex.

University starts work on 39GWh energy centre

The official ground-breaking ceremony for Lancaster University’s new Net Zero Energy Centre took place last month.

It was a key milestone in the delivery of the new centre, which is designed to virtually eliminate the use of gas for heating on the university’s Lancaster campus.

The centre is projected to generate 39 gigawatt hours (GWh) of low carbon energy, enough to heat 95% of campus buildings using an array of air and water source heat pumps

To carry the heat across campus, 6.5km of additional district heating pipework is being installed. This

extension will add 247 buildings to the district heat network, expanding its coverage from approximately 65% to 95% of the campus.

The centre will also include 1,500 cubic metres of thermal stores, which will help ensure consistent heat during peak times of the day.

The project is being delivered by renewable energy company Vital Energi, which is located in nearby Blackburn. Scott Lutton, regional director at Vital, said the new energy centre will save 2,700 tonnes of carbon annually and make a ‘significant contribution’ to Lancaster’s journey towards carbon neutrality.

Angela Rayner announces new construction regulator

Defective ventilation delayed hospital opening

Edinburgh children’s hospital put back by two years

The opening of Edinburgh’s new children’s hospital was delayed by 20 months because of the installation of ‘defective’ ventilation systems in a critical-care department, an official inquiry has found.

In July 2019, just five days before the facility was due to open its doors, the then Scottish Cabinet Secretary for Health, Jeane Freeman, announced that the opening of the Royal Hospital for Children and Young People would be postponed.

Following remedial works, the hospital – which also houses a new department of clinical neuroscience –only fully opened in March 2021, with the delay estimated to have cost £16.8m.

Freeman’s decision to postpone the hospital’s opening was triggered by the discovery that features of the hospital’s ventilation system did not comply with national Scottish guidance on ventilation for healthcare premises.

The project subcontractor that designed and installed the ventilation system believed it was complying with legal requirements, but was not, the inquiry found.

The inquiry said engineers and contractors should not be expected to have the necessary understanding of a hospital’s clinical requirements to be able to identify appropriate output specifications. It said it should be specified as part of the NHS brief.

More than 40% of new homes have solar PV

The proportion of new homes and buildings equipped with solar photovoltaic (PV) panels has tripled in the past 12 months, new figures show.

The Microgeneration Certification Scheme, the standards body for sustainable energy systems, said there were 18,954 solar PV installations on new-build properties in the last quarter of 2024. This marks a ‘dramatic jump’ on the 5,731 in the final quarter of 2023, said Solar Energy UK.

Assuming that all the panels were fitted on the 45,070 new-build homes completed in England over the fourth quarter of last year, it would indicate that 42% of the new dwellings are solar-powered.

This compares with just 13% of the 44,310 new builds in the last quarter of 2023, a threefold jump.

Façade Design and Engineering Awards open for entries

Winners of the 10th annual SFE accolades will be announced in London on 5 November

Entries are now open for the Society of Façade Engineering’s (SFE’s) Façade 2025 Design and Engineering Awards.

The awards, which celebrate their 10th anniversary this year, recognise and reward excellence and achievements in façade engineering. They also raise the profile of, and draw attention to, the importance of this discipline. Categories include New Build, Refurbishment, Special Structures, and Digital Innovation.

The Special Structures Award, which was launched last year, recognises smallerenvelope interventions, such as a bridge, canopy or sculpture. The 2024 winner was Arup, for Barn Elms Ecological Kiosk, which the judges described as ‘a charming project with a sustainable approach, serving as an asset to the community’. The international award in the category went to Bellaport, for L’Oréal, Paris, which, the judges said, was ‘a beautifully finished work, sensitive to its surroundings’.

Notable projects recognised with façade awards in the past 10 years include: Beijing Library, one of last year’s winners; the Museum of the Future in Dubai; Battersea Power Station,

Training

Life safety BS 8519 training course

Updates of BS 7671 18th edition and BS 8519 mean life-safety requirements have expanded across various Building Regulations and British Standards. This new course, taking place at CIBSE’s Saffron Hill offices on 29 April and online on 17 June, will provide attendees with a better understanding of the Building Regulations and life-safety requirements of BS 9999, BS 8519 and BS 7671. The course includes details of: separation of electrical equipment; approved primary and secondary power supplies; automatic transfer switches; life-safety cables; protected escape routes; and power supplies.

For full details and booking: www.cibse.org/training

The Museum of the Future won in 2022

in London; and Zaha Hadid’s Morpheus Hotel in Macau.

Rimmy Vij, SFE chair, said: ‘Having been involved in this industry for many years, I have witnessed the extraordinary evolution of façade engineering. I, along with the SFE, am committed to ensuring these awards continue to highlight the pinnacle of façade design and drive industry standards forward.’

The deadline for entries is 5 May, and this year’s winners will be announced at a ceremony on 5 November, at Old Billingsgate, London.

For more information, visit: bit.ly/CJFAC25

CIBSE on-demand training

CIBSE on-demand training allows you to learn at your own pace. Courses are divided into two main areas: core engineering modules and courses, and digital engineering. The core engineering modules include:

l Introduction to mechanical and electrical building services

l Hot and chilled water pipework systems

l Low-voltage distribution

l Heating systems design

Energy strategy reports

Building services explained 28-30 April and 3-5 June

Energy surveys 29 April

April and

l Lighting design

l Ventilation design

l High-voltage distribution

l Electrical commissioning and testing

l Commissioning and testing of mechanical services

l Above-ground drainage

l Life-cycle carbon assessment foundation training

l AM18.2 Medium-voltage distribution: equipment

l Cable sizing

l Mechanical services overview

l Practical controls for HVAC systems

l Energy monitoring and targeting

l Fire sprinkler systems to BS EN 12845

l Building services overview www.cibse.org/training

Decarbonisation conference to tackle future of cooling

CIBSE’s Decarbonisation of Heating and Cooling 2025 takes place in London next month

The future of cooling, and the decarbonisation of heat pumps and heat network systems, will be key sessions at CIBSE’s Decarbonisation of Heating and Cooling 2025 event, on 21 May.

With a new CIBSE sustainable cooling group and updates to regulatory compliance, this conference will be a vital platform for knowledge sharing and collaboration.

Confirmed speakers include Professor Graeme Maidment, cooling technical lead at the Department for Energy Security and Net Zero, and Olivia Shears, senior analyst for the Climate Change Committee.

Heating and cooling are central areas covered in the UK Net Zero Carbon Buildings Standard, which includes the trajectory for the decarbonisation of heating and cooling networks.

In April

Events

CIBSE Lifts Group

Scotland Seminar

23 April, London

An in-person seminar focused on the key areas of lift industry standards, maintenance and risk management. The event will provide insights from industry experts on compliance, service quality, and hidden risks in the sector. There is the opportunity to network and enhance your understanding of the latest developments in lift operations. bit.ly/CJLGSS25

CIBSE Patrons: manufactured embodied carbon

9 April, British Land, London

This event aims to help the supply chain address the challenges of manufactured embodied carbon. Speakers include representatives from British Land, Swegon, Swep and CIBSE Certification. bit.ly/CJECPat

The CIBSE conference takes place at the Congress Centre, 28 Great Russell St, London WC1B 3LS.

For further details and to book, visit: bit.ly/CJdecarb25

Fujitsu VRF products gain embodied carbon certification

Fujitsu General Air Conditioning (UK) has been awarded Embodied Carbon Verification (ECV) for its J-VS VRF Series.

The scheme, run by CIBSE Certification, has developed to advance environmentally friendly practices within the built environment, and covers MEP products used for heating, cooling, ventilation, lighting, electrical and public health.

FGAC(UK), following other well-known manufacturers, has become an early adopter of CIBSE’s ECV scheme and plans to expand the verification across its portfolio in the future.

CIBSE Certification uses profits generated from its operations to expand its services and fund CIBSE.

l Find out more about the ECV scheme at bit.ly/3Cr5P5p

CIBSE joins Asbec as voting member

CIBSE has joined the Australian Sustainable Built Environment Council (Asbec).

Its membership will allow for closer collaboration and active participation by CIBSE in shaping the future of sustainable building practices in Australia.

Intelligent Buildings Group: innovating with smart technologies in the NHS

30 April, online

How tech is transforming healthcare delivery and patient outcomes. With Steve Hipwell, Lancashire New Hospitals Programme; Jamie Clegg, Milton Keynes University Hospital NHS Trust, and Declan Hadley, Cisco.

Webinars

Redefining VRF air conditioning systems: meeting carbon targets and enhancing building performance

3 April

Maximising UPS reliability: essential maintenance strategies

29 April

Register at: www.cibsejournal.com/webinars

Asbec comprises industry leaders, professionals and experts dedicated to sustainable building and development. As a voting member, CIBSE will have a direct voice in the council’s key decisions, policy formulations and advocacy efforts.

Asbec advocates for policies and practices that support sustainable growth, reduce environmental impact, and enhance the resilience of the built environment.

Mark Davie, chair of CIBSE Australia and New Zealand Region, said: ‘This affiliation represents a significant step forward in our efforts to promote sustainability within the built environment.’

CIBSE supports research into net zero and health outcomes

CIBSE is a project partner in the National Hub on Net Zero, Health and Extreme Heat (Hearth), a £7.4m initiative funded by UK Research and Innovation and the National Institute for Health and Care Research.

Hearth will explore how the transition to net zero can improve health outcomes, particularly for vulnerable populations, by tackling the risks of extreme heat. It will focus on homes, care facilities, hospitals and prisons.

CIBSE will bring its expertise in building performance and climateresponsive design to help translate findings into actionable strategies for the built environment.

Bungalow retrofit in focus in BSER&T

A paper presenting the energy and environmental performance of whole-house energy systems implemented in six 1970s bungalows in South Wales features in the latest edition of Building Services Engineering Research and Technology (BSER&T).

The objective of the research was to reduce energy demand and carbon emissions, and maximise renewable supply, while ensuring a comfortable and affordable home for the residents. It involved installing a combination of passive and active low carbon solutions.

Detailed monitoring was carried out for a year before the work, and for more than two years after. Analysis of the data confirms that Standard Assessment Performance ratings improved from 12 to 95. The average annual energy consumption across the six bungalows was reduced from 16,117kWh to 4,560kWh. Indoor conditions were also improved and residents reported increased comfort satisfaction.

l The article is available at bit.ly/BSBun25 BSER&T content is free to CIBSE members; go to bit.ly/CJBSERT to access the research journals

Chinese engineers visit Saffron Hill

CIBSE welcomed a delegation of Chinese businesses and trade bodies to its head office in March.

Building on the UK-China policy workshops on decarbonisation and climate resilience in buildings, discussions centred on opportunities for future collaboration to drive sustainable solutions.

Inaugural firms close in on endorsement programme

The first companies are finalising their applications for CIBSE’s Endorsed Organisations programme, which provides a robust framework for showcasing levels of competency, professionalism and adherence to the highest standards.

By participating in this initiative, organisations of all sizes can differentiate themselves in terms of quality. Extensive market research – involving consultation with companies ranging from one-person consultancies to tier-one multidisciplinary firms – has helped craft a programme that caters for every organisation’s journey towards excellence.

To be eligible to join, a percentage of the company’s leaders and staff must be professionally registered members of CIBSE, with building services engineers completing annual CPD on sustainability and building safety. The organisation must also be able to demonstrate best practice in key policy areas. CIBSE hopes to announce the scheme’s first companies in the next couple of months.

For more information, visit go.cibse.org/endorsed-organisations-journal

Ken Dale: a building services engineering legacy

The CIBSE Ken Dale Travel Bursary, a competition offering up to £4,000 to an early-career engineer to travel and research an area of building services engineering, celebrates its 17th anniversary this year. But who was the man after whom the bursary is named?

Ken Dale was born in Birmingham in 1925. After serving in the Royal Air Force from 1942-1946, he was among the first students at the National College of Heating, Ventilating, Refrigeration and Fan Engineering.

Dale gained experience with various contracting and consulting engineering firms before setting up his own practice in 1954, working on iconic buildings such as the Royal Opera House and Chatsworth House.

He held key leadership roles within the industry, including president of the Institution of Heating and Ventilating Engineers and of the Federation of European Heating, Ventilation and Air Conditioning Associations.

Dale was instrumental in securing a Royal Charter for what would become CIBSE, and in 1982 he was made an OBE for his dedication to engineering and to public and military service.

The Ken Dale Travel Bursary was established in his honour, and gives CIBSE members the opportunity to explore international engineering innovations and gain valuable experience. Applications for the 2025 bursary are open. To enter, visit: bit.ly/CJKDTB – deadline is 25 April.

