Expert: Dave Johnson - 5/30/2008

Question
We have stripped the interior of our 1920's three season cabin in Pa. down to the studs and have had it rewired.  The exterior is painted cedar clapboard with no vapor barrier. The roof is metal over apshalt shingles and has a ridge vent.  The ceiling will be a modified cathedral. We would like to use a combination of t&g wood and drywall for the interior walls and ceiling.  I am unsure of how and/or whether to insulate. Loss of heat is not a concern, however creating/avoiding a moisture/mold/mildew problem is a big concern of mine.  The cabin sits through extremes of temperature and gets virtually no winter use with the exception of one or two visits to check on it's safety/security.  We have a fireplace and a propane heater to warm it up when we use it in cooler periods in fall and spring.  Water is shut off in October.  When we stripped off the old interior homosote and cheesy paneling there did not appear to be any significant mold problem - just a pretty musty old smell in the homostote.

Questions????

I was thinking of using blue foam board insulation cut to fit snugly into the joist cavities and sit tight against the exterior between the wall joists.  That would still leave a cavity between the foam board and the finished wall surface.  Would that create more problems than it solves?

Should I use a moisture resistant drywall, like the kind you use in bathrooms?  

We do not want to strip off the exterior siding to wrap it in tyvek because the siding is in good shape.  

What would you do if this was your cabin?  We need interior walls because the wiring shows and frankly the joist cavities are not very pretty to look at.

I appreciate any suggestions.  I have heard that spray-in insulation would be perfect but I am worried about the high cost and the inability to make any changes within the wall cavities after insulation.

Susan

Answer
Hi Susan,
First: Thank you for the detail!!

If heat loss isn't a factor, I wouldn't waste money on any expensive insulation (and most of it is!)

The foam won't cause any problems...
I do like the idea of MR board, just in case...
Don't worry about tyvek/typar its all over-rated anyway...

If it were mine, I wouldn't insulate, I'd use MR board or wood walls/ceilings and let it breath.

If you do decide to make it a year-round place, go with the spray foam in the walls, blown cellulose in the lid and VENT the area above the ceiling insulation.

Best of luck,
Dave