Just like automobiles, airplanes, and computers, roofing materials have improved markedly over time. Today’s products are more durable, weigh less and offer improved aesthetics compared to what roofers installed in the late 1800s and early 1900s. Thatching, for instance, which stayed popular in the 18th and 19th centuries among America’s earliest settlers, is no longer a viable roofing alternative. Today’s roofers, however, are faced with a challenging task. Build- ing owners, and government officials, are pressing for more energy- efficient materials and designs. America’s increased emphasis on improved energy efficiency in building products started out, oddly enough, in one of the nation’s most favorable temperate climates. In 2015, Hawaii – where the average temperature on the islands ranges between 78-85 year-round – Governor David Ige signed four energy bills, including one that directed the utilities to generate 100 percent of their electricity sales from renewable energy resources by 2045. Within a few years of that legislation, the race toward the “Green New Deal” began in earnest. Last year, New York joined the green energy arms race by calling for dramatic changes over the next 30 years. It calls for the state’s electricity to come from renewable, carbon-free resources, such as solar, wind and hydropower. Roofing materials are, and will continue to be, among the most scrutinized build- ing materials that architects weigh toward helping Energy Efficient Roofing: The Race is On Systems Require Integration to Meet Demands Of Government Officials Hungry for Green and Clean By Thomas Renner
sues, insurance requirements, foot traffic, and a wide assortment of variables to design the most environmentally efficient roof. “It’s not a product question, really, it’s a system question,” said James Kirby, a Building and Roofing Science Architect for GAF. Energy-efficient roofs are going to be a focus of the industry in the years ahead. There are a lot of details to consider and solving that equa- tion can be incredibly complex. Energy-Efficient Roofs An energy-efficient roof is environmentally-friendly, reduces energy costs and consumption, and includes materials that provide a higher R-value rating. A cool roof, for instance, can help save up to 15 percent annual air- conditioning energy use, and can help mitigate the urban heat island effect. A cool roof delivers higher solar reflectance and higher thermal emittance than standard roofing projects. When first introduced, cool roofs were mostly white or other light shades. Now, manufacturers have developed cool roof products in dark colors, even black. They also can enhance roof durability. Energy-efficient materials, such as air barriers and vapor retarders, can also reduce costs. Air barriers are systems of materials designed and constructed to control airflow between a conditioned space and an unconditioned space. The air barrier system is the primary air en- closure boundary that separates indoor (conditioned) air and outdoor (unconditioned) air. Vapor retarders are made from one of a variety of materials that are designed to impede the moisture flow through the wall assembly and protect the building envelope from condensation damage. Vapor bar- riers can also act as an interior barrier, minimizing the flow of air into insulated cavities during cold weather. Both products are frequently used in construction in the United States because of the wide temperature ranges in different sections of the nation and the overwhelming reliance on air conditioning. Americans spend about $40 billion annually to air condition buildings, and is used by 87 percent of homes in the United States. Air conditioning costs account for 12 percent of total household energy costs, and 17 percent of electricity expenditures. In some regions, however, air conditioning makes up 27 percent of home energy expenditures. The EnergyStar. gov website can help identify products and provides a roof calculator to help estimate energy savings by converting to different materials. Additionally, building owners can improve energy efficiency by select- ing materials with higher R-values. That R-value is a material’s ability to resist the movement of heat through it. The higher the R-value, the more insulation the materials provide by limiting heat flow between the outside of the building. “We are seeing a trend toward increased R-value requirements,” said Glen Clapper, AIA, Director of Technical Services for the National Roofing Contractors Association. “That generally means thicker in-
achieve the energy efficiency govern- ment leaders crave. Architects today de- sign commercial and residential buildings with improved insu- lation compared to predecessors. There is more, however, to installing energy- efficient roofs than just improving insu- lation. Some types of insulation are not compatible with certain roof types. Managers also need to consider code is-
More roofing products are becoming energy efficient, including a thermally broken roof hatch manufactured by BILCO. The roof hatch (shown is the Type S model) has an R-value of 20.3 in the cover and curb, and meets code requirements and standards currently in line with today’s commercial roofing systems. Photo: The BILCO Company
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november 2020
csengineermag.com
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