Product manufacturers play a critical role in ensuring buildings are specified with safe, sustainable materials. With offsite construction increasingly utilising high pre-manufactured value (PMV), specifiers must scrutinise product performance claims and verify how they are tested. Glidevale Protect, a UK based manufacturer of wall, floor, ceiling and roofing membranes, takes this responsibility seriously and as John Mellor, Head of Marketing explains, when it comes to demonstrating thermal efficiency, transparency and testing is everything.
Reflecting on U-values
Offsite manufactured structural timber buildings are designed to deliver quality construction with high insulating properties and good airtightness. Using reflective wall membranes, both on the cold and warm side of the insulation, can further enhance the level of thermal performance and improve the energy efficiency of the structure. The thermal resistance (R-value) of these membranes is a key metric to aid specification but results can vary by supplier based on testing methods, whether products have been assessed pre- or post-aging, fixing centre distances, and the presence of printed logos on the reflective surface. Even small variations in R-values can impact the overall U-value of the wall build up, making it vital to compare like-for-like technical data from different suppliers.
Guidance from the Structural Timber Association’s (STA) Advice Note 18 underscores the importance of manufacturers providing clear, verified data for reflective wall membranes. This includes testing to required thermal and emissivity performance standards, with aged surface emissivity (Ɛ) and R-values fully verified by a UKAS-accredited third party.
The Role of ‘Hidden Protectors’
Creating energy-efficient homes requires a balance of thermal efficiency, airtightness, ventilation, and condensation control. This can be achieved through early collaboration with manufactures who can offer a holistic ‘whole house’ solution.
Reflective wall membranes, which can arguably be seen as ‘hidden protectors’ within the building envelope, have a prominent role to play in helping to reduce U-values in timber-framed buildings. When placed with the reflective surface facing still airspace cavities – such as the use of a service void – these low-emissivity surfaces can enhance thermal resistance without increasing overall wall thickness.
Reflective membranes also function as radiant barriers, reducing heat loss in winter and minimising heat gain in summer. However, their effectiveness depends on material composition and for our part, Glidevale Protect’s TF200 Thermo and VC Foil Ultra membranes use high-purity aluminium foil to achieve a low emiss
ivity of 0.03 (aged) and a reflectivity of 97%. When specifying reflective membranes, a simple way to remember the link
between thermal resistance and emissivity is that the lower the ‘E’ (emissivity), the high
er the ‘R’ (thermal resistance) and the better the membrane’s thermal performance when facing into a still airspace.
Challenging claims
It is vital that all thermal efficiency claims are backed by testing and that results are transparent. Ultimately, correct and clear thermal resistance values are critical in order to not over inflate the overall performance level of the wall structure and confuse the specifier.
Suppliers should be able to provide unbiased information about their products when asked – is the thermal resistance data aged and quoted in the worst-case scenario? Does testing incorporate printed logos on the surface which can affect the overall emissivity of the membrane? Does the thermal resistance value achieved use realistic and correct fixing centres that would be typically used on a timber frame wall panel and is the claimed result in line with testing requirements? Not only do these questions need to be answered effectively, but they should be backed up by independent, third-party certification and meet the guidance requirements detailed in STA Advice Note 18. Only then can membrane manufacturers truly build trust within the construction industry and help close the performance gap so that the building fabric can perform exactly as intended.
For more information, visit www.glidevaleprotect.com, call 0161 905 5700, or email [email protected]. Follow Glidevale Protect on LinkedIn.
