Vapor Barrier Below Grade? - Insulation - DIY Chatroom Home Improvement Forum

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Old 09-17-2012, 01:57 PM   #1
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Vapor Barrier Below Grade?

Hi All!

My late 1970s house is in the mid-Atlantic region (Virginia). I am remodeling a portion of my basement. Washer/dryer area and small bathroom. The area has a 8' high cinder block foundation wall...all of it below grade. The room has (had!) a 7' high suspended ceiling since alot of electrical boxes, mechanical lines, drains, etc for the main floor run thru the area. I will be installing a new suspended ceiling. Obviously this means alot of air flow above in the open space. The A/C and furnace are very close so there is alot of residual dry air in the entire area.

When I tore down the drywall, the previous owner had thin styro boards against the cinder blocks between furring strips. Plastic sheeting ran from top to botton between the styro and drywall but was not taped anywhere.

When I re-do, I'm not sure what the best approach is. I know spray foam is a good option but I will probably be selling in 5-7 yrs. I want to do it right to avoid moisture and mold, but not interested in the most expensive option.

Some options...
1. Replace as before. Fresh styro boards between furring strips (or faced fiberglass insulation if I put up a 2x3 or 2x4 stud wall), then untaped plastic sheeting, then drywall.

2. Same as #1 but tape the plastic tight at all seams

3. No plastic at all and allow the wall to "breathe" to the open space above the suspended ceiling.

Advice needed and welcomed!! Thanks!

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Old 09-17-2012, 02:14 PM   #2
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Rigid board is your friend here.

Rigid board over the wall with furring strips on top. Don't put the wood to the cinder block. Put it overtop of the foam.

Seal up the ribbon and band joist areas.

Put enough foam up and drywall right overtop the foam. Seal all the seams and have an air tight drywall to prevent any moisture/air movement to the wall.
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