New fellows, members and associates

FELLOWS

Muthukumar, Ragu

Muscat, Oman

Wong, Yat Wai

Tai Po, Hong Kong

MEMBERS

Abiyati, Saleh

Oxford, United Kingdom

Araya Castro, Esteban

JVC, United Arab Emirates

A Shawky, Osama

London, United Kingdom

Aziz, Mina

Riyadh Ksa, Saudi Arabia

Balachandran, Vishnu

Melbourne, Australia

Blackstone, Henry

Sydney, Australia

Bootes, Tony

South Shields, United Kingdom

Boselli, Rocco

Croydon, United Kingdom

Campbell, Constance

Leeds, United Kingdom

Chan, Hin Cheung

Sham Shui Po, Hong Kong

Chan, Kwok Wai

Woking, United Kingdom

Chan, Man Ching

Shatin, Hong Kong

Chan, Wai Ki

Tung Chung, Hong Kong

Chan, Chi Ping

Tung Chung, Hong Kong

Chau, Hin Tat

Kai Tak, Hong Kong

Cheng, Wing Lam

Sha Tin, Hong Kong

Chung, Chi Kuen

Kwai Chung, Hong Kong

De Souza, Villiers

Brisbane, Australia

Doumanoglou, Konstantinos

Salford, United Kingdom

Hui, Wan Ching

Tai Po, Hong Kong

Hung, Tsz Shun

Kowloon, Hong Kong

Ibe, Chukwumaobi

Leeds, United Kingdom

Isakov, Rodion

London, United Kingdom

Jones, Alex

Nottingham, United Kingdom

Kelly, Stephen Anthony

Abu Dhabi, United Arab Emirates

Ku, Kwan Wai Joseph

Tung Chung, Hong Kong

Kwok, Chi Ho

New Territories, Hong Kong

McFarlane, Adam Wernigerode, Germany

McGorman, Stephen Waterford, Ireland

Mendoza, Christian

Dubai, United Arab Emirates

Moustafa Derbala, Mahmoud Hussein

Abu Dhabi, United Arab Emirates

Murphy, Billy

Dublin, Ireland

Pan, Weijian

NT, Hong Kong

Patteth, Shemy

Dubai, United Arab Emirates

Quinton, Stephen Emsworth, United Kingdom

Root, Alex

Cambridge, United Kingdom

Stamp, Samuel Southampton, United Kingdom

Still, Gwilym

Cambridge, United Kingdom

Strong, Nick Sherburn in Elmet, United Kingdom

Tee, Matthew Balham, United Kingdom

Wan, Kin Fu

Sai Wan Ho, Hong Kong

Wong, Chun Ho Simon

Kowloon, Hong Kong

Wong, Tak Wa

Tsing Yi, Hong Kong

Yu, Tsz Kit

Yuen Long, Hong Kong

ASSOCIATES

Ainscough, Andrew

Liverpool, United Kingdom

Bham, Aamirah

Batley, United Kingdom

Bishop, Jack Northallerton, United Kingdom

Blake, Dominic Deansgate, United Kingdom

Cockerill, Adam

Deansgate, United Kingdom

Connick, Owen

Coulsdon, United Kingdom

Davies, Billy Ashford, United Kingdom

Davies, Harry Owen

Bishop’s Stortford, United Kingdom

Field, George Tonbridge, United Kingdom

Holohan, Robert Ruislip, United Kingdom

Jones, Christopher

Liverpool, United Kingdom

Lee-Ramsey, Alexandrea

Manchester, United Kingdom

McIldowie, James Ryan Rickmansworth, United Kingdom

McNulty-Kavanagh, Conor Barnet, United Kingdom

Simm, Mark Liverpool, United Kingdom

Standing, Danny Burwell, United Kingdom

Walker, Dominic Stockport, United Kingdom

LICENTIATES

Abdool-Raman, Mohammad Rizwan

London, United Kingdom

Banol Mora, Valentina London, United Kingdom

Bayley, David

Bristol, United Kingdom

Beghi, Giorgio

London, United Kingdom

Camm, Elliott Keighley, United Kingdom

Carter, Jack Leeds, United Kingdom

Chandler, Michael New Malden, United Kingdom Dixon-Lever, Grace South Stockport, United Kingdom Ellison, Tom Leeds, United Kingdom Fall, Edward London, United Kingdom Fenwick, Sonny Hockley, United Kingdom Fowler, Simon Plymouth, United Kingdom

Gill, Nathan Leeds, United Kingdom

Hall, Oliver

Leigh-on-Sea, United Kingdom

Hargreaves, Sidney Barnet, United Kingdom

Hayman, Jack Caterham, United Kingdom Jenkinson, Lucas Newark, United Kingdom

Jeyapahan, Varanika Thornton Heath, United Kingdom Kennedy, Matthew Beckenham, United Kingdom Kistell, Bradley Doncaster, United Kingdom Lewis, Harrison Worthing, United Kingdom

Mahmoud Aboul-Fotouh, Zaynab London, United Kingdom

Matthias, Ashley Nottingham, United Kingdom Mitchell, Edward Otley, United Kingdom Moores, Lex Stockport, United Kingdom

Murray, Benjamin Edenbridge, United Kingdom Norris, Ben Cotgrave, United Kingdom Owens, Jack Swadlincote, United Kingdom Park, Matthew Wigan, United Kingdom Roberts, Christopher Hull, United Kingdom Roussos, Johnny Leeds, United Kingdom Sheldon, Alex Dartford, United Kingdom Short, Lewis Leeds, United Kingdom Smith, Gavin Ayrshire, United Kingdom Stevens, Theo Newark, United Kingdom Taylor, Lucas Bradford, United Kingdom

Thakur, Fasih London, United Kingdom Tippett, Nathan Chilcompton, United Kingdom

• Eurovent certified performance

• First air-source multifunctional heat pump and chiller unit using propane as a near zero GWP, natural refrigerant solution.

The ties that bind

Uncertainty over America’s international relationships may have been the backdrop to the ASHRAE Winter Conference, but CIBSE and its US counterparts continue to work together on key decarbonisation projects

It is always a great pleasure to attend the ASHRAE Winter Conference and meet in person with the various technical committees, and the ASHRAE members and management.

This year, in Orlando, CIBSE organised a seminar on the true value of building performance. Supported by the CIBSE ASHRAE Liaison Committee and the ASHRAE Technical Committee 7.6 Building Energy Performance, the seminar explored the critical intersection of building performance and investing for sustainability.

The speakers – Parag CameronRastogi, Edith Blennerhassett, Mark Walker, Thomas H Phoenix and myself – delved into key topics, including: the importance of building performance data in sustainable investing; delivering environmental, social and governance goals through building performance optimisation; strategies for improving health via building performance; holistic approaches to enhance overall building performance; and reimagining highperformance buildings for a positive societal impact.

I was invited to join the discussions of the International Decarbonisation Panel, as well as the meetings of the climate change and weather data technical committees. It was pleasing to hear that the UK and CIBSE are regarded as global leaders in climate adaptation and decarbonisation – CIBSE’s TM65 and the future weather files, and the UK Net Zero Carbon Buildings Standard, were consistently mentioned as examples of best-practice standards.

A survey by the International Decarbonisation Panel, on the technical priority areas for the ASHRAE international members, revealed the focus to be energy efficiency, electrification, facilities management, and passive design with decarbonisation and climate resilience as overarching themes. The European members’ priorities were the changes to the

“At national level, efforts in the US are focusing on reducing operational energy”

Energy Performance of Buildings Directive; for Australia it was Nabers; and for India it was the introduction of carbon credits. The chair of the panel, Clay Nesler, called for close collaboration to understand and tackle the complexity and variety of the approaches, policies and standards of the various international regions.

Conversations with delegates revealed the challenges that the US is facing under the current administration in promoting environmental policies, further hindered by policy variations between cities, counties and the state. At national level, current efforts in America are focusing on reducing operational energy, with local government working with utilities companies to provide financial incentives or penalties to reduce energy demand and peaks. Embodied carbon of building services is not high on the national or local agendas, but the recent publication of the TM65 North America addendum has been received as a

positive step towards increasing awareness and understanding of embodied carbon in the market.

I have been closely following the activities of the ASHRAE climate change and weather data technical committees, which are looking to update the weather information for the sizing of systems. They are also discussing the creation of future weather data for climate adaptation, which, in my opinion, is long overdue.

Their challenges lie in the variation of climate zones and heating/cooling demand between the different US states, and access to reliable climate information. CIBSE has been asked to support these activities and to participate in a research project that will look at using future Test Reference Years (TRYs) and Design Summer Years (DSYs) in the performance analysis of buildings in selected areas.

The CIBSE ASHRAE Liaison Committee meeting revealed common areas for collaboration, such as artificial intelligence (AI) and cybersecurity. CIBSE is forming an AI working group to establish a policy on its use in building design and operation. It will also look at the implications of the Internet of Things for cybersecurity. Members of the ASHRAE AI Multidisciplinary Task Group will be invited to join this initiative.

We also had the chance to celebrate the institutions’ ongoing relationship and our volunteers. CIBSE CEO Ruth Carter, President Elect Vince Arnold and I hosted a drinks reception, strengthening ties between our institutions and acknowledging the volunteers’ commitment to sharing knowledge.

As a token of appreciation for the ever-growing relationship between CIBSE and ASHRAE, Vince Arnold presented a glass Tree of Life to ASHRAE President M. Dennis Knight. We also celebrated Helen Meutermans, CIBSE ASHRAE Graduate of the Year 2024, as she received her YEN award. l

Keynote speaker for CIBSE Technical Symposium 2025 announced

Professor Tadj Oreszczyn will open event on 24 April at UCL

CIBSE has announced that Professor Tadj Oreszczyn, Professor of Energy and Environment at UCL, will be the keynote speaker at the CIBSE IBPSA-England Technical Symposium 2025, where he will discuss how domestic energy ratings may evolve to meet the future energy transition challenges based on modelled and monitored comparisons of the Great British building stock.

The symposium, taking place on 24-25 April at UCL, Bentham House, London, is themed ‘Fit for 2050 –Achieving net zero through intelligent, resilient and sustainable design’. It will explore the latest advancements in design and building performance.

CIBSE President Fiona Cousins will open the symposium with a welcome address, setting the stage for two days of discussions. The event will host sessions across four venues, including a main theatre and three conference rooms.

The main theatre talks include benchmarks and strategies for unlocking net zero, and integrating buildings with district heating networks. Another panel discussion will focus on passive design strategies and there will be sessions on embodied carbon, retrofits, and nature-based climate resilient strategies.

An awards presentation at the end of the event will recognise the symposium papers that have made ‘outstanding contributions to the field’, and there will be an evening buffet and reception at the end of day one.

Join us at the CIBSE Technical Symposium 2025 by visiting cibse.org/symposium and book your place today.

Commercial heat pumps will be key

TWhen considering the government’s heat pump installation targets, we should not forget the impact of commercial projects, says Mitsubishi Electric’s Graham Temple

he Climate Change Committee’s (CCC’s) 7th Carbon Budget is suggesting that the government abandon the previous target of installing 600,000 heat pumps a year.

Instead, the CCC sets out a pathway to get us from 60,000 heat pump installations in 2023, to 450,000 a year by 2030, and around 1.5 million a year by 2035.

This gives us five years to really make an impact. To do so, however, we need to change the narrative. Currently, the broad assumption seems to be that we are talking about 450,000 installations into homes. This ignores the significant potential that the commercial sector has to offer.

A colleague of mine was trying to find a simple way of explaining the importance of commercial buildings in decarbonising the nation, and while his maths is simplistic, in essence it goes as follows:

A commercial heat pump installation can include anything from heating a dental practice, an office block, a hotel, a school, or an entire leisure centre. That can mean a small installation of around 40-50kW of heating, right up to a system that is supplying 1,000kW or more.

So, while there isn’t a typical commercial installation, it is important to take a broad look at the types of buildings and technologies available.

Factoring this in, we can estimate that an ‘average’ commercial heat pump installation equates to around 15 residential ones.

Around 1.6 million gas boilers are sold domestically each year, which is why housing is such an important focus in the decarbonisation debate.

There are also around 35,000 commercial heating opportunities each year. Not all of these will be suitable for a heat pump, but there are an estimated 30,000 commercial buildings each year that could be eligible for one.

Using the simple maths of my colleague: 1 commercial heat pump = 15 domestic heat pumps, and 30,000 commercial installations a year = 450,000 domestic equivalents So, we can get to 450,000 heat pumps a year without fitting a single home!

l

Graham Temple is marketing

manager at Mitsubishi

Electric

cibse.org/FacadeAwards

Closing date: Monday 5 May 2025

The unintended consequences of fire safety reform

Changes to fire safety rules are having unintended consequences that are stifling design and stalling delivery of high-rise flats, according to a new report by fire engineers and developers, who offer their proposals for improving the system

The 2017 Grenfell Tower tragedy fundamentally transformed the UK’s approach to fire safety and Building Regulations, most notably through the Building Safety Act (BSA).

The BSA introduced a new regulatory framework, establishing the Building Safety Regulator (BSR) to oversee the process, which has resulted in several positive outcomes, including: more comprehensive documentation and detailed initial planning; improved consistency through standardised processes; better audit trails for design decisions; and less reliance on approving authorities for developing design solutions. There are now also mandatory competency assessments for decision-makers, clear ownership of decisions, improved inspection regimes, and earlier involvement of building owners and operators in the design process.

Beneath these improvements, however, lies a complex reality. The new system has created significant challenges for the industry that may, ultimately, undermine its effectiveness. A new report by Ashton Fire, Olympian Homes and RG Group examines these unintended consequences in depth.

The compression effect on design phases

A major change under the BSA is the introduction of the Gateway procedure, with three mandatory review points during the design, construction and completion of high-risk residential buildings. Gateway 2 has proven particularly problematic, imposing a mandatory 12-week review period, during which construction cannot commence.

l The authors are: Michael Kinsey, associate director and Harry McDaid, director at Ashton Fire; Richard Goodwin, construction director at Olympian Homes; and Adam Crabtree, director at RG Group

In reality, applications are taking, on average, 34% longer (16.3 weeks) than the stated period, with many taking longer. This has created the risk of developers and clients compressing design timelines to maintain project viability, and rushed decision-making. There is also the issue of professionals defaulting to overly conservative solutions and design teams caught between obligations and practical constraints.

Communication vacuum

Pre-Grenfell, building design approvals involved ongoing collaboration between stakeholders. The BSR process has dismantled these traditional channels of communication, replacing them with more rigid and formalised outcomes.

The BSR has explicitly stated it will not assist applicants by issuing advice or guidance on applications. This communication vacuum has increased the risk of misunderstandings regarding interpretation of fire-design guidance, and protracted back-and-forth exchanges that could have been resolved through discussion.

There is a higher likelihood of mistakes and oversights, and a reduced capacity to develop innovative solutions to complex design challenges that support sustainability goals. The resolution of issues is also slower and costlier.

Resource constraints have compounded these problems. With the BSR struggling to employ essential technical staff, it is outsourcing application reviews to multidisciplinary teams (MDTs), the assembly of which has proven challenging, contributing to delays and inconsistent approaches.

The paradox of more documentation and less scrutiny

The increased volume and detail of documentation required for submissions, combined with compressed timelines, creates the risk of critical details being missed.

Fire engineers are now expected to review detailed design documentation beyond their traditional remit, which primarily involves developing fire strategies that define key principles, rather than detailed technical reviews. This creates the potential for fire engineers shouldering greater professional risk, without commensurate increases in fees or time.

Over-reliance on guidance-based designs

One of Dame Judith Hackitt’s recommendations is to retain an ‘outcome-based’ approach, rather than defaulting to prescriptive requirements. However, BSR Gateway 2 responses reveal a tendency to treat guidance as mandatory requirements, rather than tools for achieving compliance with broader regulatory objectives. This undermines the flexibility needed for complex projects and stifles innovation.

By focusing narrowly on adherence to specific prescriptive elements, the opportunity to assess safety strategies holistically risks being lost.

