What Are TPO And Modified Bitumen Roofs?
TPO roofing is a single-ply roofing membrane that has gained significant popularity in recent years. There are 3 distinct layers of a TPO roofing system that include: a TPO polymer base, a polyester-reinforced scrim, and a TPO compounded top ply. TPO stands for Thermoplastic Polyolefin, which is a blend of polypropylene and ethylene-propylene rubber. Although TPO roofs were introduced about 30 years ago, the chemical formula has continued to evolve, making it one of the fastest-growing commercial roofing systems on the market.
On the other hand, Modified Bitumen roofing, also known as Mod-bit or Torch Down roofing, is a hybrid material that combines asphalt membranes with polymerized rubber or plastic. This roofing system is reinforced with fiberglass, creating a sturdy yet flexible roofing material. Mod Bit roofing typically comprises two or more layers, providing enhanced durability. Introduced in the 1960s as an improvement over traditional built-up roofing systems, Modified Bitumen roofs have been a go-to solution for commercial properties with flat or low-slope roofs.
By the end of this comparison, you’ll likely choose either TPO or Mod Bit for your roofing system. Regardless of which option you pick, be sure to request a quote from Best Roofing LA – we are the go-to choice for locals who are looking for Los Angeles Roof Installation.
TPO Roofing Vs. Modified Bitumen Roofing
The primary difference between TPO roofing and Modified Bitumen roofing lies in their composition and history.
TPO roofs, which belong to the family of single-ply roofing systems, are thermoplastic membranes that entered the market in the 1990s. These relatively newer roofing systems continue to evolve, with U.S. manufacturers constantly modifying their formulations to enhance performance.
In contrast, Modified Bitumen (Mod-bit) roofs are a type of built-up roofing that combines asphalt with performance-enhancing modifiers. Mod-bit roofing has a longer track record, having been the preferred choice for commercial flat roofing since the 1970s.
1. Lifespan
The lifespan of a roof is a crucial consideration for any building owner. TPO roofs typically last between 15 and 20 years, with proper maintenance potentially extending their life up to 30 years. In comparison, a well-installed Modified Bitumen roof can last up to 20 years, and with timely maintenance, it can easily reach 25 years. While the difference in lifespan isn’t significant, TPO roofs might have a slight edge in longevity with optimal care.
2. Cost
When it comes to cost, both TPO and Mod-bit roofing systems are relatively affordable options for flat or low-slope roofs. TPO roofing costs range from $3.5 to $10 per square foot installed, depending on factors such as roof size, membrane system, and insulation thickness. The TPO membrane itself typically costs between $1.00 to $2.50 per square foot. Modified Bitumen roofing, on the other hand, generally costs $4–$8 per square foot. While Mod-bit roofs might have a slightly lower upfront cost, TPO roofs often have a lower total cost over the roof’s life due to differences in labor, maintenance, and installation costs.
3. Installation Method
The installation methods for TPO and Modified Bitumen roofs differ significantly. TPO membranes can be installed using mechanical fasteners, bonding adhesives, or a ballasting system. The installation process involves adding one roll at a time, with heat welding at the seams to create a watertight seal. Modified Bitumen roofing is typically applied directly to the substrate using an adhesive. The installation process may involve heat welding, cold adhesion, or in some cases, self-adhesion. Some Mod-bit membranes can also be mechanically attached.
4. Energy Efficiency
In terms of energy efficiency, TPO roofs have a clear advantage. TPO membranes feature a white, reflective surface that reduces heat absorption and cooling costs during warm weather. This characteristic makes TPO roofing systems more energy-efficient than Modified Bitumen roofs. While Mod-bit roofing systems are also effective at blocking the sun’s harmful rays and reflecting heat, they generally don’t match the energy efficiency of TPO roofs. The distinctive light color and UV-resistant, reflective surface of TPO allow it to reflect sunlight and heat more effectively, potentially leading to significant energy savings in cooling costs.
