Skylights can brighten a home with abundant natural light, especially during the winter months when days are shorter and tend to be darker. Strategically placed, skylights can lighten the gloomiest corners of a house without resorting to artificial light during daytime hours. And, of course, this saves electricity and reduces utility bills. Interestingly, the same area of glass in a window as in a skylight does not provide the same effectiveness of illumination.
However, because skylights penetrate the roof, they have the negative reputation of almost automatically leading to leaks. Any penetration of a roof should always be given careful consideration, but leaks need not be the result. When installing a skylight, always use the best water management materials and methods, and hire a reputable contractor to do the job. Installing a skylight is not a do-it-yourself project, unless you wish to be placing buckets beneath it with each future rain storm.
Two other potential downsides of skylights, depending on the orientation and size, are (1) making the room too bright and glary and (2) overheating. These tend to occur in summertime but can happen even on a sunny winter day. Installing the unit on a north-facing roof can mitigate both these drawbacks. A different strategy to address these issues, but only applicable in homes with attics, is to place the skylight higher up on the roof to take advantage of a longer light well. (Make sure the shaft is well insulated to avoid unwanted heat loss in winter.) Another effective solution to keeping out excessive sunlight and heat is to buy skylights with integral blinds or shades, or in the worst case, to install them separately.
As with windows, it is important to select skylights with the best specifications and performance that you can afford. In our region, that means double-pane units to provide good insulation, plus glazing coatings (usually low emissivity coatings called low-e) to keep exterior summer heat out and interior heat in during the winter. To create an effective passive solar house, skylights are often a key component, designed to bring in the sun’s warmth when needed. The sun’s entering infrared rays need to be accompanied by sufficient thermal mass to distribute the heat and avoid big temperature swings.
Another feature that skylights can provide is ventilation. Venting a building with an operable skylight releases the heat that naturally accumulates near the ceiling. This stack effect venting of hot air is often an important part of natural cooling in a passive solar house. When skylights bring in controlled light and brightness, together with desired cold weather warmth and cool replacement air in summertime, they are an outright boon.