By Mark Gregory, General Manager at RSS Roofing Services & Solutions
Architects, specifiers and roofing contractors play an important role when working with a building owner to design a commercial structure that protects the building’s occupants from the outside environment. A building’s roofing system is an essential part of the building design phase, and planning the roof construction from the beginning can be extremely complicated. Producing the best design possible at an affordable price is of the utmost importance for everyone involved.
To select, detail and specify the most appropriate roof system for a project, it is recommended that the commercial roofing contractors have past experience with several of the available material options, an understanding of roof assembly materials and system options, and an understating of roof design considerations. Utilizing a collaborative approach from the first phase of the design process is imperative in order to identify all of the criteria and required performance characteristics early. The design phase should involve clear communication of the designer’s overall concept with specifications and drawings the can then be executed by a professional roofing contractor.
Components to Consider
When selecting a roofing system, there are many different options available including thermoplastic, EPDM, metal, green roofs and more. While each of these roofing systems has its own advantages and disadvantages, it’s vital that the choice of roofing system fits the building’s usage, climate or location, energy and environmental performance and warranty.
A primary consideration during the design phase is the intended use of the building. The building’s occupancy, insulation needs and maintenance schedule will need to be fleshed out. For example, a warehouse would require a different roof system compared to an educational institution or hospital. Also, the aesthetics would be more important for a school or healthcare facility and the design of the roofing system may need to include certain textures and colors for brand identify or curb appeal.
The aspects of the climate that most affect the design of the roof system are the amount and type of precipitation, temperature and wind. A building in a dry climate does not need the same type of roof as a building subjected to daily rains. High rain climates should also factor in the annual amount of snow accumulation. Snow can drift and collect in corners, topping flashings and leak in the facility. Hail can puncture a roof system therefore a roof that can withstand the harsh elements is needed.
If the geographical location of the building experiences large temperature spreads between summer and winter, a roof system that will expand and contract with thermal movement is a good choice. Climate will affect the amount of insulation needed in the roof. Predominately hot areas should consider a reflective roof system to save on cooling bills. Savings in cold climates depends on several factors including cost of heating energy compared with cooling, the slope of the roof, insulation and size of the building.
In areas that are prone to high winds, identifying wind uplift requirements is important. Any location with the wind gusts higher than gale force should take wind speeds into consideration. Even a 40-mile-per-hour wind can cause a poorly attached roof to detach from the building.
Today’s construction climate places a heavy emphasis on energy efficiency. A building’s roof was once just thought to be a way to keep the inside of a building dry, but the impact of a roof can have on energy consumption is understood now more than ever. The roof system is one of the largest surfaces of the building envelope; therefore it has a significant impact on the energy-efficient operations of the building.
Every roofing system has a pre-determined rate of reflectivity and emissivity. These characteristics help determine whether the membrane will reflect or absorb solar energy. The greater the reflectivity, the less energy is absorbed, which helps cut the transfer of radiant energy. The lower rate of reflectivity, the greater the rate of energy absorption and the transfer of radiant energy.
Factors such as roof membrane color, increased insulation thickness as well as different insulation types should be considered. After developing multiple scenarios, a well-thought decision can be made to which option makes the most sense and produces the best return on investment.
There are many programs that offer the ability to develop different options for improving the energy efficiency of the roof system. Collaborating with a professional commercial roofing contractor is ideal as they have in-depth knowledge that can provide feedback for architects, specifiers and building owners regarding how the choice of the roofing system affects energy performance.
Roofing system warranties can sometimes be confusing. Many times, manufacturers don’t have a published warranty and in some situations, the manufacturer or roofing product has been on the market less than 10 years, with warranties ranging from 10-20 years. Features that you want to consider for a commercial warranty are exclusions for consequential damages, additional cost for the warranty, exclusions for ponding water, whether it is a “repair or replace” warranty and whether the warranty is transferable.
A roof system is arguably the most vulnerable part of a building’s exterior. Ultraviolet radiation, wind, rain, hail, snow and sleet all affect a roof system’s performance. Performance is based on good design, quality materials, proper installation and a preventative maintenance program. There are an abundance of roofing systems, but below are the most common systems for commercial buildings.
Thermoplastic polyolefin (TPO) is a single-ply reflective roofing membrane made from polyprophylene and ethylene-propylene rubber polymerized together. TPO is typically installed in a fully adhered or mechanically attached roofing system, allowing the white membrane to remain exposed throughout the life of the roof. TPO’s are highly utilized in colder regions. TPO membranes reflect UV radiation keeping the surface of the roof and the building cool during summer months.
Ultraply TPO is available in three different thicknesses, 0.045”, 0.060”, and 0.080.” TPOs can be installed on low and high slope surfaces and can be heated and reshaped. TPO membranes are available in rolls ranging from 5’ x 100’ to 12.4’ x 200’ and the seams are welded for long-lasting performance at 926°C with a hot-air gun.
