When it comes to commercial low-slope roof systems, the range of available materials can make selecting the ideal solution challenging. You may be familiar with EPDM, TPO, PVC and KEE as popular membrane options, but not all roof membranes perform equally. Making an informed choice can significantly impact your building’s long-term operational security.

A roof serves as the first line of defense against the elements, protecting critical infrastructure in warehouses, universities, hospitals, data centers and manufacturing plants. When a roof fails, the resulting downtime can be extremely costly, reinforcing the importance of this investment. For example, the estimated cost of downtime for data centers—an industry experiencing rapid growth in the United States—can cost an estimated $9,000 per minute, totaling more than $12 million per day.

Understanding the types of roof systems available in today’s market will help you make the best choice for your facility. In this article, we’ll explore the construction of roof systems, compare the performance of different membranes, and highlight how high-performance systems differentiate themselves through innovative design, ensuring long-term protection for your operations. 

Commercial Roof Construction: A Quick Primer

To start, it’s helpful to understand the different components and how they come together to make up a complete low-slope commercial roof system.

The exact system makeup can vary from building to building, depending on the needs of the facility, but a typical system may consist of: 

1. Substrate Board: Installed over the roof deck, it provides an initial thermal barrier that contributes to the roof’s fire performance.
2. Air/Vapor Retarder/Barrier Sheet: Either bituminous or non-bituminous, this layer restricts air and moisture infiltration into the roofing assembly.
3. Insulation Layer: Improves the building’s thermal performance and energy efficiency.
4. Cover Board: Adds durability, increasing resistance to foot traffic and environmental stressors.
5. Roof Membrane: The building’s first line of defense against the elements, protects not only what’s inside the building but also all of the materials beneath.

Although individual design specifications for a commercial roof may vary, these components all contribute to the performance of your roof system. Different materials can be selected in each category, but one of the most important factors is the performance provided by the membrane—which can make all the difference in your roof system’s resilience and longevity.  

Membrane Construction and Why It Matters

Several different material technologies are used to produce roof membranes. These include:

• PVC: Polyvinyl Chloride
• EPDM: Ethylene Propylene Diene Monomer 
• TPO: Thermoplastic Olefin 
• KEE: Ketone Ethylene Ester 

It is worth noting that KEE is not used as a standalone material. Instead, it is combined with PVC (more on this in the next section) to enhance the performance of that material.

Many roof membranes contain a fabric reinforcement layer, either knit or woven. On top of that, a coating layer is applied to form a certain thickness. The integrity of the reinforcement layer can vary greatly across available membranes, depending on the overall construction and number of yarns included within the design. This can provide numerous benefits through overall membrane performance, avoiding unnecessary maintenance costs and leading to longer service lives.

It is important to weigh the integrity of the reinforcement fabric against the recommended thickness of the polymeric layer. Some suppliers may offer an open-weave reinforcement and will instead recommend a thicker polymer sheet that offers the promise of comparable durability. But in reality, thicker is not always better. A strong fabric layer that forms a monolithic system when combined with a high-performance polymer will provide enhanced performance at thickness levels as low as 36 millimeters. 

For example, an enhanced, tightly packed fabric reinforcement combined with a KEE -based coating for an overall thickness of just 36 mil demonstrates superior tensile strength and puncture resistance to 60-mil TPO or PVC systems that incorporate reinforcements produced with fewer yarns. Why? Because it is the reinforcement layer that provides the majority of a membrane’s integrity, to the degree that overall membrane thickness becomes less relevant. 

A Comparison of Polymeric Materials

When choosing a roofing system, consider how different membrane coating materials impact performance:

KEE-based membranes provide exceptional resistance to chemicals, with the ability to withstand exposure to animal fats, hydrocarbons, and other common industrial exhaust debris. For example, a roof system that is near an airport may benefit from a membrane that exhibits excellent resistance to jet fuel. 

KEE-based membranes may also demonstrate greater fire resistance than other common polymers. They typically maintain self-extinguishing properties and can help to further reduce flame spread and severity of a roof fire, contributing to overall operational security and safety.

It's also important to ensure your material choice meets rigorous testing standards. A high-quality KEE-based membrane should comply with the ASTM D6754 standard, which specifies that the flexible sheet be formulated from KEE as the primary polymer and be reinforced with fabric to ensure durability and performance. Building owners can be confident in a higher level of performance from a system that meets such requirements.

The Benefits of a High-Performance Roof System

Commercial roofs must be able to withstand more than just the elements. Regular foot traffic associated with common maintenance needs—commercial HVAC systems, solar panels, and other infrastructure upkeep—can stress the roof system’s membrane. A high-performance system provides greater resistance to punctures, chemicals, fire, and wear, reducing maintenance costs and extending the roof’s lifespan. Indeed, high-performance KEE-based systems have been shown to deliver up to 40 years of proven performance—more than double that of baseline systems composed of comparative materials.

For building owners and facility managers, roof membrane selection matters. By staying informed on material performance and construction quality, you can make the best choice for your facility, improving operational security and protecting your bottom line.