Will a dehumidifier help cure mould/damp on bedroom wall bedroom gets no sun north facing?
No, not at all. Dampness should not be getting into the room in the first place. All a dehumidifier will do is dry the air in the room. Chances are that if enough moisture is getting in to cause mold, the dampness is coming from outside the room. I’d check to see if part of the AC unit or its ducts are going over the damp spot, or if any plumbing, or ventillation is going through there. If there’s attic space above it, climb up there, and have a good look around. Move the insulation to see what’s going on near the wall. You may need to re-roof, work on the siding, reseal around the windowsills.
The mold is caused by the damp. The damp on the wall is probably caused by lack of insulation or by cold air getting in from outside, since this is probably the heating season where you live. A wall with poor or no insulation, or with air leaks to the outside, will get cold on the inside; the water vapor from the house (from your breathing, your plants breathing, your cooking, etc.) will condense on the cold wall, and the mold or mildew then has a great source of moisture to grow in. A dehumidifier is one way to slow down the spread of the mold, and to cut the damp. But it’s far better to find the cause of the condensation – as I said, lack of insulation or too much air leakage are the most likely culprits. That way you solve the problem once and for all, don’t have to buy a cheap, energy-wasting dehumidifier, or an expensive, energy efficient one, and don’t have to pay to run the thing every winter for months on end. Also you won’t have to listen to the dehumidifier running at night w
