One such new-fangled device is an exterior roller shutter. They may also be more accepted in historic areas and condominium communities, where many new-fangled exterior attachments are not allowed. Hinged shutters generally block views from the interior, though, and are more popular for weather protection. Similarly, hinged exterior shutters (unlike the common decorative kind) shade the window while allowing ventilation as well as daylight some hinged shutters can be manipulated with adjustable louvers. These work much the same way that interior shades do-rolling down in front of the window-but go on the outside of the house.Įxterior shades are generally more effective than interior shades at preventing solar heat gain, providing up to 85% blockage, and tend to offer better ventilation. Like awnings, exterior roller shades, made of vinyl-coated polyester or fiberglass fabric, block solar heat gain while still allowing a filtered view through the window from the inside. ![]() Stationary metal awnings are available for homes, but be aware that a fixed exterior attachment works best if orientation, climate, and other factors are taken into account using computer modeling-a service used routinely for commercial buildings but almost never for homes. However, Gant cautions that "products from different manufacturers may look the same but perform differently due to the quality of pigments and materials and fabric construction." In general, a heavier fabric in a darker color will provide more shading. Awnings also block direct ultraviolet (UV) radiation that can damage upholstery, and they protect the window assembly from the weather.Īccording to John Gant, sustainable development manager for Glen Raven, maker of Sunbrella exterior shading products, awnings "have a different SHGC depending on indoor and outdoor temperature and the position of the sun" as well as fabric weight and color. Awnings leave the heat outsideĪwnings reduce glare without affecting views too much, and they block up to 90% of solar heat gain on south-facing windows-before the heat can come through the window. One drawback of using curtains or drapes is that you may end up with dark rooms and need to turn on lights, which can cut into energy savings. While that means that those windows block 80% of solar gain while still permitting a somewhat darkened view, they don't provide much privacy, so many people will still use curtains or blinds.Ĭombining the two is a good bet: the curtains offer privacy, while the low-SHGC windows block the sunlight before it gets into the house, which is much more effective. For comparison, the highest-performing low-solar-gain windows on the market have an SHGC of 0.20 or lower. See membership options » Curtains and drapes block up to 60% of solar gainĬurtains and drapes, the old standby, work pretty well: when installed over clear (uncoated) glass, these attachments alone can block 20%–60% of solar gain (depending on material and color), reducing or preventing the need for air conditioning. SUPPORT INDEPENDENT SUSTAINABILITY REPORTINGīuildingGreen relies on our premium members, not on advertisers. We use windows to give us views, fresh air, and passive solar heating in the winter, but are there good ways to modify them to prevent too much solar gain in the summer? Yes, and new research from BuildingGreen (my company) and Lawrence Berkeley National Lab (LBNL) tells us which "window attachments" are worth using. Cranking the AC only drives up the power bill. For buildings with windows-which is most of them-retreating inside gets you out of the shade, but it can be hotter and stuffier. That may be true, but a lot of us are turning away from the sun this time of year. The crucial detail that I got wrong, says Gordon: "No relative of mine would ever turn back from a dark night, I can assure you." Out of the sun and into the frying pan They pulled into a gas station, had a confab and decided it was too dark-they couldn't proceed-and they turned around and drove home. ![]() They got across the Tappan Zee Bridge and onto the New Jersey Turnpike when all of a sudden there were no more streetlights. The whole family, in three cars, left Dorchester in the evening heading for Florida. They thought there were at least three bears outside. They asked Gordon how anyone here ever slept at night: it was so dark and quiet that none of them got a wink. Three aunts of a young man from Dorchester, Mass., came up to celebrate his graduation from a Vermont boarding school. Well, a lot changed in the telling, and Gordon got back to me with what really happened. A few weeks ago I told a story in this space that was third-hand from Gordon Hayward.
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