Guest peter Posted December 3, 2009 Share Posted December 3, 2009 I must admit we've never heated our boat and it's sitting in the water. The only time we had a problem was when we covered it and got mould on the seats. Needless to say the cover went into the skip and it's been fine since. The best way to stop condensation is to have the temperature equalised in and outside.. Link to comment Share on other sites More sharing options...
Ranger Posted December 3, 2009 Share Posted December 3, 2009 peter - 2009-12-03 10:46 PM I must admit we've never heated our boat and it's sitting in the water. The only time we had a problem was when we covered it and got mould on the seats. Needless to say the cover went into the skip and it's been fine since. The best way to stop condensation is to have the temperature equalised in and outside.. At this time of year the water the boat is moored in, is a lot warmer than the air is above the water line, so in theory you have bit of warmth rising from the bilges to keep the air in the boat above freezing point????????? Link to comment Share on other sites More sharing options...
Brian Kirby Posted December 4, 2009 Share Posted December 4, 2009 peter - 2009-12-03 10:46 PM I must admit we've never heated our boat and it's sitting in the water. The only time we had a problem was when we covered it and got mould on the seats. Needless to say the cover went into the skip and it's been fine since. The best way to stop condensation is to have the temperature equalised in and outside.. This is only true if both temperatures remain more or less constant. Fact is, of course, they don't, with the external temperature changing more, and more quickly, than the internal temperature. As has been pointed out, a boat sitting in water has its temperature change rate "ballasted" by the much slower temperature change rate of the water.If the weather is cold, and the van unheated, then everything in the van, including all of its structure, furniture, and furnishings, will tend to the general ambient (external) air temperature. You now have a cold and, because cold air contains little moisture, a relatively dry, van.If the weather warms up two things happen. First, the van will begin warming as it gains heat from the warmer external air, and possibly (even!) the sun, but it will respond much more slowly than the ambient conditions because it is insulated. Second, as the external air warms, it will begin drawing moisture from the environment. You thus now have warmer, but moister, external air, that will slowly permeate into the van. When that moister air gets to the relatively colder surfaces in the van, some of the moisture will condense. It may not be visible as condensation because, unless conditions are very extreme, it will be absorbed into furnishings and wood pretty much as quickly as it forms. The absorbed moisture will cause wood to swell slightly, and may cause mildew in furnishings, especially where traces of perspiration remain.When the van has been warmed for long enough its structure etc will also warm, and the absorbed moisture will be re-evaporated back into the air. If this co-incides with a warm season, say spring, the moisture absorbed by internal finishes and fittings will evaporate permanently (or at least till next autumn), and the wood will shrink back to its original size, possibly opening joints slightly, especially in framed and panelled cabinet doors. Unfortunately, any mildew that has formed, will remain!The point of installing heating is to keep the relative humidity of air inside the van low, by warming the air in the van, and so to gently warm all its internal surfaces, meaning that the invisible condensation does not occur, the wooden bits remain more dimensionally constant, and any furnishings left inside stay mildew free.The alternative is to install a dehumidifier to allow the van air to chill down, but to extract any excess airborne moisture that permeates in from outside, so preventing condensation by that route. How much risk of condensation there is, and what the risk of mildew etc, depends on too many variables to be generally predictable in useful way. What can be said, is that either gentle heat, or dehumidification, will eliminate the risk. Other approaches may work under some conditions, but not under others, depending mostly on where you live. Link to comment Share on other sites More sharing options...
peterrosey Posted December 4, 2009 Share Posted December 4, 2009 Thought I'd better drain the tanks of my van over winter, only to discover that the much-maligned boiler drain valve on my Truma heater had already done it for me... which was nice! Dumped the water tanks (with the taps all open at midway point) and that was that. Have it hooked up sporadically to the mains and will run a dehumidifier in it from time to time, as well as starting it / moving it every two weeks or so. Sick of these dark nights now - roll on spring! Link to comment Share on other sites More sharing options...
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