New technologies are extremely effective at keeping the heat out.In the last column, ways of keeping the sun’s heat from coming in through the windows were discussed. Shading from the outside (interior curtains and drapes block the light but the heat has already come inside) is the most effective method. For existing homes, a variety of high-performance window films (especially those rated Energy Star) can reduce the amount of heat and ultraviolet radiation entering your home, and still give you good visibility. Make sure you read the labels, because not all films will keep the heat out.
If you’re building a new home, you might want to explore high-tech solar control windows. New materials and manufacturing techniques can make these high-performance windows extremely effective at keeping the heat out while letting the daylight shine through. Sometimes called “low-e” (for “low-emissivity”) windows, these can be more costly than other window treatments, so you might want to use them where other techniques don’t work well—for a west-facing picture windows which give you a glorious sunset view, for instance.
Make sure that you specify “tropical,” “sunbelt,” or “low-e squared” (low-e2) windows. There are other “low-e2” windows used on the Mainland which are not designed for Maui’s climate.
As with the window films we discussed in the last column, low-e2 windows’ performance is measured in Solar Heat Gain Coefficient (SHGC), Visible Light Transmission (VLT) and Ultraviolet (UV) light. You want a low SHGC to ensure that not much heat can come through the window, and a fairly high VLT so you can still enjoy the view and the ambiance of natural lighting in your home. The UV percentage should also be low to protect your furnishings and yourselves from the damaging ultraviolet rays of the sun.
Some low-e2 windows and high-performance window films are extremely effective at keeping the heat out, and yet the “tint” is barely noticeable—it looks like an ordinary window. Heavy gray films are not necessarily what you’re looking for; they probably are better at reducing the amount of light transmitted than they are at reducing the heat. Look for Energy Star labels to make sure you’re getting the best!
In partnership with the state’s energy office, the Maui Weekly provides this feature to help Valley Isle homeowners reduce their utility bills and increase their environmental awareness. For more information, visit www.hawaii.gov/dbedt/info/energy.