The whole question of dehumidifier use in caravans during overwintering has me puzzled so, as usual, I'm going to be controversial and suggest that they are a waste of time. At least it should, I hope, stimulate debate. The facts as I understand them (and as ever, I'm open to correction) are that:

1. Condensation occurs when warm, moist air comes into contact with cold surfaces. We've all seen that on the aluminium trim around the poptop interior trim on a cold morning. The best way to prevent condensation is to warm up the cold surfaces through insulation to raise their surface temperature above the dew point (not always possible) and to increase ventilation to keep the air moving.

2. Mould is caused by fungal spores in the atmosphere that thrive in warm and humid environments. The best way to prevent them from reproducing and damaging fabrics and internal surfaces is to provide through ventilation.

3. It follows, therefore, that to prevent condensation and mould damage inside a caravan during winter storage, it needs a constant flow of air through it.

4. This would suggest that it is better to leave some windows partially open to allow adequate circulation of the air as I doubt if the door and floor vents will be adequate on their own to ensure this over long periods.

5. Putting a cover, however 'breathable,' over a caravan can only reduce the through-flow of air and thus make it more likely that stagnant conditions suitable for mould growth will be created inside. It will protect the exterior of the caravan from dirt, bird droppings etc but if put on over dirty surfaces will lead to rapid deterioration of the paint, gel coat and acrylic windows due to abrasion. Covers can also cause damage if they are not adequately secured and are allowed to flap around in the wind.

So, if a constant circulation of air is desirable, how can a dehumidifier whether electric or in the form of absorbent salts have any effect on the internal humidity of a stored caravan? In effect, users will not be dehumidifying their caravan but trying to extract the water from the Earth's atmosphere. To be effective, all the vents in the caravan would have to be sealed to make them airtight but who hermetically seals a caravan every autumn?

I say that I'm confused about the whole subject because one winter I stored the caravan under a Protec cover with all the windows fully closed and had no problems. The next winter I did the same and ended up with some horrible mould growths on various surfaces. Last winter I put an 800 Watt oil-filled heater inside the caravan on the lowest thermostatic setting, no cover, windows all closed - no problems with mould (but I did have a noticeably larger electricity bill).

I still haven't decided what to do this year but if I do use the cover again I'll crack open some windows and make sure that I check the interior regularly and leave the door open during dry periods whenever possible.

What I won't be doing is going out and buying a dehumidifier.