Professional Practice

Using Low-Impact Materials: Reflective Materials

Over 7,500 square feet of asphalt was replaced by landscape areas and high albedo paving, reducing the urban heat island effect. Taylor 28, Seattle, Washington / Mithun.

Solar Reflectance has a significant impact on surface air temperatures in the built environment. Materials with low solar reflectance absorb a larger amount of solar energy, which leads to higher air temperatures and increased energy use. In cities, this contributes to the urban heat island effect. Using reflective, "cool," or white materials helps reduce air temperatures and energy costs by minimizing the use of air conditioning to cool buildings.

Reflective materials offer high solar reflectance – they have an innate ability to reflect sunlight and reduce solar heat absorption. These materials can stay cool in the sun and also have high thermal emittance – they radiate instead of absorb heat. Roofs with high thermal emittance and solar reflectance can stay up to 50-60°F cooler than roofs with conventional materials.

Reflective materials also last longer than conventional materials, which absorb heat and break down faster.

Roofs and pavement can account for 60 percent of ground surfaces in many urban areas. The Environmental Protection Agency (EPA) has actively promoted the use of reflective roofs and roadways as a cheap and effective way to reduce greenhouse gas (GHG) emissions. Chicago has issued a reflective roof ordinance, and California has announced reflective roof rules for government-financed buildings. Reflective pavements should also be considered.

Sources: Using Cool Roofs to Reduce Heat Islands, Environmental Protection Agency; “Global Cooling: Increasing world-wide urban albedos to offset CO2," Hashem Akbari, Surabi, Arthur Rosenfeld, Springer Science + Business Media B.V., 2008

Organizations

Cool Roof Rating Council

Global Cool Cities

European Cool Roofs Council

White Roof Project

Cool California

Heat Island Group

Los Angeles Urban Cooling Collaborative

Resources

A Practical Guide to Cool Roofs and Cool Pavements, Global Cool Cities Alliance

Cooling Cities by Painting Roofs and Roads White, The Dirt, American Society of Landscape Architects

Cool Roofs, U.S. Environmental Protection Agency

Energy Efficient / Cool Roof Resources, EPDM Roofing Association

Interview with Sadhu Johnston, Chief Environment Officer, City of Chicago, American Society of Landscape Architects  

U.S. Energy Secretary Steven Chu: Paint Roofs and Surfaces White, The Dirt, American Society of Landscape Architects

Sticks, Stones, Fabric: The Evolution of Sustainable Building Materials, Smart Cities Dive

Cool Pavements, Lawrence Berkeley National Laboratory

Cool Pavements: The Essential Guide, Landscape Architecture Network

War Over Pavements Heats Up, Landscape Architecture Magazine

Case Study: Natural Stone Solar Reflectance Index and the Urban Heat Island Effect, University of Tennessee Center for Clean Products, 2009

Research

“Global Cooling: Increasing world-wide urban albedos to offset CO2," Hashem Akbari, Surabi, Arthur Rosenfeld, Springer Science + Business Media B.V., 2008

“Examples of Cooler Reflective Streets for Urban Heat-Island Mitigation,” Pomerantz, M., Akbari, H., Chang, S., Levinson, R., Pon, B., Lawrence Berkeley National Laboratory

Government Resources

NYC CoolRoofs, City of New York

Cool Roof Regulations, California Energy Commission

Reflective Roof Products, Energy Star

Cool Roofs, Department of Energy

Projects

Taylor 28, Seattle, Washington
Mithun

Park Seventeen Roof Garden, Dallas, Texas
TBG Partners