TPO vs. Modified bitumen is a common debate for many commercial building owners.
Generally speaking, two kinds of commercial flat roofing systems are most commonly found in the Northeast. These are modified bitumen and thermoplastic polyolefin or TPO. The former has been around since the 1970s and is one of the more traditional methods of flat commercial roofing.
TPO has been around since the 1990s, and both do well in extreme temperatures, both extremely hot and bitterly cold. And given the locale (the Northeast), this is a perfect set of traits to have to stand up to the huge swings in temperature.
However, TPO commercial roofing is surging in popularity. You might not have realized that TPO roofs are installed more than all other flat roof alternatives combined, including a PVC flat roof.
The following post will examine both kinds of roof systems in depth. It will include the cost, expected life and longevity, and overall value of each roofing system so that you can make the most informed decision possible.
Key Takeaway
TPO is clearly better than modified bitumen because of its energy efficiency, longevity, reliability, customization, and versatility. As a result, TPO roofs are also more expensive.
Modified Bitumen Flat Roofs
One of the primary benefits of using a modified bitumen roof is that it comes at a lower installation cost. However, one of the biggest disadvantages is that many major commercial roofing contractors have stopped installing them, mostly due to the surge in popularity of TPO roofs. Some have gone as far as to start installing TPO over modified bitumen.
As stated previously, modified bitumen began in the 1970s and became a major upgrade over traditional asphalt roofs of the time. It is termed “modified” because of the addition of substances like styrene butadiene styrene (SBS) or atactic polypropylene (APP), which were intended to enhance both flexibility and longevity of the roof, especially compared to those old asphalt roofs.
Over the years, several issues have arisen with modified bitumen roofs.
Lack of APP Modifier
The first is that, although an APP-modified bitumen roof is designed to resist things like UV-light damage, cracking, blistering, and oxidation, there has been a lack of standards in the industry which has led to manufacturers skimping on the addition of that APP as a modifier.
What is the downside of that, exactly? This omission causes the roof to underperform, leading to costly repairs. In the worst case, it could mean that your commercial roof needs replacing, adding another costly endeavor to your plate.
Drainage Issues
The second issue with modified bitumen flat roofs is that, although the gravel spread over a modified bitumen roof is intended to offer hazard and UV protection, that granular surface makes it more difficult to correct drainage issues and detect leaks.
Those drainage issues and leaks can persist far longer than they might with a TPO roof, which means that there can be a buildup of water that can damage the roof’s structure. When something like this happens, it can create structural integrity issues that can lead to even more costly repairs to your commercial business than you had ever expected.
Fire Hazard
The third issue with modified bitumen flat roofs is that using an open flame torch during installation can be a fire hazard. Mishandled torch use has caused more than a few instances of building burning. The risk here is definitely substantial, and it can be substantial enough that some insurers will not even cover roofers who apply modified bitumen using the open torch method.
Open torch installations of modified bitumen are becoming rarer. That said, the cost of a modified bitumen roof remains appealing to some.
Thermoplastic Polyolefin (TPO) Flat Roofs
TPO is also known as flexible thermoplastic polyolefin (FTPO) roofing. Generally speaking, three different kinds of commercial roof installations involve TPO: ballasted, fully adhered, and mechanically fastened.
TPO is considered one of the best values in commercial roofing because it offers a variety of key advantages. Value and longevity are two of the most critical aspects of a commercial roof.
Eco-Friendly
The tear-resistant single-ply membrane is tough and resists oil, grease, and chemical spills. Not only that, but TPO roof systems are also fully recyclable and UV-resistant. Best of all, TPO single-ply roofing is often considered a “green” option because no plasticizers are included in the formulation process.
Color Variety
One of the cool aspects of the rise of TPO roofs in commercial roofing installations is that many building owners and managers now have the option of selecting from over a dozen colors, including white, which has proven to be energy-saving.
The great thing about this is that now you can match your new roof to the exterior color of your building. This might not seem like much, but matching that color scheme can make your building stand out to passersby.
Reduced Energy Costs
Some of those initial costs of installing an Energy Star-rated TPO roof can be recovered through lower energy costs over the life of that commercial roof. That makes it easier to take on the initial costs of installing the TPO roof to your commercial building.
No Tear-Off
Additionally, it is possible to apply TPO roofing systems over preexisting modified bitumen and metal roofs as long as the current roof is in sound condition and not substantially worn or damaged. Applying the new roofing system over the top of an existing roofing system eliminates additional tear-off costs and will reduce the overall disposal expenses. That is a win-win across the board.
Reheatable and Weldable
TPO is also reheatable and weldable, meaning that it is possible to re-weld any seams that require it years later. Smooth-surfaced TPO roof systems are easier to maintain and clean than granular-surfaced roofs, like modified bitumen. Cleaning and maintaining your roof properly means that the roof will hold up for longer, saving you from having to get a new roof for a long time to come.
Thickness Variance
The thickness of the standard TPO single-ply membranes can vary a bit. The “default” is around 45 mils but can be as big as 800 mils. If your roof is in an area where punctures are more likely – due to falling large branches or other sharp objects – you might want to look into a thicker membrane to ensure that your roof does not get punctured by any of those falling objects.
Installation Quality
As with any commercial roofing system, the installation here is key. Whenever a TPO roof fails, it is often the result of damage done during the installation process. If it doesn’t, it is because seams were not properly welded during the installation process.
These seam failures can lead to leaks or potential catastrophic failures when extreme winds occur, causing wind uplift. While these are certainly worst-case scenarios, they are things to be aware of when installing a TPO roof. When you hire a skilled, experienced roofing contractor to handle the installation process, you generally don’t have to worry about these worst-case TPO scenarios.
The premier TPO manufacturers consistently produce high-quality, longer-lasting TPO membranes that you can be confident in and that will last longer than ever before.
Proper TPO installation methods from a certified commercial roofing contractor will ensure that the TPO roof is installed properly and likely won’t fail.
Final Call: Modified Bitumen vs. TPO (TPO is King)
Despite being cheaper, there are just too many downsides to using a modified bitumen roof to make it a viable option anymore. TPO is more energy-efficient, more reliable, and more versatile than its counterparts in the roofing industry.
Combined with the ability to customize the color of your roofing surface, there is just no matching TPO as a commercial roofing option. They also last longer than bitumen flat roofs, meaning you save on the costs of a potential installation that would occur sooner rather than later with a bitumen roofing system.
When you run a commercial business, there are a million things you must keep in mind and worry about; your commercial roof should be at the bottom of that list. When installing a TPO flat roof on your building, you properly protect it from even the most extreme elements for a long time.
When your heating and cooling bills are far less than ever, you can save a ton on installation costs over the years. You can have confidence in your commercial roof’s ability to stand the test of time and handle the elements easily, allowing you to focus on the most important aspects of your business, like generating revenue to keep that business going.
TPO is the reigning king of roofing materials and will likely continue to hold that spot for a long time.
