Roofing Strategies for Energy Efficiency

April 5, 2021

Somebody mentions energy efficiency and all eyes are on the heating, ventilation, and air-conditioning system. But what about the building envelope – specifically, your roof? It is a contributing factor to how big your energy bills are. Let’s explore some of the strategies you can implement to make a commercial flat roof more energy efficient.

Install a Climate-Appropriate Roof Membrane

When it’s time to reroof, identify the ideal solar reflectance and thermal emittance for the climate in your geographic location. The weather where your facility is located will help determine if heat absorption or reflection is most advantageous.

Cool roof membranes, according to the Cool Roof Rating Council (CRRC), reflect and emit the sun’s heat back into the sky, instead of transferring it into the building. This means air-conditioning units run less, utility bills are smaller, and power plant emissions are decreased. According to the CRRC, you can expect savings in the range of 10 to 30 percent for cooling energy and extended service life of air-conditioning equipment. Some areas (mostly those in the south with warm weather) have mandated these types of membrane roofs.

If your existing roof is in good condition, consider applying a reflective roof coating. The U.S. Department of Energy explains how they work: “Cool roof coatings are white or special reflective pigments that reflect sunlight.” Not only can these coatings offer you greater reflectivity, but they can also extend roof life.

Because cool roofs in northern climates can cause an increase in heating demand during the winter, its important to work with a professional to evaluate whether a reflective roof is right for your facility.

Size Your Insulation Right

Insulation is the most widely understood energy-efficient roofing strategy. When right-sized, it limits the escape of conditioned indoor air and prevents outside air from penetrating. The HVAC system doesn’t have to work harder to compensate, lowering energy usage.

A roofing professional can help you determine the appropriate amount of insulation to install. They will look at long-term thermal resistance values, initial R-value, the International Energy Conservation Code (IECC 2012), as well as other application building codes/requirements of Authorities Having Jurisdiction (AHJ). The NRCA’s EnergyWise Roofing Calculator can help you evaluate virtual roof assemblies for thermal efficiency and estimate the heating and cooling cost reductions resulting from each option.

Install for Maximum Efficiency

It’s not enough to specify energy-efficient roofing materials; how they are installed is equally important. While some contractors reach an R-value of 20 by specifying a single layer of 3-inch isocyanurate, two layers of staggered 1.5-inch isocyanurate eliminates the thermal short.

Reduce thermal discontinuities during installation by reducing gaps and voids. Your roofing contractor can eliminate thermal bridging with these additional strategies:
• A ballasted system.
• A mechanically fastened bottom layer and fully adhered remaining layers.
• Non-thermal bridging fasteners.
• Spray polyurethane foam.

Perform Routine Roof Maintenance

When the installation is complete, keep people off the roof (especially if cover board was not installed) and fix leaks promptly. The thermal efficiency of wet and compressed insulation is severely diminished. Proactive roof maintenance retains the efficiency of insulation by keeping it dry, which results in lower utility bills and reduced energy consumption.

Restrict Air Movement

An air barrier can be installed to impede or restrict the passage of air through a roof assembly. If used, it needs to be part of a complete building envelope evaluation. According to Single-Ply Roofing Industry (SPRI), “Air barrier requirements can be found in the 2012 and 2015 editions of IECC, and in the 2011 and 2015 editions of the National Energy Code of Canada for Buildings (NECB).” Building design professionals can help you evaluate the need for and implementation of an air barrier.

Consider Recovering the Roof

Installing a new roof system over the existing one can be energy efficient. If the old roof assembly is dry, it probably still has some R-value you can benefit from. Additionally, less new insulation needs to be installed, resulting in project savings.

Contact D. C. Taylor Co. today at 319.731.4118 to discuss the most practical approaches to energy-efficient roofing at your facility.

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