The fundamental elements of green construction result in energy conservation, water conservation, improved indoor air quality, and a more durable structure.
Having covered orientation and design, sealing the building envelope, improving the insulation, and upgrading the HVAC system in the first two articles, we continue the series with two more energy-saving basic green features.
5—Upgraded Windows: The windows are another feature that will influence the energy efficiency of the building envelope. The energy saving attributes of windows, such as insulated, gas-filled, double-pane glass; low-E coatings; and vinyl, wood, or fiberglass composite frames contribute to a lower SHGC (solar heat gain coefficient) and U-Value.
Solar Heat Gain Coefficient (SHGC): This rating is a measure of the percentage of solar radiation that enters a building as heat gain through a window, door, or skylight, a primary concern if you live in a warm climate. The SHGC rating tells you how well the product blocks heat caused by the sun. The lower the SHGC, the less solar heat is transmitted. For example, a window with an SHGC of 0.39 allows only 39 percent of the solar heat that hits that window to be admitted to the house; the remaining 61 percent is blocked. If you live in a warm region, look for windows and doors with a low SHGC.
U-Factor: The U-Factor or U-Value, as mentioned in the discussion of Low-E glass earlier in this chapter, is a measurement of the rate of heat loss. The lower the U-Factor of a window, the greater its resistance to heat flow and the better its insulation value. U-Factor is of primary concern if you live in a cold region. The NFRC tests for U-Factor in a simulated environment where it is 70°F inside the house and 0°F outside. It measures the heat loss passing through a window from the inside to the exterior. If you live in a cold part of the country, select windows with a U-Factor of 0.35 or lower.
These two figures appear on the NFRC (National Fenestration Rating Council) label affixed to the window. Check with your supplier to make sure the recommended windows have been rated by the NFRC.
The Energy Star® program uses NFRC ratings to determine if a particular window qualifies for an Energy Star® designation. The criteria for earning the Energy Star® seal vary from region to region. Visit EnergyStar to find the Energy Star® SHGC and U-Factor requirements for Orlando and all of Central Florida.
Window size, placement, quantity, and specifications are considered in conjunction with home orientation and design, the first component of green building discussed in Part I of this series. This is just one of the reasons why a home design that’s focused on retaining the sun’s heat in winter and blocking it in summer can play a significant role in energy savings.
6— Energy-Saving Appliances: Energy Star® qualified appliances incorporate advanced technologies that use 10 to 50 percent less energy and water than standard models.
Not only are Energy Star® appliances more energy-efficient, they’re also quieter. And let’s address the water usage issue. For example, Energy Star qualified dishwashers not only use at least 41 percent less energy than the federal minimum standard for energy consumption, they also use about one-third less water than non-qualified models.
Front-loading washing machines also use less water, about 15 gallons less than older, top-loading models. When considering an Energy Star® machine, take a look at the Water Factor — the lower this number, the more efficient the machine. (Water Factor is a measurement of the number of gallons per cycle, per cubic foot, that a clothes washer uses. For example, if a machine uses 30 gallons per cycle and has a tub volume of 3.0 cubic feet, the Water Factor for that device is 10.0.)
Visit EnergyStar for a list of Energy Star® washing machines and their corresponding Water Factor.
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Guest Writer Tracy DeCarlo
Tracy DeCarlo is author of The Difference is in the Details: The Homeowner’s Planning Guide for Building a Functional Home and owner of One Stop Green Home Certification.
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