When selecting a quality, energy efficient solution for a commercial roofing system, there are generally two most widely used methods on most projects today. Whether to go for a Thermoplastic Polyolefin (TPO) roof system or an Ethylene Propylene Diene Monomer (EPDM) synthetic rubber roofing membrane, it can be difficult to distinguish between the two products, as both are single ply roofing membranes. They do have many similarities, but there are also some significant differences between the two types of roofing.
Unlike most residential roofing, construction plans for many commercial buildings and industrial complexes will typically include some form of low slope or flat roofing system. Commercial buildings generally cover a much larger area than residential roofs typically do.
In this discussion, I will guide you through the differences between these two popular commercial roofing systems. Reviewing the properties, cost, longevity, durability, maintenance, ease of installation, and energy efficiency of these roofing systems will help determine which best meets the demands of your upcoming project. First, let us look at each roofing system individually.
TPO Roofing Systems
TPO roofing systems involve a layer of a single-ply membrane composed of synthetic components along with a fabric reinforcing scrim that stabilizes and strengthens the membrane for improved and increased performance. It consists of different rubber types that are usually a combination of polypropylene and ethylene-propylene rubber. A TPO membrane is either mechanically fastened or affixed through an adhesive that bonds to the cover board.
Although EPDM roofing systems have been the industry leader for single-ply roofing more than half a century, TPO is rapidly gaining in popularity. There are many advantages offered by TPO which make it so popular for commercial roofing, starting with its energy efficiency. TPO roofing reflects sunlight, allowing commercial air conditioners to work more efficiently; whereas EPDM has a dark surface, which in summer conditions will absorb heat, forcing cooling systems to work overtime. TPO offers reduced cooling costs and energy savings for facilities located in warmer climates.
TPO also has a somewhat higher resistance to punctures than EPDM. It offers roughly three times more protection against punctures, which translate to leaks during rain events. When being installed, TPO roofing systems are always welded, making the system extremely durable, but can also complicate installation because welding requires an electrical source. For this same reason, any repairs which might become necessary for a TPO system are more difficult to implement because electricity will be required to do the repair work.
EPDM ROOFING SYSTEMS
EPDM roofing systems involve an extremely durable synthetic rubber roofing membrane. Its two primary ingredients, ethylene and propylene, are derived from oil and natural gas. Mechanically attached EPDM systems can be installed using large panels and attached through the membrane, or using narrow panels attached in the side laps. Non-reinforced or scrim reinforced membranes can also be used. The membrane is then attached using fasteners to the underlying steel deck.
If your commercial building project is in an area which typically receives a significant number of hailstorms, EPDM is the way to go. Its synthetic rubber surface will essentially bounce the hail off with little to no damage to the roof surface or system. TPO systems, on the other hand, which are made of thermoplastic, will produce concentric circles that remain in place and may compromise the membrane of the roofing system when struck by hailstones.
As mentioned above, when it is necessary to conduct repairs on an EPDM roofing system, it is somewhat easier for roofing specialists to implement them because no electrical source is needed for welding. Also, if your commercial building has solar panels installed or if you are thinking about having them installed, you would be better off choosing EPDM because it will not interfere with the absorption of sunlight. TPO systems reflect sunlight back off the surface and into the solar panels, which might cause them to fail during operation.
TPO vs. EPDM: a comparison
Left: TPO, Right: EPDM
Choosing one roofing system over the other may depend on your geographic location, as well as considering heat, hail, rain, snow, or other external factors, such as your intent to mount solar panels on the roof, as previously noted. Other important factors are cost, longevity, durability, maintenance, ease of installation and energy efficiency. Both systems can be mechanically fastened, which is advantageous in cold weather installations like we have here in the Midwest, but they can also be fully adhered systems, which is the best approach for the sake of durability and warranty usage.
