Energy Efficient Roofing: The Race is On

Systems Require Integration to Meet Demands Of Government Officials Hungry for Green and Clean

By Thomas Renner

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. Building 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 building materials that architects weigh toward helping achieve the energy efficiency government leaders crave.

Architects today design commercial and residential buildings with improved insulation compared to predecessors. There is more, however, to installing energy-efficient roofs than just improving insulation. Some types of insulation are not compatible with certain roof types. Managers also need to consider code issues, 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 equation 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 enclosure 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 barriers 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 selecting 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 insulation. “We’ve seen some new materials, such as vacuum-sealed insulated panels and fasteners with thermal breaks that are helping to improve energy efficiency.”

Understanding R-Values

The United States is divided into seven climate zones for commercial and industrial buildings and homeowners to reach recommended insulation levels. Energy codes for commercial buildings are established by the International Energy Conservation Code.

“There’s not a one-size-fits-all approach for commercial construction,” Clapper said. “Requirements vary based upon climate zone and building type. R-value and solar reflectance are also factors that have to be determined.”

The seven climate zones in the U.S. are defined along state and county lines. The zones establish a baseline for energy efficiency by setting performance standards for the building envelope. The codes account for mechanical systems, lighting systems, and service water heating systems in homes and commercial businesses.

The zones are identified by their mix of weather. Zone 7, for instance, is classified as “very cold” and includes almost all of Alaska and portions of some other states. Zones 5 and 6 stretch across the nation, and includes states such as Pennsylvania and Massachusetts in the Northeast and Nevada and Nevada and Oregon in the West. Zone 2, which endures hot and humid weather, includes states such as Florida, Louisiana, and Texas.

The climate zones, coupled with different building types, construction costs and material selection can make the roofing task on any building exceedingly challenging. “Each building is unique in its energy demands,” said Andrew Imbus, Product Manager for Imbus Roofing, whose company has been part of the Cincinnati community since 1873. “Roofing is just one element of a building’s architecture. Roofers, architects and even legislatures governing building codes need to consider regional demands for energy efficiency, building typology demands, and architectural demands.”

Maintaining Efficiency

With roof construction, it is critical for architects to maintain the building’s energy efficiency and construction integrity when adding roof openings. Besides keeping moisture, debris, and pests out of the building, holes for accessibility to mechanical equipment and ventilation must also integrate with the building envelope to control energy costs.

“The R-value of insulation hasn’t increased on a product-by-product basis, but recognizing that attachment methods for insulation, the inclusion of air barriers and vapor retarders into roof designs will improve energy efficiency,” Kirby said.

One of the most popular sellers for the roofing industry in recent years has been a thermally broken roof hatch, manufactured by The BILCO Company. The product features a thermally broken frame and cover design to minimize both heat transfer and effects of condensation.

The product features three inches of polyisocyanurate insulation with an R-value of 20.3 in both the cover and curb. The R-value meets code requirements and standards currently in line with today’s commercial roofing systems.

The hatch reduces harmful condensation since it is thermally broken, which means interior and exterior metal surfaces are separated by non-conductive material to eliminate heat transfer. It is particularly beneficial in buildings in which there is a wide fluctuation in temperature. The hatch helps keep heat inside the building when a roof is covered by snow and on cold, dreary winter days but helps air-conditioned buildings keep cool as the sun beats down on sweltering summer months.

The BILCO thermally broken roof hatch is supplied with the standard features on the company’s standard roof hatches, including engineered lift assistance for easy, one-hand operation to a fully open or closed position. Other standard features include a fully gasketed cover for weathertightness, an automatic hold-open arm, and a slam latch with interior and exterior padlock hasps. The product is constructed of aluminum for corrosion resistance and has a high solar reflective index.

A World-Wide Commitment

From a simplistic standpoint, the role of the roof has not changed. Its purpose is to keep the elements out of the building. While their primary function has not altered, technical details in roofing have grown significantly. Architects, builders, and roofing companies can offer options that would never have been dreamed of a century ago.

The current trend is directed at improving energy efficiency and it’s not just in the United States. In India, 40 percent of the population is expected to live in cities by 2030. More than 60 percent of the roofs trap heat are made of concrete, metal, and asbestos, which can trap heat. “Further, buildings account for more than 30 percent of India’s electricity consumption and a significant share of annual carbon dioxide emissions,” Arvind Kumar and Rajkiran V. Biloikar wrote in The Indian Express. “It is thus imperative that any effort towards energy conservation must include a focused approach to urban areas and more specifically on buildings and built-up areas.” The article says government mandates on improving energy efficiency are on the horizon. Other nations can expect to see similar government mandates.

Change will not come swiftly. The clean energy movement is going to evolve over time, and there is a lot of work that has to be done. While still in the infant stages, some government leaders and international institutions are pushing for change to occur sooner rather than later.

“In the building and construction sector, much attention was concentrated on operational energy efficiency, the energy used in buildings and which can be influenced by building design, insulation, passive solutions for heating and cooling, appliances, and systems improvements as well as maintenance and usage,” said Martina Otto, head of the United Nations Environment Program Cities Unit. “But we also need to look at materials to reduce pressure on natural resources and embodied carbon (the amount of CO² or CO² emission to produce a material).”

Thomas Renner writes on building, construction, manufacturing, and other trade industry topics for publications based in the United States and Canada.