Energy-efficient windows Let the light in but keep the heat out with these tips for energy-efficient windows Window basics Windows should be double-paned, weather-stripped, and caulked for minimal air transfer when closed. Single-paned or poorly installed windows can let up to 25 percent of your inside heated or cooled air out of the house, wasting the energy it took to create it. Pinterest Make old windows eco-friendly It may seem quicker and easier to replace windows that aren't energy efficient, but the most eco-friendly option is to have old windows refurbished. Add weather stripping, install new sash locks for a tighter seal, and add insulation in the weight pockets and under the sill. Replacing old windows If you would like to replace your old windows for more eco-friendly ones, or are in the process of building a home, make sure you look for Energy-Star rated windows. Getting them installed by an expert will ensure that there are no leaks of water or air. Passive heating When sunlight shines through south-facing glass and hits a surface with thermal mass inside the house (such as concrete, stone, or brick), the material absorbs and later releases the heat into the surrounding air. The trick is to size and place your windows and skylights appropriately, and add correctly sized overhangs or shading, to get the right amount of heat. An experienced architect can help you determine the right mix for your particular climate. Indirect lighting Deep overhangs on the south side of the house protect windows from too much direct sun, so the homeowner won’t turn on the air conditioner as much, if at all. But, with the large picture windows, they will get enough indirect sunlight to light their house during the day. Energy-efficient window treatments Window treatments help minimize heat transfer from windows. Drapes, blinds, shutters, and shades can all block sunlight from heating up the house on hot days and keep warm or cool air from escaping through leaky windows. Look for eco-friendly fabrics such as organic cotton and hemp, and shutters made of FSC-certified hardwood. Avoid plastic shutters and blinds, as well as polyester fabrics that won’t biodegrade. Woven shades made of bamboo, reeds, and grasses are another green option, as long as they aren’t treated with oil-based finishes. Maintain privacy Placing windows high on a wall allows light to stream in without sacrificing privacy. When these high-placed windows are operable, they can be opened to release the hot air that naturally rises. Proper ventilation A bank of windows on the second story of this house brings light in and moves hot air out. Skylights in the patio roof allow light into first-floor windows as well, but with enough of an overhang to protect the windows from too much direct sun. Naturally-lit rooms A healthful bedroom needs fresh air and natural light, and people fall asleep better when their body temperatute is right. Consider any possible wayof increasing the amount ot natural light the bedroom gets, so you don't have to use electric lights during the day. In single-story homes or in top-floor bedrooms, a well-placed skylight can make all the difference. Get fresh air Use a combination of cross ventilation and mechanical ventilation to ensure you have fresh air that won't stagnate in your home. Bringing outside air into the house is usually an easy and good way to clean out stale air.