Join Date: Feb 2010
Location: Narragansett Bay
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Re: Winter Moisture Control
I've never really been tempted to live aboard over the winter in cold weather. Looking forward to it down south one day. However, there are moments where we've thought about it.
There are two problems with moisture. First, the amount of water vapor available and the dew point, which will determine whether it remains in the air.
On a boat, it is nearly impossible to keep water from being evaporated into the air. Boiling water, showers, wet bilges, breathing, etc, etc. You will add moisture to the air, there is no stopping that.
The dew point is more complicated. It is expressed as a temperature, but is really a factor of ambient temperature and how much moisture has been evaporated into the surrounding air. The more moisture in the air, the higher the dew point will be, meaning the closer to the ambient temperature it will be. Said differently, it is the temperature at which the air would no longer be able to hold onto the amount of moisture absorbed within it. The warmer the air the more moisture it can hold. 70 degree air can hold more than 50 degree air, which can hold more than 30 degree air, which can hold more than 10 degree air, etc, etc. Reduce the temperature and there is a point where it can no longer hold the moisture within it and it condensates out.
The biggest problem with a boat in the winter, is not keeping the interior air above the dew point, its keeping the hull above the dew point. While you may keep the salon table relatively warm, put your hand on the hull inside a hanging locker or galley cabinet. It will be much colder, maybe by tens of degrees and undoubtedly below the dew point. That's why you get condensation, followed by mildew, and not necessarily where you can see it. Insulation helps, but as some have pointed out, it may only transfer the problem behind the insulation if the moist air can get behind the insulation.
The only good solution, IMO, is to substantially reduce the actual humidity in the air, thereby, reducing the dew point below even the cold hull temperature. That can only be done effectively with electric powered dehumidifiers IMHO.
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Last edited by Minnewaska; 11-07-2012 at 05:54 AM.