Embodied Carbon in the Built Environment ― Executive Summary

Embodied Carbon in the Built Environment ― Executive Summary

April 22, 2020

In response to climate emergencies declared around the world, the building industry must rapidly transition into a zero carbon sector that takes into account both operational and embodied carbon.

The building sector, which is responsible for 39% of global carbon emissions,

Global CO₂ Emissions by Sector: Image adapted from Architecture 2030

presents a key opportunity to make an impactful reduction in global greenhouse gas (GHG) emissions. A breakdown of these emissions shows that 28% can be attributed to building operations with the remaining 11% attributed to the carbon embodied in building materials and generated by the construction process.¹

Lo Industry re m 30% ip su m

The implementation of widespread energy efficiency codes and regulations has substantially reduced operational carbon emissions. A similar concerted focus on

Other 9%

Building Operations 28%

quantifying and reducing embodied carbon would further the industry’s ability to reduce its carbon footprint.

Transportation 22%

In light of the climate crisis, the building industry has a collective responsibility to design buildings, communities, and cities with the lowest possible carbon emissions and with the aspirational goal of creating net zero operational and embodied carbon buildings. If we rise to this challenge, we will stay ahead of regulatory pressures and demonstrate the kind of leadership building industry

Building Materials and Construction 11%

professionals are capable of.

This primer focuses on the practical measures that our industry can immediately implement to limit embodied carbon in the built environment. As a companion to our more detailed Embodied Carbon in the Built Environment ― A Primer, this document provides an abbreviated synopsis of embodied carbon, and key tools, metrics, and opportunities for implementing embodied carbon conservation measures during a typical building design process.

The significance of tackling embodied carbon emissions has become magnified as a result of higher energy efficiency (lower operational carbon) in buildings.

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

Operational Carbon



Embodied Carbon

A building’s whole life carbon is made up of the following life cycle stages: product stage, construction process stage, use stage, and end of life stage.

WHO

LE LIFE CARBON

PR OD

E

UC

EC

LIF

ND E

E STAG

ES S

PR OC

ON

A4 Transport

TI

BO

A3 Manufacturing

N

RU C

A ST

G

R

IFE

CA

FL

IFE

DO

OPERATIONAL CARBON

FL

EN C3 Waste Processing

RONT CARBON

BEYO

UPF

END O

C4 Disposal

A2 Transport

E AG ST

D Benefits and Loads beyond the Life Cycle

CL

A1 Raw Material Supply

T

Y

EMBO C ARB DIED ON

B6 Operational Energy Use

USE C ARBON

C2 Transport

N CO

USE STAGE B1 Use B2 Maintenance C1 De-construction Demolition

B3 Repair B4 Refurbishment B5 Replacement

Image adapted from BS EN 15978:2011 Sustainability of Construction Works— Assessment of Environmental Performance of Buildings—Calculation Method

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ST

A5 ConstructionInstallation Process

Timelines for Action The Intergovernmental Panel on Climate Change (IPCC) warns the world that limiting global warming to 1.5°C will require “rapid and far-reaching” action to reach a 45% reduction in CO2 emissions by 2030 and net zero emissions by 2050.² Building upon this call for action, many organizations, such as the World Green Building Council, the American Institute of Architects, Microsoft, and the City of Vancouver have set accelerated timelines for carbon emissions reductions.

Currently, embodied carbon reduction targets are voluntary, but France, Norway, the City of Vancouver, Washington State, and California have indicated that mandatory embodied carbon reduction targets for whole buildings and specific materials will be implemented in the near future.

Timeline outlining embodied carbon reduction targets set by leading organizations.

Getting to Zero

2020

2025

2030

2040

Embodied Carbon Reduction Targets

World GBC

40%

AIA 2030 Challenge

50%

City of Vancouver Climate Emergency Response

40%

Microsoft’s commitment to be “carbon negative” by 2030 means that they will remove more carbon than they emit each year.

Microsoft

LETI Climate Emergency Design Guide RIBA Sustainable Outcomes Guide 2019

40%

48–55%

65%

62–70%

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2050

Embodied Carbon Conservation Measures

Structural Columns

6% ←

Structural Framing

10%

More than 80% of embodied carbon in a building’s structure is in the floor slabs, walls, and structural foundations.

Structural Foundation

Reference: Adapted from the project-based study of the embodied carbon of more than 600 buildings by Thornton Tomasetti.

20% Walls

↓

21%

The GHG emissions by energy end use for commercial and institutional buildings in 2017. Space heating, lighting, and auxiliary equipment make up 85% of the total GHG emissions for operations. The GHG emissions of each end use is a function of energy use and fuel source.

Floors

43%

Reference: Natural Resources Canada (NRCAN) - Canada’s GHG Emissions by Sector, End Use and Subsector – Including ElectricityRelated Emissions.

