Excess Moisture in Garage - Winter-

[Black_Z28]

Hey guys, just curious what can be done about excess moisture within a heated/insulted/sheet rocked garage?

On my attached garage, which we use for our daily vehicles, we get a lot of moisture in the winter. I'm aware this is from the snow on our vehicles(or changed outside conditions), but even when I have the heater cranked up, it doesn't seem to diminish. There's enough moisture that it just doesn't collect on the windows, but on the walls, and of course the garage doors, which are insulated, but they are the cheaper insulated doors. Just the steel door, with the foam board on the inside.

I didn't have this issue at my last garage, and also had the same style garage door. So, I'm just curious what my options might be, if any.

 

[bdbecker]

I had to get a dehumidifier for my garage once I had it sealed up and insulated. I only have to run it during the spring/summer, but it makes a huge difference.

 

[stingry]

What type of heater?

 

[ericm]

I also have to run a dehumidifier in the garage, just because of the rain that one car brings in. In my climate that's all winter (the worst time to run a dehumidifier as they lose efficiency when cold).

A heater that's not vented to the outside will be adding even more water from combustion.

An inexpensive thermometer/humidity meter would be useful.

 

[Black_Z28]

What type of heater?

It's a Reznor unit heater, horizontally vented outside.

 

[nadogail]

Ah Ha, your heater is a moisture generator better start looking for a dehumidifier.

 

[yeldogt]

What's your location? What temp do you heat to?

I'm in the mid-atlantic -- we have had a few warm wet days recently. Yesterday -- it was warmer outside then in my studio. You don't want to be opening and allow any outside air to come in on this type of day ..... all that moisture comes in and condenses on everything. Like a cold drink on a summer day.

In NYC I have a garage -- sometimes when it raining I have to crank up the heater (NG thankfully) -- and when the space is warm I open the door and all the hotter moist air flows out.

Normally in the winter with low humidity outside I don't have the problem unless the cars have lots of snow. The late spring snow is a problem.

 

[Black_Z28]

Ah Ha, your heater is a moisture generator better start looking for a dehumidifier.

See that's the thing. I haven't even started using it yet this year. It stays almost 50* in it with the warm vehicles and 3 sides attached to the house.

But, I will get a dehumidifier and see how that helps.

 

[yeldogt]

See that's the thing. I haven't even started using it yet this year. It stays almost 50* in it with the warm vehicles and 3 sides attached to the house.

But, I will get a dehumidifier and see how that helps.

I would raise the temp before spending on running dehumidifier .... what's the fuel for the heater ?

 

[Black_Z28]

I would raise the temp before spending on running dehumidifier .... what's the fuel for the heater ?

I had the same issue last year with the heater running. Fuel is NG.

I'm located in central MN, and normally heat the garage to 50*.

 

[ripperd]

Ah Ha, your heater is a moisture generator better start looking for a dehumidifier.

No, a unit heater that vents outside will not add humidity. It actually will slightly decrease humidity if it is drawing inside air because typically outdoor air is less humid and the make-up air comes from outside.

 

[Don1357]

You have a lot of humidity in the garage warm air, and there is a ton of cold dry air outside....

What you need is venting. Install a through the wall venting fan, pump all that wet air outside, which will **** cold dry air in.

 

[Black_Z28]

You have a lot of humidity in the garage warm air, and there is a ton of cold dry air outside....

What you need is venting. Install a through the wall venting fan, pump all that wet air outside, which will **** cold dry air in.

Do these run on some sort of trigger system, via humidity? Or are they just continuously on?

Any recommendations? I assume there there needs to be two holes, to compensate for negative air?

 

[yeldogt]

I had the same issue last year with the heater running. Fuel is NG.

I'm located in central MN, and normally heat the garage to 50*.

The heater is not the problem ....

Raising the temp will allow the air to hold more moisture .... reduce the potential for any dew point problems.

Have you checked the slab ? Tape plastic square on it

Are you in a wet area?

Using a dehumidifier to take standing water away -- from cars. better to run the heater and open the door for a few minutes.

 

[Black_Z28]

The heater is not the problem ....

Raising the temp will allow the air to hold more moisture .... reduce the potential for any dew point problems.

Have you checked the slab ? Tape plastic square on it

Are you in a wet area?

Using a dehumidifier to take standing water away -- from cars. better to run the heater and open the door for a few minutes.

What would I check the slab for? Not sure what you mean by tape plastic square on it.


I would not consider my home to be in a wet area.

The issue is much worse when snowing, and driving the vehicles inside the garage, then melt the snow...although this is obviously going to cause the moisture to rise. I'm just trying to find a way to remove the moisture more efficiently. Opening the door would help with minor snow or moisture on vehicle, but it can be a steam bath in there at times.

 

[Showkey]

It’s NOT the heater............the heater is actually drying the air somewhat. Remember humidity levels are relative to the temperature.

There are many prior post on this exact topic.

It’s the vehicles bringing in gallon of moisture every day.

