Dynamic heat transfer will optimize the thermal performance of the entire system.
system directly beneath the metal roof surface. Dynamic heat transfer will optimize
the thermal performance of the entire system. Any heat that is transferred from the outer roof is useful to the solar- thermal water-heating system located between the old and new roof surfaces. As the heat is absorbed into the water/ glycol heat-exchange medium in the solar- thermal system, it reduces the heat that could otherwise flow into the building space beneath the roof system. The space between the two roof surfaces also allows for natural convective cooling by dissipat- ing residual heat out of the ridge vent, rather than allowing it to become part of the solar gain into the building.
Cool Roofi ng Cool metal roofing technologies are
described in The Whole Building Design Guide (WBDG), a document with a goal of creating successful high-performance buildings by applying an integrated de- sign and team approach during the plan- ning and programming phases. Because DoD and other government agencies fol- low the WBDG, cool roofing technologies are an important aspect of their buildings. Today’s metal roof coatings and paint
finishes are more advanced and durable than ever before. Alloys of aluminum and zinc have replaced the basic galva- nized-coated steel that was once the mainstream of agricultural and light- commercial buildings. More corrosion-
resistant metallic coatings and durable paint finishes resistant to fade and chalk now offer architects and building owners unlimited design opportunities. Galvalume sheet steel, which was used
on Goodfellow AFB’s test roof, is protected with a 55 percent aluminum-zinc alloy hot-dip coating to provide excellent corro- sion resistance. Inspections of Galvalume roof installations since its introduction to the marketplace in 1972 have suggested the estimated service life of this type of metal roof will exceed 60 years in most climates. The Goodfellow AFB roof is Energy
Star-labeled and listed on the Oakland, Calif.-based Cool Roof Rating Council’s directory. The paint finish is a polyvinyli- dine fluoride formulation, using special ceramic pigments that are highly reflec- tive in the infrared solar spectrum. Using cool technology in paint finishes allows for darker colors, such as the medium bronze used on the Goodfellow AFB retrofit, to reflect significant levels of solar energy. The cool roof can significantly lower the surface temperature of the roof and the space beneath by reflecting more solar en- ergy from the surface, which helps lower the air-conditioning load on the building. Combining the synergistic effect of a cool roof surface with rooftop photovoltaics also extends the life and efficiency of the solar-energy system atop the air force base’s roof.
A Turnkey Package A holistic retrofit roof system is appro-
Thin-film photovolta- ics can be attached to
metal roof panels without penetrations.
priate for a variety of building types, oc- cupancies and climate regions. Integrated building systems, when applied to the DoD infrastructure and/or the commer- cial building market, can dramatically contribute to reducing energy and water consumption by providing retrofit roofing,
Stackable and integrated roofing technologies that produce electricity, heat and hot water – for new and retrofit installations.
Is your roof ready? Ask for “Building Integrated PV–Thermal”!
Pfister Energy is a Goodfellow AFB ESTCP
integrated metal roofing technology project partner. Project info and video are at www.pfisterenergy.com.
Circle No. 16 January-February 2013 // RETROFIT 35