Insulate basement myself or hire it out?

where_am_iAugust 28, 2006

In the process of finishing my basement a little at a time as the money tree grows new leaves. Right now it is framed in by the builders and I would like some insulation up before it starts to get cold. If I hire an insulation company to come in and do it, will they have something that I wouldn't be able to get from a home center? Any other reason to not do it myself?

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No reason to hire it done because a professional will not have access to anything special unless you want an expansive foam.

I take it that your studs are in place. You can use 3.5" thick fiberglass and it is relatively inexpensive. The home centers will likely have fall sales on this product.

I have heard differing thoughts on basement insulation from time-to-time. One is that you only need to insulate to below your frost line. Another that you should not use fiberglass near the floor where, if flooded, water would saturate it. Last one I have been told is that styrofoam against the concrete will provide a vapor and mold barrier. All make sense but not being an expert I cannot weigh in with factual knowledge on one vs. another. In my case, I used 2" styrofoam between the studs top to bottom which permits electrical conduit and boxes to fit in front of the insulation. Basement is certainly more comfortable but without maximum R value.

    Bookmark   August 28, 2006 at 3:40PM
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I insulated mine last winter, and I used 2 1/2" rigid foam insulation glued with construction adhesive, directly to the concrete between the studs.

    Bookmark   August 28, 2006 at 5:03PM
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Two of my walls are 2/3 above ground with the last 1/3 being block the other 2 are block floor to ceiling. If I went with 2" rigid foam, could I fill in the rest with fiberglass after the electrical is run? Regardless of foam or fiberglass, a vapor barrier is still needed, correct?

    Bookmark   August 28, 2006 at 6:31PM
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What about basements that have those thick "white" insulation "blankets"?

    Bookmark   August 28, 2006 at 7:50PM
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Are you talking the type for water heaters?

    Bookmark   August 28, 2006 at 9:02PM
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There seems to be several schools of thought on basement insulation although I'm not convinced that any one is better than the next.

I'd suggest using ordinary kraft faced R-11 or R-13 fiberglass stapled to the studs. You'll want to do that AFTER the electrical rough in.


    Bookmark   August 29, 2006 at 7:36AM
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Check out the technical reference section of - Fiberglass is not recommended for basement wall insulation, nor is the use of a vapor barrier. The wall assembly has to be able to handle the entry of water vapor and be able to breathe to the interior in order to dry. Rigid foam insulation is the preferred choice - white bead board is fine - and it is comparatively inexpensive and vapor permeable.

    Bookmark   August 29, 2006 at 9:27AM
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"Fiberglass is not recommended for basement wall insulation, nor is the use of a vapor barrier."

In our Building Code (Ontario), batt type insulation must be protected by a vapour barrier on the warm side, and a moisture barrier on the cold side (the interior of the foundation wall). FWIW, on my most recent house, I mechanically fastened 1" Styrofoam board directly to the foundation, taped the joints, then built a steel framed wall over it, put batts between, then a 6mil vapour barrier and drywall. At the rim joists we sprayed in high expansion insulation (150:1) to seal all those hard to reach spots. This has been the only basement I've done that didn't need supplementary baseboard heaters. (On the above grade walls, Styrofoam was used as sheathing, and the space between the studs was filled with R18 batts. Again, it feels the tightest of any home I've built.)

    Bookmark   September 3, 2006 at 5:11PM
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I downloaded a PDF of my city's checklist prior to applying for a permit to finish a basement. The section under insulation reads

"Insulated exterior walls must be covered on the interior with not less than a 4-mil vapor barrier. Provide a moisture barrier over concrete walls prior to framework. (Poly vapor barrier is not a moisture barrier when used alone.)"

So, my house was built in 1992 and the basement was framed in during its construction but never finished. The builder did fill the walls with fiberglass and covered them with poly. After moving in a few months ago, I had to take out all the insulation due to a rodent problem so I am back down to the studs. There is no moisture barrier against the concrete block. First, what is a moisture barrier, and second, am I going to have to rip out all the framed walls?

    Bookmark   September 5, 2006 at 11:14PM
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In regards to fiberglass, is it harmful to the health if they are not covered. Our unfinished basement has some pink fiberglass that our builder did not cover it.

We plan to leave it as is and use it as rec room. Is it safe to do so, if not what should we do (what can we use to cover it)?

Thanks for your input.

    Bookmark   September 7, 2006 at 1:01PM
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I was going to give you the stock answer--dampproof the interior foundation wall, replace the batts and vapour barrier as per Codes.

But the fact is that Building Codes are woefully behind building science research into the best ways to ensure healthy, energy efficient basement living space. (See the link below.)

I'd rip out the framing you have--chances are the builder didn't even place dampproofing beneath the plate. Then fix board-type insulation against the walls, eg., Styrofoam SM, with either the appropriate adhesive or concrete fasteners and fender washers, seal the joints with air-barrier tape (red and very sticky) caulk the joints at the top and insulate and caulk between the joists at the rim (NO BATTS).

Next, build a stud wall, preferably of light gauge steel, add batts if you want to superinsulate or just drywall without a vapour barrier. (This is the way I did our custom home last year--though unfortunately, the inspector insisted on the vapour barrier.) And it's the way I intend to finish a custom home I am doing for a client starting next January.

Here is a link that might be useful: Basement Insulation Systems

    Bookmark   September 13, 2006 at 8:16PM
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A cheaper way of finishing the walls would be to fix furring strips to the foundation wall through the insulation and use these to affix the wallboard. But this precludes electrical receptacles etc. on your exterior walls.

Also, be sure to provide dehumidfication during the summer months.

    Bookmark   September 13, 2006 at 8:40PM
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Don't use fiberglass. It holds moisture, attracts moisture and even with vapour barrier, glass fibers will still make it into the house where they can cause health issues. Do some research on the web about it. Check out sustainable enterprises website. I just replaced a dumpster load of professionally installed fiberglass batts that were full of mold. Use sprayfoam or foamboard only. Check out Mike Holmes book on home renovation. If I had, I'd have saved about $30,000 in "professional" mistakes.

    Bookmark   January 4, 2007 at 1:00PM
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