Rigid XPS Foam And Poured Concrete Foundation. - Insulation - DIY Chatroom Home Improvement Forum

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Old 05-28-2013, 12:01 PM   #1
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Rigid XPS Foam and Poured Concrete Foundation.

I live in South Eastern Ontario. I've done a lot of research on insulating the basement of my raised Bungalow. Here's what I'm planning on doing, and if there's room for improvement please let me know.
The house is 5 years old, and when bought had a sealer applied to the foundation below grade, with about 1-2 inches of a fiberglass insulation on that. For the 2-3 feet above grade there is just plain unfinished poured concrete.
For the inside foundation walls I'm looking to put up 2 Inch XPS, with R12 Fiberglass insulation, covered with Gyp-rock.
For the Floors 1 Inch XPS, and 1/2 inch Chip Board.
For the 16in Headers I'm going to put 2 inch XPS, then spray foam the edges, and then cover with R12 Roxul. I have 1 header running the other way (20 feet) with about 7 wires stapled to it, and was thinking of just sealing the edges with Silicone Caulking, and then putting R22 Roxul over it. I'm not sure if it's a good idea to spray foam over all those wires?
I'm concerned about the permability and the Concrete foundation. Someone mentioned something about the Concrete freezing because it's not getting heat from the house. And with everything being so well insulated Permeability wise, will the lack of moisture going to the Concrete cause it to weaken in any way over time?
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Old 05-28-2013, 02:56 PM   #2
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You are really on the right track.

Your research and thoughtful approach should be commended.

Wires, provided they are properly covered and not exposed, don't mind spray foam at all. Spray foam, for lack of a better descriptor, is basically plastic. Works quite well at insulating them for that matter.

If you go the Roxul only route in that case, it would be best if you could cover it with some sort of air barrier. If not, the relative humidity could still reach the cold framing and condense. 2" of closed cell foam will prevent this.

Everything else looks spot on.

The person about the concrete is mistaken. If the foundation is not leaking, most moisture is from the conditioned air in the winter and does nothing to "help" the concrete.

If the foundation is leaking, you will see it soon enough.

ADA (Airtight Drywall Approach) and are you good to go.
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Old 05-28-2013, 09:13 PM   #3
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I'd ask your local AHJ on the SPF/wiring; http://www.sprayfoam.com/mnps/fullth...id=5&startat=1 Must be up-dated somewhere since then...

If I could get a large city close to you we could calculate the dew-point with using 1" foamboard on the floor for the spring/summer (due to lag) outside air condensation risks on the slab; http://archive.nrc-cnrc.gc.ca/eng/ib...igest-180.html

http://www.buildingscience.com/docum...g-your-basment Did you do a moisture test of the slab in various places yet?

Or find your location between temperature bands here and add 10*F to the total because slab is 6' below grade; http://www.epa.gov/athens/learn2mode...enrys_map.html

Early study of radiation/heat loss at slab in Canada; http://www.google.com/url?sa=t&rct=j...W2MrVA&cad=rja

The foundation would still get heat from the warmed rooms, enough that moisture freezing would not be a problem; Figs.9-12, or add some "wing" insulation, Fig.13. Also note the rigid f.b. rim insulation at Fig. 26 and SPF at Fig.31.

Slab insulation over a membrane as Delta fl or similar as in Fig.36, all found here; http://www.buildingscience.com/docum...sure-guideline

More on the concrete wall/moisture drive for summer/winter if needed, just ask.

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Old 05-29-2013, 09:32 AM   #4
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Thanks for the great replies. Those were some great links there Gary.
From one of the links, I'm happy to see that I'll be saving 3 Liters of water per day, from entering my basement once completed. That should save a lot of power with the dehumidifier.
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