we just bought a house last fall. this summer it seemed as if our garage was cooler than our home, and even warmer than our house now that its getting cold. we checked all the vents, and there isnt any open to the garage, but yet this summer we started to notice our things we have in boxes was getting mold on it. some say we need a dehummidifier? if so, isnt there one i can have put on my heating & cooling system..

helena, November 2010

And if you keep a car in the garage - let it cool down outside before putting it to bed - it will also be bringing in lots of damp air if you put it away when it's still warm.

Peccavi, November 2010

The garage will probably not have much insulation - the walls and roof will tend to be cold. Items close to the walls roof will be cold.

Warm air in the garage either from heating or air escaping from the house - particularly steamy air - will meet the cold surfaces and cool down - dumping the moisture it carries.

Over time the moisture builds up and mould will form.

Keep the warm air out of the garage
Ventilate the garage as much as you can
Wipe up any condensation you see
Consider insulating walls and roof
Consider buying a cheap greenhouse humidity meter $5
Consider buying or hiring a dehumidifier to dry out the moisture already there.

http://www.scotland.gov.uk/Publications/2005/05/10103020/30217

Good luck...

Peccavi, November 2010