Glossary of Skylight Terms


Learning some common industry terms and descriptions can help you navigate your skylight installation project from start to finish. Here are some key terms to know:

acrylic skylights
These skylights are covered and protected by a glazing material with outstanding optical clarity. This material helps with weathering and has good chemical resistance and insulating ability.

bent glass skylights
These skylights feature glass that’s curved by heating it above its softening point. The glass is then bent by either gravity or press molds.

Also known as: curved glass

In the glazing channel, this is the depth of the glass engagement

Also known as: purchase, edge engagement

blinds for skylights
In addition to providing more lighting, skylights can provide unwanted heat loss/gain and UV exposure. Skylight blinds will lower your energy bills and help insulate your house by blocking out unwanted light.

Also known as: Solar blinds, custom blinds, blinds for skylights, skylight shades blinds, motorized skylight blinds, skylight window blinds, blackout skylight blinds

cap flashing
This protects and waterproofs the skylight by overlapping the top edges

Also known as: counter flashing

This exterior covering is applied to a frame or structure for protective purposes

Also known as: exterior cladding, wooden cladding, aluminum cladding, granite cladding, skylight cladding

condensation gutter
A trough that carries off condensed water. This water may be drained to the outside or just evaporate.

Also known as: condensation channels

cross rafter
This structural framing part is used in a skylight system between the rafters. It sits generally near horizontal.

Also known as: purlin

curb flashing
This is used for waterproofing at a curb or base

Also known as: base flashing

curb mount skylights
A skylight frame design that allows a skylight to be installed and anchored to a wood curb that will be a permanent part of the roof structure. It’s typically used on low slope roofs.

custom skylights
Skylights can be built to accommodate unique rooms and situations.

double glazed
Two panes of glazing divided by air space

Also known as: double glazed window, double glazed glass, double glazing panels

fiberglass reinforced polyesters (FRP)
Composite material that’s made of a plastic matrix comprised of reinforcing glass fibers to increase strength or stiffness.

Corrosion-resistant material that’s used to control, redirect or prevent water from entering a structure

Also known as: roof flashing

haze factor
This tells the percentage of light through a glazing material that doesn’t get diffused. Codes require that skylights have a minimum of a 90% haze factor.

heat-strengthened glass skylights
Glass that’s heated  in a controlled environment to provide a degree of surface compression. This glass is commonly considered to be twice as strong as annealed glass.

Also known as: tempered glass, safety glass

high impact acrylic skylights
This type of skylight uses a glazing material that has an impact modifier that blended with acrylic resin to meet specific impact requirements.

insulating glass unit
This factory-made double glazing has the periphery of air space sealed to minimize infiltration of any water vapor

laminated glass
Two or more glass plies that are bonded together with resilient plastic interlayers, usually polyvinyl butyral (PVB)

Also known as: laminated tempered glass, laminated glass windows, laminated tempered glass

leaking skylights
Leaks may occur in aging or improperly sealed skylights. Signs of leaking skylights are skylight condensation, nearby water puddling and ceiling stains.

A single glazing pane. The use of the term “lite” is chosen to avoid confusion. It’s most often referred to as “pane.”

Also known as: pane, light

low emittance (low-E) coating
This skylight coating has the reduced ability to radiate heat energy. If it faces an air space, this coating reduces the heat transfer across this space.

Also known as: low e glass, low e insulation, low e window coating, low e glass coatings, low e windows, low emissivity coating, e glass, lo e windows

motorized skylights
Besides admitting natural light and controlling temperature levels, these skylights allow the window to fully open for ventilation

motorized skylight shades
You can switch between natural room light and unparalleled glare and heat reduction with motorized shades. With the push of a button, the shade smoothly glides into place and blocks 99% of the sun’s UV rays.

A strip of wood or metal that separates and holds panes of glass in skylights
Also known as: sklight muntins, skylight window bars, muntin bar, skylight mullions

replacement skylights
Skylights come in standard sizes. When a skylight needs to be replaced due to age or other problems, a new skylight can fit right into the current hole in the roof.

skylight accessories
Many accessories can be included with your skylight. You can select wood frames and sash, aluminum cladding, and insect screens. Manual and motorized telescopic rods help with manual blinds.

A base for a skylight that mounts directly to the roof and doesn’t require a curb

A glazing and framing assembly made up of sloped and vertical surfaces. Skylights are generally implanted into the roof of a structure to admit daylight.

Also known as: tubular skylights, dome skylights, skylight tube, custom skylights, round skylight, roof skylight, solar tube skylight, sky tunnel skylight, new skylights, acrylic skylights, home skylights, vented skylights, skylight dome, skylight window, venting skylights, motorized skylights

snow load
The accumulation of snow on a roof or skylight. This is generally a long-term load.
Also known as: skylight snowload, sky light snow loads, snow load for skylights, snow load of skylights

The measure of how well a product stops heat from being transmitted. The better the product’s insulating value, the lower the U-factor will be.

Also known as: window u factor, u factor windows, window u factor ratings, solar heat gain coefficient, energy efficient windows

vented skylights
These skylights are mounted in the ceiling to exhaust hot air and create a breeze in the home

Also known as: venting skylights, skylight vent, opening skylights, vented skylight, operable skylights, electric skylights