# Raleigh basement insulation



## Todd1561 (Oct 14, 2013)

Anyone have any thoughts?


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## Gary in WA (Mar 11, 2009)

Zone 4, Wake county; http://energycode.pnl.gov/EnergyCodeReqs/index.jsp?state=North Carolina requires R-10 XPS (2").

Add the strapping of 2x2 over the foam board, no need to cavity fill with any fibrous insulation, leave it empty. Glue it in 1'sq. grid patterns, canned foam the perimeters. Tape will loosen as the FB shrinks- eventually; better still; furnace mastic/fiber tape on joints for air-tight, or canned foam. Add a strip of FB under the bottom plate for thermal/air/capillary break; may want to use a 2x4 on edge for attaching base later... second thought; NA the FB under as you are new build (requires poly) and not a cold climate.

No vapor barrier or retarder above or below grade for your Zone 4; http://www.buildingscience.com/docu...heet-310-vapor-control-layer-recommendations/

Gary
PS. Welcome to the forums!


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## Todd1561 (Oct 14, 2013)

Gary,

Thanks for the input and for the welcome, sounds about like what I was thinking. And I'm glad you don't think the fiberglass batts will be necessary now that I've calculated the cost of just the XPS I'll need! And yes there is poly under the slab, forgot to mention that. Another thing I forgot to mention is the ceilings are 12' tall. Do you think just 2x2 will be adequate for studs? I'll want to be able to hang drywall and some cabinets. 12' seems like a long span for a 2x2, not to mention trying to find a straight one that long! I'm wondering if I should do 2x4 on their side with a few concrete spikes evenly on each stud? What about doing 2' centers instead of traditional 16"? Oh and does traditional faced (or should I do unfaced?) batts sound ok for the foundation walls that are above grade 2x6?

Thanks again,
Todd


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## Gary in WA (Mar 11, 2009)

You need to at least read a little of the links.... lol; *No vapor barrier or retarder above or below grade* for your Zone 4; http://www.buildingscience.com/docum...commendations/

I would pin the 2x2 anyways.... 12' wall- use 2x4 with 2-1/2' pins. 24"o.c. is fine. Add backing at cabinet top rails.... add XPS at rims; http://www.diychatroom.com/f103/how-insulate-rim-joists-simply-190336/

Air seal any holes in top plates they may have missed. ADA the drywall; http://www.buildingscience.com/documents/information-sheets/air-barriers-airtight-drywall-approach/

Gary


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## Todd1561 (Oct 14, 2013)

Yeah yeah sorry. I know you said no vapor barrier but it doesn't seem like kraft paper is considered to be much of a vapor barrier these days. But I'll be sure to use unfaced batts in those walls. Thanks for the links, I'll be sure to do the rim joists as well


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