Protecting Heritage Commercial Buildings
Invisible window insulation for castles, stately homes, historic commercial spaces and sacred spaces
Where Heritage Meets High Performance
At Cocoon, we believe that beauty and performance should never be at odds — especially when it comes to our most treasured buildings.
From castles and stately homes to civic landmarks and sacred spaces, our InvisiTherm® system helps protect what matters most: comfort, conservation, and character.
InvisiTherm® was designed to solve the problems traditional buildings face — without introducing new ones. No aluminium frames. No rigid fixings. No compromise.
Our slim, breathable system provides a powerful thermal and acoustic upgrade for original windows, while respecting the character and heritage of the buildings it protects, remaining virtually invisible. It helps improve energy efficiency, stabilise indoor temperatures, and reduce external noise, without altering the appearance of your original windows. Whether you manage a historic estate, oversee a conservation project, or are responsible for the upkeep of a landmark property, Cocoon offers a proven solution that respects the past while improving the future.
INVISITHERM® BENEFITS
InvisiTherm® is designed to deliver excellent insulation without compromising aesthetics, making it the ideal solution for listed buildings and heritage properties. Key benefits include:
Glaze heat loss reduced from 95% loss to just 33% making InvisiTherm® extremely energy efficient
Instant draught proofing
Our discrete frames and magnet fixings eradicate draughts and pollution making rooms more healthy
Water vapour permeable
The system can absorb and release moisture preventing mould and condensation
Increase thermal comfort
Dramatic heat gain 95%
Reduces temperature swings in summer an winter creating wellbeing
Improved energy performance certificate
Achieve double glazing rating and add value
Dramatic noise reduction
Our innovative system delivers a minimum reduction of 68% on single glaze and 58% on double glazing and a maximum saving of up to 88%
Heat loss for original window
Cool in summer
By blocking the sun’s heat by 27%
Shatterproof
Virtually unbreakable and 250 times stronger than glass
Heat loss with InvisiTherm® installed
Almost invisible
86% transparent so very discreet, glass is 76%
Easy to clean
Systems easily removed to allow cleaning of windows unlike traditional fixed secondary glazing
Moves with seasons
Allows the window to expand and contract with seasonal temperatures unlike traditional secondary glazing which is rigid and often sticks
Ironmongery & shutters
You can keep and use these as you have always
No fading
Block ultraviolet by 99.99% protecting your valuables
Net zero
Keeping original windows, which will last many decades is good for the environment and property value
Fireproof
Class 1Y status meaning the system won’t burn and will slow down glass from blowing
Protecting Iconic Buildings
InvisiTherm® is trusted by conservation professionals, estate managers, and heritage organisations across Scotland and beyond. From castles and colleges to galleries and civic landmarks, our discreet insulation system is helping protect some of our most treasured buildings — quietly, effectively, and without compromise.
The system has been used to stabilise unheated rooms, improve energy ratings, and reduce condensation in buildings where full double glazing would never be permitted. With InvisiTherm®, unused spaces become functional again. Valuable interiors are shielded from UV damage. Historic character is preserved for generations to come.
Whether your priority is energy efficiency, visitor comfort, or fabric conservation, InvisiTherm® offers a proven path forward.
“We have to tell our members and visitors we have secondary glazing as it’s practically invisible. It’s now so easy to remove and clean the windows; this is a great benefit that we didn’t get from the traditional secondary glazing we’ve inherited.”
Dr Burke, National Trust
“We have to tell our members and visitors we have secondary glazing as it’s practically invisible. It’s now so easy to remove and clean the windows; this is a great benefit that we didn’t get from the traditional secondary glazing we’ve inherited.”
