by Don Vandervort, © HomeTips
Skylights provide up to 30% more natural light than vertical windows, making a small space seem larger. In a bathroom with limited wall space, a skylight may be your best—if not your only—means of bringing in significant daylight. Skylights with clear glass focus bright light on a small spot; those with obscure glass or acrylic supply more-ambient illumination.
Old-fashioned skylights were simply a single thickness of glass in a frame, but today they come with low-e and tinted coatings to control heat transmission and UV radiation. Skylights are rated for their thermal efficiency in the same way windows are, so you can compare R-values and U-values. As an alternative to tinted glass, which darkens a room, you can get shades or blinds for skylights. Ventilating skylights can also be equipped with screens to keep bugs out.
When a full-size skylight is too big for a bathroom, you can get almost as much light from a tubular skylight (see below). Just 10 to 18 inches in diameter, tubular skylights consist of a clear dome over a reflective shaft that ends at the ceiling with a sealed diffuser. The system provides an enormous amount of light for its small size, and it’s sealed to minimize heat gain and loss.
Skylights: Fixed vs. Operable
Like windows, skylights are either stationary or operable. Fixed skylights, which provide illumination only, may be flat or dome-shaped. Most operable, or “venting,” skylights hinge at the top and open a few inches to allow for air circulation. Though a venting skylight may cost about 40% more than a fixed one, it can make a terrific difference in summertime comfort. When open, a ventilating skylight can create an updraft to draw hot, humid air out of a room. And, since cold air stays near the ground, an open skylight is compatible with air conditioning.
Because most skylights are up out of reach, manufacturers provide several methods for opening them. The most common and affordable is a pole that you crank, but this only works for ceilings less than 15 feet high. Some offer a battery-powered, motorized pole.
Nearly all major manufacturers offer motorized, operable skylights as an option. Controlled at a wall switch or by a hand-held remote, these cost a bit more than manually operated types and require routing electrical wires to the skylight, but they pay big dividends when a skylight is opened and closed frequently.
Some remote-controlled versions feature a rain sensor that automatically closes the skylight when it detects moisture. In other sophisticated models, heat sensors can trigger the skylight to open when the room’s heat reaches a certain temperature. Some wireless remote controls can be programmed to operate the skylight at preset times.
Sky windows, also called roof windows, are quite different from standard operable skylights. These are built more like a window and pivot at the center. Meant for mounting in an attic room or similar location where they can be reached, these are designed to be opened wide. In fact, you can pivot them all the way around for easy cleaning of the outside surface.
Skylight Blinds & Shades
Although standard skylights are great at illuminating otherwise dark interior spaces, they can also be problematic in certain situations because you cannot “turn them off.” Fortunately, skylight manufacturers have worked around this problem by introducing integrated skylight blinds and shades.
Blinds or shades are important for preventing heat loss at night. Clear skylights tend to lose a large amount of heat toward the night sky in winter, a principle called “clear-night-sky re-radiation.” Amazingly, the area around a skylight can drop 5 to 10 degrees below ambient temperatures due to this phenomenon. A shade or blind can help minimize this heat loss.
Most operable skylights also include insect screening that mounts below the opening; some fiberglass insect screens reduce UV rays by up to 70%.
Following are the main types of skylight shades and blinds:
Light-blocking shades. These virtually turn day into night. They are made of aluminum-coated fabric and are extremely energy efficient. Some models are powered by a built-in solar battery, which means no wiring.
Pleated or cellular shades. These shades diffuse and soften the light coming in, reducing glare and protecting furniture and carpeting from fading.
Venetian blinds. Great at redirecting and reducing incoming light, the aluminum construction of these Venetian blinds makes them ideal for kitchens, bathrooms, and other humid environments. Some manufacturers make skylights with blinds built into the space between the double-insulated glass.
Heat-blocking awnings. A retractable awning glides in tracks across the exterior of the skylight, entirely blocking heat from entering the house. Most are electric, controlled by a push button.
Tubular Skylights Save Energy
Need to bring a little light into a dark hallway, landing, or closet? With tubular skylights, you can install a little bit of sunshine.
Tubular skylights operate better than traditional skylights to deliver light to a living area by utilizing a roof-mounted light collector that consists of an acrylic lens set in a metal frame. The rooftop assembly directs sunlight into a metal or plastic tube, which has a highly reflective interior coating. The reflective tube guides the sunlight to a diffuser lens, mounted on the interior ceiling surface, which spreads light evenly.
Because of the shape of the “scoop” at the top, tubular skylights can draw light regardless of the sun’s angle in the sky. Research has shown that the lights can provide the equivalent light output of up to one 700-watt incandescent bulb in December and one 1,200-watt bulb in June. New models feature light fixtures so the dark areas of your home can be lit both day and night.
Tubular skylights are relatively easy to install as they fit between rafters well and require very little intrusion into the roof, but, as with any puncture in the roofing, care must be taken with flashing to prevent water from seeping in.
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Top three photos courtesy Velux
Bottom illustration courtesy Solatube