This article is the fourth part in an ongoing series about the integrated met- al roof retrofit assembly at Goodfellow Air Force Base, San Angelo, Texas. The first part appeared in retrofit’s September- October 2012 issue, page 30, and was an overview about the demonstra- tion project. The second part was published in the November-December 2012 issue, page 34, and focused on the roof’s in- tegrated solar-power and -thermal system. The third part covered the standing- seam metal roof and appeared in the January- February issue, page 32. The next installment of the series will appear in the May-June issue and will address the sub- purlins used to retrofit the roof and the role of a turnkey contractor for this type of installation.
building stock is poorly insulated. At an es- timated cost of $3 per square foot, commer- cial building energy expenditures currently approach $210 billion annually. The Washington, D.C.-based U.S. Green
Building Council and the U.S. Environmental Protection Agency, Washington, estimate buildings account for 40 percent of our nation’s primary energy usage and almost 75 percent of all electricity consumption. Ac- cording to Andre Desjarlais, group leader of the Building Envelope Engineering Science and Technology Division of the Washington- based U.S. Department of Energy’s Oak Ridge National Laboratory, Oak Ridge, Tenn., in an average low-rise building, heating and cooling energy accounts for about 30 percent of total energy used. About half of heating and cooling energy is attributed to heat loss in cooler weather and/or heat gain in warmer weather at the roof. U.S. codes and standards are recognizing this and have become signifi cantly more stringent in their insulation requirements. The International Energy Conservation Code and ASHRAE 90.1 standards have increased the levels of ac- ceptable insulation in walls and roofs in the more recent versions. The U.S. military also has recognized the
importance of increasing its buildings’ en- ergy effi ciency. Reduction of greenhouse-gas emissions, related to cooling and heating loads, is now a priority for all federal agen- cies, thanks in part to Executive Order 13514, Federal Leadership in Environmental, Energy and Economic Performance, which was signed Oct. 5, 2009. Various branches of the military stipu-
late that signifi cant renovations meet the minimum requirements of USGBC’s LEED Silver certifi cation. LEED emphasizes energy optimization by going beyond the ASHRAE
standards for insulation and energy-conser- vation measures. These facts point to a need to increase
the level of insulation and lower the cool- ing/heating energy usage in existing build- ings. With today’s retrofi t market increasing in popularity, the addition of more and different types of insulation in a retrofi t roof application becomes more important. An Environmental Security Technologies
Certifi cation Program (ESTCP) demonstra- tion project featuring an integrated metal roof retrofi t system at Goodfellow Air Force Base, San Angelo, Texas, used additional insulation in the design. (To learn more about ESTCP, see the fi rst of this series in the September-October issue, page 30.) To comply with the ASHRAE 90.1 2010 standard, a layer of 2 1/2-inch-thick high-density rigid insulation board was installed onto the existing metal roof to the top of the new sub-framing. An additional 1-inch-thick layer of high-density rigid insulation board with a refl ective radiant barrier facing was in- stalled above the fi rst layer. All board joints were taped with aluminum foil to minimize heat gain into the building and hold the heat in the area where a solar-thermal water-heating system was also installed. This confi guration increased the R-value of the existing building from R-19 to R-51.9.
Insulation at Goodfellow At the most basic level, insulation is rated in
terms of thermal resistance, called R-value. The R-value is the resistance to heat fl ow. The thermal resistance depends on the type of material, thickness of the insula- tion and density of the insulating material. Depending on the type of materials used and manufacturing method, R-values can range from around R-3 to close to R-7 per 1
At R-6.5 per 1 inch of material thickness, plus the added R-value from the reflective facing and air space, the thermal level of insulation was increased by more than 250 percent.
32 RETROFIT // March-April 2013 PHOTOS: GOODFELLOW AIR FORCE BASE