On 20/12/2012 22:43, JakeD wrote:
snip

The garage is already very well ventilated and there is no significant damp
inside coming up through the floor or walls, as it has a proper DPC, etc.

Perhaps I should make it even more well-ventilated, somehow. I don't know
though; you get dew forming on grass, outside, and "outside" is VERY well-
ventilated!


Indeed - and look at the condensation /dew / hoar frost you get on a car
parked outside, but not (so often) on one parked under a carport. Point
your infrared thermometer at a clear night sky, and you'll see why your
garage roof, or your car windscreen, is desperate to radiate to it,
causing its temperature to drop below that of the air above and below it.

--
Kevin