EPDM roofs are the most economical choice for single ply roofing membranes. TPO roofing membranes are more expensive than EPDM. Regardless of which membrane you choose, it is better to spend more money and invest in a thicker membrane. Both EPDM and TPO roofs perform better and last longer if they are thicker.
By far the most important aspect that will determine the longevity of a single ply roofing membrane is the method by which the overlapping seams have been attached together. Permanently attached seams are the safest solution, and improper attachment can be the cause of 99% of leaks.
It is difficult to determine the longevity of TPO roofing membranes for a couple of reasons. First, this is a new roofing product and there are no TPO membranes in the U.S. today that are older than 15 years. Second, TPO membranes continue to be an experimental product. They are all in their 2nd, 3rd and in some cases 4th generation of formulations, so it is not possible to definitively say how long any of these will last. Also, some TPO products have been pulled off the market in the past for seam and material failures.
An EPDM roof has a solid reputation for durability. Made of rubber compound, EPDM roofs have been on the market for decades. Having properly tapered seams and detailed flashings, an EPDM roof will last up to 25 years. It is a dependable roofing material that offers resistance against ultraviolet light, ozone, oxidants, and severe weather conditions. An EPDM membrane will also perform better than TPO in colder climates.
TPO seam strength is three to four times that of EPDM adhesive and tape seams and manufactured to be as durable as EPDM. However, because of continuous changes and improvements to the formulation, different TPO membranes perform differently. TPO is known to respond poorly to ponding water, causing splits and cracks, and does not have strong resistance to high thermal and solar overload.
In the beginning of its service life, a properly installed EPDM membrane will not require much maintenance. However, unlike TPO, an EPDM’s seams are treated with an adhesive, making them ultimately vulnerable to coming apart. This means that in the long run, an EPDM roof will require maintenance to remain intact. EPDM also responds very poorly to any kind of solvents and oils. It is not advised for the use of any cleaners/conditioners that contain petroleum solvents, harsh abrasives, or citric based cleaners as these may cause irreparable damage to an EPDM membrane.
TPO membranes are not as easy to maintain as EPDM roofing membranes. It is problematic to weld new materials to a TPO membrane, because as compounds age, they lose their pliability and their subsequent thermoplastic capabilities. Consequently, to effectively heat weld new material to an old membrane, an activator may be required to seal repairs.
EASE OF INSTALLATION
An EPDM rubber roof is easier and faster to install than a TPO roofing membrane. EPDM requires no special equipment for installation while TPO needs to be hot air welded. This makes installing a TPO roofing membrane a more complex and costly process that also requires specialized knowledge. While a beginner roofing contractor will most likely be able to properly install an EPDM membrane, you should only hire an experienced contractor to install a TPO roof. Improper installation will invariably cause leaks and will require costly repairs or replacement.
TPO membranes have become an increasingly popular single ply roofing choice because they offer energy efficiency. White TPO membranes are a “cool” roofing technology, but other colors of TPO are also formulated to have sun reflective properties. With a TPO roof, it is possible to save money on cooling costs on commercial properties, especially in southern climates. By reflecting solar heat, a TPO roof can maintain a cooler thermal balance inside the space, reducing the need for additional air conditioning. Energy efficiency makes TPO roofs particularly popular in hot sunny regions where days requiring cooling are numerous.
While EPDM roofing membranes are also available in white and will offer better reflective properties than darker colored EPDM, an EPDM roof will not offer the same level of energy and financial savings as a TPO roof.
TPO VS. EPDM COMPARISON TABLE
There are many factors to consider when choosing a roofing system for a commercial building, including the geographic location, as well as considering heat, hail, rain, snow, and other external factors. Ultimately, the important factors to balance are cost, longevity, durability, maintenance, ease of installation and energy efficiency.
Nick Bentley started as a project manager with Shingobee Builders earlier this year. He has nearly 20 years of experience in various facets of the construction industry, with a background in commercial and industrial construction. He is located in Shingobee’s Waite Park office and is currently overseeing convenience store and retail projects.