Thread: Why is my heated garage getting so damp?

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  1. #1
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    Default Why is my heated garage getting so damp?

    I have a dehumidifier in the garage, along with a natural gas vent free heater to provide heat, but doggone it, the garage windows are sweating inside, and there is dampness in there. I insulated the walls and ceiling when the garage was built, but what the heck is going on, and how can I stop it from happening? Anybody else getting this to happen in their heated garage too?


  2. #2
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    Default Re: Why is my heated garage getting so damp?

    My guess is it coming up though the un sealed floor.I used vinyl tile on my floor.Heat is residual heat from the hot watertank and furnace being in there.Just checked.Outside temp 31.Inside temp 68 with 40% humidity.Doors fit tight and are insulated . Bruce


  3. #3
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    Default Re: Why is my heated garage getting so damp?

    Second thought.Are you parking other wet vehicles in the same garage? Bruce


  4. #4
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    Default Re: Why is my heated garage getting so damp?

    Happy New Year, Roland...agree with Bruce on both suggestions...I our case, we have NOT parked daily drivers inside for years as they bring in WAY TOO MUCH moisture.


  5. #5
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    Default Re: Why is my heated garage getting so damp?

    Absolutely not, it is a 1 1/2 car garage, and the only car in it is the Viper, that's it. Good thought though about the floor, I will have to do something about that this spring and seal it, to see if that works. I have also heard that the vent free heaters generate lots of moisture as a by product, so I will change that next season too. But one step at a time to see which one does the trick. Thanks for the help!


  6. #6
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    Default Re: Why is my heated garage getting so damp?

    Water is getting in, period.

    If you have insulted walls/ceiling, you could have a problem there that you cannot see.

    Is the outside ground level higher than the floor? If so, there could be leakage thru the walls. You might be able to test the floor by placing a piece of plastic on the floor so that it is closely pressed again the surface and then see if the concrete gets wet. If this happens then the moisture is coming thru the concrete. Do this where the floor is lowest relative to the outside grade.

    Also, is the outside ground graded higher around the garage so that rain water runs away from the garage? If the garage is sitting in a low area, rain water will pool and find its way into the garage. It is absolutely imperative that the landscaping runs rain water away from the structure. (If you have this problem, fixing this could easily make your moisture problem "mysteriously" go away.)

    Usually when floors are laid, they put plastic down to form a vapor barrior. If this wasn't done, that could be your problem.

    In my home town, I know a lot of the older buildings on main street have the condensation on the inside of the display windows. This invariably comes from water getting into the basement.

    What is very dangerous, is that you could create a mold/mildew problem. If this should happen, you can "exterminate" it with formaldehyde packets used to keep closets dry.


  7. #7
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    Default Re: Why is my heated garage getting so damp?

    I think the gas heater is doing it.


  8. #8
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    Default Re: Why is my heated garage getting so damp?

    Joe I think you have it.

    The vent free gas heater produces H2O and CO2 as combustion products.

    So its dumping water into the air!!!!!

    A friend of mine has one of these in his office in his taxi garage and you can fee the hot muggy moist air when you enter.

    Turn it off and see if the place dries out!




  9. #9
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    Default Re: Why is my heated garage getting so damp?

    This is great info for me as I too am comtemplating heating solutions for my garage (detached and insulated). Admittedly, the ventless solution seems almost too good to be true. No electricity, low cost, no odor, etc. If it indeed produces excess moisture then I will definitely go to the Modine gas heater. They make a unit which is small (hotdawg I think they call it)and seems very nice. Moisture in the air is a real killer on the toys.


  10. #10
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    Default Re: Why is my heated garage getting so damp?

    <BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Tom and Vipers:

    If you have insulted walls/ceiling, you could have a problem there that you cannot see.<HR></BLOCKQUOTE>


    Precisely how does one "insult" a wall or ceiling?!?

    Look here, Wall...You are as dumb as a brick! Rock stupid I tell you! Same goes for the Ceiling...




  11. #11
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    Default Re: Why is my heated garage getting so damp?

    "If you have insulted walls/ceiling, you could have a problem there that you cannot see."

    Er.... would that be being French?

    There are console heaters that have ducting. I had one. You can still have the no electricity feature, but you want that flu to exhaust the combustion products.


  12. #12
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    Default Re: Why is my heated garage getting so damp?

    Is there a specific % of humidity that is considered excessive?

    I realize 0% would be ideal, but at what number is condensation starting to become an issue, apart from the obvious sweating meter on windows?




  13. #13
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    Default Re: Why is my heated garage getting so damp?

    <BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by genXgts:
    Is there a specific % of humidity that is considered excessive?

    I realize 0% would be ideal, but at what number is condensation starting to become an issue, apart from the obvious sweating meter on windows?

    <HR></BLOCKQUOTE>

    I think 0% would be bad. Cracked leather, plastic, rubber...

    Get one of those weather station thingies that measures actual humidity. They are like $30 at places like Radio Shack. Then find some engineer type that know about temp differences and humidity that can tell you what's reasonable.




  14. #14
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    Default Re: Why is my heated garage getting so damp?

    I am pretty sure the optimal relative humidity should be below 50%. I would think somewhere around the 40-45% mark is a good number to strive for, although I am by no means an expert.


  15. #15
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    Default Re: Why is my heated garage getting so damp?

    I think you need to do the Dew Point calculation.

    It is based on temperature and relative humidity.

    To measure, you spin a hygrometer which has a wet and dry bulb thermometer. I think you then reference a table to get the temperature at which condensation occurs.


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