Dehumidifier will help.......but:
It need to emptied daily or every other day.
It will likely run continuously but can be set to 50% humidity level......continuous because it won’t be able to keep up if gallons of water are on the floor and saturated air that is likely at plus 70% humidity levels.
It cost $ to run.
Most need a minimum 50* temperature and will spend time and money in defrost mode.

 

[yeldogt]

What would I check the slab for? Not sure what you mean by tape plastic square on it.


I would not consider my home to be in a wet area.

The issue is much worse when snowing, and driving the vehicles inside the garage, then melt the snow...although this is obviously going to cause the moisture to rise. I'm just trying to find a way to remove the moisture more efficiently. Opening the door would help with minor snow or moisture on vehicle, but it can be a steam bath in there at times.

Slab can be a source of moisture depending on the ground moisture --- they also hold water should you bring it in. Is the slab sealed ?

To see if the slab is holding water .... you tape a square on the slab and see if moisture is under it.

 

[Shop Specialties]

I would bump the heater up to 60* and give it a full week to see if you have any improvement.

 

[Don1357]

Do these run on some sort of trigger system, via humidity? Or are they just continuously on?

Any recommendations? I assume there there needs to be two holes, to compensate for negative air?

The simplest way is just to turn it on as needed, but Amazon has humidity controllers where you can select at what point it goes off.

You shouldn't need an intake hole, most houses and garages are not as draft-proof as we would like to think. Once you turn the fan on you can feel how much air is blowing out. Rest assured that the same volume of air is coming right back in from elsewhere. Ideally it would be pulling outside dry air rather than household air.

 

[Don1357]

I would bump the heater up to 60* and give it a full week to see if you have any improvement.

That doesn't work because the warmer the air, the more humidity it can carry; it won't 'dry' the air. Dehumidifiers works in the very opposite principle; a cold coil to condense the humidity off the air and collapse it in a bucket.

As previously stated the humidity is suspended in the air (right until it hits colder surfaces and condenses) so the fastest way to get rid of it is to shove all that moist air outside.

 

[yeldogt]

That doesn't work because the warmer the air, the more humidity it can carry; it won't 'dry' the air. Dehumidifiers works in the very opposite principle; a cold coil to condense the humidity off the air and collapse it in a bucket.

As previously stated the humidity is suspended in the air (right until it hits colder surfaces and condenses) so the fastest way to get rid of it is to shove all that moist air outside.

Raising the temp allows the air to remove the water ... at 50 degrees even a cold operation dehumidifier is at the limit.

Crank it up -- open the door for a few .... dry it out.

The other way is a controlled exhaust -- but only if humidity is lower. I need a dehumidifier in September when there is no AC anymore and not cold enough for heat.

 

[Shop Specialties]

That doesn't work because the warmer the air, the more humidity it can carry; it won't 'dry' the air. Dehumidifiers works in the very opposite principle; a cold coil to condense the humidity off the air and collapse it in a bucket.

As previously stated the humidity is suspended in the air (right until it hits colder surfaces and condenses) so the fastest way to get rid of it is to shove all that moist air outside.

It has worked for my customers for the past 30 years and not one of them has used a dehumidifier. The OP has stated he has not run his heater yet this season. Get the air heated up and moving and it will dry out.

 

[Showkey]

Yes adding heat will help. Especially now with no snow.
Here’s an example for 1000 sqft shop that does not have wet cars coming and going. Man door is used often, overhead door is not used often. It is heated to 60* well insulated and sealed. If it was not heated the current temperature would about 38-45* with a humidity level above 70%.
Dehumidifier is not needed in winter in my situation. Heat has been on for the last 30 days. There been a outdoor temperature range of 75* to 18* on the last 30days.




In the summer months ( May to Sept) the temperature rarely gets above 75* but humidity levels would climb to 75% +/-10. Dehumidifier running set at 50% controls the humidity to reasonable and comfortable levels.

Typical summer conditions:

View attachment 1070648



Prolonged summer 70% plus humidity will cause indoor mold, mildew, funky smells first noticed on organic materials like leather, paper, rubber, wood, card board.

The OP issue is compounded by the wet vehicles coming a going.

 

[ericm]

The humidity you're seeing there is relative humidity- the amount of water in the air vs what it can hold. Warmer air can hold more water. If the amount of water remains the same, when the air is warmer the RH is lower.

One of the OP's problems though is condensation on the cold garage door. Heating the room air isn't going to help that much. The door will still be cold and it will still collect condensation. Like condensation on the outside of a glass holding a cold drink on a hot day.

Bringing in cold outside air could help but it's got to be drier than the inside air. In my climate it's often not. And then the OP will have to spend more for heat to warm up that cold air if he wants the garage to be warm.

Dehumidifying would reduce the condensation on the cold garage door frame and not require heating the outdoors. However my dehumidifier does not work well when the garage temp is below 50. Maybe other work better at low temps.

 

[yeldogt]

I'm with showkey. I have a commercial dehumidifier in my studio -- it will run when needed.

Adding heat to a building is energy .... this energy will create a stack effect. Even in a tight building adding heat will add air changes.