I started a home renovation and the client would like to insulate the exterior wall that is now 1×3 staping on solid brick with lath over, the house is small and spce an issue.
I thougth of putting 3/4-1″ high grade foam over strapping as the spce between the straps is uneven and only 3/8 in some areas, tape foam joints to form a continues seal and drywall over???
George
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It would be wise to add foam between the straps when the thickness allows -- every little extra bit of insulation helps when you're dealing with fairly thin amounts.
Different foam types have both different R values (varying about 2:1 between types) and different permeabilities for moisture. Some can serve as vapor barriers (if taped), others should have a vapor barrier added or should be foil faced (and taped). A vapor barrier isn't quite as critical with a stone structure, but is still worthwhile.
Does get a little tricky, though, if any of the wall is below grade. Then you may need some sort of ventillation behind the insulation to allow moistre to escape.
The rigid insulation that has the vapour barrier is a lower R value but comes in 4x8 sheets. The higher r value is only 2x8, I am leaning towards the built on vapour barrier to reduce air transfer form the cold brick wall to the warm drywall back. and use a 1/2 higher value between the strappong.
Thanks for the advice.
George