Garage moisture issues

Dan

Dan

Active member
How are you guys dealing with moisture in your garage?

I bought a new to me house and the previous owners were pretty oblivious to a mold problem in the garage. There were a few really nasty spots. I did cast some judgement on them for that but in a twist of irony while cleaning out my old garage I found a few minor spots as well. They were behind my big tool chest and my detailing cabinet.

I didn’t even regularly wash in the garage, only ONR when the weather was too cold. And I rarely parked wet cars in there.

Some googling reveals this is a pretty common issue as the spaces aren’t conditioned and you have hot, wet cars parked in there. Bonus because most garages don’t have windows, mold loves dark and hates UV.

I’m thinking of throwing a dehumidifier in there but maybe an ac unit with dehumidify might be the more practical answer.
 
I think I`d start with an oscillating fan and see if you might get some relief from that, Dan. Does the garage seem damp when you are in there? Ground water high in your area?
 
Tom, I think the fan will help if I keep the doors open and it`s not too humid outside. At times it does feel a little humid but it`s not crazy, I grew up down south where it`s always pretty humid.

The crazy thing for me was reading the EPAs documents stating that even mid 60% is enough for mold growth!
 
That sounds about right for mold growth. I know our basement is 60% RH and higher in the summer months. The basement is large, and the house is built on a hill, so the ground tends to be dry. If I run the dehumidifier, it can get it down to 35% or so and that`s very comfortable for me. However, then you`ve got the cost of running the dehumidifier all the time.

I bought a med size wall mounted fan (Air Monster) a couple years ago. That works pretty good in terms of helping the garage dry when the floor is wet. Someone gave me last year a large Lasky fan that stands on the floor. That moves a LOT of air even on the lowest speed. Blade diameter on that is probably 20".

There`s also the HVAC mini-split installation, but I`d guess something like that would be at least $5k unless you can handle the install. Those typically have a separate de-humidification function, and you`d end up with heating and cooling, as needed.
 
tom p. said:
There`s also the HVAC mini-split installation, but I`d guess something like that would be at least $5k unless you can handle the install. Those typically have a separate de-humidification function, and you`d end up with heating and cooling, as needed.
Click to expand...

They do? Are you describing reheat? I don`t see how you could do that with a mini-split. Fill me in.
 
tom p. said:
That sounds about right for mold growth. I know our basement is 60% RH and higher in the summer months. The basement is large, and the house is built on a hill, so the ground tends to be dry. If I run the dehumidifier, it can get it down to 35% or so and that`s very comfortable for me. However, then you`ve got the cost of running the dehumidifier all the time.

I bought a med size wall mounted fan (Air Monster) a couple years ago. That works pretty good in terms of helping the garage dry when the floor is wet. Someone gave me last year a large Lasky fan that stands on the floor. That moves a LOT of air even on the lowest speed. Blade diameter on that is probably 20".

There`s also the HVAC mini-split installation, but I`d guess something like that would be at least $5k unless you can handle the install. Those typically have a separate de-humidification function, and you`d end up with heating and cooling, as needed.
Click to expand...


I`m seeing similar numbers in my basement as well, mid 60`s if the AC isn`t running regularly, like after it rains, cools down, but yet the rain soaks into the ground. The garage is at a bigger disadvantage with wet/hot cars coming in and has no AC to help drop humidity.

I would have never even look/thought to look if it wasn`t for my new house having obvious issues. But the old house, and by old, it was ~10 years old, had a few patches behind my big tool box and my rubbermaid detailing cabinet.
 
I run a dehumidifier in the shop, with its discharge hose dumping into one of the floor drains. NOT packing stuff up against the walls so much has also helped, better airflow/etc.

I don`t run the AC unless it`s really hot and I have a lot of work to do...cooling the house is costly enough without doing that building too (unless I need to..not gonna suffer actual discomfort if I can avoid it ;) ).
 
Accumulator said:
I run a dehumidifier in the shop, with its discharge hose dumping into one of the floor drains. NOT packing stuff up against the walls so much has also helped, better airflow/etc.
Click to expand...

That was probably my issue, I packed those two items as close to the wall as I could (more space for other junk!!!!). No UV, no airflow, lots of humidity=happy mold!
 
Setec Astronomy said:
They do? Are you describing reheat?
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Setec, I`m not sure I know what "reheat" is.

We had a room finished a year ago and the contractor did an LG mini split with a ceiling cassette. The unit installed heats and cools. The remote control has a dehumidify setting and I believe it runs continuously when selected. You lose the ability to select a temperature when using that, but you can still control the fan speed and the swinging motion of the louvers.

If you are asking about an HVAC that mixes in a little resistance heating to dry the air, that`s not what this is. I think my father-in-law`s system in FL had that feature, I remember him talking about it. Said it cost $$$$ to use it.
 
tom p. said:
Setec, I`m not sure I know what "reheat" is.
Click to expand...

Sure you do, you explain it below.

tom p. said:
If you are asking about an HVAC that mixes in a little resistance heating to dry the air, that`s not what this is. I think my father-in-law`s system in FL had that feature, I remember him talking about it. Said it cost $$$$ to use it.
Click to expand...

That`s the traditional way to do it, some package units as I noted put a condensing coil after the evaporator that can be switched in provide some reheat (so the discharge doesn`t become subcooled). I guess since you can`t pick a temp when you put the mini-split into dehumidify, it`s just subcooling the space. Maybe like setting it to "-11".
 
OK, just never heard the term "reheat" before. Not an HVAC guy.

Yeah, when the mini-split is in dehumidify mode, it just feels like A/C at some minimal output level.
 
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