# Rigid XPS Foam and Poured Concrete Foundation.



## Windows on Wash (Aug 30, 2011)

You are really on the right track.

Your research and thoughtful approach should be commended. :thumbsup:

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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## Gary in WA (Mar 11, 2009)

I'd ask your local AHJ on the SPF/wiring; http://www.sprayfoam.com/mnps/fullthread.cfm?threadid=4603&mnforumid=2&mnboardid=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/ibp/irc/cbd/building-digest-180.html

http://www.buildingscience.com/documents/reports/rr-0309-renovating-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/learn2model/part-two/onsite/ex/jne_henrys_map.html

Early study of radiation/heat loss at slab in Canada; http://www.google.com/url?sa=t&rct=...sg=AFQjCNFTd1V1OUx_SYg8SFtGAAhpW2MrVA&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/docu...ybrid-foundations-retrofits-measure-guideline

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

Gary


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## BigB (May 28, 2013)

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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