Topic Of Cool Roofing Heating Up Again
By Scott Kriner, Green Metal Consulting
The cool roofing movement has been with us for over a decade. But over the past year or so, there has been a renaissance in the interest in cool roofing. When the Department of Energy Secretary Dr. Steven Chu remarked that all roofs should be white in order to save energy, it created a new buzz around the merits of cool roofing. Combining that comment with the start of another revision cycle in the California Building Energy Efficiency Standards, Part 6 – commonly referred to as Title 24 – has put the subject of cool roofing back on the front page.
Proposals from California’s utilities and from the California Energy Commission are already raising eyebrows and raising the bar for aged solar reflectance requirements. Left unchanged, some of the proposals would in essence remove color from the choice of building owners or homeowners in many areas, since only white or very light colors would meet the criteria in these proposals. The Cool Metal Roofing Coalition is involved in this discussion, having participated in several industry stakeholder workshops in the past, and again in the June 10 workshop. The metal roofing industry is working with other roofing industries to see that reasonable changes are made to Title 24 with a balance between energy efficiency, color choice, and of course cost.
In addition to the California state energy code, the International Energy Conservation Code, International Green Construction Code and the ASHRAE 189.1 Standard for the Design of High Performance Green Buildings have all introduced cool roof provisions. In many of the codes and standards, cool roofing is part of the mitigation of urban heat island effects, in addition to being part of the energy conservation measures.
The Cool Roof Rating Council remains active in developing and refining testing methods used for evaluating all types of roof products. The Council is also working to support the California Title 24 revision cycle. Work to determine formulae that would predict the aged solar reflectance (SR) based solely on the initial SR values on the CRRC directory is being conducted by Lawrence Berkeley National Laboratory and by the CRRC. Different formulae for each of the roof product categories were recently presented to the CRRC Technical Committee. The use of these equations to establish an aged SR temporarily until the actual aged value is measured, will be considered as a suggestion to make at a future Title 24 workshop.
The use of a predictive equation for aged SR is also under discussion in the Roofing Industry Committee on Weathering Issues (RICOWI). In this case, the equation that is presently in Title 24 would be used to predict the aged SR based on the initial value, in order to obtain an Energy Star label on the product, provided it meets the minimum SR criteria. Again, the SR obtained from this equation would be a default value until the actual aged SR value is measured – thereby eliminating the three-year waiting period.. The RICOWI proposal will be presented to the Energy Star program managers in the near future.
Another sign of resurgence in cool roofing was the launch in 2010 of the White Roofs Alliance, which later was renamed the Global Cool Cities Alliance (GCCA). This global initiative is dedicated to the advancement of policies and actions that increase the solar reflectance of roofs and pavements in urban settings. The GCCA has recruited cities around the world to commit to widespread implementation of cool surfaces by 2020. The agenda for this organization includes efforts to make 100 cool cities across the globe by 2015, national legislation to implement cool surfaces by 2020, new building and pavement codes that promote cool surfaces, developing financial incentives that support installing cool roofs, and research and development on cool surfaces.
We are also seeing more research into cool roofs that are integrated into dynamic roof assemblies. The Metal Construction Association continues with their research at Oak Ridge National Laboratory on dynamic building envelope systems, both roof and wall, that utilize the solar heat that is captured at the outer surface and use it for process or space heating of air and/or water. Cool metal roofing or wall surfaces are part of that effort to develop the next generation building envelope assemblies. The roofing systems utilize cool roofing, insulation, radiant barrier, above sheathing ventilation, phase change materials, integrated photovoltaics, solar heat recovery, and can also include solar water heating in the design.
In the field of product development, there are new advances in cool roofing being announced. One cool roof concept was recently introduced at a Cool Roof Rating Council meeting. The concept uses directional coatings or special profiles on steep slope roofs that allow a building or home owner to see a darker color from the ground, while the surface that is receiving solar energy is actually very light in color. These are referred to as “responsive roofing”. Another cool roof technology development was recently announced in India, using nanotechnology. Details are sketchy at this time, but it has captured the attention of the US Department of Energy who is reportedly sending scientists to India to investigate the claims.
Amidst this growing interest and activity in the cool roof arena, the metal roofing industry’s interests are being advanced by the Cool Metal Roofing Coalition. And as another sign of the growing importance of cool roofing, the Coalition’s Technical Committee agenda of topics is long and getting longer every month.
Scott Kriner is the president and founder of Green Metal Consulting Inc. He is a LEED Accredited Professional who began his career in the metal construction industry in 1981. His company is a member of the U.S. Green Building Council, the California Association of Building Energy Consultants and the Residential Energy Services Network (RESNET). Scott can be reached by email at skriner1@verizon.net or by phone at (610) 966-2430. You can also visit him on the web at www.greenmetalconsulting.com.
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