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Moisture Issue in Garage

Posted by sue36 (My Page) on
Fri, Feb 15, 08 at 10:37

Has anyone else had a problem like this? Our garage is 26x26 and has ceilings that are about 12'. I keep my SUV in there. We are having a big issue with excess moisture, presumably from what comes off the SUV in the winter (bits, or snow and slush). The windows often have condensation on them. The back door, a Thermatru with double pane glass on the upper half, has it even worse than the windows. The hinges on that back door are all rusted. It is heated to about 48 degrees via a Modine and is fully insulated (R21 walls, R38 ceiling, doors are R19) and finished.

Do others run a dehumidifier in the garage?


Follow-Up Postings:

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RE: Moisture Issue in Garage

Car collectors and collectors in general not only use dehumidifiers, but heat and cool the garage same as the living space. It is less efficient via the garage door even if insulated, but i've never heard of excessive moisture that you are experiencing. If they ran plastic sheeting, (visquine), on the inside before wallboard, that could be some of it as it isn't conditioned as a living space.


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RE: Moisture Issue in Garage

"...it isn't conditioned as a living space..."

Do you mean we are keeping it too cold?


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RE: Moisture Issue in Garage

First check to see if water is getting in under the garage door.

I don't know what kind of Modine heater you have but an unvented gas-fired heater would also cause this condition.

It is also best to use brass hardware in rough duty spaces.


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RE: Moisture Issue in Garage

No water is getting in under the garage doors. The Modine is a hot water zone off the boiler, so there shouldn't be any moisture from combustion, correct?

The back garage door is currently about a foot off the ground because we excavated out soil to build a patio back there and didn't get it finished before winter. Under the door (outside) is a PT 2x4 (I am going to replace this with Azek when we finish the patio). However, there is some moisture coming in under the door, somehow. When we get driving rain the concrete will appear wet, but there won't be standing water. The door was a pre-hung door and has flashing over it. But water/moisture is getting under there somehow. Once we get warm, dry weater (oh, maybe June) I was planning to figure out how that moisture is getting in. But I don't think this could be the entire cause of the problem since the windows show a LOT of moisture and the amount at the door is minor. Of course, this happens mostly when a wet vehicle has been put in the garage. Last summer all my hand clippers rusted up pretty bad.

The hinges are white metal because the door knobs inside the garage are brushed nickel. I was thinking of getting stainless hinges.

I would think this happens to a lot of people. Wet vehicles are brought into a space that has no way for the moisture to get out (no vents, for example). I guess I need to just bite the bullet and get a dehumidifier. Does the fact that it is insulated and finished make it worse (harder for the moisture to exit through the walls)?


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RE: Moisture Issue in Garage

The most important thing to check is that there is no leak from a nearby gas fired device into the garage. A CO detector might tell you and cut flowers will wilt.

Do you idle the vehicle in the garage?

I suppose if the room is very warm and the vehicle is very large it might be possible to build up the kind of water vapor you would expect in a pool area but it's still hard to imagine in a garage.

The cheapest solution would probably be an exhaust fan. Put a small fan in a window first to see if it improves the condition. A dehumidifier is expensive to buy and operate and will have to be replaced often because when they run continuously they freeze up.(get a big one and run it so it cycles on and off)

Lowering the thermostat might help too.

See if there is a leak in the coil of the heater.

Does the floor slope toward the doors for drainage? Is there a floor drain?

Do you live in a swamp?


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also

Make sure no dryer or bathroom vents terminate in the garage.


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RE: Moisture Issue in Garage

Hi Sue

I also have a Modine feed off a hot water line. I also have alot of condensation on the windows. I run the garage temp at about 45 degrees only. The lowest the thermostat will go.

I am in Westchester New York. Zone 5.