Economic impact

The BSA Gateway system has transformed development economics by requiring extensive upfront investment before securing site acquisition and funding. This frontloading of costs creates significant commercial risk, making some projects unviable.

Gateway 3 presents perhaps the most critical

Proposals to improve the system

1. Create improved communication channels between all stakeholders

2. Reconsider the timelines of the approval process

3. Emphasise the distinction between guidance and regulatory requirements

4. Define competency frameworks, with robust checking systems

5. Formally define the roles of principal designers and fire engineers

6. Implement a Gateway 2 pre-application period with early MDT formation

7. Establish a publicly accessible database of decisions

8. Acknowledge progress already made in fire safety standards

“The path forward acknowledges the merits of previous practices and current shortcomings”

challenge, occurring at a time of maximum financial exposure before developers receive income. The delays already experienced at Gateway 2 extend the period during which they must service debt without offsetting income.

Additional challenges include practical completion concepts becoming largely obsolete without contractual frameworks for Gateway 3, and difficulty defining responsibility for delays beyond the statutory period. There is also uncertainty about the administration of design changes during construction and additional insurance risks during the registration period before occupation.

Future uncertainty

The UK government’s response to the Grenfell Tower Inquiry Phase 2 Report accepts all 58 recommendations, outlining numerous further reforms. These include the creation of a new Super Regulator by 2028 and a licensing system for contractors undertaking high-risk buildings.

While well intentioned, these changes create further uncertainty in a sector struggling with a paradigm shift in construction processes. The responses prioritise consultation and review over decisive action, potentially contradicting the government’s wider economic aims, including the delivery of more housing.

The legacy of Grenfell demands substantive improvements to fire safety in building design, but these must be evaluated by practical outcomes, rather than just the breadth of oversight. A more strategic approach is needed, with enhanced focus on existing building stock, where risks are demonstrably higher. Several improvements to the current system would support the practicality and effectiveness of the desired intentions (see panel, ‘Proposals to improve the system’).

The path forward requires a nuanced approach that acknowledges the merits of previous regulatory practices and current shortcomings. Focus must shift from layering additional oversight towards implementing more efficient, outcome-focused processes that enhance building safety while supporting essential development activity. l

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Rewriting the rules of retrofit

The Entopia Building sets a new benchmark for sustainable retrofits.

Andy Pearson explores how CIBSE’s 2025 Building Performance Champion used a fabric-first approach to cut whole life carbon by 84%

Entopia is an exemplary retrofit. It had to be. The 1930s building in Cambridge, originally a telephone exchange, has been transformed into a new energyefficient home for the Cambridge Institute for Sustainability Leadership (CISL).

The brief set by CISL for the retrofit was for the revamped building to achieve Breeam Outstanding, EnerPHit Classic and Well Gold. The client also wanted the scheme to target low embodied carbon and to maximise its use of bio-based materials. Most challenging of all, CISL wanted the scheme to demonstrate that, with a challenging brief and a committed design team, a deep, green retrofit could be delivered at a cost competitive with that for a conventional office refurbishment.

As with all Passivhaus projects, the starting point in delivering this ambitious retrofit was adopting a fabric-first approach. Although not listed, the concrete-framed, brick-clad, fivestorey building (plus basement) is located within a conservation area, and the planners were keen to retain its somewhat utilitarian appearance.

To improve the thermal performance of the building envelope, the mock Georgian sash

Project team

Client: Cambridge Institute for Sustainability Leadership

MEP & Passivhaus: Max Fordham

MEP engineers up to RIBA stage 3 and BREEAM

assessors: BDP

Architect: Architype/ Feilden & Mawson

Main contractor: ISG

Mechanical contractor: Kershaw

Electrical contractor: REL

Controls specialist: Learnd

Air handling units: Swegon

VRV system: Daikin

windows were replaced with energy-efficient triple-glazed units. Without the timber lattice of transoms and mullions, the new windows had 60% more glazed area, which helped increase daylight levels. Internally, wood-fibre insulation and lime and cork plaster were added to the walls, to improve their thermal performance and enhance fabric airtightness.

‘The massing of the building is fairly efficient, so by the time we’d made the glazing work hard and improved the airtightness, we didn’t need to fit a huge amount of insulation,’ says Gwilym Still, director of Passivhaus at the project’s MEP engineers, Max Fordham.

The benefit of having a thermally efficient envelope is that it contributes to the efficient control of internal conditions and reduces reliance on building services. ‘Improving the thermal fabric performance significantly reduced the amount of plant required, which, typically, is one of the largest impacts on a refurbishment project,’ Still explains.

To enable the removal of the building’s gas supply, the building services solution is all electric. Max Fordham’s approach is based on the conventional Passivhaus methodology of

The Entopia Building

supplying fresh air via a mechanical ventilation with heat recovery (MVHR) air handling unit (AHU). This supplies variable air volume (VAV) boxes, linked to temperature and CO2 sensors, to control the volume of air supplied to each space. A master VAV box controls the total volume of air supplied to each of the floors. Air extract is via corridors and WCs, back to the thermal wheel heat exchanger in the AHU before being expelled.

The AHU is the main source of heating for the building. As such, it incorporates an integral air source heat pump. ‘The AHU can supply about 80% of the total heat demand,’ says Still.

In winter, the heat exchanger pre-warms the incoming supply air using heat reclaimed from the exhaust air. Supply air then passes over the heat pump heating coil, which can further heat it up to a maximum temperature of 27°C.

The amount of heat that can be supplied to a space is limited by fresh air flowrates and the temperature of the supply, so some of the spaces also incorporate wall-mounted, direct electric radiators to top up the heating provision. These are under occupant control and operate independently of the building’s Trend BMS.

Summer comfort provision relies on a combination of the building’s exposed thermal mass, natural ventilation provided by opening windows, summer bypass on the AHU heat exchanger fresh air supply, and night cooling using the mechanical ventilation system. The temperature of the supply air can also be lowered to around 23°C by running the AHU heat pump in cooling mode.

Still says: ‘The temperature of supply air is based on outside air temperature, but the flowrates into the spaces are based on space temperatures and CO2 levels; if a room is getting a bit warm, it will get more mechanical ventilation and occupants can open the window.’

This cooling strategy is supplemented with a variable refrigerant volume (VRV) system linked

Embodied carbon

A major focus of the project was the optimisation of carbon over a 100-year period, with upfront and long-term costs and carbon influencing every design decision. In addition to retaining the main building superstructure, materials used in the refurbishment were either repurposed or selected to minimise embodied carbon.

Bespoke assessments included the existing WCs; while replacing them added more upfront carbon, it also significantly reduced water usage, which meant this carbon was paid back quickly.

Existing materials were reused where possible, including carpet tiles in the entrance area and raised access floor panels, which were cleaned and put back without a floor finish.

In addition to the steel from a film studio for the PV rooftop canopy, and the 350 light fittings from a fit-out project in London, the building incorporates a reception desk recycled from Netflix and is finished using paint with 35% recycled content.

According to CISL, the total whole life embodied carbon of the refurbished building was 409kgCO2e/m2, including in-use and end-of-life carbon, over a 100-year building life (based on a RIBA Stage 5 construction stage assessment), which, CISL says, ‘compares very favourably to new construction’. Omitting in-use and future phases, and considering only the carbon embodied in the building at handover stage, the figure stated by CISL is much lower, at 130kgCO2e/m2

PVs are mounted on a steel frame that was used on a Marvel film set

The AHU heat pump can supply air down to 23°C in the summer

Building Performance Champion Entopia Building

to fan coil units (FCUs) to provide local cooling, as well as heating in winter. The system was introduced after detailed thermal modelling showed that rooms with higher occupancy and/ or solar gains would require active cooling to keep them at a comfortable temperature. FCUs are controlled via the BMS and by occupants via wall-mounted local controls. Branch selector boxes allow the FCUs in different zones to operate in heating and cooling modes simultaneously. This hybrid cooling strategy was tested against current weather files and showed a pass for Well and Breeam, and for adaptive comfort criteria, based on 2050s weather data.

Blinds are installed on the windows to prevent glare and reduce the risk of overheating. Still says

Winter heating and ventilation strategy overview

The 1930s building was formerly a telephone exchange

Carbon: retrofit versus build anew

Desk-based Sankey analysis compared the impact of refurbishing this building with the creation of a notional new building. This comparison suggested that a newly constructed building, including demolition of the existing structure, would generate between 970 and 1,620 kgCO2e m-2. In contrast, it was estimated that a deep retrofit would generate 400 kgCO2e.m-2 – hence it was the preferred option.

there are ‘opportunities’ to improve summer comfort and future-proof the building. These include: enhancements to the cooling delivered by the central AHU beyond ‘the peak lopping base case’; increasing night-purge ventilation; and leaving windows on upper floors open overnight. Other potential interventions include the addition of solar-control film on the glazing and external shading, and increasing the capacity and extent of the VRF system.

Artificial light levels in the offices are controlled by both daylight levels and presence detection, while over-desk downlighting is controlled manually. Light fittings are a mixture of recycled and new. Recycled fittings were supplied by the main contractor, having been salvaged from a Cat A fit-out in London. New fittings

incorporate a 3D-printed plastic case, which Still says is capable of being reprocessed and reused up to six times when the fitting reaches the end of its useful life.

Domestic hot water is supplied through low-flow fittings to wash hand basins and showers using electric point-of-use heaters.

The design team even found space on a flat roof at the rear of the building to squeeze in a small photovoltaic (PV) array. This is expected to generate 13,800kWh/yr. The PVs are mounted on a steel frame salvaged from a Marvel Eternals film set to support it above seating. Still says: ‘I really like this bit of the project; it used to be a plant enclosure with boilers and ventilation kit; now it’s amenity space with the PVs generating renewable energy and providing shade to make the space more comfortable.’

The building was occupied in September 2022. Since then, post-occupancy evaluation and ongoing seasonal commissioning have been used to fine-tune the building, with additional input from the main contractor, AHU manufacturer, and the controls specialist. Occupant feedback was sought as part of the seasonal commissioning process. This highlighted an intermittent issue of cold air being supplied to spaces through the ventilation system when in heating mode. Investigations found the issue corresponded with the times the AHU heat pump was running in defrost cycle.

The solution has been to reduce the supply air temperature and advance the ‘on’ time of the AHU in the mornings, to enable spaces to be preheated more steadily before occupancy.

Predicted energy use intensity (EUI) was 54kWh·m-2 per year. However, the actual EUI is slightly lower, at 52kWh·m-2 per year, dropping to 49kWh·m-2 per year if the contribution from the PVs is included. Still says these figures ‘compare

Heating and cooling is supplemented by a VRV system linked to fan coil units

well’ with industry targets for new-build offices, including the LETI Climate Emergency Design Guide and the RIBA 2030 Climate Challenge, which both have a target of 55kWh·m-2 per year. At £12.69m, the project is estimated to have cost 8% more than a conventional refurbishment. However, CISL expects the additional cost to be ‘recouped within five to eight years from operational energy savings’. ‘That the Entopia Building uses dramatically less energy than its predecessor is a success in its own right,’ said the client. ‘That it has minimised the use of new materials through circular design and concurrently reaches three challenging building standards is exceptional. Its true impact is still to come, however, through its role as a beacon project: an exemplar and teachable resource that creates positive ripples of change throughout the built environment, influencing the course of other projects, policies and investments.’

Judges at the CIBSE Building Performance Awards were equally impressed, and the scheme won Project of the Year - Refurbishment, plus the coveted Building Performance Champion award. They said: ‘The Entopia Building showcases the future of environmentally conscious design, achieving a staggering 84% reduction in whole life carbon compared with standard retrofits.’ l

For more on this project and to access the project data, go to https://bit.ly/CJEntBP

Sash windows were replaced with energy-efficient triple-glazed units

Model future

The model set to replace SAP for home energy assessments is designed to work dynamically with new-era technologies such as energy storage, advanced control systems and dynamic tariffs.

Sustenic’s John Henderson and Jose Ortiz FCIBSE highlight the potential of the Home Energy Model

The UK’s energy landscape is set to change with the introduction of the Home Energy Model (HEM), which is due to replace the Standard Assessment Procedure (SAP) in 2025. SAP has been the primary framework for assessing home energy performance since 1993. As technology and energy usage patterns evolve, however, its reliance on outdated methods has become a limitation. HEM promises to address these shortcomings, using a more accurate, sub-hourly, dynamic modelling approach.

Despite numerous refinements, SAP’s core methodology has remained unchanged, employing a ‘steady state’ method to average energy usage over a month. This limits precision, particularly in accounting for modern dynamic technologies such as energy storage, advanced control systems, and dynamic energy tariffs, which operate on a much faster timescale.

Easy access

SAP’s rigid software specification often limited the scope of participation and innovation. In contrast, HEM’s open, modular structure allows anyone with basic software skills to download, use and modify the model. Individual components can be updated or replaced independently, allowing continual refinement without overhauling the entire system. This accessibility encourages a dynamic process of improvement and adaptation, where users can identify bugs, suggest changes, or even propose code enhancements that can be integrated swiftly into the main codebase after appropriate reviews.

Procedural limitations have also arisen. For instance, SAP enforces fixed assumptions about occupancy, used across all applications to facilitate direct comparisons. As SAP’s role expanded to support various policies, however, this one-size-fits-all approach was found to cause differences in predicted and actual energy consumption.

Recognising these challenges, the UK government initiated the development of a new model – HEM. This will use a sub-hourly modelling approach to capture granular variation in energy usage, significantly improving its ability to model the interplay of various building technologies and user behaviours.

HEM promises a framework that can adapt to innovation in energy technology, anticipating advancements in residential spaces. Aligned with the Future Homes Standard, it will ensure energy assessments are accurate and reflect current and future energy dynamics. (See panel, ‘The architecture behind HEM’.)

A significant advancement in HEM is the introduction of ‘wrappers’ – layers of code that integrate specific policy or use-case assumptions into the core model without altering its underlying structure. This addresses SAP’s rigidity by allowing dynamic input of assumptions regarding occupancy, climate and appliance, enabling more accurate energy profiles that reflect real-world usage. This makes HEM adaptable for various applications, from occupancy-standardised asset ratings to modelling the energy use of dwellings of specific occupants.

Validation

HEM has undergone extensive inter-model comparisons to validate its building physics algorithms against established modelling tools, such as the Passivhaus Planning Package and Environmental Systems Performance –Research (ESP-r). These comparisons align input values across models, ensuring a fair assessment of each model’s ability to simulate energy dynamics within dwellings accurately.

