TPO (thermoplastic polyolefin) is the newest technology in heat-reflective and energy efficient single-ply roof membranes. This product combines the EPDM rubber durability and the performance characteristics of hot air weldable seams. The system is constructed from ethylene propylene rubber and performs extremely well in tests for combating deterioration due to ozone and UV exposure, as well as impeding algae growth. Chemicals and liquids have virtually no effect on the performance of the material.
The TPO material is eco-friendly (it is free of chlorine and plasticizers) and is safe to install.The membrane is highly reflective which helps reduce energy requirements to keep the building cool. This smaller energy footprint lessens Urban Heat Island (UHI) effects and contributes to a cooler and cleaner environment.
When properly installed, the welded seams result in a membrane system that compares favorably with monolithic (seamless) roofing systems.This is due to the extremely strong seam strengths, reported at three to four times those of EPDM tape and adhesive seams. It is very lightweight but its strength makes it highly resistant to wind uplift. Most manufacturers’ TPO products also meet Underwriters Laboratories (UL) 790 requirements for external fire, as well as Class A and UL P assemblies for internal hourly fire-ratings.
TPO manufacturing standards make it extremely durable and the material withstands impacts, and resists punctures and tears. The material is flexible so it readily conforms to building movement and surface irregularities. Standard TPO contains no plasticizers or chlorine so it retains its flexibility and will not become brittle over time. Both 60mm (.060″) and 45mm (.045″) thickness is available and color choices include black, white and light gray. Widths vary with individual manufacturers, but are typically 6 to 6 1/2 feet and come in 100 foot lengths. These wider sheets mean fewer seams and less labor compared to standard PVC sheets.
TPO membrane can be installed in a number of ways. In a fully-adhered installation the material is glued to the underlying substrate using material specific adhesive. The glue chemically bonds to the membrane to lock it to the underlayment material. In a ballasted system, the membrane is laid over the roof structure with no adhesive or fasteners. It is then sealed at the perimeter and at all penetration points and then covered with ballast to keep it in place. Smooth stones, two to three inches in diameter are often used. An alternative ballast that is also regularly used are concrete pavers which typically average 20 pounds per square foot.In a mechanically-attached system, specially designed and manufactured fasteners are used to secure the membrane to the roof substrates. The type of fastener varies on the substrate material, but generally screw-type hardware is employed.
TPO is suitable for use in new, re-roofing and re-covering construction. A TPO roof has a service life of 10 to 20 years, depending on installation conditions and preparation. For the best performance, full removal of the existing roof is recommended. Other factors such as roof slope (steeper slopes facilitate quicker water run-off), climate conditions (hail, high winds, extreme heat and cold can deteriorate material more quickly), and proper installation procedure also affect longevity.
With proper preparation and installation, a TPO roof system will provide years of service with a minimum of maintenance and worry.