The garage gets very wet when there is snow. The snow sticks to the cars and then melts in the garage. The garage floor is graded such that the water runs to the garage doors. I get a puddle around the doors because the rubber draft sealant on the doors tends to keep the water in. I think water is not getting in under the door, but it is the snow melt not being able to get out. Note the rest of your garage is dry because it is up hill, and most water has evporated when you check the garage in the morning. Hence the illusion of water seeping in under the door.

To try and reduce this I use a broom to sweep up the drop snow and push this out the door. I usuall flip the emergency catch and use one of those home depot buckets to raise the door by about one foot and the push all the slush out. That helps a bit.

In the summer we have a damp corner in the garage mainly from condensation and humidity. It is not that bad though.

The doors and the windows are the coldest in the garage, and all that wter does then to collect on them. To fix the hinge rusting issue I recomend putting some WD-40 on it. That should keep the water off and the sqeaks away. A longer lasting solution is car grease, but it is sort of messy.

Best, Mike.


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RE: Moisture Issue in Garage

Thanks MA and Stinkytiger (I'd love to know the origination of that screen name!)

I know a little moisture is coming in under the rear door, but not enough to cause the moisture issues. Nothing terminates in the garage (dryer, etc.) and no signs of a leak from the Modine.

I think the cause is just slush, snow, etc. from the cars. It's been cold and dry the last several days (Thursday on) and the garage is now none dry. No condensation on windows. I'm surprised this doesn't happen to a lot of people.

I don't want the windows to get damaged and don't like everything rusting in there, so I think I'll just put the dehumidifier on 50 percent and see if that helps.


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RE: Moisture Issue in Garage

we have the same problem and have partially solved it by opening one of the windows in the garage a bit. This allows some of the humidity to escape. We keep the garage @ about 45 degrees.

Our problem is pretty bad because we have three snowy vehicles and the tractor/plow that brings in quite of bit of snow (which subsequently melts). The windows fog up/frost over depending on how cold it is outside. So far we haven't seen any signs of window damage.


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RE: Moisture Issue in Garage

Condensation occurs on the windows when the interior surface drops below its dewpoint. This means when you bring in slush and snow and then heat the space, the cold exterior surface of the window causes condensation on the interior. You need to raise the dewpoint inside your space, i.e. raise the temperature.

The heater flue vent pipe may experience condensation if the gas pressure is not set correctly. Check out the troubleshooting guide below for more info.

Unfortunately you are probably doing a # on the heat exchanger of the heater. If it gets replaced, be sure to upgrade to stainless steel.

Here is a link that might be useful: Modine Heaters Troubleshooting Guide


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RE: Moisture Issue in Garage

jb40,
Thanks for the info. Our Modine is not gas, it is a hot water zone off a Viessman oil burner (which is in the house basement). There are no signs of a water leak. I hate to heat the garage anymore than we do, it's such a waste of money. Do you think running a dehumidifier would work? That's such a PITA since there is nothing to drain it into. Thoughts?


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RE: Moisture Issue in Garage

Must you heat the garage? Seems you'd need to heat it to a higher temp...or not at all. (Only a guess. Our garage is unheated, but we only 'store' cars in it.)


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RE: Moisture Issue in Garage

Would you consider drilling a very small hole in an exterior wall through which a hose could be run? We bought a portable dehumidifier and connected a short (6') length of hose to the drain, then ran the hose outside through a hole that dh drilled in the brick. He sealed around the hose so that we'd have no trouble with insects. The dehumidifier throws off some heat, although it may not be enough by itself for your needs.


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RE: Moisture Issue in Garage

We have to heat the garage because the master bedroom and bathroom are over it, so there are pipes in the garage ceilings. We only heat it to 45, it's insulated to the same degree as the house and the doors are insulated steel (R18).

I'll ask DH about drilling a hole in the side wall of the garage. I don't have an issue with it per se, I just don't know if it will work because it may freeze. We have an issue with the drain for out water filtration back flush system freezing and it's about the size of a garden hose. Of course, if I'd know about this when we built I would have put a pipe from the garage to the house french drain, but that's not going to happen now.


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