5. VOC-Free Installation
Both TPO and Modified Bitumen roofing systems have made strides in offering VOC-free installation options. TPO roofing can be adhered to without the use of additional VOC-containing adhesives, making it an environmentally friendly choice. Similarly, the latest innovation in Mod-bit installation includes self-adhering sheets, which eliminate the risks associated with torches and hot asphalt while being completely free of VOC fumes during and after application.
6. Maintenance Requirements
When it comes to maintenance, both TPO and Modified Bitumen roofs require regular care to ensure optimal performance and longevity. TPO roofs need a regular maintenance schedule, including routine washing and debris removal. While Mod-bit roofs are generally considered low maintenance, they still require regular inspections, cleanings, and repairs when damaged.
7. Puncture Resistance
In terms of puncture resistance, Modified Bitumen roofing has an advantage over TPO membranes. The multiple layers typically found in Mod-bit roofing systems make them less likely to be punctured compared to single-ply TPO membranes.
8. Chemical Resistance
TPO roofing systems generally offer superior resistance to a wider range of chemicals compared to Modified Bitumen roofs. While Mod-bit roofing provides good resistance to water and some chemicals, it may not perform as well as TPO against certain solvents or oils. However, Modified Bitumen roofs are more flexible and can handle thermal expansion better, which can help prevent damage from chemical exposure.
9. Fire Resistance
Both TPO and Modified Bitumen roofing systems have achieved Class A fire ratings based on ASTM testing. However, Mod-bit roofs often show superior performance in flame spread tests, giving them a slight edge in this category.
10. UV Rays And Heat Resistance
TPO roofing membranes excel in UV resistance due to their reflective properties. Many TPO roofs are designed to reflect sunlight, which helps reduce heat absorption and keeps the building cooler. They can also withstand high temperatures, making them suitable for warmer climates. Modified Bitumen roofs also offer good UV resistance, especially when coated with reflective granules. However, they can absorb more heat compared to TPO, depending on the color and granule type used. While durable, Mod-bit roofs can be more prone to softening in extreme heat compared to TPO roofing systems.
11. Cold Resistance
TPO roofing material can expand and contract without cracking, making it ideal for varying weather conditions. TPO roofs can withstand impact from temperatures as low as -50°F. Modified Bitumen roofs can also perform effectively in cold weather, but their success largely depends on the specific product and formulation. For areas with harsh winters, TPO might be the preferable option over Mod-bit roofing.
12. Wind Resistance
When it comes to wind resistance, TPO roofs have a slight advantage. TPO roofing systems can resist winds from Category 3 hurricanes with speeds between 110 mph to 130 mph. In comparison, Modified Bitumen roofs can typically withstand wind speeds between 90 mph and 110 mph.
13. Hail Resistance
Both TPO and Modified Bitumen roofing systems offer good hail resistance. TPO roofing membranes can resist damage from hailstones up to 1.75 inches in diameter. Mod-bit roofing systems, due to their durability and flexibility, can handle hailstones up to 1.5 inches in diameter (about the size of a golf ball) without significant damage.
14. Material’s Strength
When comparing the strength of the materials, both TPO and Modified Bitumen roofing systems have their strengths. TPO roofing has a slightly lower tear strength (55 lbf) compared to Mod-bit roofing (60 lbf). However, TPO outperforms in break strength (427 lbf vs. at least 400 lbf for Mod-bit) and tensile strength (2973 lbf vs. 1000 lbf for Mod-bit). TPO also has a higher compressive strength (7977 lbf) compared to Modified Bitumen roofing (6295 lbf).
TPO Or Modified Bitumen Roof? Which Roofing System Is Better?
In conclusion, both TPO and Modified Bitumen roofing systems have their unique strengths and potential drawbacks. The choice between a TPO roof and a Mod-bit roof ultimately depends on your specific needs, budget, and local climate conditions.
TPO roofing systems excel in energy efficiency, chemical resistance, and overall strength, making them an excellent choice for buildings in warmer climates or those prioritizing energy savings.
On the other hand, Modified Bitumen roofs offer superior puncture resistance and potentially lower upfront costs, making them a solid choice for buildings in areas with moderate climates or those requiring enhanced durability.
