The thing to think about is how and why condensation occurs. If you consider first the wall or window of your garage. The air inside the garage contains a certain amount of moisture, as all air does. The ability of the air to retain this moisture depends on the temperature of the air. Now, I assume that your garage has a single skin wall ie only one layer of brick as opposed to a cavity wall that you would find in a house where there are actually two walls, one inside the other, with a gap in between. So, the garage wall is cold (in the winter) due to the fact that it is cooled by the outside temperature and this cools the brick all the way through to the inside. So, when the relatively warm air in the garage comes into contact with the wall, it is cooled down and then its ability to retain the moisture is reduced. If the air cannot retain the moisture that it contains because it gets too cool, then the moisture is released from water vapour into water on the wall and this is what condensation is.
So, there are, as I see it, 2 things you can do (perhaps both). If you can, stop heating the garage - this will mean that the air on the inside is the same temperature as the outside and this should help. Also make sure the garage is well ventillated, perhaps by inserting some air bricks - if there is a good gentle flow of air throughout the garage then it is less likely that there will be a build up of moisture heavy air in the inside. The reason you don't tend to get condensation in a house is that there are usually cavity walls so the bricks on the outside can be cold while the bricks on the inside can be warm, so the air on the the inside doesn't come into contact with cold bricks. This also tends to be the reason that double glazed windows suffer less from condensation. So, turn off the heat if you can and increase the ventillation.
Anyway, hope some of this is useful!
Gareth, March 2007
