Condensation in attic above garage

Old 01-13-15, 10:16 PM
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Condensation in attic above garage

Around Thanksgiving while getting Christmas decorations from my attic space above my garage I saw and felt moisture on the nails and some of the decorations. Now after some really cold nights the entire north side of decking material is reasonably wet. I've seen some wetness on the other side but it is very minimal. I'm in and out of the space quite a bit and didn't notice this happening last winter when we experienced worse cold weather than we've been experiencing.

Let me first explain my house to you.
New Construction
1 level main that has blown insulation in the rafters above all heated space.
Garage is below attic storage space. It is heated at night with small elecric heater for dogs(Garage rafters weren't insulated until last week. This seems to have slowed condensation I see on nails and the wood seems to be drying a bit)
There is approximately 750 sq/ft of heated bonus space adjacent to the unfinished attic space.
No soffitt or Ridge Vent
Interior Door with threshold separates the heated and nonheated space.
Strairwell and door into attic space are 2 feet apart. (only mention this because is seems this is where a lot of heat accumulates as we keep the door closed between the upstairs and downstairs spaces)

I've tried to list all the information that I believe could have a bearing on my issues.

I understand the need for ventilation but I'd like to find the culprit for the warm air. Should I put an exterior door in into the attic space?
Old 01-14-15, 02:50 AM
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Welcome to the forums! Rafter insulation is not called for. The temperature of the attic space will replicate the outdoor temperatures to a degree. You should have soffit venting and ridge venting to allow fresh air to circulate. You say you have blown in insulation in the "rafters", but I believe you meant "joists". No door adjoining the two structures unless it is closable, which would negate your intent. Good insulation and ventilation is your answer.

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