A holistic approach to achieve total carbon reductions in the built environment should include operational carbon, embodied carbon, and carbon associated with the transportation of building users.

In this report we focus on opportunities to limit embodied

Street Lighting 1% Space Cooling 4%

carbon. With more than 80% of embodied carbon residing in a building’s structure, carbon can be mitigated through careful specification of three main structural materials: nj Concrete: Request Environmental Product Declarations

Auxiliary Motors 3%

(EPDs) for design mixes and establish a concrete carbon

Lighting 10%

budget for the project in collaboration with concrete suppliers. nj Steel: Request high recycled content, source steel from

Auxiliary Equipment 12%

mills that use Electric Arc Furnaces (EAFs), understand the local energy grid of the mill, and the distance the product will be transported.

Water Heating 7%

nj Wood: Source wood from sustainably managed forests so

Space Heating 63%

there is confidence that the forest will be maintained to maximize carbon sequestration.

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Carbon Conservation Measures in the Design Process

nj Establish massing to study the embodied carbon impacts of potential building forms through WBLCA

EMBODIED CARBON

nj Host design workshop to explore embodied carbon conservation measures (ECCMs)

nj Refine program to eliminate redundancies

nj Initiate energy analysis—box modelling or conceptual design modelling nj Discuss fuel sources

nj Update WBLCA model

nj Conduct thermal bridge calculations nj Complete energy model to assess load reductions and systems selection nj Draft outline specification to identify components critical to energy performance nj Establish Basis of Design for assemblies, glazing ratios, occupancy usage, ventilation strategy, shading strategies

OPERATIONAL CARBON

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Design Development

nj Establish Basis of Design for structural system, envelope, foundations, landscape, hardscape, and other assemblies with high embodied carbon impact

Schematic Design

Establish a carbon budget in kg CO2e

nj Discuss structural options, their associated carbon footprint, and the cost and schedule implications

nj Complete environmental analysis—climate and site

nj Collaborate with the builder to develop embodied carbon requirements in the specifications and ensure follow through in the procurement process

nj Draft outline specification to identify materials and systems critical to reducing embodied carbon

nj Reduce material use by exploring various massing and foundation options

Concept Establish a carbon budget in kg CO2e

nj Collaborate with landscape and civil designers to analyze carbon impact of landscape and hardscape

nj Complete an early stage WBLCA

nj Host design workshop to explore energy conservation measures (ECMs)

nj Optimize structure, including column sizing, column spacing, slab depth, and roof assembly

nj Study structural and envelope systems

nj Study the possibility of retaining existing building components and materials

nj Establish goals to design for flexibility, adaptability, future disassembly, deconstruction, and reuse

nj Identify assemblies and materials with the largest embodied carbon impact and study reduction strategies through WBLCA

nj When assessing EPDs of comparable products take into account the LCA scope, declared units, and whether it is industry wide or product specific

nj Optimize design, establish occupancy rates, reconcile ASHRAE/code requirements, and study ECMs nj Update energy model nj Collaborate with mechanical designer and HVAC supplier to select equipment that uses refrigerants with low global warming potential and avoid refrigerant leakages

As a design firm, we strive to achieve carbon reductions

Non-design reduction strategies are measures that cannot

in all projects. Achieving low carbon designs requires the

be quantified using Whole Building Life Cycle Assessment

engagement of the entire project team. This iterative

(WBLCA) or other quantitative tools, yet they can accelerate

process, which ideally starts in early design, is continually

the adoption of low carbon products, technologies, and

refined throughout design and construction. By integrating

design strategies.

low carbon thinking and practices from the beginning,

The World Green Building Council emphasizes the

we are able to make informed decisions based on the

importance of enabling change in the building sector

project’s goals.

through collaboration, communication, education,

This design timeline illustrates key considerations to reduce

innovation, and regulation. The adoption of these actions by

the operational and embodied carbon of our projects.

supply side players, demand side players, policy makers, and non-governmental organizations will also accelerate the shift to zero or low carbon solutions.

nj Incorporate EPD requirements and CO2e limits for key materials in the specifications

nj Confirm the impact of material choices and efficiencies established in design through WBLCA

nj Prepare drawings and specifications incorporating all elements critical to energy performance, including airtightness detailing, and thermal bridge detailing nj Review value engineering proposals and potential implications on energy performance goals

nj Review submittals and product substitutions to confirm low carbon materials are maintained throughout procurement and construction nj Update WBLCA as required

nj Monitor on-site practices to ensure compliance with energy performance requirements nj Update energy model as required nj Conduct airtightness testing nj Commission building systems to ensure design intent is met

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Post Occupancy

nj Review structural drawings and specifications to confirm the embodied carbon impact as the structural design is refined

