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 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 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 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.
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
Acralight’s new NanoStar Skylights are your blueprint for unsurpassed energy-efficient performance and reduced sound transmission. Utilizing the Nanogel Aerogel insulating material, the NanoStar Skylight is 80% more energy efficient. The NanoStar Skylight provides eco-daylighting and reduced energy consumption and emissions. To satisfy the new Energy Codes, select the NanoStar Skylight, which is available for commercial, industrial, and residential unit skylight applications in numerous standard sizes. Custom sizes are also available. www.acralight.com
The ODL 10” EZ10ECL Tubular Skylight with Solar-Powered Dimmer enables you to bring natural light into up to 150 square feet of interior space and control that light with a solar-powered remote-control dimmer. The skylight’s LED nightlight delivers up to four hours of soft, subtle light while the sun is down. The acrylic diffuser can be removed for easy cleaning. A three-button remote-control dimmer is easy to use, and the dimmer is solar powered and comes with four rechargeable batteries. www.odl.com
Southwall Technologies recently announced the ability of Heat Mirror insulating glass to insulate against heat loss at a record-breaking center of glass R-20/U 0.05 insulation value. R-20 Heat Mirror insulating glass consists of three heat reflective coated films mounted inside an insulating glass unit between two pieces of low-e coated glass. This super insulating glass construction creates four heat-impeding gas-filled cavities and achieves R-20 performance. Heat Mirror R-20 is a product of Serious Materials, a leading Southwall customer licensed to fabricate Heat Mirror insulating glass. Heat Mirror is a technologically advanced low-emissivity and solar reflective film that can be mounted inside an insulating glass unit in a variety of configurations (one, two, or three coated films, uncoated or low-e coated glass) to provide energy conservation performance ranging from R-6 to R-20 to meet the unique requirements of commercial and residential new construction and renovation projects. Heat Mirror is the technological alternative to coated glass that extends performance well beyond that of generic low-e glass available today. Heat Mirror insulating glass, as well as other innovative glass technologies currently under development, is driving the U.S. Department of Energy to revise the window performance standards of its Energy Star program that rates the energy efficiency of appliances and building components. Revised Energy Star window performance standards make clear that generic low-e glass, with a maximum insulating performance level of R-4, no longer represents a level of energy efficiency required to “transform the market,” a key charter of the agency’s ratings and standards program. Among Energy Star’s objectives is increased market penetration of glass achieving insulating performance of R-10 an objective achieved by Heat Mirror technology today. Why is increasing the energy efficiency of glass important? According to Chris Mathis, a founding member of the National Fenestration Rating Council (NFRC), which sets standards for window energy efficiency, 64% of the 110 million existing homes in the United States have single-pane windows. This contributes 25%–35% of the total energy wasted in buildings and 10% of the total carbon emissions in the United States annually.
Solatube International is introducing an innovative, versatile metal roof flashing that makes it easier for architects to bring daylight into buildings without sacrificing the elegant design of metal roofs. The new Solatube Metal Roof Flashing features a round-edge, leak-proof design that reduces the exposed surface area by 50% (as compared with traditional flashings), eliminates the need for bulky crickets to divert water, and can be adapted to fit virtually any Standing Seam Rib roof profile. Its unique, diverted flange design reduces roof clutter by concealing the fasteners; while Solatube International’s innovative DryLock Technique provides a triple-seal approach that locks the flashing to the metal roof deck. Fully paintable, the new flashing provides a sleek, low-profile appearance that complements any roof design. The new Solatube Metal Roof Flashing is compatible with roofs from leading manufacturers, including Butler Metal Roof Systems, MBCI, Metal Sales, and Pac-Clad. It has been tested in international markets and is now available in North America through Solatube Commercial Distributors nationwide. www.solatube.com