NEW PRODUCTS Smart green choices
Hot Spots on a Cool Roof
Our collection of skylights gives you more options to bring daylight into dark interiors, especially when units use state-of- the-art, film-based, multi-cavity insulating glass. By Bruce Lang
Total Skylight Control io-homecontrol is a wireless
communication protocol enabling interaction among products from different manufacturers. It brings new solutions for improved home comfort, energy savings, security, and indoor climate control. It allows new benefits for professionals and end-users with no additional infrastructure or installation costs. The io-homecontrol association has been launched by some of the world’s leading firms in home comfort technology, including Honeywell, the global leader for solutions of residential and commercial building controls; Somfy, the international specialist in automatic control of openings and closures in homes and buildings; and VELUX, a world leader in roof windows. io-homecontrol members today also include Renson, NIKO, WindowMaster, Hormann, and ASSA ABLOY.
www.velux.com
must not only reflect solar radiation, they need to reduce heat transfer via convection and conduction as well. Energy conservation performance requirements for residential skylights are primarily a function of the glass. Skylight glass
should maintain a high R value, (resistance to heat flow); a low shading coefficient (amount of solar heat radiating through the glass); and a high light transmission. Suspended film insulating glass, in which one or more heat reflective coated films create heat-resisting cavities inside the insulating glass unit, provides optimal performance and comes closest to duplicating the energy efficiency of a cool roof while transmitting visible light and providing transparency to the environment. In addition, clear, colorless
suspended film insulating glass is capable of reducing damaging levels of ultraviolet radiation that cause fading as well as maintaining visual clarity and normal color rendition. Clearly, film-based, multi-cavity
Cool roof technology is increasingly popular as more residential builders increase roof insulation to reduce HVAC capital expense and year-round operating cost. Unfortunately, skylights, so desired for
their ability to transmit visible light into otherwise dark interiors, function as roof-top solar collectors, acting to defeat the ability of cool roof technology to help reduce the cost to operate air conditioning. If the benefits of daylighting via skylights
outweigh their negative impact on the overall performance of a cool roof, they need to maximize visible light transmission while
44 GreenBuilder October 2010
maximizing solar heat reflection. Equally important, typical Low-e glass,
when put in skylights, can lose up to 30% of its ability to insulate against heat transfer as a function of convection. At night and in the winter this means the heat in a home is going out the skylight much more than through the same glass in a vertical window. Due to the same convective forces, during the day, outdoor ambient heat is moving through glass in a skylight more quickly than in a vertically mounted window. Given this reality, to compete with the energy efficiency of a cool roof, skylights
insulating glass is tomorrow’s state- of-the-art skylight, window and patio door glass available today. It has been saving energy in thousands of homes and in such landmark buildings as the Hoover Dam Visitor Center, the Boulder, Colorado Municipal Library and in the National Gallery of Art in Washington, DC.
Bruce Lang is Vice President of
Marketing & Business Development at Southwall Technologies, in Palo Alto, Calif. He can be reached at blang@
southwall.com. Southwall’s Heat Mirror suspended film insulating glass has been selected to be retrofitted into all 6,500 windows in New York’s Empire State Building.
www.greenbuildermag.com
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