It is important to consider NZ's unique environment and high UV levels when specifying modern single ply thermoplastic membranes such as PVC and TPO.
Modern single ply thermoplastic membranes, such as PVC and TPO have become more mainstream in New Zealand recently.
In certain situations, single ply membranes have advantages over traditional membrane roofing as the sheets are physically much bigger, reducing the number of welded laps required, saving on labour and potentially providing a cost savings on large simple shaped roofs. Thermoplastic membranes also provide a distinctly different aesthetic than traditional bitumen torch on roofs.
With a single ply membrane measuring from 1 – 2mm in total thickness, we don't have the thickness or additional redundancy as we would have in our traditional torch on systems of 7 – 8mm.
It is also important to note that while most Thermoplastic membranes are 1 – 2mm thick, it is only the thickness above the reinforcing scrim that does the weathering and waterproofing — which is usually around only half the thickness of the total membrane!
Thickness above the scrim:
Therefore, the quality and long term performance of a single ply membrane is extremely important.
GAF is the world's largest producer of single ply membranes along with rigid polyisocyanurate insulation boards and a full list of associated roofing accessories. GAF also produces a range of 23 membrane colours ranging from white to red to blues and some very unique blends specific to certain customers. An example of these colours can be seen in this giant American flag on display in the Gainesville, Texas production facility, completely assembled using the GAF TPO and it's various colour options.
I remember vividly having the discussion with the GAF laboratory staff about our unique New Zealand UV exposure levels. From this discussion/debate and investigation we were strongly advised by the GAF technical staff to only supply a light grey colour (Grey 345) or a white due to New Zealand's unique and specific environmental factors.
An SRI independent TPO study shows that one particular TPO membrane is the most durable amongst the four manufacturer's tested. These tests also highlighted that extreme heat is detrimental to ALL thermoplastic membranes. By having a lighter colour or higher Light Reflectance Value (LRV), less heat is gained by the membrane thus providing a long term, more durable membrane system.