Dr Burke, National Trust
TRUSTED BY Inveraray Castle • Drum Castle • Glenalmond College • Edinburgh Castle • Bristo Baptist
Church
Church of Scotland
Perth Methodist Church
National Trust
Private Estates
Commercial Sites
TRUSTED BY Inveraray Castle • Drum Castle • Glenalmond College • Edinburgh Castle • Bristo Baptist
Bristo Baptist Church, Edinburgh
Church of Scotland
National Trust
Perth Methodist Church
TRUSTED BY Inveraray Castle • Drum Castle • Glenalmond College • Edinburgh Castle • Bristo Baptist
Church of Scotland
National Trust
Church of Scotland, Pitlochry
TRUSTED BY Inveraray Castle • Drum Castle • Glenalmond College • Edinburgh Castle • Bristo Baptist
Church of Scotland
Perth Methodist Church
National Trust
Private Estates
Commercial Sites
TRUSTED BY Inveraray Castle • Drum Castle • Glenalmond College • Edinburgh Castle • Bristo Baptist
Glenrothes Church
St Catherine’s Church, Blairgowrie
TRUSTED BY Inveraray Castle • Drum Castle • Glenalmond College • Edinburgh Castle • Bristo Baptist
Church of Scotland
Perth Methodist Church
National Trust
Orwell Church, Milnathort
TRUSTED BY Inveraray Castle • Drum Castle • Glenalmond College • Edinburgh Castle • Bristo Baptist
Church of Scotland
Perth Methodist Church
National Trust
Private Estates
Commercial Sites
TRUSTED BY Inveraray Castle • Drum Castle • Glenalmond College • Edinburgh Castle • Bristo Baptist
St Mary’s Church, Dalmahay
National Trust
TRUSTED BY Inveraray Castle • Drum Castle • Glenalmond College • Edinburgh Castle • Bristo Baptist
St Andrews Church
National Trust
TRUSTED BY Inveraray Castle • Drum Castle • Glenalmond College • Edinburgh Castle • Bristo Baptist
St. James Church, Leith
Caputh Village Hall, Perthshire
Stirling Methodist Church
TRUSTED BY Inveraray Castle • Drum Castle • Glenalmond College • Edinburgh Castle • Bristo Baptist
Church of Scotland
Perth Methodist Church
National Trust
Private Estates
Commercial Sites
Private Residence, Aboyne
TRUSTED BY Inveraray Castle • Drum Castle • Glenalmond College • Edinburgh Castle • Bristo Baptist
Private Residence, Balfron
TRUSTED BY Inveraray Castle • Drum Castle • Glenalmond College • Edinburgh Castle • Bristo Baptist
Church of Scotland
Perth Methodist Church
National Trust
Commercial Sites
Private Residence, Fife
TRUSTED BY Inveraray Castle • Drum Castle • Glenalmond College • Edinburgh Castle • Bristo Baptist
TRUSTED BY Inveraray Castle • Drum Castle • Glenalmond College • Edinburgh Castle • Bristo Baptist
Inverary Castle
Church of Scotland
National Trust
Expertly Installed. Carefully Considered.
Every building is different — and so is every InvisiTherm® installation.
Our systems are handcrafted to the exact shape and detail of each window on site by our team of trained professionals. Led by time-served finishing joiners, Cocoon installers work with respect for historic materials, original ironmongery, and delicate finishes — from timber panelling to stained glass surrounds.
We understand the sensitivities of working in historic and occupied spaces. That’s why every step of our process is designed to minimise disruption, preserve character, and deliver a flawless fit.
What Sets Us Apart
• Non-invasive installation
• No screws, no glue, no damage — systems are fully removable
• On-site shaping and fitting
• Ensures a perfect match to curves, arches and frame details
• Compatible with working shutters and original hardware
• We fit around features rather than removing or replacing them
• Colour-matched finishes
• Frames and beading tailored to painted or natural timber tones
• Trusted and accredited
• Cocoon is a Guild of Master Craftsmen member, City of Edinburgh Trusted Trader, and Living Wage employer
“The installers were fantastic cut to shape on site and found it.”
Commercial client, Perthshire
fantastic — everything was left exactly as they
Perthshire
INVISITHERM® TECHNICAL DATA
DESCRIPTION
Invisitherm® sheet is a transparent polycarbonate sheet with proprietary UV protection on both sides offering excellent weathering properties. With its outstanding impact resistance, fire resistance, noise dampening qualities and light weight it offers a uniquely high-performing option for window and door insulation.