Ethylene Propylene Diene Terpolymer
Ethylene Propylene Diene Terpolymer (EPDM) is a single-ply rubber roofing membrane that is resistant to a high degree of ozone, ultraviolet, weathering and abrasion damage. Because of its tolerance to a wide array of weather conditions including wind and hail, EPDM is one of the most sustainable and environmentally friendly materials currently used in the industry.
EPDM is available in both white and black, and is a sold in broad variety of widths ranging from 7.5 feet to fifty feet, and in two thicknesses, 45 and 60 mils. It can be installed fully adhered, mechanically attached or ballasted, with the seams of the roofing system sealed with liquid adhesives or specially formulated tape.
Modified bitumen is an asphalt-based roofing system reinforced with either polymer or fiberglass. Modified bitumen systems are a blend of traditional and modern roofing technologies. This system is excellent for roofs that are susceptible to foot traffic, punctures and tears.
Two different polymers, Atactic Polypropylene polymer (APP) and Styrene-Butadiene-Styrene (SBS), are used to modify the elasticity and temperature flexibility of the membrane. In a heat application process, the seams are heated to melt the asphalt together and create a seal. For a hot-mopped application, the process is similar to how conventional built-up roofs are installed. Cold-applied adhesive membranes are one of the most common options.
Built-up roof (BUR) systems consist of multiple piles of felts, fabrics or mats that are laminated together with bitumen, asphalt or coal tar pitch. The application incorporates alternating layers of piles and bitumen and is finished with gravel application, mineral cap sheet or weather-resistant coating. BUR is designed to meet a broad range of waterproofing applications and is highly resistant to punctures and weathering.
Metal roofs are systems in which standing seams, R-panels or corrugated metal panels are mechanically fastened to existing structure points. Metal roofs provide architects, building designers and owners with a variety of choices ranging from the type of metal to dozens of color options. Because of its excellent strength, durability and fire resistance, metal roofs are the rising star of the energy-efficient and sustainable building movement. This roof system has a longer lifespan, but can be a costly upfront investment.
Cool and Green Roofs
Cool roofs use a highly reflective surface to emit the radiant heat back instead of transferring the heat into the building below. Cool roofs are beneficial to a building and its occupants by reducing energy bills decreasing air conditioning needs and decreasing roof temperatures that can help extend the service life of the roof. Also, cool roofs offer benefits beyond the building itself as it can reduce the local air temperatures, lower peak electricity demand and reduce power plant emissions.
Green roofs or “living roofs” contain an abundance of plant life absorbing rainwater, providing insulation and helping lower urban air temperatures. Green roofs provide insulation, lower the need for heating and cooling, and can reduce the urban heat island effect. This roof type can be more expensive to implement compared to others.
Coated roof systems are a cost-effective solution for extending the life of an existing roof system. Coatings provide a highly reflective surface that may lower roof surface temperature, decrease indoor cooling costs, and ultimately, reduce overall expenditures. By forming to irregular roof surfaces, coatings seal cracks and splits in the roof surface. Once applied, coatings form a seamless, watertight seal over the entire roof.
A collaborative approach including the architects, specifiers, commercial roofing contractor and building owner to design and install a roofing system is essential to prevent critical mistakes from occurring. The right roofing system will protect the investment for decades, while the wrong roofing system could result in costly repairs, damage to the building and its contents and possibly an early tear-off or re-roof. The protection of the investment doesn’t end with the right roofing system, but relies heavily on the roof maintenance program.
Installing a formal, in-house roof maintenance program is the first step in preventative or proactive maintenance, extending the service life of the roofing system. Not all roof maintenance needs to be performed by commercial roofing professionals, but can be done by the building’s maintenance personnel. The building’s personnel can help with basic maintenance items, such as keeping the roof free of debris as it can block the flow of water to the roof drains and cause ponding. Extreme cases of ponding can cause a roof collapse.
Roof inspections should be performed regularly by trained commercial roofing professionals. Early problem detection makes repairs manageable before they become serious. Inspections and maintenance should also be made after extreme weather events such as tornadoes and hurricanes.
The roof is one of the most important parts of a commercial building. A poorly designed or installed roofing system affects the rest of the structure. Fostering a collaborative working relationship with commercial roofing contractors and designers with consideration for both parties input and expertise will improve the state of commercial roofing design. An extremely knowledgeable commercial roofing contractor will be able to provide specific roofing systems, allowing the design team to select the proper roof system for the buildings usage and climate.
About the Author
Mark Gregory is the general manager of RSS Roofing Services & Solutions in Florida. RSS, headquartered in St. Louis, Mo. and with multiple locations in the Central and Southeastern region of the United States, is a leader in commercial, industrial and institutional roofing services. The company has multiple locations including Florida; St. Louis, MO; Evansville, IN; Nashville, TN; Columbia, MO and a special projects division. RSS is a subsidiary of MHS Legacy Group, a diversified national holding corporation also based in St. Louis with roots back to 1895. For more information, please email Mark at firstname.lastname@example.org or visit www.roofingsands.com.
This was originally published in Construction Specifier magazine’s January issue.