Validation phases confirm HEM’s potential while highlighting areas for refinement, ensuring that the model evolves in response to emerging technologies and standards (See Figure 1).

While HEM is a significant advancement, it has limitations that require ongoing refinement. One challenge is its simplified approach to handling ventilation-related losses and gains, which can affect accuracy, particularly in assessing cooling energy requirements and the potential for overheating. Currently, HEM is configured as a two-zone model, which may not fully capture the complexity of overheating in different rooms. Planned enhancements will improve granularity and accuracy.

Another challenge is operational speed. Unlike SAP, which provides near-instantaneous results, HEM simulations take approximately one minute. While a step forward in computational detail and accuracy, it poses challenges for applications such as stock modelling, where numerous simulations must be run quickly. As the model is optimised, processing times are expected to decrease.

HEM also requires detailed inputs from users, which enables accurate modelling but increases complexity. Guidance and tools are being developed to help users navigate this.

Despite these challenges, HEM’s opensource, modular nature allows for continuous

The architecture behind HEM

HEM is built on the EN 52016 suite of standards, incorporating both new and existing methodologies. The core EN 52016 model conducts heat-balance analyses that compute the movement of heat within and between the building’s structural and internal components. This includes calculating temperature changes and heat flows for each component, such as walls and air spaces, for each timestep. The design allows it to perform simulations using any desired timestep, although it has been configured and tested using a half-hourly step to match the UK’s energy metering systems. Developed in Python, its architecture is open-source and inherently modular, encouraging ongoing enhancements and collaborative development. A user-friendly codebase makes it accessible to a broad audience.

improvements by a broad community, facilitating immediate enhancements.

Looking forward

HEM’s potential extends beyond individual homes. Its flexible, open-source architecture could enhance neighbourhood energy models and financial tools, leveraging detailed, real-time data to aid smart, sustainable energy use. By engaging with HEM, manufacturers and stakeholders can refine their products and drive innovation in energy solutions. (See panel, ‘Easy access’.)

Its success relies on diverse insights and adaptability to feedback. The UK government is promoting engagement through public consultations and transparent processes for proposing and integrating code changes, and must continue to facilitate widespread input into the model’s development.

User and developer forums will provide a structured environment where improvements can be discussed and integrated, while clear guidelines for codebase modifications will help focus efforts on changes that offer significant benefits.

We are on the threshold of a new era in home energy assessment. The open nature of HEM’s codebase has the potential to revolutionise how energy modelling is conducted, encouraging collaborative development and potentially spurring the creation of spin-off software products and systems.

HEM is poised to adapt continually to the evolving landscape of building technology, driving forward the UK’s energy efficiency and decarbonisation goals. l

l John Henderson is a principal consultant and Jose Ortiz a director at Sustenic

Figure 1: Free-floating temperature comparison between ESP-r and HEM, as part of its validation

Zone 1: Half-hourly operative temperature [winter week]

Zone 2: Half-hourly operative temperature [winter week]

Power struggle

AI is driving an exponential demand for data centres, which is leading to surging energy requirements, rising cooling demand and grid limitations. Molly Tooher-Rudd finds out how engineers are responding to sustainability challenges in the sector

Artificial Intelligence (AI) has surged to the forefront of UK innovation, but are we equipped with the infrastructure to support it?

In January, Prime Minister Sir Keir Starmer unveiled the government’s AI Opportunities Action Plan to harness the technology to boost economic growth and public service efficiency, with the broad objective of making the UK ‘one of the great AI superpowers’.

Central to this ambition is the expansion of data centres. Such growth presents significant challenges, however, including energy consumption, Grid capacity and cooling demands. At the same time, it also opens up opportunities for sustainable development and technological innovation.

Electricity demand

‘What we’re seeing is an increase in highperformance computing [HPC],’ says Malcolm Howe, partner at Cundall, leading the firm’s critical systems sector. ’The power density of our devices is rising dramatically, which is driving these changes in data centre function.’

The power demands of these facilities have skyrocketed. ‘When I entered the industry, data halls with 700kW of equipment were a reasonable size. Now, we’re routinely designing data halls with 10MW of kit, and hyperscalers have started talking about GW campuses,’ says Howe.

In September 2024, the National Grid’s

chief executive, John Pettigrew, cautioned that AI-driven energy consumption could increase sixfold in the next decade, raising the UK’s energy demand by 500%.

‘It’s a double whammy from an energy point of view,’ warns Howe. ‘Not only do the servers demand significantly more energy, but the cooling systems needed to regulate temperatures also consume substantial power. It’s becoming increasingly less energy efficient.’

Asad Kwaja, associate director, district energy and low carbon infrastructure, at Aecom, highlights the limitations of the UK’s National Grid. ‘One of the big barriers is the constraints around power use and these large centralised demands,’ he says.

The Oxford-Cambridge Arc, a designated growth zone with strong academic and research ties, has been identified as an area for data centre expansion in the government’s AI drive. Arup director Gareth Williams believes that ‘while there’s an aspiration to concentrate development in one area, the power demands

AI could increase the UK’s total electricity demand by 500% in the next decade

are likely to place limits on how concentrated this can really be. We’d benefit from taking a more holistic and strategic view.’

Howe agrees. ‘Where you put a data centre is governed by multiple factors – power supply, fibre connectivity and water availability. There is an evident lack of understanding of these tick boxes,’ he says.

To alleviate the pressure of increased energy demands, Kwaja highlights an opportunity to develop data centres in areas with surplus renewable energy, such as Scotland, where wind power is abundant. However, Howe believes that renewables alone won’t suffice.

One potential solution could be onsite nuclear generation, and some facilities in the US are exploring the use of small modular reactors to support a net zero hyperscale data centre. But this isn’t a solution that can be replicated for all data centres, Kwaja advises. ‘It’s important to keep in mind that building a data centre is complex and expensive enough,’ he says. ‘Adding a reactor alongside is another huge project in itself. Its perhaps underestimated how difficult that would be to locate and deliver.’

Cooling challenges

The shift towards AI-centric data centres has led to design modifications, particularly in cooling infrastructure. Traditional data centres rely on hot- and cold-aisle configurations, where air passes through server racks to carry heat away. However, Howe explains that the increase in airflow required to cool high-power racks has led to forceful gales in cold aisles, necessitating wider rack spacing.

‘As a result, despite the higher power of individual racks, the overall power density per square metre of the data hall remains the same because of the reduced number of racks and increased spacing,’ he says.

‘This means we’ve passed the point where it’s sensible or efficient to cool servers using just air. Direct liquid cooling to the chip is becoming essential,’ Williams adds.

‘We are also drastically reducing the opportunity for free cooling. You’re introducing more mechanical cooling during the peak summer period, and that is impacting power usage effectiveness [PUE],’ Howe says.

PUE is the ratio of energy used by a computer data centre facility and the energy delivered to computing equipment, with a low PUE indicating better efficiency. ‘We’re seeing PUE stats creeping back up for the first time in years. From a sustainability perspective, that’s a big problem,’ warns Howe.

CIBSE Data Centres group:

The new CIBSE Data Centres special interest group (SIG), launched on 5 March, unites industry professionals to drive sustainable, energy-efficient data centre design. Chair Austin Williamson emphasised the committee’s role in fostering innovation. ‘Disruptive technologies are reshaping design, and this group will lead to new developments,’ he said.

The committee will focus on knowledge sharing and developing CIBSE white papers, recognising data centres’ cross-sector impact, from lighting and sustainability to heat networks and facilities management. ‘Fire safety is also a growing concern as buildings become more complex,’ one SIG member noted, while another said: ‘We must understand [AI’s] impact, management, and future legislation.’ The group will also address infrastructure challenges and power demands. Iain MacDougall MCIBSE, the UK Net Zero Carbon Buildings Standard data centre group lead and head of sustainability solutions & climate change at RED, said: ‘Being here fills me with confidence.’

For more on the group, visit bit.ly/CIBSEDC

Innovation in cooling systems is crucial for sustainable design. In one project, Williams describes how Arup helped the client implement an advanced cooling strategy using thermal energy storage tanks based on water stratification. ‘By leveraging water’s density properties, hot and cold water is naturally separated,’ he says. ‘We used computational fluid dynamics to design inlet and outlet diffusers, ensuring steady water flow and effective temperature stratification for efficient cooling.’

Heat recovery

A key solution for reducing carbon impact and improving sustainability is residual heat reclaim. Williams notes that Germany was the first European country to make the reuse of waste heat mandatory when it implemented the Energy Efficiency Directive through the Energy Efficiency Act (2023).

Howe believes it’s vital that the huge amount of heat that data centres produce is captured and re-used: ‘This heat can displace burning fuel somewhere else.’ Kwaja agrees: ‘Wherever there is an opportunity, heat recovery should be encouraged.’

The power density of our devices is rising dramatically, which is driving these changes in data centre function

A prime example of waste heat recovery is in Odense, Denmark, where Meta’s data centre, designed by Cundall, recovers 45MW. This is transferred to ammonia heat pumps operated by the local energy services company, supplying hot water to a district heat network that covers the whole city. ‘Generally, when connecting a data centre to a heat network, for every megawatt you might be able to deliver heat to 1,500 to 2,000 homes,’ says Kwaja.

‘Domestic heating is one of the major sources of fossil fuel consumption in the UK,’ states Howe, who highlights challenges in the UK, where district heating infrastructure is lacking. Denmark’s success stems from a diverse mix of energy sources and users, balancing seasonal demand. ‘It works really well in Denmark because of its scale, and the different types of customer and, therefore, different load profiles,’ says Howe.

‘District heat networks tend to want the most heat in the winter, when it’s cold, whereas data centres work at their most energy efficient in the winter, when they can make use of free cooling. Peak summertime is when a data centre rejects the most heat, so you want to be connected to industrial plants or sports centres that are going to use it all year,’ says Howe. (See the Open project on page 44.)

Williams agrees, and says the investment needed to connect the right consumers

presents a challenge. Kwaja, meanwhile, hopes that a big policy drive on heat network zoning will aid this, and encourage the uptake of heat networks across the country.

‘We need to be better at forward planning. Between the growth of networks and data centres, there’s a real opportunity to harness the synergies between both, he says.’

Future-proofing

In September, technology Secretary of State Peter Kyle announced that data centres are now categorised as critical national infrastructure, essential for the wellbeing of society. However, a report from trade association techUK, Future-proofing digital infrastructure: Climate resilience in the data centre sector, warns that data centres are at increasing risk of heatwaves, flooding and power outages because of climate change.

Legacy data centres are at significant risk, often ill-equipped to manage rising data demands and technological developments, says Williams. ‘Without adequate attention, this could result in spiralling operational costs, inability to support increased power densities, failure to meet sustainability requirements, and challenges with energy accessibility.’

The UK Net Zero Carbon Buildings Standard provides specific guidelines for data centres. While new-build data centres are exempt from its general energy demand limits, they must meet all space-heating demands through heat reuse within the facility.

‘We’ve got to get there somehow, otherwise we’re going to bake the planet,’ says Howe. ‘Necessity is the mother of invention.’

Williams agrees, and is hopeful. ’The scale of next-generation data centre campus developments creates opportunities to do things differently,’ he says. ‘It’s an exciting time to be working in the data centre business.’ l

Class act

The UK’s largest Passivhaus education building has operational energy use of just 45kWh·m-² per year. Andy Pearson looks at how the project team optimised performance and qualified for an outcome-based funding boost

Woodmill High School and St Columba’s RC High School make up the largest Passivhaus education building in the UK.

Sitting within the Dunfermline Learning Campus masterplan, the 23,000m2 (26,666m2 GIFA) structure is designed to accommodate both schools into a single building, to enable 2,700 pupils to benefit from sharing resources, while ensuring each school remains operationally separate, with its own identity.

‘Fife Council saw an opportunity to bring two schools together on one site and to do something a bit different,’ says Jamie Gregory associate director and Passivhaus designer at the project’s architect AHR.

Fife Council mandated that the new £122m building be designed to achieve Passivhaus Classic Certification – a decision made in response to the Scottish Government/Scottish Futures Trust (SFT) outcomes-based funding contribution for new learning buildings, which provides up to 50% of schools’ costs, based on various categories, including energy efficiency.

SFT funding is awarded in the building’s third year of operation. This gives the school two years in which to optimise its operation. To receive

Project Team

Client: Fife Council

Architect and Passivhaus designer: AHR

Building services consultant: Rybka

Passivhaus certification: WARM

Main contractor: BAM

100% of the SFT funding, the school must have in-use energy consumption lower than 84kWh·m-² per year. Should the school fail to achieve this target, the SFT’s funding contribution is reduced progressively to reflect the scale of the operational performance gap, all the way down to 0% (see panel, ‘Performance-based funding’)

Mandating that the schools be built to the Passivhaus standard provided a formal quality assurance process on the design and construction, to give Fife Council peace of mind that the scheme would secure maximum SFT energy funding. ‘With Passivhaus, you have a proven methodology that ensures a building will perform as designed,’ says Gregory.

Woodmill and St Columba’s was procured under the Scotland-wide hub programme, a public-private sector partnership to deliver community facilities. BAM was appointed as the Tier 1 design and build contractor to deliver the schools, with AHR and building services designer Rybka novated to it.

Designing a single energy efficient building to integrate two schools was ‘tricky’, says Gregory. To inform its design, AHR ran engagement sessions and design-validation workshops with staff and department heads.

The subsequent scheme is based on two three-storey wings linked by a central block to house all the shared spaces, including the main entrance foyer, and dining and assembly spaces. ‘The three distinct massing blocks – one for each school and a shared central space connecting them – provides clarity of function, ownership and use,’ Gregory explains.

Targeting Passivhaus meant minimising the building’s form factor. ‘Because it’s so big, this arrangement of the blocks ensures an efficient form factor [the ratio of thermal envelope surface area to treated floor area] of 1.6,’ says Gregory.

The sports building is connected to the main teaching building via a two-storey link. This enables the schools to enter the facility on different levels, each with its own changing facilities. Being a separate block ensures the sports facilities can be used in the evening and at weekends by the local community.

AHR orientated the building so that the main entrance and shared-facilities block face east. The two teaching wings project from this block on an east-west axis so that their façades face north and south. ‘The majority of the glazing is located on these façades, while glazing to the east and west is minimised because solar is more difficult to control on these elevations,’ says Gregory, who adds that natural light and ventilation are fundamental to Passivhaus.

