Condensation in my garage

[Jacko264]

Hi all
I have had new metal up and over doors fitted and now when I put my car away ( wet car ) the next day water is running down the inside of the doors .
there is no air vents in the garage .
If I fitted a vent high up and run a pipe over the car bonnet do you think this would stop the condensation
no heating in the garage apart from the car engine
thanks
Graham

 

[LopezBart]

As the temperature drops at night, the capacity of the air in the garage to hold moisture decreases. You likely have saturated the air w/ water vapor by parking a warm wet car in the garage; that vapor will condense on any cool surfaces (think dew) as the temperature drops over the evening.. The surface temperature of metal tends to remain cool hence the condensation; wood and another surfaces w/ poor heat conductivity will experience much less condensation since the surface can cool down w/o cooling the rest of the object.

A vent may help since it can reduce the amount of water vapor in the garage, but... looking at your current weather forecast, I see 97% humidity. If you have a window you can safely leave open, you can test if a vent would reduce the problem. A lot has to do with how cold the doors remain.

 

[Skyman]

If you have (or can add) electricity in the garage, a dehumidifier is your solution.

 

[Jacko264]

Hi
sorry no windows I can open so today I have drilled five 2ins holes high up in the wall and made a canapé over them the opening is 17 x3 ins so I hope that will stop the condensation
I will take photos tomorrow
thanks Graham

 

[Bunsen Honeydew]

Hopefully. You may have to make ventilation in an opposite wall for air to flow through.

 

[Jacko264]

I can’t do that it goes into another garage I could put one in the same wall or the back wall
G

 

[Jacko264]

Thinking about it I wonder is I should put a vent between the two garages for circulation
G

 

[Bunsen Honeydew]

Give your vents a while to see the results. You may have to insulate the doors.

 

[Jacko264]

I hope not but if I do what would be best to use?
G

 

[LopezBart]

I'm building my shop (see thread in signature); we're having what's called an atmospheric river storm here right now. The storms come up from the tropics and bring sometimes heavy rains and warm temperatures (nearly 12C). Since the shop is still w/o doors or windows, the warm moist air comes in and the concrete slab is quite wet, as is the aluminum level I left out as the moist warm air condenses on the cooler surfaces.

 

[duneslider]

Sometimes even just air movement helps, can you just run a fan in there so air is moving around. That can be helpful at getting it to dry out quicker.

 

[Jacko264]

Funny that but I’ve just been looking at bathroom fans that push air / condensation out side
but if I can stop the condensation with out all the better
G

 

[toolmiser]

My parents had a two car garage that had condensation issues, mostly in the summer (Wisconsin). Garage was insulated and sealed fairly well. They found out if they opened the attic hatch in the summer, the moisture would get drawn out by the attic vents. They did make a screen for the opening in case a bird or other would get into the garage.

 

[mm08822]

What type of roof venting is possible to use in conjunction with the set of holes you just made?

If you were to vent through the wall into the other garage, is there also a possibility for that other garage to vent to the exterior also so there is some possibility of airflow?

Does this happen only with the warm car parked in the garage and it is cooling down? Can you leave the car outside? Open the door, close it after a few minutes simulating the events of bring in the car. Then enter in the morning and inspect walls, doors? (Need similar weather conditions.)

 

[atch]

Sometimes even just air movement helps, can you just run a fan in there so air is moving around. That can be helpful at getting it to dry out quicker.

My 360x60 unheated uninsulated shop used to occasionally smell musty. I hung a cheap box fan about 7-8 feet above the floor and let it run 24/7. The shop has never had that musty smell since. This may or may not help your case.

Among other benefits this didn't require any penetrations in the exterior envelope of the shop.

 

[Jacko264]

What type of roof venting is possible to use in conjunction with the set of holes you just made?

If you were to vent through the wall into the other garage, is there also a possibility for that other garage to vent to the exterior also so there is some possibility of airflow?

Does this happen only with the warm car parked in the garage and it is cooling down? Can you leave the car outside? Open the door, close it after a few minutes simulating the events of bring in the car. Then enter in the morning and inspect walls, doors? (Need similar weather conditions.)

Hi the roof is steel but has polystyrene 2ins under the steel so a air gap.
i have just put the car in the garage it’s cold and raining the car is hot so I will go and see what has happened as far as condensation.

on a night after picking my daughter up from work at 10 pm I don’t want to go out later after the car cools to put it away
Graham

 

[Jacko264]

Good news so far I’ve just been in the garage and there is no condensation on the door

Hi the roof is steel but has polystyrene 2ins under the steel so a air gap.
i have just put the car in the garage it’s cold and raining the car is hot so I will go and see what has happened as far as condensation.

on a night after picking my daughter up from work at 10 pm I don’t want to go out later after the car cools to put it away
Graham

 

[Fav Onefour]

Condensation is essentially dew on the inside of a building.
When the building surfaces are at the dew point or colder, it becomes condensation.
@LopezBart , Did a nice job of defining the issue in post #2.
The hot, wet car is causing high humidity inside relative to outdoor colder temps. You are combining higher humidity with cold surface temps which is causing condensation. Letting the car cool before parking inside has a dual effect. The indoor and outdoor temp of the building is close so the surface isn't at a condensation point. You are also eliminating much of the warm air moisture holding capacity. That helps because the water isn't looking for a place to condense as indoor temps drop and the air loses ability to hold water.

Lowering humidity levels will help. Changing the building surface temp variation will help. Air exchange by venting or active air movement will help balance indoor vs. outdoor surface temps. Even with air movement, your building will cross the condensation threshold at times.


There isn't a quick fix that will work every time unless you can lower the "dew point" on cold exterior surfaces and keep it low.

 

[Recoveryman]

Jacko264: I agree with skyman in that a dehumidifier will take out the water. It is better if you have a place to drain the dehumidifier into, then it needs very little attention. Good luck.
Recoveryman

 

[jack stand]

Hi
sorry no windows I can open so today I have drilled five 2ins holes high up in the wall and made a canapé over them the opening is 17 x3 ins so I hope that will stop the condensation
I will take photos tomorrow
thanks Graham

I've had 3 wall - open front "machinery sheds" darn near rain inside with the right conditions. One in particular was about 20' deep by 80' long so I'd stop drilling holes in your wall, it's not going to help anything.

 

[Jacko264]

Good morning all
ive just been in the garage to check on the condensation and it looks a lot better not perfect
it has been horrible weather this last few days
this is what i have done so far the help the situation

 

[Jacko264]

Looking good so far no condensation today