Construction Administration

Tender and Construction Documents

nj Include requirements for substitutions and alternate products in the specifications

nj Reflect on lessons learned and apply them on future projects

nj Complete measurement and verification to refine operations and meet energy reduction goals nj Reflect on lessons learned and apply them on future projects

Embodied Carbon Calculation Tools

Conclusion

Common tools used to complete a whole building life

The world shares a finite carbon budget and a tight deadline

cycle assessment (WBLCA) of projects located in North

before we see irreversible changes in our climate. For this

America are:

reason, gaps in data and technology cannot halt progress in further decoupling development of the built environment

nj Athena Impact Estimator for Buildings,

from carbon emissions.

nj Tally, and

We expect to see policies emerge from local jurisdictions

nj OneClick LCA.

and planning authorities that will target embodied carbon

Another notable tool is the Embodied Carbon in

reductions in the built environment. We each have a responsibility and role to play in sending market signals to

Construction Calculator (EC3). While not a WBLCA tool, it

our clients, consultants, contractors, and manufacturers

allows users to view, benchmark, and compare the carbon impact of specific building materials.

to invest in innovative products. Above all, achieving

As there are many tools available to meet different user

collaboration.

a zero carbon future for the industry will require major

needs, in choosing the right tool, it is important to consider factors such as:

Now more than ever, we are being urged to make bold

nj Project location,

way. By focusing on the most impactful design decisions, we

commitments, learn by doing, and share lessons along the

nj Stage of the project,

believe we can decarbonize the built environment.

nj Available project data, and

For more information please refer to our report Embodied Carbon in the Built Environment―A Primer, which

nj The format of the project’s bill of materials.

provides a more complete overview of embodied carbon conservation strategies, baselines and benchmarks, and emerging reduction targets.

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Definitions

Acronyms

Anthropogenic emissions: The IPCC defines anthropogenic emissions as “emissions of greenhouse gases (GHGs), precursors of GHGs and aerosols caused by human activities”.

CO2e: Carbon Dioxide Equivalent ECM: Energy Conservation Measures ECCM: Embodied Carbon Conservation Measures

Baseline: A baseline design is produced by the WBLCA modeller and is based on what is typical for the building type, a previous project that is similar, or an earlier iteration of the proposed project.

EPD: Environmental Product Declaration GHG: Greenhouse Gas

Benchmark: A benchmark is based on a statistical analysis of the current building stock and represents an “average performance” of a building archetype.

LCA: Life Cycle Assessment LCI: Life Cycle Inventory

Carbon dioxide equivalent (CO2e): A standard unit for measuring carbon footprints, it expresses the impact of a greenhouse gas in terms of the amount of CO2 it would take to create the same amount of warming.

WBLCA: Whole Building Life Cycle Assessment

Endnotes

Embodied carbon conservation measures (ECCMs): Strategies and technologies implemented to reduce the embodied carbon in building assemblies and materials.

1. Canada Green Building Council. Zero Carbon Building

Embodied carbon emissions: Carbon emissions associated with materials and construction processes throughout the whole life cycle of a building.

– Design Standard Version 2. Canada Green Building Council, 2020.

Energy conservation measures (ECMs): Strategies and technologies implemented to reduce the energy consumption of a building.

2. Masson-Delmotte, Valerie, et al. “Global warming of 1.5°C. An IPCC Special Report on the impacts of global

Environmental Product Declaration (EPD): A document that quantifies environmental information on the life cycle of a product to enable comparisons between products fulfilling the same function.

warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context

Greenhouse gas (GHG): Any gas that absorbs heat energy emitted from Earth’s surface, traps heat in the atmosphere, and radiates that heat back to Earth’s surface. These gases include carbon dioxide, methane, water vapour, ozone, nitrous oxide, and chlorofluorocarbons (CFCs).

of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty.” 2018. In Press.

Life cycle assessment (LCA): A scientific method for calculating the environmental footprint of materials, products and services over their entire lifetime.

Low-carbon energy sources: Energy sources that emit low amounts of GHGs, including hydropower, solar power, wind power, and nuclear power.

Net negative emissions: According to the IPCC, “a situation of net negative emissions is achieved when, as result of human activities, more greenhouse gases are removed from the atmosphere than are emitted into it.”

Net zero carbon: Achieved when CO2 emissions from human activities are balanced globally by CO2 removals over a specified period.

ACKNOWLEDGEMENTS

Operational carbon emissions: Carbon emissions associated with the energy used to operate a building.

This report was authored by the research and sustainability team of the Vancouver and Calgary studios of Perkins and Will: Principal-in-charge: Kathy Wardle, Associate Principal and Director of Sustainability Lead Researcher: Manuela Londono, Sustainable Building Advisor Research Review Committee: Cheney Chen, Cillian Collins, Susan Gushe, Aaron Knorr, Mona Lemoine, Sindhu Mahadevan, Derek Newby. t +1 604 684 5446

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