Foam Insulated Detached Garage Problem

[jehjr68]

Hi folks ... got a problem. Just finished a detached 2 car garage. The garage is "tight" with spray foam in walls and under roof. Complete envelope. No ridge or soffit vents.

I am having a heck of a time with high humidity levels. Any recommendations for ventilation/humidity control ? I could put a window AC unit in but the temp is not the issue and the humidity is high at temperatures I would not typically run it.

Thanks
Johnny

 

[Grumpy365]

You can do a house the way you describe , because of the AC system and the fact that a well designed will bring in fresh air.

A garage is going to be a problem. The space needs to breathe. I would explore an attic fan and a louvered intake / exhaust setup

 

[p_mori7]

Air exchanger.

 

[walrus]

It may get better with time, when was the concrete poured?

 

[77thor]

Where do you live? Northern or southern climate?

 

[jehjr68]

Concrete poured in December. I live in south Georgia ... Savannah.

Thanks

 

[Grumpy365]

I assume it is icenyne?

Call the dealer and post there response.

I am curious.

I don't think it is concrete. A walk in cooler will smell like swamp *** when it turned off and sits closed up. It needs air circulation..

I love the sealed envelope theory. And I believe in it in a climate controlled environment , but a garage has special needs and considerations that should be addressed, especially in your climate .

 

[Highbeam]

Good thing you tried so hard to seal up that shop. You were successful and that is the problem. Now you need to unseal it.

 

[gpalmer77]

Hi folks ... got a problem. Just finished a detached 2 car garage. The garage is "tight" with spray foam in walls and under roof. Complete envelope. No ridge or soffit vents.

I am having a heck of a time with high humidity levels. Any recommendations for ventilation/humidity control ? I could put a window AC unit in but the temp is not the issue and the humidity is high at temperatures I would not typically run it.

Thanks
Johnny

1) Run a dehumidifer, or if your window A/C has a dehumidification function, do that. Doesn't have to be temperature dependent.

2) It is not a spray foam issue, a conventionally insulated building with a sealed vapor barrier can be just as tight..... you don't want the humidity traveling through the insulation, that is the whole point. The only way to blame the spray foam is that it is better than conventional insulation, so your A/C has to run less, and the humidity builds more easily.

3) Essentially, you have fitted the garage with insulation as though it will be a conditioned space, so you need to condition it. Not just heat and A/C..... dehumidification too. You'd do the same in your house if it was too humid by running a dehumidifer in the basement. At least I would.

4) Determine the source of the humidity..... wet cars, outside air when the doors are opened?

 

[jehjr68]

Thanks for the input. I installed a 12,000 btu window AC yesterday that has a "dry" dehumidification mode as well. Will give it a shot.

-J

 

[danski0224]

Vapor barrier under the concrete?

 

[jehjr68]

yes. Floor is also epoxy coated.

thx

 

[CNGsaves]

Now we know you've built very air-tight garage, it would be nice to see this handiwork . . . . any pics??

What tangible symptoms of high humidity are you having?? Condensation?? Uncomfortable even though temperature is appropriate?

Have you tried moving the air with some large standing fans (ie like one at each end of garage moving air in circular pattern to burn off some of that humidity)??

More expensive solutions obviously are Dehumidifier or Air Conditioner.

What all is happening in garage and what are goals and budget??

 

[danski0224]

I recall reading that it takes quite a long time for concrete to dry out- something like a year. Might not be enough to cause issues with the epoxy, but it may be enough to add lots of humidity.

Echoing above, how do you know the humidity is high?

 

[Cobra6]

I live in south Georgia ... Savannah.

Thanks

You are going to have big-time problems with the humidity and condensation unless you have some kind of vent - you need soffit vents and either a gable vent or ridge vents on the roof.

 

[bd8134]

I recently have had my attic rafters spray foamed in both my house and garage. I previously had foam sprayed in the garage walls when it was being built. I recently had an energy assessment done on my house and it showed it was pretty tight. I expect my garage is the same. I run a dehumidifier summer and winter, my heating comes on when below 50 degrees. If I have water / snow that is carried in by cars, I clean that up asap if I can be bothered. I also run an oscillating pedestal fan occasionally to get the air moving. If the humidity is bad because of the water etc I get condensation on inside of double glazed glass in my door. It will clear within a day or so. My floor is also epoxied.

I second what gpalmer77 has said.

Jehjr68, controlling the humidity with an a/c unit during the summer and using a dehumidifier year round should solve your humidity issues, it's a lot more humid where you are though. Use a fan also to get the air moving.
I installed my house a/c in my garage when I added an extension. It has a super dehumidifier option and water pours out the drain during hot summers. I can kick it off when it hits a certain humidity within a certain temp range.You might not have that option on a window unit and in your area it might need to be a fair size.

Don't put soffit or gable vents in, you paid good money to have a sealed garage, you just need to control the humidity. You could consider heat exchangers if the building is very tight and the air is stale, but most likely not needed in a garage.

 

[lariat]

I concur with Cobra, you need soffit vents and ridge vent to draw humidity off.

 

[bd8134]

Adding vents to conditioned space is not the correct approach unless it it is controlled ventilation. Google conditioned space and read about it.
Here is one link. http://www.greenbuildingadvisor.com/green-basics/vented-or-unvented-attic

 

[lariat]

Sorry, thought you were dealing with a conventional attic over workspace when I recomended soffit vents and ridge vent.

 

[cowboyjosh]

This is what I call an un-intentional consequence. You wanted a tight garage and now it's too tight and you need a solution to this. In new homes we are installing HRV units, you might find a HVR or other mechanical ventilation to help mitigate your humidity problem, because even without spray foam in Georgia you have humidity issues.