What is a Thermoplastic Polyolefin (TPO) Roof
Thermoplastic Polyolefin (TPO) Single-Ply Roofing Membranes are one of the fastest growing in popularity roofing products available and are rapidly gaining wide-spread acceptance due to their many performance and installation advantages. High Performance and Energy Efficient Construction Techniques demand heat-reflective roofing systems that contribute to lower household energy consumption.
TPO Roofing systems provide this required reflectivity and energy efficiency, as well as provide outstanding resistance to ultraviolet radiation and ozone exposure and by using white TPO, the solar heat gain of a building is significantly reduced.
TPO is designed to provide the durability of rubber (EPDM), yet have greater flexibility and ease of installation by having hot air weldable seams. In fact, seam strength on a TPO roof is typically three to four times stronger than the seams that would be found on a traditional rubber roof. TPO can be welded in a very wide temperature range and this is extremely important because the roof is only going to be as good as the welds that are joining the sheets of TPO together.
Most of the welds on a TPO roof are done with a self-propelled hot air welder, as can be seen in our video, “TPO Roof Installation – Video One – Bluffside”. The hot air welder can weld up to sixteen feet per minute, however, a more optimal speed is approximately twelve feet per minute. The air temperature where the weld is occurring is approximately 1,000 degrees Fahrenheit. A hand-held hot air welder can be used in areas where the self-propelled welder is impractical or will not be able to operate.
TPO is very resistant to tears, punctures and impacts and has excellent flexibility, which allows it to move and “flex” with the building. The membrane is typically available in white, gray, tan or black and will usually have a thickness of 45 or 60 mils (.045” or .060”). The rolls that TPO comes in are usually six feet wide and one hundred feet long.
TPO membranes are installed by adhesion, mechanical attachment, or through ballasting. When using adhesion, the roofing membrane is glued to the roof deck, or insulation sheets, using a special glue that creates a chemical bond with the TPO membrane. If the membrane is being adhered to sheets of insulation, these sheets have already been mechanically attached to the roof decking below them, which can be seen in this video. This type of installation process is very resistant to wind driven events and the associated “uplift” forces.
A completed TPO roof installation can be seen on our video here, “TPO Roof Installation – Video Two – Bluffside”.
Ballasting is simply laying the TPO membrane on the roof, welding the seams, and then using a ballast to hold the membrane in place. Typically, two to three inch smooth river rock is used as a ballast, or in some instances, concrete roof pavers may be used. Obviously, when building for Performance and Energy Efficiency, it doesn’t make a lot of sense to put a highly reflective roof on a structure and then cover the roof with heat absorbing materials.
Mechanically-attached membranes are fastened to the roof deck with some type of screw-type fastener that is specifically designed to be used with a TPO roofing membrane. However, in most instances, it doesn’t make a lot of sense to install what can be described as a seamless roofing system on a structure and then put a bunch of screws in it.
Properly installed and maintained, a TPO roofing system should have a serviceable lifetime of ten to twenty years. The substrate that it is applied upon, the type of installation, the amount of slope on the roof, the environmental conditions and proper maintenance are all things that will impact the serviceable life of the roof. TPO roofs will not “last a lifetime” nor do they have “lifetime” warranties. As with any other roof, they need to be properly maintained and inspected on an annual basis.
Please remember that the most important factor that will contribute to the longevity (or lack thereof) of any type of roofing system, not just a TPO roofing system, is a proper installation by qualified individuals. Most roofing system failures are not product driven but are created as a result of applicator error.