Cabin Insulation and condensation

[catman]

I have had my SO379 for nearly a year now, and in UK cooler weather experience quite a lot of condensation on the underside of the deck mouldings. This tends to drip onto the sleeping crew underneath.

I am planning to insulate and build a additional headlining (similar to the saloon) and would welcome other owners comments.

I am thinking of using closed cell foam, probably neoprene or EPDM rubber?

This is my first post, and I am generally very happy with the boat.

[MalcolmP]

Guess that will be hard to do without making it look really unsightly?

In our own 39i we find that it is important to ensure good ventilation in the colder weather- even if it is very cold make sure hatches are vented when moored and onboard - best to put on the heater or provide a thicker duvet if sleeping people are cold. Most of the condensation will be from the occupants.

We regularly use a large dehumidifier when we are on board in the marginal seasons - makes a great difference and keeps things really dry - it is also well worthwhile lifting all the mattresses and standing on edge when you leave the boat to make sure any trapped moisture below the berth cushions can evaporate

The only time we find heavy condensation in the stern cabin is when guests, despite my suggestion to the contrary, keep the cabin door and all hatches closed tight all night

Malcolm

[pio]

In my SO32 I have the same problem. I took an old computer 12 Volt ventilator and made a plastic shelf where the ventilator is installed on. I can put it under an open hatch (rain cannot get in, airstream going to the outside) and now I have no condensation anymore. Cost less than Euro 10,-.

[catman]

Thanks for your suggestions guys. I was thinking of making up a whole new false ceiling a la main saloon to conceal the insulation. I hope I can do a good job and make it look professional. I am keen to get some guidance as to the insulation levels of neoprene foam. I am happy in a 4mm wetsuit, but my VW camper uses up to 38mm foam!!! I think 20-25mm would be a good balance on cost?

A good idea to use 12v PC fans - very low wattage too.
Fair Winds
Malcolm

[electricmonk]

what you are proposing will decrease the heat-loss or heat gain from and to the boat but will do nothing to prevent the condensation you complain of; water laden air will remain trapped below deck and the water will condense on the relatively coldest surface. Your insulation will simply move it to another location INSIDE the boat.

To reduce or eliminate condensation you have only 2 remedies, ventilate the boat - let the wet air out, or use a mechanical method like a dehumidifier to dry the air, as others have said keeping a hatch cover open is the cheapest and most effective solution.

Its all about DEW POINT and PSYCHROMETRICS fascinating stuff

[Seagem]

I agree with MalcolmP and Electric Monk, ventilation or dehumidifier is the answer, do not waste your time and money on insulation there will be plenty of other things to spend it on!

If I get any condensation I always dry it up with kitchen roll or a dry cloth, open all the hatches and let it have a good blow through to dry it out. Remember to lift the mattresses and dry under them also. If there is condensation above then there will probably be some under them also. I have made a wooden sprung slatted base to go under my mattresses to stop condensation but there is also some special matting on the market.

[super g]

In summer we ventilate, but in winter and trying to keep warm then leaving a hatch ajar is not ideal, so out comes the dehumidifier. Interestingly a dehumidifier while keeping the boat dry also releases the latent energy in the water vapour it condenses to produce more heat than electricity provided (e.g 250watts in 400watts heat out).

[jdl01]

Our 379 also develops condensation on the underside of the foredeck in cool conditions. We installed a small -4"- low draw 12 volt fan on top of the starboard locker and it seems to reduce most of the moisture buildup.