Skylights 101

We have tried here to anticipate several questions not explained in other sections of the site. If we are not successful in addressing your concern, please contact us directly.

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Curb - the frame the skylight is mounted on, which can be either integral to the unit as in a self-flashed skylight, or a separate piece as in a curb-mounted unit. Curbs are usually made of either 2 x 4's or 2 x 6's, though unusual applications may call for a larger curb. A curb should always be insulated, preferably with underlayment and flashing.

Outside curb dimension - the dimension most commonly quoted when ordering or quoting skylights. The OCD is usually ½" shorter per dimension that the "make size" or the measurement from vertical flange to vertical flange. For example, a 25 ½" x 49 ½" outside curb dimension will yield a 26" x 50" make size skylight.

Energy Star - A rating program sponsored by the EPA and Department of Energy which provides energy saving standards met by several of our product lines.

Flashing - the weatherproofing system that is either integral in your unit as in a self-flashed skylight, or separate as in a curb-mount. Flashing can be made to match any roofing material, and can be interwoven as in the case of step flashing to shingle roofs to seal the skylight without sealants that can break down over time.

Glazing - a term descriptive of the light part of the skylight, in other words, the part you see through. Skylights will always be double-glazed, or will have two layers, otherwise you are looking for a "hatch cover".

Tempered glass - a standard safety function that allows glass to shatter into small pieces rather than large dangerous shards

Laminated Glass - the lower layer of glazing is made of two panes of heat strengthened glass bonded together around a vinyl layer that holds the glass together if it is broken. Laminate is an additional safety feature made for areas more prone to extreme weather or that sit directly under or in close proximity to trees.

Low E - is a microscopically thin film on a glazing surface that suppresses radiative heat flow through the skylight. Also known as a spectrally-selective coating.

Argon - is an inert gas that provides added insulation windows and skylights

Acrylic - used most often on flat roofs due to it's natural dome shaped once formed, acrylic is an inexpensive alternative to glass that is lighter and can be used in a wider array of applications

Polycarbonate - also lightweight and particularly impact resistant, most skylights made with polycarbonate use a flat sheet design which has the benefit of being more durable than acrylic or glass, but is often not completely translucent and can't be used in as many applications

Cladding - part of the exterior aluminum framing of the skylight

R and U values - U value is the measure of heat flow through the glazing surface of the skylight expressed in units of Btu/hr-ft2 -deg.F The higher a skylights U-value, the lower its insulating value. An R value is the inverse of the U-value, expressed in units of hr-ft2 -Btu. The higher the R value is the greater resistance to heat flow, and accordingly the greater insulating factor.

Underlayment - another level of protection from the elements that most contractors use to "wrap" the curb of a skylight and we always recommend using where possible.

Pitch - the angle of your roof or the ratio of rise to span that will often determine what kind of skylight you can use. For example, a 15 degree (or 3/12) pitch is often the lowest a flat glass unit can be applied to without custom building a pitched curb and/or voiding the warranty. This is an often over-looked aspect of buying a skylight.

Sash -the part of a venting unit that opens out, or the frame in which the glass panes are set

Glazing Options

Clear glass or acrylic will always afford you the most light entering your house, however if you are concerned about the room's exposure to UV radiation [finish this text]

  • Glass Options
  • Tempered over tempered glass
  • Tempered over tempered with Low-E (Low-Emissivity, an invisible film stretched between the layers)
  • Gas filled
  • Tempered over Laminated (the laminate is a safety option)
  • Tempered over Laminated with Low-E
  • Tinted glass - gray and bronze are standard colors, almost any other color is possible, though considered custom
  • Tinted acrylic - bronze, white and gray are considered standard and will add very little to your price; most other colors are custom

Frame Color

The frame color will change depending on material; unfinished aluminum will be a different color than copper, but almost any color can be applied (usually using baked enamel on top of a anodized frame). Bronze (a dark almost black) is used most often as it matches standard shingles perfectly.


Flashing Kits - Flashing, usually L-shaped aluminum or copper bent to the specifications of your skylight that is necessary to make your unit weather tight, can often be purchased as a kit made specifically for your unit. If one is not available from the manufacturer which is often the case for a custom size, your contractor should be able to construct his own rather easily.

Self Flashed - A self-flashed skylight incorporates all three pieces: the skylight, curb, and flashing into one, easy to install unit. Self flashing is an option that can be adapted to almost all skylight models.

Curb Mounted - a term describing a skylight without an integral curb (the frame, usually wooden, that is between the skylight and the roof). Curb mounts are often desirable for more extreme roof pitches, though often the choice between self-flashed or curb-mounted is made according to what the contractor has more comfort installing.

Flat Roof Curbing Systems - Very simply, flat roof curbs add pitch to glass skylights and are tremendously convenient (and necessary) when adapting a flat glass unit to a flat or low pitch (below 3/12 or 15 degree). Your contractor can sometimes fashion his own curb to allow for pitch, but this can get complicated and will often void the warranty of your unit.

Tandem Systems - Tandem or grid systems are an easy way to adapt multiple skylights to one roof and are often inexpensive as they usually incorporate standard sizes into aluminum extrusions (frames).