Hiya, William,
Sorry hear about your problem with your shed. Unfortunately, you'll always have condensation in any structure unless you either make the surface warmer so the moisture hasn't got anywhere to condense or introduce some ventilation. There's always moisture in the air and, where you have the cold surface of steel, that's where the moisture will condense. You haven't got many choices, I'm afraid. Lining the inside with a warmer surface...hardboard or something like that...may help, but then the air will always find a small gap and then the moisture will condense behind the lining causing problems which you may not be able to see. You can leave an opening for ventilation...this is usually the best way, unless, of course, you need to keep the air warm inside. This will ensure the air ciculates and will tend to dry out any moisture that does condense. Think about the outside...the air temp is the same, the humidity of the air is the same...that doesn't have condensation because the air is always moving. A dehumifidier is a possibility to draw out the moisture from the air. But you may find that it needs to be left on almost permanently to have any effect and this ain't gonna be cheap! There's really not much more you can do. I would really think ventilation is the solution out of all the options.
Unfortunately, this is something they don't tell you about with these steel buildings. They're quick and easy to erect, fairly maintenance-free and reasonably cheap, but the face of the inside does attract condensation.
I wish you luck.
Denis (HND in Building Studies, OND in Building Engineering)
Denis Langley, November 2007
