The ThermalswitchBEX is an overclad adapter panel that creates a secondary barrier opposite a new or existing façade. If placed over an existing, underperforming building façade it will increase the thermal performance and insulative values of the existing façade, reducing thermal transmission across the existing assembly while increases thermal comfort of the occupants. The system utilizes light transmissible architectural film such as ETFE and is capable of being placed over opaque or vision portions of a building façade.

The system is unique in that it is lightweight – meaning that little to no structural improvements need to be made to the primary structure or existing glazing system prior to installation, it does not impede the existing daylight transmission into the building and has the ability to manage and block infrared radiation in the film itself which has traditionally only been achieved with glass coatings.

ETFE stands for Ethelene Tetrafluoroethylene and is a fluoropolymer that can be manufactured in a variety of ways include an ultra-thin transparent foil which comes in thicknesses ranging from 60nm to 300nm. First developed in the 1940’s by DuPont, ETFE was used in a variety of ways before being utilized in architecture where in the 1980’s it was used as a zoo enclosure.

ETFE has been traditionally employed for large overhead horizontal spans which recently include both the Los Angeles SoFi Stadium and Las Vegas Allegiant Stadium. ETFE manufacturers having been able to develop techniques to actually ‘cut’ certain wavelengths from passing through the film enabling even more thermal and solar control within this ultra-thin foil.

Traditionally, ETFE can be utilized in either a stretched, prestressed skin or in a pillow assembly where two foils are joined and inflated by a mechanical pump with check valve. The stretched skin assemblies are passive in nature and do not require a pump, but tend to need more robust connections to keep the foil stretched, whereas the pillow relies primarily on the pump to inflate the pillow to the necessary pressures to resist the environmental loads.

ETFE is 95-98% light transmissible whereas with clear glass this value is typically 100%.

Glass has a Global Warming Potential (GWP) per ton of 1430 whereas ETFE has 14 times that per ton at 20,869. However, when we look at square footage and weight comparisons, a 1x1 meter insulated glazing unit (IGU), utilizing two 6mm glass lites, weighs 50lb, compared to two layers of ETFE foil of the same size which weighs 0.8lbs, resulting in 62 times less than the IGU.

Like glass, ETFE foils can be fritted by a printing process and current studies are being performed to confirm the ability to apply coatings such as LowE to the foil rolls. Additionally, unlike typical clear class, ETFE foils can have various properties embedded in the polymer itself, where they can ‘cut’ out particular wavelengths of the light spectrum such as infrared and ultraviolet.

Fluoropolymers, such as ETFE or PTFE, are considered safe according to the most recent EPA study from 2021 on PFAS identified ETFE specifically as a polymer of low concern, additional research corroborated these findings due to the face that ETFE molecules are less bio available and “believed to be too large to cross the cell membrane” (EPA’s Multi-industry per- and polyfluoroalkyl substances (PFAS) study – 2021 Preliminary Report)

Likely yes – when utilizing an ETFE film with the required ceramic bird friendly frit patterns applied. However, ETFE has not yet been tested by the American Bird Conservatory’s Bird strike test but based on existing products that have been tested, it is likely that a fritted ETFE with the acceptable patterns would pass.

There is a chance that a non-fritted ETFE foil would pass the bird strike test simply due to the foil’s ability to slightly stretch and deflect until impact loads. This requires further study and testing before we can confirm. However, various municipalities across North America have enacted local laws that require Bird Friendly glass be utilized on all new building projects. There is a chance that If ThermalswitchBEX was to be utilized in an exterior application, the building owner could potentially benefit from improved envelope energy performance while simultaneously reducing bird strike potential.