detahed garage owners:humidity/moisture inside?

[CT2012]

i just went thru an exhaustive renovation of a detached garage with insulation & vapor barrier everywhere, sheetrock, paint, etc. etc. etc. i went overboard, generally. for exmple, when it's 35 degrees outside it's a good 10-15 degrees warmer in the structure itself (cinderblock walls with wood gable roof--which has an insulated attic).

today, here in the northeast, is a freakish weather day where the dew point is high and it's 60 degrees outside (it was 20+ colder a few days prior). the ground has been very damp all day. inside the garage almost all metal surfaces (including drywall scrapers!) have a very fine layer of moisture/dew on 'em.

i'm completely and totally stumped. could the vapor be coming through the concrete slab, which is not sealed with epoxy and only has interlocking plastic tiles (garagedeck)? i didn't do epoxy floor due to the extensive prep and so forth (and resulting expense), but am wondering if that's what's causing the humidity inside.

also, for whatever it's worth, the gable vents are temporarily sealed with a small panel of r4 foam wedged in the recessed space, so no air is circulating inside (which was needed 3-4 days ago when it was very cold out--i had to keep the cold air out).

ideas or suggestions appreciated. thanks!

 

[Eds Garage]

I find if a building is unheated, the air will tend to equalize to the average outside humidity levels. A cold concrete floor doesn't help either as humid air can condense and feel damp. I run a dehumidifier in my detached garage during humid summer days and rainy fall weather to protect the machinery and vintage cars. Cold weather isn't so much of a problem since the outdoor humidity tends to drop and the heater runs more.

 

[CT2012]

bingo. dehumidifier/heat combo. yes thank you i totally forgot about that.