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Thread: Shop condensation

  1. #1
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    Mar 2009
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    Default Shop condensation

    Iím working on a plan to address the condensation in my shop. First step is to get insulated garage doors. That will keep some moisture out. Right now, they are just barn doors.

    The other idea is to run a fan. An interesting proposition being off grid.

    Running a 75 watt box fan 8 hours a day is going to be a lot easier on my battery than 24/7. My initial thought/hope is that condensation mostly forms in the morning when the warm daytime air hits things that have cooled overnight.

    Wishful thinking? Or is 24/7 the way to go?

    Thanks

  2. #2
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    Default Re: Shop condensation

    I would think that it’s really an issue of sufficient ventilation on the roof… maybe one of those wind-powered rotating vents up top, with adjustable vents down low on a wall or two… let natural convection work it’s magic. Warmer moist air will rise, I think.
    "Reason and facts are sacrificed to opinion and myth. Demonstrable falsehoods are circulated and recycled as fact. Narrow minded opinion refuses to be subjected to thought and analysis. Too many now subject events to a prefabricated set of interpretations, usually provided by a biased media source. The myth is more comfortable than the often difficult search for truth."







  3. #3
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    Default Re: Shop condensation

    How much moisture is coming up through the slab? Tape a square of visqueen to the floor overnight and see if there is a wet spot there a couple of days later.
    ITS CHAOS, BE KIND

  4. #4
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    Default Re: Shop condensation

    i find it odd that you have condensation issues inside. it suggests that relative humidity is very high in there for some reason.

    are you seeing dewpoint temps at night outdoors?

  5. #5
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    Default Re: Shop condensation

    Currently 100 percent humidity. The dew point is 64F. And the low was around 40F. Good plastic under the slab. And it is elevated off the ground by 8”. And on a hill. Pretty sure it’s not coming up from below.

    There is some movement up through the stairwell to the well ventilated structure above. But as far as I can tell, it’s just pulling in warm moist air.

    I’m hoping moving the air a bit will help.

  6. #6
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    Sep 2015
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    Default Re: Shop condensation

    Quote Originally Posted by bluedog225 View Post
    Currently 100 percent humidity.
    In your shop? Or outside?

    Shop heated at all or just the space at the bottom of the stairwell you mentioned?

    Quote Originally Posted by bluedog225 View Post
    I’m hoping moving the air a bit will help.
    It ought to but maybe not as much as you're hoping it will.

    Water vapor's lighter than air, rises, why ridge/roof vents are a good solution though you need to have some means by which to close 'em when you want to keep heat in. As you're off-grid there are products sold for greenhouse use that open & close dampers by means of temperature differentials that may help you reduce drain on batteries from powered thingies.

    Doing a job of closing off that stairwell, so warmer humid air from below can't get into your shop, may help too if that's where most of the humidity's coming from. Insulating your barn doors won't help much unless you also do something to get decent sealing around the edges. That's where much of your humidity's coming in from when outside's 100% RHI.

  7. #7
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    northern Georgia, or Mississippi Delta USA
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    Default Re: Shop condensation

    Yes, Austin is showing 100% humidity, both temperature and dew point are 64. As long as outside air can get in and the slab is cooler than the dew point, you are going to get condensation.

  8. #8
    Join Date
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    Default Re: Shop condensation

    So warm air hitting cold slab? Fan is all I can think of, or some kind of hard insulation on the concrete.

  9. #9
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    Default Re: Shop condensation

    I’ve come to the same conclusion.

    The wacky weed farmers have some direct drive, direct current fans. Done right, they are pretty slick. Best to ignore the garbage google searches produces.

    Too bad they are so pricey.

    EC63AE5B-32E4-4A69-8498-B1895B3D9BC7.jpg

  10. #10
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    Default Re: Shop condensation

    I’d think a cheap box fan would suffice. Why not a bunch of plywood painted a nice blue gray color?

  11. #11
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    Default Re: Shop condensation

    Box fan, battery, small inverter, mppt charge controller. It adds up.

  12. #12
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    Default Re: Shop condensation

    If you can seal it up really tight, a dehumidifier might help. What is the interior volume, and how much water can it hold?

  13. #13
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    Default Re: Shop condensation

    I may be able to seal it up after I get the garage doors. But running a dehumidifier is going to be a problem off grid. Later, I’ll have my grown up solar system put together, conditioning the space becomes possible.

  14. #14
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    Default Re: Shop condensation

    are your walls still bare concrete?

    would be interesting to measure actual temperature of your concrete surfaces.

    i'd expect walls to be colder than the slab.

  15. #15
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    Default Re: Shop condensation

    I’m afraid so. Not optimal. I may be able to do something later. Getting the upstairs ready for insulation is my priority before it heats up. And garage doors. And septic. And a water line. And solar. Etc. f me. I’ll never finish. ��

  16. #16
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    Long Beach, CA
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    Default Re: Shop condensation

    A 100 watt light bulb in the main salon once solved the condensation problem for me on a 30' plastic boat.

    Maybe worth a try.
    Schooner sailors love to get blown offshore!

  17. #17
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    Default Re: Shop condensation

    Quote Originally Posted by bluedog225 View Post
    Iíll never finish. ��
    Yes, you will.

    House I bought in 1987:
    D584ED27-9296-4534-8817-026A0F805065.jpg

    Started 'remodel' in '81, then went to work full-time in '83 with a 4+ hour commute:

    8E498B73-B0DD-41E4-A0DF-4E78CC35BDCF.jpg

    Then in '87:

    A6FB007D-FE52-46B4-AF94-43A16F91ACD2.jpg

    When I sold it in 2014:

    2B8FD5C9-F09F-4320-A324-2642748C2C77.jpg

    Recession in '08 killed my last full-time job a year later so I had some 'spare time' to do trim inside I'd been putting off. We lived in it year-round all those years so it had some irritation in the doing.

    You'll get yours done. You'll be older too when that time comes, probably tired as well, but proud of a job well done.

  18. #18
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    Isle of Mull, Scotland
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    Default Re: Shop condensation

    Presume you have a bit of power in the shop- if you can afford 200-300 watts, get a dehumidifier. You can pipe the condensate out if you don't like emptying the darn things.
    Got one in my uninsulated garage- try and make it as airtight as poss.

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