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Thread: Ventilation versus Dehumidification

  1. #1
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    Default Ventilation versus Dehumidification

    Lots of natural ventilation throughout the interior is a known key to a sweet and mold-free interior, but would it be better to seal the interior, close vents, run dehumidifiers to a preset %, and just employ small fans to keep air circulating in lockers bilges etc?


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  2. #2
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    Default Re: Ventilation versus Dehumidification

    If the natural ventilation is working well throughout the boat, stick with it.
    There is nothing quite as permanent as a good temporary repair.

  3. #3
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    Default Re: Ventilation versus Dehumidification

    A lack of it sure grows mushrooms were you don't want them.
    '' You ain't gonna learn what you don't want to know. ''
    Grateful Dead

  4. #4
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    Default Re: Ventilation versus Dehumidification

    I like the idea of a PV panel on a hatch with as many computer fans as possible underneath and an IN vent at the other end of the boat.
    '' You ain't gonna learn what you don't want to know. ''
    Grateful Dead

  5. #5
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    Default Re: Ventilation versus Dehumidification

    Ventilation enables interior and exterior temps to be more balanced -- good for my wooden boats at least.

    Had one of those small solar powered exhaust vents in the roof, almost in the forepeak, a louvered vent in the companionway hatchboard, and a small intake opening in the transom. Screens everywhere. Never a worry. Always clean and dry. That was a 32' plywooden trimaran in Florida Keys weather.
    Last edited by tom151; 04-26-2017 at 03:28 AM. Reason: spelling

  6. #6
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    Default Re: Ventilation versus Dehumidification

    Quote Originally Posted by tom151 View Post
    Ventilation enables interior and exterior temps to be more balanced.
    +1
    You don't want too much difference in humidity
    Quote Originally Posted by Yeadon View Post
    Probably the greatest thread in the history of the WoodenBoat Forum.
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    Probably the greatest post in the history of the WoodenBoat Forum.
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  7. #7
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    Default Re: Ventilation versus Dehumidification

    Mine is shut with dehumidifier in cool months and AC set to about 78 in warm months. It has worked well so far. I'm in a hot climate though. If I were somewhere more moderate, I'd probably just rely on ventilation.
    Chuck Thompson

  8. #8
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    Default Re: Ventilation versus Dehumidification

    Quote Originally Posted by makobuilders View Post
    Lots of natural ventilation throughout the interior is a known key to a sweet and mold-free interior, but would it be better to seal the interior, close vents, run dehumidifiers to a preset %, and just employ small fans to keep air circulating in lockers bilges etc?
    A dehumidifier also generates a surprising amount of heat. It's like having a space heater running on low. That works fine in colder temps, but in the summer heat, don't be surprised if it overheats and catches fire in a small space. There have been a whole string of recalls for dehumidifiers that have caught fire too easily.

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    Joe
    These days, everything I do is just "puttering around"

  9. #9
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    Default

    Here's the problem: summer conditions here are 120 degrees, very high humidity and extremely dusty air.


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  10. #10
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    Default Re: Ventilation versus Dehumidification

    You'd think a dehumidifier would be a good solution, but if you think it out, it's really pretty much pointless to run a dehumidifier on a boat. I dealt with a big Alden yawl that was afloat, but on her last legs prior to a turn on the hard and a complete restoration, which I can't say ever finally occurred, but anyway... A well-intentioned but inexperienced harbormaster, recognizing that the long-neglected vessel (on account of whose owner was enduring a last illness) was soaking wet inside due to being "wrapped" in blue plastic tarps and left to leak from above and below, opened all the ports and put a big portable industrial strength dehumidifier below to "dry her out." Well, the open ports probably did more good than the big dehumidifier because all the dehumidifier did was remove moisture from the ambient air, which, of course was air coming through the ports and with an inexhaustible moisture content of exactly what you'd expect from air that was a couple of feet above the water! They'd have done a lot better with just a fan.

    A fan, or even a mild heat source like a light bulb down low in the boat, sufficient to keep the air circulating in through ample ventilation ports, is as good as it will get and, providing the circulation isn't impaired by closed lockers and compartments, is all that's needed. There's no need to remove moisture from the air, which is a fool's errand in any event in the marine environment. All that is required is to spread out the excess humidity in the boat so that it is absorbed the less humid ambient air outside. As humidity is going to equalize if given a chance, maintaining the ambient humidity outside the boat inside the boat is pretty much all that's required to keep a boat dry. Wastemarine sells, or used to sell, a round aluminum flat "can" sort of thing with a 120 VAC plug that put out a very low temperature heat, just enough to keep air circulating as the heat rose upwards. (It's not the heat that dries out the boat, it's the heat rising and promoting circulation that dries out the boat.) The same effect can come from an incandescent 25 W bulb, but, these days, incandescent bulbs are being phased out. I've used both and they worked very well. It doesn't take much to circulate enough air to dry out a boat, if the air is given half a chance. It's the differences in temperatures and condensation that cause "wetness" below on any boat. The ambient air outside the boat, even though it's humidity may be high due to the marine environment, will always be sufficient to absorb and carry off excess dampness in a boat if it's allowed to get in and out of the darn boat. Unfortunately, without adequate ventilation and heating up like a sauna in the summer time, a lot of boats turn into fungus farms right quick.
    Last edited by Bob Cleek; 04-27-2017 at 04:51 PM.

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