This expert skylight buying guide discusses types of skylights, planning a skylight’s location, glazing options, energy efficiency, and more.
A skylight can save you money, too. In addition to reducing the need to use electric lights, it can deliver warmth in the winter and cooling in the summer, minimizing the need for fuel-based heating and air conditioning. On winter days, the sun’s radiant energy can shine through a south- or west-facing skylight to warm interior surfaces. And in the summer, a ventilating skylight can promote air circulation by releasing the warm air that naturally rises.
Types of Skylights
Skylights may be plastic or glass, fixed or operable, and made in any number of sizes and styles. They can have insulated glazing, UV-blocking capabilities, louvers, shades, and more.
Knowing the right materials, the proper size, and the appropriate features to meet your needs is critically important.
To help you focus on the particular qualities to look for in a skylight, please see:
Planning a Skylight
Keep in mind one important fact: A skylight will only work in a room that is either directly below the roof or is below an unfinished attic space. If you want to install a skylight in a room that has an attic above, you’ll need to build a light shaft through the attic.
The shape of a light shaft controls the spread of the natural light beam. A shaft that’s flared on all four sides spreads light over the widest area. A perpendicular shaft with vertical sides focuses the light straight below. A shaft flared on only one or two sides sends more light in the direction of the flared sides. For more about building a skylight shaft, seeHow to Install a Skylight.
When planning a skylight installation, be sure to take into consideration the sun’s path. Skylights on the south- or west-facing portion of the roof will collect direct sun—skylights facing north or east may not get any direct sunlight. A skylight that receives direct sun can become an intense heat trap in the summer unless it includes shades, blinds, or some form of controlling sunlight (seeSkylight Blinds & Shades).
Similarly, a skylight placed in a bedroom can offer a nighttime view of the stars but, if it doesn’t have some form of daylight blocking shade, it can also offer a rude awakening at daybreak. Of course, any skylight that is intended to provide a view must be kept clean, so ease of maintenance becomes a factor in choice of location and the type of skylight.
Be sure any skylight you intend to install will meet local codes for load, wind resistance, and related factors. Building permits are required for installation in most regions.
Glass or Plastic?
Skylights are glazed with several variations of glass and plastic in single, double, and even triple glazing. Several manufacturers make both glass and plastic.
体重是一个重要因素。与大约120磅相同的玻璃天窗相比，4 x 4英尺的塑料型天窗重约65磅。
Glass is generally preferred for skylights because it has a more elegant appearance than plastic, offers a clear view, doesn’t scratch, and can be ordered in a wide variety of sizes and types. Of course, the more features you want, the more expensive the glazing will be.
Tempered, double-insulated glass.This is the minimum standard for most quality products: tempered for safety and two layers of glass with an air space in-between for energy efficiency.
Tempered, double-insulated glass with low-e (low-emissivity) coatings.With this glass, the outer pane is tempered, and the inner pane has an invisible low-e coating that helps hold heat in during the winter, reduces heat gain in the summer, and cuts ultraviolet (UV) rays, which bleach fabrics and damage furniture and floors.
Tempered, double-insulated glass with low-e coatings and an argon gas filling between panes.该玻璃与上面的玻璃相同，但具有更大的绝缘值。一些公司，例如Marvin和Pella，以标准配置为低E-E型氩气玻璃；其他制造商将其作为选择。
Tempered, low-e, argon-filled glass with a bronze tint.这具有与上述两个相同的品质，但旨在减少太阳热的增益。
Tempered-over-laminated, low-e, argon-filled glass,有或没有一个青铜色。旨在eliminate the danger of interior glass breakage in areas that require laminated glass, this type blocks nearly all UV rays. It’s a sensible glazing for regions where the sun’s heat buildup is a problem, such as on south- and west-facing roofs in hot climates.
The following chart compares values of Velux’s glazing options. The best glazing to choose depends on the performance needed for a particular application.
Most skylight manufacturers test their products for heat loss, solar heat gain, and blockage of the sun’s ultraviolet (UV) rays. These measurements are expressed numerically. It’s helpful to know these terms before you shop:
U-value, which depends not only on the glazing but also on the frame and all related parts, measures the rate of heat flow (from either side) through a skylight. This measurement does not include solar heat gain. The lower the U-value, the better the product resists heat flow.
R-value米easures a material’s insulation value—the resistance a material has to heat flow. In reference to skylights, this value is usually placed on the glazing. The higher the R-value, the better it insulates. Skylights with the best R-values have low-e insulating glass with argon gas between the panes— these yield about twice the insulating value of standard dual-glazed panes.
遮阳系数米easures solar heat gain through glass. This coefficient compares a particular glazing with a single pane of 1/8-inch-thick, double-strength glass. A low shading coefficient means low solar heat gain.
UV blockageis a value approximated by glazing manufacturers, expressed as a percentage of ultraviolet rays blocked by the glazing.
Visible light transmittance (VLT)是一些制造商使用的测量值，可见光的百分比是天窗传输。在房主想要大量自然光线的地方，他们选择高VLT值。有色玻璃通过较少的光线阻止眩光，其VLT等级较低。
接下来见：Fixed or Operable Skylights