ETFE is an exciting, new and modern approach to roofing with benefits which outweigh glass and other products. However, there are certain aspects of the product which might deter some contractors – how can we allay these concerns?As a clear material with a high level of light transmission and good insulation properties, ETFE foil, when made into cushions, suffers from many of the same problems as glass – most critically solar gain leading to spaces overheating. A well recognised problem, ETFE foil is often fritted, or printed, with a geometric pattern in a silver ink to reflect some sunlight off the membrane surface and away from the space below. Whilst some of these fritting patterns cover up to 70% or 80% of the surface of the membrane, cutting out up to ?? of light transmitted through the foil, the eye naturally sees the view through the clear spaces rather than the fritted pattern and therefore the ETFE roof retains its impression of being clear. Whilst effective, however, fritting this is not always enough and depending on the thermal performance of a building, additional layers of membrane can be drawn upon to assist.
For installations which suffer from acoustic problems, we recommend the application of a rain suppression layer (heavy netting) over the top layer of the ETFE cushions. From an acoustic point of view, this tensioned netting controls the reverberation of rain noise on the surface of the ETFE and dampens the sound. However, by adding a rain suppression layer there is an added effect of reducing the levels of light allowed to pass through the ETFE and into the space below. In turn this affects the heat and solar gain created. As a guideline the addition of a standard rain suppression mesh can reduce the light transmission by an average of 50%. For one of our projects which suffered terribly from solar gain, this method was used to control the G-value in the space.
On any Architen Landrell structure the design allows for a rain suppression layer to be added as a retrofitted item either for light transmission or acoustic problems.
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