with respect to the TPO the jury is still out on that membrane .... see below from the MRCA dated 2/10/10..... Not good for TPO ......
February 10, 2010
T&R Committee Advisory on TPO
Information is being circulated in the industry indicating that high solar loading and elevated temperature lead to the premature exhaustion of anti aging components such as anti oxidants, UV absorbers and heat and light stabilizing compounds within TPO. This could lead to the breakdown of the sheet in affected areas.
This also might explain some reported problem applications with localized deterioration of membrane. One manufacture has recently changed formulation to account for this problem; another advises their product not be "subjected" to high thermal or solar loading; while others remain silent. Southern states appear to have this problematic local condition due to the heat load these roofs experience.
The committee believes that enough information has surfaced concerning TPO accelerated weathering due to solar or thermal loading to advise members to:
Review roof plans for situations where sun light is reflected back on membrane; such as areas below metal and glass or highly reflective curtain walls, or high profile reflective wall flashings.
Look for heat emitting equipment or heat exhausting vents or dark emissive materials laid on the roof that can elevate the temperature of the covered sheet; as well as areas under or over elevated temperature operations.
If situations exist that may commonly elevate temperatures over 160 degrees or increase solar loads beyond "normal" incoming solar load, question the manufacturer as to the suitability of their product for the situation; consider changing the product to a material that will clearly withstand the loading; consider changes in design to forestall the loading.
If you have existing TPO roofing subjected to these situations you may well want to inspect the applications for incipient, developing or obvious local problems. The manufacturer can then be approached for direction in addressing or rectifying any deficiency.
Please inform the committee of any problem found as well as any reaction from the manufacturer involved.
For flat roofs its better to stick with time tested and proven PVC "IB,Sarnafil,Fibertight,etc" or EPDM "Carlisle,Firestone,Versico,etc.." or the ultimate flat roof a 4ply Koppers "coal tar pitch" BUR. When I was a union roofer back in the day we would get another dollar per hour to install that system."don't ask why" :)
Great post, thanks Jim.
We've had mediocre luck with EPDM, workmanship on seams mostly. Exacerbated by the changeover from 'high test' VOC-laden glue to low-VOC versions that take even longer to dry. So the TPO heat welding seemed like it would address that issue. Sorry to hear it's having other issues.
I guess it's true, until a product is widely used for ten years it's experimental...
They like it because its cheap. PVC membranes "like Sarnafil,Fibertight,IB etc." are an exellent choice and a long lasting roof but are more money. EPDM rubber "like Carlisle,Firestone etc" are also a long lasting roof and price out very affordable . TPO reminds me of the old hypalon membranes "remember JP Stevens". Time will tell.