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ctote 07-21-2011 11:47 AM

Should I insulate my basement floor?
 
*Insulate

I live in Southwest Virginia (section 4A), and am about to start finishing my basement. My question is, should I insulate my floor? It's concrete slab, and the basement is a walkout.

I was watching an episode of Holmes on Homes where he was finishing a basement - as part of the insulation process, he put down 2" foam board beneath plywood - and then carpet. Is this something I should consider? I'm looking at about 1000sqft. of floor I would need to cover.

Done That 07-22-2011 02:41 PM

My opinion is it would be overkill. I am in St. Louis MO area also with a walk out and when I finished ours I used laminate with Silent Blue pad under it for 90% of the floor, and tile by the walkout door and for the bathroom. I also have FLOR carpet squares in a bedroom....direct on the concrete. My finished area is probably about 65% below grade.

We use the basement constantly, daughter has a room down there, and I do not find anyone complaining about cold floors. I guess it never hurts, but I think the effort might give greater returns somewhere else. For example, I wish I had put something like rockwool above the basement bedroom for better soundproofing.

ctote 07-22-2011 02:53 PM

Quote:

Originally Posted by Done That (Post 691441)
My opinion is it would be overkill. I am in St. Louis MO area also with a walk out and when I finished ours I used laminate with Silent Blue pad under it for 90% of the floor, and tile by the walkout door and for the bathroom. I also have FLOR carpet squares in a bedroom....direct on the concrete. My finished area is probably about 65% below grade.

We use the basement constantly, daughter has a room down there, and I do not find anyone complaining about cold floors. I guess it never hurts, but I think the effort might give greater returns somewhere else. For example, I wish I had put something like rockwool above the basement bedroom for better soundproofing.


Thanks for the tips!

AGWhitehouse 07-22-2011 04:37 PM

Your heating needs are huge down there, but remember that raw earth is usually around 50-55 degrees. If you like your living space at 68-70 then there is a delta T (temperature difference) of 15 or so degrees over a 1,000 s.f. surface area. Putting flooring directly on the concete won't address it. Holmes method did. As far as Done That, the pad beneath the floor seperates the floor surface from the direct heat sink of the concrete and thus results in the "not-cold" feeling. But, the heat loss is definately still there.

With that said, if you have the extra $ and energy savings is something your interested in, then the insulation is a good idea. If you don't have the $ and don't care about the savings, then go for Done That's method.

Gary in WA 07-22-2011 05:08 PM

As AGW brought out, above, pp.4; http://www.buildingscience.com/docum...g-your-basment

Did you read about the concrete slab absorbing any rising moisture right away so it “looks” dry? A simple test: tape all edges of a 6mill plastic (2’x2’) down on the slab in different locations, leave for two days, check for condensation on the slab side of plastic…… This only tells if moisture is present at this time of year in that particular spot, unless you know there is a vapor barrier plastic under the slab when poured.
More info from BSC, end of article: http://www.buildingscience.com/docum...ms?full_view=1

Gary

ctote 07-22-2011 09:54 PM

Oh ok awesome, thanks guys. I think I might do the insulation, but probably can't afford the 2" - maybe I'll go with a 3/4" tongue and groove.

As for the moisture in the slab, I'll try your test, but I don't think there is any moisture rising. The floor is extremely dusty.

Done That 07-25-2011 07:46 AM

2200 sq ft first floor ranch, 1200 sq ft finished basement. All electric 12 year old home. I added 5 supply air drops to our existing 16 SEER heat pump system, as well as two returns. Added small 240V electric baseboard heaters for the bedroom and bathroom....they almost never get used.

We keep our house about 70 degrees year round. Budget billing went up about $5/month with the basement finish. Can lights, TV's etc sometimes put more heat into a space than expected. My heating needs did not appear to be huge down there.

I took a bigger utility hit putting a hot tub outside last year ($20/month). Just sharing some data, so many factors go into the mix on a question like this.


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