As such, habitable rooms have openable triple-glazed windows. Brise soleil provides solar control on the southern elevation, while vertical fins protect glazing on the east and west elevations against lower-angle sun in the morning and evening. Where necessary, ventilation can be supplemented by opening windows. ‘All of these elements reduce overheating risk in the summer months while allowing the building to benefit from direct solar gains from the lower-angled winter sun when it is most needed,’ explains Gregory.

Windows are relatively tall, at 2.1m high, and are positioned with their heads as high as possible in the room to maximise daylight penetration. Daylight levels in the schools are supplemented by two internal courtyards, which ensure natural light can reach deep into the heart of the building. ‘The windows have a lot of glass, but not a lot of frame, to ensure we can achieve the light levels we need at the back of the classrooms,’ says Gregory.

Natural light levels are supplemented by an LED-based lighting solution with daylight and occupancy controls.

Unusually, the building has three different structural framing systems. ‘We undertook a thorough building-frame analysis at RIBA Stage 1-2, with the whole project team to help us understand the best solution for balancing the

Performance-based funding

Scottish Futures Trust sliding scale of funding for new schools, based on in-use energy use after two years

key criteria of airtightness, embodied carbon and buildability,’ says Gregory. This resulted in a hybrid frame solution being adopted.

‘We wanted to build with cross -laminated timber [CLT], but there was not enough available to build at this scale in the timescale available, so that pushed us down the precast concrete route for the teaching wings,’ explains Gregory. These have a three-storey precast concrete frame with load-bearing precast walls and columns supporting precast hollowcore floor slabs with structural concrete topping. Joints between panels are pressure grouted to maintain the airtight line. Gregory says this ‘maximised delivery of an airtight envelope and simplified detailing’.

The larger spans in the central block resulted in a two-storey braced steel frame being selected to support the precast hollowcore floor slabs. ’We undertook considerable 3D thermal bridge modelling on the column to foundation connections, to ensure the design meets Passivhaus requirements,’ explains Gregory.

The campus is being built on a brownfield site. Unfortunately, ground conditions beneath the sports block meant it was incapable of supporting the weight of a precast concrete frame, so it is supported on a two-storey CLT

Fife Council is not alone in adopting the Passivhaus approach for schools; the Passivhaus Trust estimates that 35 Passivhaus schools are currently under way or in the pipeline in Scotland

frame. The upper floor and roof deck are formed with CLT, supported by load-bearing CLT walls. Gregory says: ‘CLT is approximately five times lighter than concrete and has a much higher weight-to-strength ratio.’

As a panellised system, CLT has similar benefits to using precast concrete for the simplification of detailing. ‘Adopting the outside face of the CLT panel as the airtight line enables the internal timber face to be celebrated and enjoyed,’ explains Gregory. The airtightness was assessed at 0.45 ACH at 50Pa, significantly lower than the Passivhaus target of 0.6 ACH at 50Pa.

As is usual for a Passivhaus scheme, ventilation is provided by MVHR units. There are 32 units, most of which are located on the roof, along with a PV array. The ventilation system is designed to enable both schools to operate independently and to allow spaces to be used by the community at evenings and weekends.

Ducts from the air handling units (AHUs) run into what Gregory calls ‘dog boxes’. These are a series of CLT housings built to form an airtight enclosure to surround each cluster of ducts where they penetrate the roof airtightness layer.

Ducted supplies generally service multiple teaching spaces, although some spaces, such as the home economics and design and technology rooms, are served by dedicated MVHR units.

In the main building, the MVHR units supply tempered fresh air at 18.5°C to the teaching spaces, which have a design temperature of 20°C. For the sports building, which is maintained at a temperature of 18.5°C, air is supplied at 18.5°C. In winter, supply is 18.5°C to the sports block and 20°C to the main building.

‘Even though all AHUs are Passivhauscertified, having so many units and the associated ductwork meant we had reasonably high losses in the PHPP [Passivhaus Planning Package] energy balance from the ventilation systems, which had to be offset with additional fabric insulation,’ explains Gregory. As a consequence, the main building has 250mm-thick

insulation, while the lower-temperature sports hall has 220mm.

Clusters of air source heat pumps (ASHPs) supply heat to the schools. Larger spaces are heated using underfloor heating, while low temperature hot water radiant panels provide heat to teaching spaces. The all-electric scheme also makes use of dedicated ASHPs for domestic hot water to the high-demand areas, such as the main kitchen and the sports-block changing rooms. Localised storage tanks ensure sufficient hot water is always available, while point-of-use heaters provide hot water to wash hand basins in the main building’s toilets.

When it came to finessing the design, the building’s size meant using two PHPP spreadsheets, one for the main block and one for the sports building, which has a lower operating temperature. The PHPP spreadsheets calculated the operational energy use of the entire building as 45kWh·m-² per year before the contribution made by the PVs is taken into account. ‘With the PVs, we’re down to 37 kWh·m-² per year – so, very low energy in use,’ says Gregory.

In fact, the schools’ calculated energy use is so low that it far exceeds the operational target of 60kWh·m-² per year for secondary schools (for a 2025 start on site) set out in the pilot UK Net Zero Carbon Buildings Standard. The schools even meet the standard’s 2040 target of 45kWh·m-² per year for secondary schools.

The schools opened in 2024. A soft landings approach has been adopted to fine-tune it in operation and align it with the Scottish Net Zero Public Sector Buildings Standard. ‘We haven’t had a full year’s use yet,’ says Gregory, ‘but it appears to be performing as expected and well within the Category A funding metric.’ l

The building’s form is energy efficient, even with courtyards set into the structure

The Scottish Net Zero Public Sector Buildings Standard

Woodmill and St Columba’s RC high schools are part of a pathfinder project for the Scottish Government/Scottish Futures Trust‘s (SFT’s) new Net Zero Public Sector Buildings (NZPSB) Standard. This is a voluntary standard, and has been introduced to help public bodies define objectives for new construction and refurbishment projects in pursuit of a credible path to net zero operational energy.

The standard sets an operational energy target of 100kWh·m -² per year for schools, a figure higher than the 83kWh·m -² per year that the school had to achieve to obtain 100% of the SFT’s funding contribution. It is also significantly higher than the 60kWh·m -² per year for secondary schools (for a 2025 start on site) set out in the pilot UK Net Zero Carbon Buildings Standard (UK-NZCBS).

Of course, as operational energy use is reduced, the amount of carbon embodied in materials used to construct the building becomes increasingly significant; there is little point in building a scheme that is low carbon in operation if the carbon used in its construction will never be recouped. The standard says new-build projects should have an embodied carbon target of no more than 600kg CO2e 2m -².

Fife Council’s brief for this school was set before the publication of the UKNZCBS standard, which has a target of 650kg CO2e 2m -². The project exceeded this, with an embodied carbon figure of 626kg CO2e 2m -². Gregory says the 600kg CO2e 2m -² target set by the NZPSB is achievable for schools. ‘We’re currently working on another school for the same council and that one is mandated for the RIBA 2030 figure of 540kg CO2e 2m -², which is significantly lower than the target set in the NZPSB,’ he adds.

Gregory says the Passivhaus standard and the NZPSB are complementary, because they are ‘both aligned to the same goals’ – and because Passivhaus is focused on operational energy, whereas the NZPSB also includes embodied carbon targets.

Pathfinder monitoring and reporting for the NZPSB has been incorporated into the project’s soft landings process, to ensure that the schools align with the standard.

Race to net zero: why schools must act now

UK schools produce 2% of UK carbon emissions, yet retrofits lag behind net zero targets. Professor Dejan Mumovic FCIBSE explains to Alex Smith how large-scale models can accelerate decarbonisation while minimising overheating risk

The decarbonisation of UK schools will be critical in achieving net zero carbon in public sector buildings by 2020. They contribute 24% of carbon emissions in the sector and are responsible for 2% of all UK emissions.

For new schools, the Department for Education (DfE) requires that 500 schools delivered under the School Building Programme by 2030 be net zero carbon in operation (bit.ly/CJSOS2J). For existing schools, grants – such as the Public Sector Decarbonisation Scheme – are available for low carbon retrofits, but there is not yet a plan for wide-scale decarbonisation that would enable the school estate to meet 2050 net zero goals (bit.ly/CJSusDofE23).

Currently, only 30-50 primary and secondary schools a year are being retrofitted, but modelling by University College London (UCL) predicts that 800-1,000 schools per year will have to be retrofitted to meet 2050 targets.

The UK Parliament’s Environmental Audit Committee said the current pace of work to meet net zero lacks urgency (bit.ly/CJAOCsch23) and have called on the DfE to publish realistic and fully costed details of its sustainability plan. There is currently a £2bn annual shortfall in funding for repairing and maintaining the existing school estate, so investment

l Econ 73 (1995) l Estimated values l DfE (1999-2002) l DECs (2010-present)

(Source of annual energy intensity data)

in school decarbonisation will have to be carefully planned and justified.

To enable government to prioritise spending on decarbonisation, UCL has developed a dynamic thermal model that maps more than 67,000 buildings across 23,000 primary and secondary schools. The modelling platform is designed to simulate the performance of every building under a range of retrofit scenarios and, with the inclusion of CIBSE Weather Files, it can also assess the future risk of overheating.

The platform uses a range of data sources, including geospatial data, display energy certificates (DECs), and the ‘conditioning data collection’, a five-yearly survey of school buildings’ condition. There is also a plan to include

embodied carbon data in the model.

The good news is that school performance has been improving (Figure 1), with a decrease in median energy use over the past 20 years of 35% for fossil fuel use. However, more technology in classrooms has seen electricity use rise by 39%.

As scientific adviser for climate change at the DfE, UCL’s Professor Dejan Mumovic FCIBSE is using the university’s model to underpin multiple research projects that the government is employing to develop its decarbonisation strategy. He says it is important that the net zero strategy for existing schools considers indoor environmental quality and children’s cognitive performance.

‘We have to ensure that the 10 million schoolchildren are in a safe indoor environment. We shouldn’t look at retrofits from a purely carbon emission perspective,’ says Mumovic, who will publish a paper on the topic this year. He adds that a holistic approach to retrofit will reap benefits for society, as school improvements will lead to healthier children.

This study on cognitive performance reveals that, because of climate change and overheating in classrooms, the

Figure 1: Primary school energy intensity data 1995 to 2010

Figure 2: Cooling loads of air conditioned classrooms in 2020s, 2050s and 2080s

Primary schools

percentage of cognitive performance loss of all schools in the south of England is modelled to increase from 51% to 72% in 2050, and 81% in 2080.

Schools as heat havens

The UCL model reveals that the risk of overheating is much more prevalent in southern regions of England, and to maintain comfortable temperatures in classrooms, the cooling load in the south will increase significantly

‘We are going to have a huge shift from heating to cooling load,’ explains Mumovic. ‘The cooling load in southern England will be 67 kWh m-2 [to maintain temperatures at 21°C, assuming ventilation rate is 8 l·s-1], and if the ventilation rate is at the recommended 15 l·s-1, this will increase the load to 100kWh m-2, which is the heating load for fossil fuel consumption in inefficient schools.’ (See Figure 2).

Future overheating incidents could be mitigated by when the building stock is used, says Mumovic, who adds: ‘They would be significantly reduced if you ended the summer term on 1 June.’

He also believes schools that are resilient to overheating could be used by the wider community. ‘They could act as a safe haven during heatwaves - they should be redefined as centres for communities. They are empty after 3pm, and then for half of the summer,’ he says.

Cooling delivered via heat pumps has the potential to be decarbonised via the Grid, but Mumovic warns against focusing solely on energy supply.

‘Replacing gas boilers with ASHP [air source heat pumps] is a bridging step, because we still need to focus on retrofitting to reduce energy demand in the long run,’ he says.

Decarbonisation strategy

The UCL model has the potential to offer a decarbonisation strategy for all schools, adds Mumovic: ‘Output from the model will allow you to compare different levels of retrofit – for example, minimal, medium and full decarbonisation. This would empower school leaders with the knowledge of their building’s performance and how it compares with peers.’

This level of information is worth £5-7,000 in consultant fees per school, says Mumovic, who suggests that schools in the lower 10th percentile of performance should be tackled first, with funding help from the government.

The CIBSE Energy Benchmarking Tool (bit.ly/CJEnBT) is a good place to start, he says, because it’s an easy way of comparing a school’s energy use according to DEC data. ‘It’s not enough to hit the target; it’s about maintaining it, so a monitoring policy must be established.’

A mechanism that incentivises stakeholders to commission schools properly is also needed, so performance matches design intent. There are examples of this in Scotland, where schools funded by the Scottish Futures Trust are awarded grants according to how well they perform after

‘Do nothing’ scenario

All new builds are zero carbon but current stock is unchanged, so lots of gas heating remains Impact:

Total emissions fall, reflecting project improvement of Grid, but 2035 and 2050 targets are both missed. Rooftop PV alone cannot meet targets

two years of operation (see page 30). CIBSE has developed technical memorandums, TM61 and TM63, that help identify the causes of the energy performance gap, but they are not always used, says Mumovic, as project teams are afraid of what they might find.

What’s next?

Mumovic’s team has a project in the pipeline that looks at the long-term cost of poor environmental conditions1 and, later this year, CIBSE’s best practice TM57 Integrated school design, is due to be updated. With the UCL modelling platform and ongoing research, the foundation is being laid for a more sustainable, resilient future.

However, success will depend on coordinated action, adequate investment, and a commitment to maintaining performance beyond initial retrofits. Figure 3 shows such a scenario, where a major retrofit campaign results in net zero carbon schools by 2050. l

References: 1 P Hardelid and D Mumovic, ‘ Realising the health co-benefits of transitioning to net zero carbon of UK building stock ’, funded by UK Research and Innovation

Further reading

J Dong, Y Schwartz, I Korolija, D Mumovic. ‘Unintended consequences of English school stock energy-efficient retrofit on cognitive performance of children under climate change’, Building and Environment, Feb 2024, bit.ly/CJRetCog24

D Mumovic, D Chen and Z Zhao, ‘The combined impacts of indoor temperature and total volatile organic compounds on cognitive performance of university students: A controlled exposure study’, Science of the Total Environment, Feb 2025, bit.ly/CJTempVOC

Major school retrofits scenario

200 schools rebuilt as zero carbon, plus 800 schools are converted to ASHP with additional efficiency improvements. All new-build schools are zero carbon

Impact:

Considerable reduction in emissions by 2035 and 2050 (~85% and ~99% compared with 1990). 2035 target achieved and 2050 target almost achieved. With additional rooftop PV, the 2050 target could be met

Figure 3: Impact of major retrofit programme on annual emissions

In demand

Demand-response strategies were the hot topic at this year’s DESNZ/IEA Heat Pump Research Seminar. Molly Tooher-Rudd and Alex Smith capture the highlights, including talks on nondomestic heat pump retrofits and full-scale testing of net zero homes

The Future Homes Standard, demand-response strategies and non-domestic retrofits were among the key areas covered at the annual DESNZ/ IEA Heat Pump Research Seminar in London last month.

