We moved in a few years ago and love theold "bubble" 4' X 4' skylights in
our family room. The problem, as with all skylights, was that they
We had them replaced with V-Lux flat lenses. Our old skylights also had a
makeshift fold-down cover that we could use to keep some cold air out in
winter and warm air out in the summer.
Unfortuately, the fold-down covers had to go when they were replaced. Also,
the roofing guys (excellent reputation) who replaced the skylights, told us
we'd be responsible for doing the interior finish work, which is fine. My
question is, before I do that (probably replacing the sheet rock on the
interior walls from the ceiling to the lenses, how do I insulate behind
Also, how and what do I use to insulate between the top opening studs and
the skylight itself? I've heard that expanding foam can do real damage. It
seems too big for caulk.
There are some expanding foams (polyurethane) that don't expand very
much. A good building supply house should have these. This is your
best bet but use it sparingly. The more aggressive foams will cause
your windows to bind if too much is applied, and it's not hard to do
that until you gain some experience using the material.
In the past I have taken loose pieces of that pink fiberglass insulation and
loosely pushed it into spaces around windows that I have replaced. Don't jam
it in because the insulation looses it effectiveness if all the air is
compressed out of it.
If I understand the first part of your question correctly, as far as the
area between the ceiling and the roof?, there too I would stack layers of
thick insulation one on top of the other. Depending on the depth of the
light shaft, you may need multiple pieces. Just remember you need to let air
circulate under the roof to prevent freeze/thaw problems. There are
Styrofoam panels shapes like a squashed u to allow air flow.
I just had 3 Velux installed. The interior contractor, who is top-notch,
just put R-38 kraft-faced fiberglass stapled to the framing of the light
shafts, all the way up to the roof sheathing.
Use a good oil primer, or Benjamin Moore's Vapor Barrier interior latex
primer on the drywall. I have 2 lights in my kitchen, so I am concerned
about vapor, steam, etc.
You may want to call your building code office. In my area, a permit, and a
framing and final inspection are required for skylights, even if no
structural changes are made. I was happy to get a permit. Trust me, it's
in your best interests.
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