By Ann Robinson and Annie Vernon
Many homeowners express a desire to add skylights to their homes during a remodeling project. Perhaps it is the same psychological attraction as the sunroof in your latest car.
We all know that light cheers us up and makes a space more pleasant. The question in these days of trying to be energy smart is what price do we pay for this pleasantry? Can we justify a skylight as anything more than a frivolous extravagance?
The answer is yes, with the caveat that size and placement must be carefully considered in the design process. Skylights can provide your home with natural light (which is to say, free light) and warmth.
A skylight can be another tool to offset your heating, cooling and lighting costs if properly selected and installed.
First consider your home’s design and the climate in relation to the energy performance of your skylight. Look for an Energy Star label to assure you are selecting an energy-efficient skylight. But even with a high-performance rating, it can be ineffective if the placement is wrong within the overall design of your home.
Skylights on roofs that face north provide fairly constant but cool illumination. Those on east-facing roofs provide maximum light and solar heat gain in the morning. West-facing skylights provide afternoon sunlight and heat gain. South-facing skylights provide potential for desirable winter passive solar heat gain greater than any other location, but they often allow unwanted heat gain in the summer.
You can prevent unwanted solar heat gain by installing the skylight in the shade of deciduous (leaf-shedding) trees or by adding a movable window covering on the inside or outside of the skylight. Some units also have special glazing that can help control solar heat gain.
The physical size of the skylight has an impact on the illumination and temperature of the space below. As a rule of thumb, the area of the skylight(s) should never be more than 5 percent of the floor area in rooms with many windows and no more than 15 percent of the room’s total floor area for spaces with few windows.
Skylights are available in a variety of shapes. The most common include rectangular, circular, oval, diamond, triangular, multisided and tubular. Typically, nonrectangular skylights use plastic glazing instead of glass. Plastic glazing (most commonly acrylics and polycarbonates) is usually inexpensive and less liable to break than most other glazing materials. However, these plastic surfaces scratch easily, and they may become brittle and discolored over time. Plastics also let in more UV rays, increasing fading damage to furniture.
Skylight glazing can be flat, arched, domed, pyramidal or warped plane, which is flat on the low side and concave on the high side. When the shape is sloped or curved, it allows light to enter from more extreme angles. The raised designs also help shed moisture and leaves.
Tubular skylights can be an effective and less invasive option. Smaller than other skylights, they capture light through a dome on the roof and channel it down through an internal reflective system. This tubing is far more efficient than a traditional drywall skylight shaft, which can absorb up to half the light on its way down.
Another advantage is this tubing will fit between rafters and will install easily with no structural modification. At the ceiling level, a diffuser that resembles a recessed light fixture spreads the light evenly throughout the room, which increases the daylighting potential without the need for a larger skylight unit.
Because the rooftop dome has a small surface area, tubular skylights minimize heat loss in the winter and heat gain in summer. In addition to adding natural light and heating, operable skylights (skylights that can be opened and closed) can also be used for moisture control and venting your home.
Whatever style or type of skylight you choose, remember that placement in relation to your home’s design is the key to having a skylight that will add value and function as well as beauty to your home. As always, we welcome your home architect design questions at firstname.lastname@example.org.