A significant part of the day was dedicated to talks on demand-side flexibility, and in particular how heat pump usage can be adjusted to reduce stress on the electricity grid and cut energy bills for consumers.

Ryan Huxtable, future capability programme lead at National Grid, shared details of the three-year Equinox trial, which rewarded consumers for temporarily altering their heat pumps to relieve stress on the electricity network.

Consumers were given notice periods to turn down their heating for two hours at peak demand and three notice periods were tested. The trial found a statistically significant demand response from the 1,048 participating households. For example, across all events from 5-7pm there was a 48% reduction in the average home’s peak load, equivalent to a 0.6kW peak reduction per event.

Huxtable said that average demand response for each heat pump was scaled up across several scenarios in an area of constrained electricity capacity. It was found that heat pumps’ demand response could mitigate 20% of the area’s projected peak demand by 2028.

The Latent project, run by the University of Southampton and Good Energy, conducted a field trial to test third-party control of electric heating systems, to assess behaviour, attitudes and dwelling thermal response.

‘Heating can be contentious. We wanted to understand if we could turn off a heat pump without people being aware that it was happening,’ said Professor Patrick James, of the University of Southampton.

Before the project began, a survey

of 5,000 Igloo customers found that 55% opposed energy companies remotely controlling their heating. The trial showed that, when heating was turned off, temperatures dropped, but most participants did not notice. Even after five deferrals in one week, 62% of participants believed no events had occurred.

Shifting loads

The Centre for Net Zero’s Daniel Lopez Garcia and Nesta’s Oli Berry discussed findings from the HeatFlex project, a load-shifting trial that tested automated control of heat pumps while maintaining thermal comfort.

The collaboration between Nesta and the Centre for Net Zero aimed to shift household demand away from periods of high Grid demand by turning heat pumps down after a period of pre-heating. The intervention was automated, so no action was needed by occupants, and the trial maintained temperatures specified by households.

It was found that average temperatures changed by less than 1°C and 81% of occupants were satisfied or very satisfied with internal temperatures. There was also a 0.123kWh reduction in

Special features

Demandresponse strategies can make big inroads into energy use

Heating Water heaters

Data centres

energy consumption during the flexibility window. Garcia and Berry said the potential for flexible windows was less for homes already shifting demand through solar panels and batteries.

Andy Hackett, from the Centre for Net Zero, reported on findings from a study that analysed the impact of heat pumps and time-of-use (ToU) tariffs on energy demand, using data from Octopus Energy’s Cosy tariff. The study demonstrates the effectiveness of ToU pricing in optimising demand, cutting evening peak consumption by half and reducing energy bills by 18%.

Additionally, consumer behaviour adjustments because of pricing incentives play a crucial role in reducing peak strain on the Grid, said Hackett. The research highlights the significant

effects of heat pumps on electricity consumption, showing a notable 40% reduction in overall energy use and a 36% decrease in carbon emissionsrising to 68% over the system’s lifetime.

Measuring the heating system performance of future homes was the subject of the talk by Grant Henshaw, Energy House research fellow at the University of Salford. He discussed research at the university’s Energy House 2.0 lab, which allows for full-scale testing of homes in a climate chamber.

Two real homes are being tested at the lab: one built by Saint Gobain and Barrett, and one by Bellway Homes bit.ly/CJSalFH25. The testing is being done ahead of the Future Homes Standard, which is due this year and is expected to stipulate that new homes do not have gas boilers, are zero carbon ready, and generate 75% fewer carbon emissions compared with 2013.

As well as looking at airtightness, air leakage and heat loss, seven heating systems were tested at -5°C and 5°C external temperatures using combinations of three air source heat pumps, radiators, perimeter heating and infrared heating. Key lessons include the need for improved heat emitter design, more commitment to the installation and commissioning process, and more care around product substitution and verification of installed equipment.

Heat pump monitoring

Trystan Lea, from OpenEnergyMonitor, presented insights from HeatPumpMonitor.org, an open-source initiative sharing real-world heat pump data to support best practice. The project tracks 293 systems, with 94 having full-year data.

A key takeaway was the high level of performance of heat pumps in the dataset, contrasting with other trials such as the Electrification of Heat (EoH) trial, which found a performance gap making heat pumps 20% more expensive than gas boilers. The data shows strong correlation between lower average running temperatures and better performance.

‘Designing for 40°C saves running costs, while 45°C achieves cost parity,’ said Lea, who added that accurate heat-loss calculations are essential.

One issue highlighted was poor

weather compensation settings, particularly in EoH data. ‘Many systems, even with £3k radiator upgrades, were set to 55-60°C – way higher than needed,’ said Lea. ‘Dropping the curve could significantly improve efficiency.’

He cautioned that his data was not representative of the market. ‘We have a sample of the best installers and engaged customers. It shows how crucial commissioning and handover is.’

Lewis Bowick, a consultant at Energy Systems Catapult, shared details of the Homes for Net Zero project, which is trialling reversible air-to-air heat pumps (RAAHP) in 70 homes. It is using a mix of single-split and multi-split units, and seeks to develop an understanding of costs, design, energy consumption profiles, use of cooling, and impact on air quality.

Bowick noted that RAAHP was widely used in non-domestic buildings, but rarely in UK homes, where they could be used for cooling, dehumidification and air filtration, as well as heating. He said they were particularly suitable for homes without central heating systems.

But there were a number of barriers to their adoption in homes, he added, including not being eligible for the Boiler Upgrade Scheme and not being supported by the Microgeneration Certification Scheme. Bowick said Catapult was also comparing RAAHP with alternative heating systems using its Home Energy Dynamics model.

Non-domestic heat pumps

The focus on domestic heat pumps reflects the size of the market compared with the non-domestic sector.

During his presentation on Retrofitting heat pumps in large nondomestic buildings (Annex 60), Dr Peter Mallaburn, principal research fellow at UCL, said his research had concluded there were only 2,000 non-domestic heat pump retrofits per year in the UK.

A lack of early-stage technical guidance had been identified as a significant barrier to action, made harder by the complexity of nondomestic buildings, with their variety of form, size and function.

The UK-led IEA project aims to develop a tool that would give nondomestic clients a better understanding of the heat pump when retrofitting. The logic tool, due to be published this year, suggests 3-5 system types based on input about building type, location, orientation, and so on. Each suggestion is linked to case studies of existing retrofits of similar buildings.

In the Q&A, Twenty One Engineering’s Phil Draper reminded delegates that building performance should be checked and optimised before making any decisions about system replacement. l

To contribute to IEA’s heat pump programme, email roger.hitchin@ blueyonder.co.uk

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Tapping into efficiency

At the Passivhaus-accredited Riverside Primary School in Perth, Scotland, the selection of point-of-use water heaters played a key role in driving down energy use. Baxi’s Andy Green explains how the optimal solution was realised

Riverside Primary School in Perth, Scotland’s first Passivhaus-accredited primary school, has released its first-year report on actual operational energy performance – and the results are outstanding.

With an energy assessment of just 43kWh·m-² per year, the school, designed by Architype, is significantly outperforming the classic Passivhaus target of 60kWh·m-² per year.

Passivhaus standards and certification requirements prioritise energy efficiency and minimal heat loss. But while the focus is rightly placed on the primary building geometry and fabric performance, careful consideration must also be given to engineering solutions, plant selection and building-user operations.

‘When designing the system, the hot-water strategy was one of the main challenges, as we needed to avoid large-scale energy use and heat losses,’ says David Coulter, associate engineer and certified Passivhaus designer at BakerHicks (Motherwell), which provided mechanical and electrical design services on the project.

Traditional buildings are often designed with a centralised hot-water system, which can result in significant heat losses during distribution and long wait times for water. Both factors contribute to energy waste and increase a building’s overall energy demand. The challenge of a low-energy design solution is overcoming the key sources of energy waste associated with a centralised water-heating system. These include heat loss in long pipe runs, standing energy losses and lag time in hot-water delivery.

‘We need a solution that heats water only where and when it is needed,’ says Coulter. ‘Point-of-use [POU] water heating is an effective approach. By providing immediate hot water at the source, it ensures availability when required while significantly reducing

Energy use of Riverside Primary School

43kWh·m-² per year

distribution losses and reheat times.’

Selecting a standard POU water heater with 10-15 litres of storage volume to serve a single appliance is common practice. While the capacity typically provides sufficient hot water, and aligns with the principles of POU water heating, it can often be oversized compared with the actual hot-water demand of the appliance. Oversizing can lead to unnecessary energy consumption, reducing the overall efficiency of the system.

Working with Baxi’s sales and specification team Coulter identified the multiple POU water heaters required to serve wash hand basins (WHBs) located near classrooms at the school.

‘As these basins are primarily used for handwashing, it was possible to reduce the storage volume and associated electrical energy use [electric kW duty],’ says Coulter.

‘The general guidance for handwashing is 20 seconds per person. By comparing this timeframe with the available storage volume in the POU water heater and the maximum flowrate

of the wash hand basin, we identified an opportunity to further optimise the design, enhancing efficiency while maintaining functionality.’

A significant reduction is possible when downsizing from a standard 15-litre (3kW@240V) storage unit to a more efficient 7-litre (2.2kW@240V) storage unit. Even greater savings can be achieved by considering the temperature range against flowrates, as the water is regulated to a lower flow temperature via a mixing valve.

Making the calculation

The energy use of the 7-litre option was calculated as follows [where the flowrate l/min is WHB flowrate l/min x (mix tempcold temp)/(hot temp-cold temp].

For one specific WHB in this project (used in general teaching spaces), the calculated flowrate is 2.44 l/min, allowing for up to eight handwashes from the 7-litre storage capacity. This calculation does not account for the unit’s recovery rate, with 2.2kW equating to a 10-12 minute recovery time, which further informed the design decision.

The overall reduction in total volume and electrical energy resulted in significant energy savings compared to the standard selection process featuring

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a 15-litre vessel. When scaled across multiple units, this significantly reduced the building’s overall energy demand.

Taking into account flow rates, recovery times and usage, we were able to provide a diversified approach based on operational usage rather than a worst-case scenario of the sink always being on at 100% duty. The overall water storage for the project was reduced by 25%, with hot water W/K heat loss decreased by 30%.

A centralised approach

The concept design for the nursery followed the POU approach that had been applied successfully in the teaching spaces. However, during energy calculations, BakerHicks noted that the electrical energy use associated with the nursery was significantly higher because of the number of POU water heaters. This was having a negative impact on the building’s overall energy efficiency.

‘We investigated various solutions, including multipoint POU water heaters and a centralised storage electrical calorifier,’ says Coulter. ‘When we analysed the area in isolation, and assessed the impact of electrical demand in relation to standing energy losses and the delivery of hot water, we found that transitioning to a centralised approach could offer huge benefits.’

The electrical demand of the proposed centralised calorifier was 6kW, but, in practice, only 3kW was used, with 3kW provided for resilience. In comparison, multiple POU water heaters had a maximum demand of 15kW. The result was a significant reduction in the building’s overall energy demand by treating these isolated areas with a centralised system rather than a POU.

‘As the area contained appliances within a short distance, the centralised approach provided a saving against standing losses, reheat times and other factors,’ explained Coulter.

‘While low-energy principles were applied in selecting POUs, engineers should still explore alternative solutions [such as the centralised approach], as these may prove more beneficial when considering factors such as location, usage patterns and overall system energy demand. l

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Turning waste into warmth

Aecom has helped develop a vast energy centre in West London that will pipe waste heat from data centres into 10,000 new homes and existing businesses via a heat network. The company’s Asad Kwaja looks at the ‘architecture’ behind the design

Two major shifts are under way in the energy sector: the electrification of heat and the rapid growth of artificial intelligence (AI) and cloud computing. The transition to electric heating plays a key role in reducing reliance on fossil fuels, while advances in AI and cloud technology are reshaping how we work, learn and connect.

The vast amount of computer power required by AI has led to rapid growth in the data-centre sector in the UK, while electrification is driving a resurgence in heat networks, which the government recognises as a scalable and efficient solution for decarbonising heat.

The government’s upcoming heat network zoning policy aims to support growth by identifying areas where networks are likely to be the lowest-cost solution to decarbonising heat.

The opportunity

The synergies between data centres and heat networks present a significant opportunity. Every electron of electricity consumed by servers within data centres ultimately converts to heat, most of which is currently wasted and released into the atmosphere.

When you consider that components within a data centre can get up to 85°C, these facilities can be thought of as

giant electric boilers. Capturing this wasted heat and integrating it into a heat network can transform this byproduct into a valuable resource.

With recovery temperatures ranging from 20°C (air-cooled) to as high as 60°C (liquid-cooled), data centreconnected heat networks can have significantly higher efficiencies than typical low carbon heat solutions, such as air source heat pumps.

Consistent access to low-grade heat is an essential requirement for low carbon networks, which use heat pumps and the refrigeration cycle to ‘move’ heat into more usable forms efficiently.

Data centres are increasingly being recognised as a key contributor to heat network development, with growing momentum in policy and industry. The UK government has recently taken steps to support this opportunity and is funding a heat network in West London that will use a significant amount of waste heat from nearby data centres.

The money from the Green Heat Network Fund (GHNF) is for the Old Oak and Park Royal Development Corporation (OPDC) to develop the Old Oak Park Royal Energy Network (Open)1. Aecom has led the development of Open from its conception through to the appointment of a delivery and funding partner, which

are soon to be on board to conclude the commercialisation and construction of the network.

