Cool roofs, hot topic

Building Operating Management, May 1999 by Tatum, Rita

ENERGY STAR-labeled roof products can bring significant savings for buildings in most parts of the country

SUMMERTIME IS ANYTHING BUT easy for facility executives trying to get a handle on skyrocketing air conditioning loads. What if you could reduce your facility's peak cooling demand by 10 to 15 percent and fix the roof with the same capital expenditure? If your building is located where the sun shines brightly, and you currently have a black rooftop needing repair or maintenance or are in the process of constructing a new building, you definitely will want to investigate ENERGY STA-labeled roof products.

These reflective roof products lower roof temperatures by up to 100 degrees F, thereby decreasing the amount of heat transferred into a building's interior. Although some reflective roof products may have a higher initial price than non-reflective alternatives, ENERGY STAR-compliant roof products can save facility executives money and energy over the life of the roof by reducing the amount of air conditioning needed to keep a building comfortable. In addition, reflective roof products can potentially minimize the effects associated with thermal shock, reduce UV degradation, and extend the life of the roof.

"In general, building owners will save the most money on energy bills by installing an ENERGY STAR-labeled roof product if their building has the following characteristics: high air conditioning bills, a large roof surface as compared to the building's overall size, lower levels of insulation and/or a location in a hot, sunny climate," points out Rachel S. Schmeltz, ENERGY STAR program manager. "The most cost-effective time to install an ENERGY STAR-labeled roof product is when re-roofing, constructing new buildings or maintaining a roof by applying a coating."

In February, the U.S. Environmental Protection Agency (EPA) announced its ENERGY STAR Roof Products Charter Partner companies at the National Roofing Contractors Association (NRCA) convention in Phoenix. Under the program, manufacturers will be allowed to use the ENERGY STAR label on reflective roof products that meet EPA's specifications for solar reflectance and reliability.

EPA's ENERGY STAR roof specifications are not restricted to a particular type of roof product. However, the agency expects that initially metal roof products, single-ply membranes and roof coatings will be most widely available.

The agency also understands that the primary functions of roofs - water tightness, durability and longevity -- cannot be compromised. Manufacturers of ENERGY-STAR-labeled roof products must back their compliant roof products with warranties that are comparable to their other roof products.

Air Pollution and Urban Heat Islands

Most energy generated in the United States relies on fossil fuels, the burning of which creates the air pollution associated with smog, acid rain, greenhouse gas emissions and global climate change. EPA is committed to reducing that pollution and the reflective roofing market is one way to improve the environment particularly in urban areas and improve the building's rooftop simultaneously.

"By reducing the amount of energy needed to cool buildings, ENERGY STAR-labeled roof products help to reduce the production of these air pollutants," says Schmeltz.

"Additionally, reflective roof products can help reduce the `heat island effect,' a phenomenon in which cities can be 2 to 8 degrees F warmer than the surrounding countryside," explains Schmeltz. "Such heat islands occur, in large part, because many buildings and paved surfaces are designed with dark materials that absorb heat from the sun. This heat is released at night, causing the air temperature to remain high. The resulting elevated temperature leads to an increased demand for air conditioning in buildings, increased fuel use for vehicle air conditioning, increased levels of smog, and associated increased levels of heat-related and smog-related health problems. Installing reflective roofs helps reduce the heat island effect, decreasing the amount of smog in the air and benefiting the entire community."

"The urban areas are warmer because their dark surfaces absorb more solar heat and because there is less vegetation," explains Hashem Akbari, one of the principal investigators of heat island effects at Lawrence Berkeley National Laboratory (LBNL). "There are two quick fixes for summer heat islands. The least expensive is to move toward lighter colored surfaces, the way Mediterranean cities do. The other is to plant shade trees -- another ancient tradition."

"The heat island effect also causes an increased probability that photochemical smog will form, because smog is more likely to form as the temperature increases," says Haider Taha, an LBNL scientist with the Environmental Energy Technologies Division. "Reducing the temperature of the urban heat island could reduce the formation of photochemical smog."

In areas such as Los Angeles, for every degree the temperature rises above 70 degrees F the presence of smog increases 3 percent. Lawrence Berkeley National Laboratory scientists estimate that if all buildings in Los Angeles used ENERGY STAR-labeled roof products, the total energy and smog-related health care savings would be about $500 million annually.