Coating Futures

— By Dr. Lisa M. Gartland

Governmental research institutions and industry groups are in the process of addressing the challenges regarding the adaptation of cool coatings for commercial and institutional facilities. Significant funding for research and development comes from the U.S. Department of Energy and the U.S. Environmental Protection Agency (EPA). Industry also is involved in funding studies and in collaborating to set standards.

Researchers at Lawrence Berkeley National Laboratory (LBNL) have been conducting demonstration projects of cool coatings in California and Florida, and they are making improvements in roof heat transfer modeling to the next generation of DOE-2 building energy models, the DOE-2.2 and EnergyBase programs.

A website features a database on roofing materials and their properties 

LBNL researchers also have urban climatological and air quality modeling underway that is designed to evaluate the effects of cool surfaces in cities throughout the United States.

Moisture and heat transfer

Work on cool roofing materials also is taking place at Oak Ridge National Laboratory (ORNL), another governmental laboratory. ORNL is performing tests at a comprehensive roof and attic facility. Researchers have produced detailed models of roof and attic systems heat transfer and are studying the effects of moisture buildup on roof materials.

Recently, the EPA unveiled specifications for cool roofing materials under its EnergyStar® program.

There are two classes of specifications:

• low-sloped roofs, which have less than a 2-in-12-inch slope, must have an initial reflectivity of 65 percent or higher. This reflectivity must stay above 50 percent after three years
• sloped roofs must have an initial reflectivity of 25 percent or higher, staying above 15 percent after three years.

The two different specifications are due to the types of materials available. Low-slope roofs can apply highly reflective roof coatings to increase their reflectivity.

Coatings don’t work well over shingles used on sloped roofs, since they can block the flow of rainwater between shingles. There are very few cool roofing products on the market for sloped roofs.

Labeling roofing products

The EPA EnergyStar roofing specification is a good first step at labeling roofing products. Unfortunately, the standard only encompasses the reflectivity of roofing materials, not their emissivity. This means that metallic coatings, which have high reflectivity but aren’t actually cool due to their low emissivity, still meet this specification.

The Cool Roof Rating Council (CRRC) is working on standards that encompass the reflectivity and emissivity of materials. CRRC members, a cross-section of experts from industry, government and research arenas, are developing test methods and specifications to classify cool roofing products.

Specification challenges

The cool roofing industry has many challenges in addition to setting specifications. There is a need to evaluate the life-cycle costs and externalities of cool roofing products, and to document environmental benefits over traditional materials. There is also a need to educate end users about the science behind cool roof coatings, as well as their potential benefits.

Finally, more maintenance managers and roofing contractors need information and equipment to apply coatings effectively and consistently, as well as to measure the coating properties to ensure they achieve targeted values.

— Dr. Lisa M. Gartland