OPDC was established by the Mayor of London to secure the regeneration of the Old Oak Opportunity Area, which spans land in three London boroughs: Ealing, Brent, and Hammersmith & Fulham. The regeneration has been catalysed by the new rail interchange at Old Oak, which will link HS2, Crossrail and the London Underground. Over the next 20 years, 25,500 homes will be built in the area, which also has numerous existing businesses and warehouses, and one of the highest densities of new construction in Europe.

Given its strong transport connectivity, proximity to the City of London and high-fibre connectivity, the area has become a hot spot for data centres, with more in the pipeline. In 2022, West London was subject to significant press coverage because power constraints – brought on partly by the high number of data centres – were said to be blocking new housing development.

The proximity of planned housing to new and existing data centres has created the conditions for the development of Open, which is expected to deliver up to 95GWh of heat per year over five phases between 2028

The project team visited the Odense Heat Network to see a heat network using waste heat from a data centre. From left: Liam Caulfield, senior project manager, and Davena Wilson, director of projects, at OPDC; Asad Kwaja, associate director, and Anthony Riddle, technical director, at Aecom and 2040. It is the first new-build heat network in the UK to take waste heat from data centres on a large scale, and will recover 17MW of waste heat from two new sites, with the potential to expand and connect several more.

Project development

Aecom started work on Open in 2022 with initial heat mapping masterplanning, which led to the award of GHNF funding in 2023. The consulting firm has since been supporting procurement of the development.

Open is one of the first major pieces of infrastructure being brought forward through OPDC. This has its own challenges in terms of advanced planning and anticipating the needs of a growing urban development.

Future requirements influenced the ‘architecture’ for the network. Two options were assessed in terms of configurations: a 4th-generation and 5th-generation heat network (Figure 1).

The advantages of 5th-generation heat networks include energy sharing, distributing plant, and providing both heating and cooling more locally – whereas 4th-generation networks

centralise plant and distribute via a lowtemperature network.

A key factor influencing the configuration was the limited space available because of the land’s high development value. Spreading plant across multiple energy centres –distributed energy centres (DECs) – in a 5th-generation heat network would also have added to the risk profile, and put additional requirements on new and existing developers to accommodate heat pumps and their associated power requirements.

When a site local to the new data centres came up for sale, it was decided that this would be the perfect location for a centralised energy centre (EC), and we decided to pursue a 4th-generation heat network to connect buildings in Open. The EC concept design houses centralised 23MW water-to-water heat pumps, peaking plant, and up to 350m3 of thermal storage (to improve resilience and enable partial load shifting).

An ambient loop connects the data centres and the EC. Because of the narrow delta-T between flow and return temperatures of the ambient loop, large-diameter pipes are required

to move the 17MW of waste heat. The ground conditions are challenging in this area; with a high density of underground utilities, space is expected to be limited. At these ambient temperatures, heat loss to the surrounding ground is low, so conventional uninsulated plastic pipes can be used, which reduces capital expenditure and embodied carbon. The 4th-generation low temperature hot water (LTHW) network will use pre-insulated pipes, with a circulating flow of 65°C.

Open will potentially supply a major hospital, which requires 80°C during peak demands. A localised water source heat pump has been designed at the hospital energy centre, which will use the 65°C LTHW as the source temperature and increase it to 85°C. This will save the hospital the disruption and cost of extensive building-level upgrades that would be necessary to operate using a 65°C LTHW.

Prior to construction, OPDC is using the existing EC site as a circular economy hub for the community, where local organisations will repurpose local waste materials into new products, such as furniture, tableware and panelling, to be sold back to the community.

In its first phase, Open is planned to recover up to 17MW from two new-build data centres, with the heat captured at around 24°C. The heat-recovery circuit is connected in series on the return of the chilled water loop, acting as a pre-cooler to the data centres’ own plant. The relatively low proportion of heat being supplied compared with the facilities’ total cooling demand means that a near-constant supply of heat can be provided year round.

Technically, the equipment required to facilitate the offtake is not complex –

Schematic of 4th- and 5th-generation heat networks

Data centres Using waste heat

a pair of plate heat exchangers, valves and pumps – and working with a new facility means the requirements can be built in from the outset.

However, a major area of work has been developing the commercial understanding around which party will own, operate and maintain what. Data centres have inherent security and uptime requirements, so making operators comfortable with the expectations of the heat network, in terms of maintenance access and control signals, was a key part of developing the project.

Development of the heat offtake solution has been a collaborative effort between Aecom’s sustainability and data centre teams.

The project has led to several more conversations with data centre developers to ascertain opportunities for heat reuse and share best practice. This has included a team visit to Denmark and the Odense Heat Network, which is served in part by 45MW of heat from a Meta Data Centre. The growth of data centres is a

Schematic of Open heat network

consequence of increasing global demand for digital services, cloud computing and AI. As these facilities expand, so too does the opportunity to harness their waste heat for a more sustainable built environment.

Integration of waste heat recovery must become a standard consideration. With supportive policies, investment and collaboration, such projects can play a pivotal role in achieving the UK’s net zero ambitions. l

Open is the subject of a presentation by Aecom principal consultant Sam Pepper at the CIBSE IBPSA-England Technical Symposium, UCL London, on 24-25 April: cibse.org/symposium

References:

1 ‘Thousands of homes to be kept warm by waste heat from computer data centres in UK first’, Department for Energy Security and Net Zero, bit.ly/CJWH23

How the Open network could be expanded in the future

The Open network has the opportunity to connect to several existing data centres as it expands and further heat is required for new and existing buildings. However, retrofitting heat offtake can come with challenges.

These modifications are typically bespoke designs, and can be complex

and costly to design and develop. Additionally, older facilities may have a number of different cooling systems across the site that have been installed over time and work at different temperatures; this would make the waste-heat offtake solution more complex.

Detailed planning, phased installations and downtime management are necessary, which, again, can add to the cost and complexity.

Specific feasibility assessments will be required – but the opportunity is significant.

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COMBINE Hamworthy’s Tyneham 290HT heat pump

Using R290 natural refrigerant, the Tyneham 290HT achieves flow temperatures up to 75° C, improved efficiencies and low carbon heating.

Efficient heat pump application for heating and domestic hot water

This module considers how to ensure heat pump applications efficiently meet demands to deliver heating and domestic hot water at satisfactory temperatures

This CPD will explore how readily available, tried and trusted heat pump applications can efficiently deliver hot water at temperatures that can satisfy the demands of ‘traditional’ heating and hot water systems. Applications of many refrigerants are evolving, both natural and synthetic –this article will focus on R32 and R290 (propane) as examples of low-pressure refrigerants that are being widely used in commercially available ’subcritical’ vapour compression heat pumps.

Many believe residential and small commercial heat pumps struggle to deliver temperatures efficiently above 50-55°C. However, as shown in Table 1, there are well-established refrigerants that can meet the needs of medium- and high-temperature heat pumps. These are now widely used in applications requiring higher heating capacities or temperatures, such as space heating and domestic hot water (DHW) which were previously challenging with single-refrigerant systems.

The simplified pressure enthalpy diagram in Figure 1 indicates a basic vapour compression refrigeration cycle, with superheat at the inlet to the compressor and subcooling at the intake to the expansion device. In this basic system, the condensing process, a latent process 3⇒4, will provide much of the heat (to meet the heating load) at the condensing temperature. There will also be heat available from the higher-temperature sensible cooling process 2⇒3 and the sub-condensing

temperature sensible subcooling process 4⇒5. The evaporating process 6⇒7 provides the bulk of the ‘free’ heating, and the process 1⇒2 represents the ‘paid’ power input during compression.

The critical temperature, as shown in Figure 1, is the highest temperature at which a refrigerant can exist as a liquid, regardless of pressure. If the heat pump’s desired condensing temperature is close to the refrigerant’s critical temperature, the latent process, 3⇒4, is necessarily limited. This reduces the available latent heat transfer, making the heat pump less effective and lowering the coefficient of performance (COP). Also, as a refrigerant operates nearer its critical temperature, it requires an increasingly high compression ratio (CR) to reach the required pressure, resulting in high compressor discharge temperatures that can damage the compressor (over time) or require extra cooling (as discussed later in the article), which can lower the overall system efficiency. (CR = absolute discharge pressure/absolute suction pressure.)

The hydrofluorocarbon (HFC) refrigerant R32, a single-component refrigerant, has a relatively low critical temperature of 78.1°C, which might appear to be a limitation for higher-temperature heat pump applications. However, it remains a strong candidate because of several key factors, and is suitable for heat pumps targeting output temperatures in the range of 55°C to 60°C.

R32 675 78.1°C 8-30bar <60°C Widely used in new systems. Mildly flammable. Gas ~2x cost R2901

R-454B 466 83.6°C 8-27bar ~60°C Replacement for R-410A. Mildly flammable. Gas ~1.5x cost R2901

R290 (propane) 3 96.7°C 5-25bar ~75°C Excellent efficiency, natural refrigerant. Highly flammable.

R-1234yf <1 94.7°C 6-20bar ~80°C Mildly flammable. R134a replacement.2 Gas ~4x cost R2901

CO₂ (R-744) 1 31.1°C 50-120bar ~90°C Works in transcritical mode, very high pressures required. Gas ~0.3x cost R2901

*Important note: These are ballpark figures sourced from various references – actual values in a specific system will depend on design and operating factors (particularly evaporating temperature).

Table 1: Basic properties of common refrigerants employed in heat pumps

Continuing professional development (CPD) is the regular maintenance, improvement and broadening of your knowledge and skills to maintain professional competence. It is a requirement of CIBSE and other professional bodies. This Journal CPD programme can be used to meet your CPD requirements. Study the module and answer the questions on the final page. Each successfully completed module is equivalent to 1.5 hours of CPD. Modules are also available at cibsejournal.com/cpd

R32 possesses a high latent heat of vaporisation, allowing it to transfer more heat per unit of refrigerant mass flow, which contributes to a higher COP. Additionally, it has a superior heat transfer coefficient compared with many alternatives, ensuring better heat exchange performance even at elevated temperatures, thereby enhancing system efficiency.

A further advantage of R32 is its high volumetric cooling capacity (VCC), which determines the amount of cooling effect a refrigerant provides per unit volume of vapour at the compressor inlet. A higher VCC allows for more compact system designs, smaller compressors, and lower refrigerant mass flow, leading to reduced energy consumption. R32 exhibits high discharge temperatures, which require careful compressor management. This may require supplementary cooling mechanisms or system enhancements to prevent overheating, which will be considered below. However, its thermodynamic properties make it well suited for achieving the necessary condensing temperatures for DHW and space heating applications. Applications of R32 heat pumps will often be paired with a matched DHW storage calorifier that includes an auxiliary electrical resistance heater to allow stored water to be consistently stored above 60°C. Together with proper subcooling and system design, as discussed later in the article, R32 can function very efficiently.

A key benefit of R32, compared with older synthetic refrigerants, is its relatively low global warming potential (GWP) of 675. With many manufacturers transitioning to R32 because of its efficiency and lower environmental impact, the industry is seeing improved component availability, optimised system performance, and ongoing research and development. However, there are some challenges associated with R32, including its mild flammability – classified as A2L – which necessitates appropriate system design and safety measures.

R290 (propane) is a hydrocarbon refrigerant well suited for higher-temperature heat pumps, such as the one in Figure 2. With a higher critical temperature of 96.7°C, R290 operates more efficiently at high condensing temperatures, making it particularly well suited for applications requiring output temperatures above 75°C. At higher temperatures, as the condenser temperature gets closer to the critical temperature, subcooling becomes less effective, leading to flash gas formation and lower efficiency, so appropriate subcooling methods are normally used. However, because of its higher critical temperature, R290 can more readily maintain subcooling, while R32 will struggle as it nears the critical point.

R290 has moderate volumetric cooling

capacity and, while lower than that of R32, ensures efficient operation with lower pressure ratios, contributing to improved compressor longevity. Also, R290 demonstrates excellent heat transfer properties because of its high thermal conductivity and superior heat transfer coefficient, enhancing evaporator and condenser efficiency.

Manufacturers often recommend a water side flow-return temperature difference of around 5K to 10K for R32 heat pumps, whereas R290 heat pumps range from 10K to 30K (and higher). The higher value for R290 is especially useful in district heating where higher temperatures and efficient heat transfer are crucial. A high temperature difference provides opportunities for reducing water flowrates and pumping requirements for the load side. However, 10K may be suitable for many legacy heating applications.

One of the most compelling attributes of R290 is its extremely low GWP of approximately 3. However, despite its advantages, R290 does present challenges. It is classified as A3, meaning it is highly flammable, so stringent safety regulations and leak-prevention measures must be in place. Therefore, R290 is typically used in outdoor-located monobloc heat pumps, whereas R32 can be used in both monobloc and split systems.

Despite its moderate critical temperature, R32 remains a good choice for highertemperature heat pumps because of its high efficiency, superior heat transfer properties, and widespread industry adoption. However, for applications requiring higher temperatures or the ability to directly produce DHW temperatures above 60°C, refrigerants such as R290 or CO₂ (in a transcritical system –see module 47) may be more suitable, because of their higher critical temperatures and overall performance advantages. R290

systems have a higher COP than R32 at lower outdoor temperatures, while R32 heat pumps typically perform better at higher outdoor temperatures.

Optimising vapour compression refrigeration systems in heat pumps involves several key technical attributes that enhance efficiency, performance and longevity. Variable-speed compressors significantly improve efficiency by adjusting speed to match heating or cooling demand. This minimises frequent on/off cycling, which can be detrimental to both efficiency and component lifespan, while also delivering more stable temperatures that reduce energy consumption and improve occupant comfort. Operating at lower speeds, these compressors can also reduce noise levels compared with fixed-speed alternatives.

Multistage compression enhances the efficiency of higher-temperature heat pumps by dividing the compression process into two or more stages, rather than a single step. This reduces the pressure rise across each stage, lowering overall compression work and energy consumption. The improved volumetric efficiency allows the compressor to handle a larger refrigerant volume per cycle, while intercooling between stages cools the refrigerant – reducing its temperature and volume. In smaller residential and commercial heat pumps, this is often achieved with an air-cooled intercooler using ambient air. Multistage systems can maintain efficiency over a wider range of ambient temperatures, improving cold-weather performance. However, they are more complex than single-stage systems, requiring additional components such as intercoolers, extra piping and more advanced controls, resulting in higher initial costs and potential maintenance requirements.