TYPICAL PROPERTY VALUES
Impact
impact, notched
impact, unnotched 23°C
Izod impact, unnotched -30°C
LIGHT TRANSMISSION
Transparent Invisitherm® sheets have excellent light transmission, between 84 and 87%. However for buildings in hot climates or with south facing aspects, Invisitherm® sheet is available in translucent bronze, grey and opal white. Invisitherm® is essentially opaque to all wavelengths below 385 nanometers. This useful shielding property can help prevent discoloration of sensitive materials placed under or behind Invisitherm® sheet.
UV PROTECTION
Invisitherm® sheet has proprietary UV protected surfaces, giving excellent durability to outdoor weathering. This superior UV resistance and toughness of Invisitherm® sheet is backed by a 10 years limited written warranty against yellowing, loss of light transmission and breakage.
SOUND REDUCTION
Below graph shows the acoustic properties for different thicknesses of the sheet:
INVISITHERM® TECHNICAL DATA
SOUND INSULATION (Noise Reduction dB)
WATER VAPOUR PERMEABILITY
FIRE CLASSIFICATION
This classification has been carried out in accordance with EN 13501-1: 2018. The related harmonised product standard is EN 16420: 2013 and has been used for the mounting and fixing of the DBI specimen. The Invisitherm® product in relation to its fire behaviour has been classified as: Fire Behaviour
PRODUCT AVAILABILITY
Invisitherm® sheet is normally manufactured in the standard sizes below. Deliveries from stock or cut to size can be ordered by Cocoon.
Standard Gauge (mm)
Standard Sizes (mm) 2050 x 3050 (max size for 15mm), 2050 x 6100
Masking
Combustible materials - very limited contribution to fire
PERFORMANCE
absent or very little No
Invisitherm® sheet has a good fire performance against many national fire codes dependant on thickness and colour, please check with us for details.
Top side: Coex. opal white PE/purple print, Bottom side: Coex. transparent PE standard colours: clear code 112, solar bronze code 5109, solar grey code 713, opal white code WH7D287O and opal white code WH4D3480 (opal whites max. 8mm)
all give a hearty wave To Perthshire business Glaze & Save! If your windows let in chills, Their great glazing will cut your bills. If your house is deemed historic Savings will be meteoric! Easy to fit and also removeable Gives results so easily provable!” The team at Dundee Rep Theatre A lyrical customer testimonial...
“Let’s
Sustainably Made. Built to Last.
At Cocoon, sustainability isn’t a bolt-on — it’s at the heart of everything we do. From the materials we use to the way we manufacture, we’re committed to reducing waste, lowering emissions, and helping our clients make greener choices for even the oldest of buildings.
InvisiTherm® is designed to extend the life of original windows, reduce reliance on heating systems, and minimise environmental impact — all without compromising heritage values.
We operate with a local-first supply chain and achieve a recycling rate of over 95% on site. Every piece of timber we use for our beading is fully Chain of Custody certified, meaning it originates from responsibly managed forests.
Our Sustainability Credentials
• VIBES Award winner – Environmental Product of the Year
• >95% recycling rate – including zip-sealed hoover bags
• Local supply chain – supporting small Scottish businesses within a few miles of HQ
• Chain of Custody certified timber – all hardwood beading from sustainable sources
• Dramatically reduces energy consumption – cutting heating use by up to 25% per room
• No plastic waste – re-usable dust sheets, recycled polycarbonate
“Keeping original windows, which will last many decades, is good for the environment — and for property value.”
Dr Tanya Ewing, CEO Cocoon
Visit www.cocoon.tech to view our latest insights, videos and blog posts
Glaze and Save Ltd T/A Cocoon Window Insulation, Unit 9 Mercian Buildings, Shore Road, Perth , PH2 8BD Company No: SC464869 VAT No: 229064901 © Glaze and Save Ltd 2025