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Community and Q&A

Window film to reduce SHG from skylight?

davidmeiland | Posted in Energy Efficiency and Durability on

A client of mine has a couple of large skylights, about 5’x7′, both facing southwest, and they really get cooking when the sun is out, so we’re looking for ways to reduce the amount of solar heat coming through them They are low-e2 glass. Options we’re considering are (1) reglaze them with lower SHGC glass, (2) install interior “storm” windows below the existing glass, and (3) applying some sort of film to reduce solar heat gain. There appear to be several manufacturers of such films… 3M and SolarGard are a couple.

How well do these work? What are the issues?

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  1. GBA Editor
    Martin Holladay | | #1

    I don't have any experience with retrofit films, so I look forward to hearing from GBA readers on that issue.

    But I have to shake my head when I hear that a designer or builder installed skylights facing southwest. What were they thinking?

  2. user-659915 | | #2

    Here are three more options: (4) translucent exterior shading fabric or (5) exterior louvers, to prevent direct insolation of the glass, and (6) the nuclear option - remove the skylights entirely. Martin, I also am aghast at the orientation (and the size) of the glass. The culprit may have been neither designer nor builder - homeowners can be very insistent.

  3. davidmeiland | | #3

    OK, so far no one has used the films, I guess.

    James, your #4 is similar to the film application, and #5 is what we're going to do on some windows that suffer the same issue--I'm going to fabricate some louvered awnings to reduce insolation of the window glass. Had not thought of that on the roof because it would be a lot harder to mount something without poking holes in the shingles. Still... worth considering.

    Talked to one film guy today. He had the kinds of numbers I wanted right at his fingertips. Given the type of glass and existing SHGC/VLT, the manufacturer provides the upgraded numbers. They claim they can cut SHGC by about 75%, and of course VLT drops accordingly.

  4. wjrobinson | | #4

    Film used by friend. Film is shot now from UV. Wants me to replace glass now with better glass.

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