Microchannel heat exchangers (MCHEs) offer advantages in both outdoor and indoor

Figure 1: Sketch of generic pressure enthalpy (p-h) diagram for a vapour compression refrigeration process – note that the pressure is to a logarithmic scale

applications for air, ground and water source heat pumps. By using a network of very small channels – typically less than 1mm in diameter – they promote turbulent flow, enhancing heat transfer efficiency compared with traditional heat exchangers. Their high surface-area-to-volume ratio enables them to be smaller and lighter while maintaining the same heat transfer capacity. Despite their compact size, well-designed MCHEs can exhibit lower pressure drops, because of optimised flow distribution. They also help the heat pump achieve higher output temperatures and reduce refrigerant charge, lowering environmental impact. However, their small channel dimensions make cleaning and maintenance challenging, as fouling can significantly reduce heat transfer performance.

Suction line heat exchangers (SLHXs) play a crucial role in improving efficiency, particularly in higher-temperature heat pumps using refrigerants such as R290 and R32. Their primary function is to subcool the liquid refrigerant leaving the condenser, reducing the risk of two-phase flow entering the expansion device and improving its performance. By minimising the formation of flash gas, SLHXs allow the evaporator to operate more efficiently, enhancing heat transfer and increasing cooling capacity, while reducing compressor energy demand. Additionally, by simultaneously superheating the suction gas, SLHXs help prevent liquid refrigerant from reaching the compressor, protecting it from slugging. However, this process increases compressor discharge temperatures, which may require additional cooling strategies. Similar techniques can also be used to provide intercooling in multistage compression systems.

High compressor discharge temperatures can degrade lubricating oils, increase thermal stress on components, and reduce overall efficiency. Liquid injection cooling addresses

Heat pumps CPD programme

this issue, particularly in applications with large temperature lifts between the evaporating and condensing temperatures. In direct liquid injection, a small amount of liquid refrigerant is drawn from the liquid line before the expansion device, and injected into the compressor suction or at an intermediate compression stage via a thermostatic or electronic expansion valve. This cools the refrigerant, lowering discharge temperatures and reducing compressor strain.

A more advanced variation, the economiser cycle, is often used in screw and two-stage scroll compressors with an intermediate injection port. This method involves partially evaporating a portion of the liquid refrigerant before it enters the expansion device, using a subcooling heat exchanger. The separated subcooled liquid is then injected into an intermediate compression stage, further enhancing efficiency. Because the injected refrigerant evaporates instantly upon contact, it prevents liquid slugging while improving overall performance.

By incorporating these advanced system attributes, higher-temperature heat pumps can achieve greater efficiency, improved reliability and enhanced performance across a range of operating conditions.

A key element of heat pump operation in heating applications is to provide efficient defrosting. When the outside air temperature is below 5-7°C (for example, for ~160 days per year in London)3 and relative humidity is higher than 70%, in an air source heat pump (ASHP) the water vapour within the air freezes when flowing through the evaporator, forming ice that accumulates on the coil surface, compromising the heat pump’s ability to operate. This can significantly reduce heat transfer efficiency and even lead to system shutdowns. There are several methods employed to counter this, with the most traditional being the reverse cycle defrost.

This reverses the refrigerant flow so that the outdoor unit acts as an evaporator, transferring heat from the ambient air to the refrigerant. This heat melts the frost off the coils. This is relatively simple and energyefficient (compared with other methods), but can be time-consuming (interfering with the normal heating operation), and may not be effective in very cold climates.

Hot gas reheat defrost provides an alternative method, where hot, high-pressure gas from the compressor is directed to a separate heat exchanger within the outdoor unit. This hot gas is used to heat the refrigerant within the frozen coils, melting the frost. This provides a faster defrost cycle compared with reverse cycle defrost, minimising performance interruptions, but requires additional components and may increase energy consumption during the defrost cycle.

A simple method is to integrate electric heaters into the outdoor unit to directly heat the frozen coils and melt the frost. Although simple, relatively inexpensive and potentially fast-acting, this can be energy-intensive, as electric heaters consume significant power during the defrost cycle.

Pulse defrost employs short, intermittent periods of reverse cycle or hot gas defrost to remove small amounts of frost buildup periodically, preventing the formation of thick ice layers. This helps to minimise the impact of defrosting on overall system performance by preventing major performance drops because of significant frost buildup, but requires more sophisticated controls to manage the defrost cycles effectively.

Increasingly, there are advanced control strategies in heat pump operation that include predictive and adaptive defrosting methods. Predictive defrosting uses weather forecasts and historical data to predict frost formation and initiate defrost cycles proactively, minimising the impact on performance. Adaptive cycles dynamically adjust the defrost duration and frequency based on real-time operating conditions, such as ambient temperature, humidity and wind speed.

There are many aspects of heat pump operation that will undoubtedly be touched by artificial intelligence (AI) tools. Machine learning, or AI, is already being deployed to predict the right time to initiate defrosting, avoiding unnecessary defrost cycles and reducing energy consumption of such solutions.

With the growing availability of highertemperature heat pumps, there are expanding opportunities in both legacy and other higher-temperature systems for successful applications. l

© Tim Dwyer 2025.

Figure 2: Two 27kW air source R290 heat pumps capable of producing temperatures up to 75°C and operating at outdoor temperatures of between -20°C and +40°C, recently installed on the roof of a UK school building (Source: Hamworthy)

CPD programme Heat pumps

Module 246

April 2025

1. What is a key factor that allows R32 to transfer more heat per unit of refrigerant mass flow?

A Its ability to operate in transcritical cycles

B Its high global warming potential

C Its high latent heat of vaporisation

D Its low discharge temperature

E Its moderate volumetric cooling capacity

2. Why is liquid injection cooling used in heat pumps?

A To eliminate the need for defrost cycles

B To increase refrigerant pressure

C To reduce compressor discharge temperatures

D To reduce refrigerant flammability

E To reduce the latent heat of vaporisation

3. What is the primary advantage of using R290 in high-temperature heat pumps, compared with R32?

A Better performance at higher outdoor temperatures

B Higher critical temperature

C Higher volumetric cooling capacity

D It is a hydrocarbon and not a hydrofluorocarbon (HFC)

E Lower flammability risk

4. What is the main purpose of a suction line heat exchanger (SLHX) in a heat pump system?

A To directly heat the frozen coils during defrosting

B To increase compressor discharge temperature

C To increase the amount of flash gas in the evaporator

D To provide intercooling in multistage compressors

E To subcool the liquid refrigerant and superheat the suction gas

References:

1 bit.ly/CJApr25CPD1 – accessed 1 March 2025.

2 Munk, J et al, Field performance of R1234yf heat pump water heaters, US DOE 2023.

3 CIBSE AM16 Heat pumps in residential buildings, CIBSE 2021.

5. What is the primary reason why R32 heat pumps are often paired with an auxiliary electrical resistance heater in the DHW storage calorifier?

A To allow the condensing temperature to get closer to the critical temperature

B To ensure stored water is consistently above 60°C

C To improve the COP

D   To minimise the risk of liquid slugging in the compressor

E To reduce the global warming potential

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The CIBSE Journal CPD Programme

By participating in this CPD module, you consent to sharing your details with Hamworthy Heating. Hamworthy Heating may contact you via email and/or telephone with further information and technical insight on its services. You have the right to opt out from such communications at any time.

I understand that I will receive marketing communications from Hamworthy Heating after completing this module (please tick here).

Go to www.cibsejournal.com/cpd to complete the module online. You will receive notification by email of successful completion, which can be used to validate your CPD records. Alternatively, complete this page and post it to: N Hurley, CIBSE, 91-94 Saffron Hill, London EC1N 8QP

Munters

dehumidification systems support research at University of St Andrews

A desiccant humidification system has been designed and installed by Munters at the world-leading Colin Vincent Centre for Battery Technology, at Scotland’s University of St Andrews.

The turnkey battery dry room operates at dew points between -40°C and -50°C. It includes a Munters DSS 1300 desiccant dehumidification system that has been fully equipped with the Munters Green PowerPurge heat recovery system, which reduces the reactivation heater power by approximately 30%.

Professor John Irvine said: ‘The key advantage to working with Munters is they have a proven track record. We’re very happy with what we’ve done with Munters and would recommend them again.’

l Visit Munters.com

Hamworthy launches CPD on air source heat pumps

Hamworthy Heating has expanded its CIBSE-accredited CPD portfolio with a new module: ‘Considerations for air source heat pump selection, specification and system design’. The CPD covers key factors in selecting, sizing and specifying air source heat pumps for commercial buildings.

l Visit www.hamworthy-heating.com

Doncaster racecourse installs Hamworthy boilers

The heating system at Doncaster Racecourse has been upgraded with the installation of Upton floor-standing modular boilers from Hamworthy Heating, ensuring high efficiency with minimal disruption. Fitted by ProRite, the compact, vertically stacked Upton UF900-3 boilers provide 900kW output with up to 97% seasonal efficiency.

l Call 01202 662 552 or visit www. hamworthyheating.com

Panasonic heat pump cuts costs for 19th-century home

Seeking a sustainable heating solution, Bedfordshire homeowners replaced their inefficient system with a Panasonic Aquarea J Series T-Cap Monobloc heat pump, installed by Clima Renewables. The system ensures energy efficiency and year-round comfort in their 1890s property.

l Visit www.aircon.panasonic.eu/ GB_en

SoPHE South West networking event returns

Following last year’s successful inaugural event, the SoPHE South West committee is hosting an even bigger networking meeting for public health and mechanical engineers in early July. Attendees can connect with manufacturers, explore new products and enjoy an engaging evening.

l For event details and invitations, contact David Johnson on 07984 520515

Placement student supports Vent-Axia’s award-winning sustainability

efforts

University of Bath student Roben Els contributed to Vent-Axia winning two environmental awards during his industry placement.

Els helped establish a materials testing database for recycled plastics, aiding Vent-Axia’s shift from virgin to recycled plastic. His work has helped enable product certification and third-party accreditation. Els said his placement experience had shaped his career direction, highlighting the importance of industry placement in fostering confidence and inspiring young engineers.

l Call +44 (0)344 856 0590 or visit www.vent-axia.com

Vent-Axia advances low carbon building with embodied carbon data

Vent-Axia has completed embodied carbon calculations for its product portfolio, aiding the design of low carbon buildings. This includes its award-winning Sentinel Apex heat recovery unit that helps specifiers meet the UK’s 2050 net zero goals. The company follows CIBSE TM65 methodology, ensuring accurate carbon data.

Designed for high energy efficiency, the Sentinel Apex offers up to 93% heat recovery, ultra-low noise and enhanced indoor air quality. Vent-Axia aims to secure independent Environmental Product Declarations for further verification.

l Call 0844 856 0590 or visit www.vent-axia.com

Q&A

The Competence Framework for Sustainability in the Built Environment is designed to be used as a basis for developing discipline-specific competence requirements for sustainability across the building environment industry. It was developed under Workstream 10 of the Construction Industry Council’s (CIC’s) Climate Action Plan, coordinated by The Edge, a multidisciplinary, campaigning builtenvironment thinktank. The instigator and technical author is Simon Foxell, policy lead at The Edge.

Q

AWhy do we need a competency framework for sustainability?

It is agreed that the nature and climate emergency is the greatest challenge facing our sector, yet there has only been limited focus on the competence required to embed sustainability into working practices.

Establishing a cross-sector framework for competence in sustainability is essential for achieving a degree of consistency and commonality across different organisations covering the built environment, before they go their separate and distinct ways.

The framework sets out common ground and the language for building individual, discipline-specific competency structures, proposing core criteria and a shared approach without dictating the finer details.

Competence is a general requirement in the Building Safety Act and Building Regulations for any person carrying out building or design work. A competence framework for sustainability became a no-brainer once we realised that it didn’t exist and was clearly urgently required.

Q

Who is it aimed at and how does it relate to engineers?

A The framework is aimed at the whole sector – any organisation, whether a professional or trade body,

Developed as part of CIC’s Climate Action Plan, the Competence Framework for Sustainability lays the foundation for industry-wide standards that embed sustainability into the roles of professionals. The Edge’s Simon Foxell explains

that accredits or validates the competence of its members. Official bodies establishing registers for possible future authorised functions and roles should also use it; this might extend to developing subsidiary frameworks, as happened with building safety competence roles. It might also be used by employers and commissioning clients to ensure a design and construction team that seamlessly covers all appropriate elements of their work.

It is hoped that CIBSE, working with its aligned disciplines, will develop competency frameworks covering sustainability for the roles and disciplines within the membership, based on this sector-wide framework.

Q What is the relationship with safety competence?

A

Building safety and sustainability should be seen as deeply

“Building safety and sustainability should be seen as deeply complementary”

complementary. The same degree of skill and attention to detail is required for both. They need to work closely together, and this framework has been deliberately written to follow the same format and much of the phrasing of BS 8670: Parts 1 and 2 on building safety. It should be straightforward to follow all these documents simultaneously and, at some future date, it would be ideal if they could be merged into a joint competence framework covering the different sector needs.

Q How does it encourage crossdisciplinary collaboration?

A

The Edge’s core tenet is the importance of collaboration across and between the disciplines in our sector, and the framework is an expression of that. By establishing a common, underpinning set of core categories and use of language, it is intended to foster a collective understanding of sustainability issues and, particularly, of how the different disciplines can work together on projects - interlocking, but without gaps or unnecessary overlaps.

The framework has been developed as a seed document for a British Standard, with wide consultation and guidance from across the sector. It has been written as an addition to the Building Competence series that began with BS 8670: Part 1. As a British Standard, it would become an unavoidable part of the competence landscape in the UK and elsewhere.

Q How can people get involved?

A

The framework can be freely downloaded from bit.ly/ CJEDCFsus and it is anticipated the sector will adopt it as the base standard for a wide range of discipline-specific competence frameworks.

Feedback on its functionality in use is welcomed at contact@edgedebate.com

Simon Foxell

24 – 25 April 2025

UCL Bentham House

London

co-organised by CIBSE and IBPSA-England

Fit for 2050

Achieving net-zero through intelligent, resilient and sustainable design in the built environment.

Learn from 60+ approved speakers sharing peer-reviewed papers and case studies

Join 30+ sessions focusing on the transition to net-zero carbon, design strategies for climate resilience in the built environment, applications of AI, machine learning and parametric design, and learnings from post-occupancy evaluations

Network with built environment professionals including, practitioners, researchers, high-level decision makers, students and, many more.

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cibse.org/symposium

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