I have a small studio (550 sq ft) in my back yard that has block walls with no insulation on the inside. I am collecting bids for siding the structure and have a few questions. First, if I were to go with insulated siding such as Craneboard or Alcoa, is it ok to add insulation (polystyrene) between the firring strips that are being installed on the exterior to allow for attaching the siding? IOW, we'd have two layers of insulation. I've been told this could be a problem because of the potential for moisture building up due to two insulations being back to back. Second, if I insulate the interior block wall and then sheetrock over it, will that cause moisture problems in light of the exterior insulation(s).

Thanks!

 

No problems with insulating between exterior furring in addition to insulated siding. Also no problems with insulating the interior. It would be just like an ICF (insulated concrete form). If you plan on stud walls and fiberglass inside, be sure to space the wood away from the cement by 1/2-3/4".

Moisture problems are most often created by air leakage where warm moist air comes into contact with a colder surface. So especially on the interior side, it would be important to tape all seams if you use rigid styrofoam insulation, or apply a visqueen (6 mil poly) vapor barrier if using studs and fiberglass.

 

Thanks for your thoughtful response!!