Low level condensation

[paulstoke1975]

I've just found I have condensation on the wall at the side and head of my bed and behind my sofa, I bought a dehumidifier a few weeks ago for the saloon but it's still getting quite a lot of moister on the walls , any ideas how to prevent this ?

[Dave_P]

I've just found I have condensation on the wall at the side and head of my bed and behind my sofa, I bought a dehumidifier a few weeks ago for the saloon but it's still getting quite a lot of moister on the walls , any ideas how to prevent this ?

Pull the mattress & sofa away from the wall each morning. A couple of inches will do. It will stop the condensation forming by keeping it well ventilated there.

[Jess--]

the way I have seen it avoided is to force an airgap (usually 10mm battens and 3 ply) behind seating, usually open into cupboards / storage below and ending (open) about an inch below the top of the back cushions.

[blackrose]

What sort of insulation do you have behind the lining below the gunwales and how thick?

 

Apart from single glazed windows, the walls and floor are generally the coldest areas of the boat because they are immersed in water. The water may actually have a slightly higher temperature than the outside air in winter, however heat transfer is usually much greater to water than air, unless it's particularly windy outside.

Edited February 5, 2016 by blackrose

[ValandPete]

DRY-mat worked for us in the bedroom. We left enough when cutting to wrap up the side of the mattress against the wall. Fourth winter with it in place so worth the cost. No sign of damp on walls and mattress now so highly recommend.

 

Val

[DHutch]

Ditch the dehumidifier and get some ventilation!

 

In a boat everything is pushed closed together, and while we dont live on the boat, every winter and if we stop a night in winter we always leave mattresses pulled from the edge. Also if your mattress is on a solid base the drill some holes in the board to allow it to vent underneath. Basically all you can do.

 

 

Daniel

[cuthound]

Provided he can check regularly that the dehumidifier is working, it is adequately rated, that it drains into the sink, rather than a closed container, and that any openings are closed (to stop the dehumidifer from trying to dry the world) then that should be the best solution. The boat will be kept dry and heat from the dehumidifier will help prevent freezing in the winter.

 

If he cannot guarantee that the dehumidifier will keep working, then plenty of ventilation and either moving the mattress away from the sides and/or using drymat is the next best solution.

 

I used to go for the ventilation method, but still got some condensation when a wet spell was followed by a cold spell. Since using the dehumidifier (a Meaco DD8L Junior) I have had zero condensation.

[sjc]

Provided he can check regularly that the dehumidifier is working, it is adequately rated, that it drains into the sink, rather than a closed container, and that any openings are closed (to stop the dehumidifer from trying to dry the world) then that should be the best solution. The boat will be kept dry and heat from the dehumidifier will help prevent freezing in the winter.

 

If he cannot guarantee that the dehumidifier will keep working, then plenty of ventilation and either moving the mattress away from the sides and/or using drymat is the next best solution.

 

I used to go for the ventilation method, but still got some condensation when a wet spell was followed by a cold spell. Since using the dehumidifier (a Meaco DD8L Junior) I have had zero condensation.

 

I agree, we have the same dehumidifier and wouldn't be without it. I also think you need warmth, so keep the fire going, don't let it get cold. As already mentioned ensure there are air gaps everywhere : cupboards, wardrobes, around the matress etc.

[Drayke]

I’ve seen a lot of boats with carpeting that continues up the sides to the gunwales which seem to provide insulation and stops condensation forming.

[DHutch]

I guess it depends, and I will say again I have never lived on a boat, but as ventilation and dehumidifiers are so fundamentally incomparable I must say I would certainly start with the ventilation route.

 

If I was living on the boat I think I would try a fine-wire heat recovery ventilation unit MHRV before a dehumidifier.

 

I have an unheated conservatory I use for drying cloths though out winter, with two of the little top windows half often I can dry a 6kg load in two days even if its raining outside. No damp on the sofas etc.

 

 

Not looked in depth, but maybe this:

http://www.vent-axia.com/product/lo-carbon-tempra-t.html

 

 

 

Daniel

[blackrose]

I agree that dehumidifiers shouldn't be necessary and they must be expensive to run?

 

However, most boats should be adequately ventilated anyway in terms of providing airflow for oxygen burning appliances - including humans and pets. Adding extra ventilation may help reduce condensation, but it may also make it too cold inside the boat. Indeed, you could ventilate the boat to the point that eventually the heat losses mean it's so cold that you won't get any condensation to begin with! Problem solved (except that presumably you still want to live on the boat?)

 

So, I would start by looking at the insulation.

Edited February 7, 2016 by blackrose

[Dave_P]

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I agree that dehumidifiers shouldn't be necessary and they must be expensive to run?

 

However, most boats should be adequately ventilated anyway in terms of providing airflow for oxygen burning appliances - including humans and pets. Adding extra ventilation may help reduce condensation, but it may also make it too cold inside the boat. Indeed, you could ventilate the boat to the point that eventually the heat losses mean it's so cold that you won't get any condensation to begin with! Problem solved (except that presumably you still want to live on the boat?)

 

So, I would start by looking at the insulation.

Ventilation does not necessarily mean ventilated to the outside. It could mean allowing air to move from one part of the boat to another. My main saloon is always condensation free because the stove is drawing the moisture out. If condensation forms, it's in a corner or crevice. Simply allowing the air to move around the boat and through these crevices, solves the problem. The convection currents formed by the hot stove, keep the air moving. Just try and eliminate 'dead spots'. The back of the mattress is an obvious one.