attic insulation

m_taggartApril 22, 2012

We bought our house a few months ago; it was built in the 70's. The insulation in the attic is laughable. It appears to be the original insulation and average thickness is approximately 2 inches. I can see drywall in some spots. I'd like to add insulation at some point this year and am seeking advice.

First off, batts or blown in? I know I could do either myself, as the local hardware stores will provide the blower for free if enough insulation is purchased. We plan to have a new roof put on in the next 5 years or so, and I'm wondering which will pose less of a hassle when the crew installs soffit vents (we have gable vents only). Should I install soffit vent baffles while I'm up there in anticipation of having the soffit vents installed?

Second, cellulose or fiberglass (if we decide on blown in). My concern with the fiberglass is that it has been classified as a suspected carcinogen. Obviously once it is in place in the attic there is little to disturb and the risk is minimized. On the other hand, I've read that the cellulose, while treated with fire retardants, does pose a fire risk. We have aluminum wiring, which does pose an increased risk of fire. I plan to inspect all connections and fixing if there aren't done with co-al approved connectors. The other thing about cellulose is I've heard it settles more than fiberglass, thus decreasing the R value. True?

Third, I would like to have a bit of storage space up there. Is it possible to build a raised platform to provide room for the insulation underneath?

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Also, is a vapor barrier required with blown in insulation?

    Bookmark   April 22, 2012 at 10:11PM
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The question of where you live (or what is your climate like) is very important to answering this question.

In addition, you should probably read the recent thread about insulation in the HVAC forum.

    Bookmark   April 23, 2012 at 11:29AM
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I live in the piedmont of North Carolina near Raleigh.

    Bookmark   April 23, 2012 at 12:39PM
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as ionized posted, check out insulation thread
in hvac forum
air sealing & duct sealing should be done
prior to adding insulation.
fyi..I like batts. second choice would
be blown fg. cellulose is never a recommendation
except in walls due to borate/dust issues.

as for the walkway...
before any insulation is added
toenail 2x6's across ceiling joists
with screws. this will give you 5 1/2"
more for insulation.
when insulation is completed screw
plywood to 2x6's. mark on plywood the
location of any plumbing, electrical & anything
that you may need to access in the future.
a little foresight sure makes a difference.

best of luck.

    Bookmark   April 23, 2012 at 5:10PM
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Thanks for the advice.

Why batts? After doing a little comparison, it seems they're more expensive and take a bit more work to get in to place. Is there something I'm missing?

Is a vapor barrier required in my area?

    Bookmark   April 23, 2012 at 10:09PM
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batts are my prefrence.

easy to move when you need to get to
something rather than having to dig out
blown insulation.

cellulose is messy..messy to install
messy every time you open the attic
while I can deal with the mess once,
I wouldn't want to have to deal with
it every time I went into the attic.
just my personal experience.
I won't work in homes with cellulose.
messes up my lungs for weeks.

I'm not sure of vb location for your
area. check with local codes for specifics.

best of luck

    Bookmark   April 24, 2012 at 10:06PM
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Sophie Wheeler

I absolutely loathe blown in insulation of any kind if you're going to do any work on the home. Batts are just easier for an homeowner with an older home who is likely to want to add additional lights, or other electrical, or renovate anything at some point. They are much easier to move out of the way, do your project, and then re-use. If you're building new, and have added chases to be able to run stuff from one end of the attic to the other, then blowing in fiberglass would be fine. But if you're gonna be crawling around in the attic, and using it for storage, I'd do batts in a heartbeat.

You most likely need a vapor barrier in your climate as the first layer, with it facing down. However, the MOST important thing is air sealing to keep hot air away from your conditioned air. My cousin had what he thought was a leak coming though a recessed light. He couldn't figure out why, since there was no plumbing pipe there, and the roof was decent. Upon further investigating, there was quite the air penetration and the hot moist exterior/attic air was coming into contact with the cool air conditioned air of the home and causing condensation to form and drip down.

    Bookmark   April 26, 2012 at 5:33PM
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