Dehumidifier for garage

[Dan Babb]

My garage is insulated very well...good door and very good insulation behind the walls and roof.

On the very hot days, it gets up to about 82 in the garage, but the humidity is brutal...it can be 70-80% inside (close to what it is outside). Even with a fan moving air in the garage, it's really hot and not a lot of fun working on the car.

I have a small portable AC, but it's only good for 350sq.ft and my garage is about 900sqft with 12 foot ceilings...so it's losing the battle against the heat. It removes a bit of moisture from the air, but not enough to notice.

I don't really want to spend the money on a mini-split AC unit and a window unit option is not going to work for us (the windows face our house and neighbors house and none of us want to look at a big unit sticking out the window.

Anyone put a dehumidifyer in their garage to help beat the heat? I'm thinking if I get one more oscillating fan up on the wall and can get the humidity down, it will be tolerable in the garage.

I'm finding units that say they can remove 50 and 70 pints of water per day from the air that are reasonably priced...but don't really know what size unit I need for my space.

 

[James-W]

A dehumidifier will certain help to make the garage more comfortable for working by lowering the humidity, but it won't lower the temperature any. I can understand not really wanting to look at the back side of an air-conditioner sticking out of a window. But if I were given the choice of having a cool working place or sweating my testicles off, I think I could force myself to look at the back end of an air-conditioner during the Summer months.

 

[NKlamerus]

Go with AC and plant some Grape Vines on an arch around it.

 

[4 FN 27]

I have AC in my shop but the building is so well insulated the AC does not run enough to temper the air. Thus I am running a 70 pint dehumidifier in the Machine Shop area roughly 42 x 42 and 50 pint in the Car Shop area and that is roughly 38 x 42. The 70 pints fills a 5 gallon bucket 3/4 full every 3 days set at 40%. The Car Shop needs to be emptied every morning and every evening set at 40% also. Need to set this up on a bucket also so I can measure and see how much it is taking out.

The Car Shop has 2 big garage doors and the entry door. Don't open the garage doors very often but in and out the entry door all the time. So I believe that room gets more exposure.

I don't AC the storage area and I run a 70 pint in there. The room is 80 x 68 and it keeps up so long as I keep the doors closed. Stays about 78-80° in there. If I wash something using the Pressure Washer inside like I did yesterday I hook up a second 70 pint and is back to 40% by the next day. These dump directly into a floor drain.

It does help a ton but costs a fortune to run all 3 dehumidifiers 24-7 (and sometimes a 4th). But I will pay to be comfortable and not watch all my equipment get rusty.

Your investment in a dehumidifier will be money well spent. Once you get the humidity down to an acceptable level a energy efficient unit will shut down and sample the air and kick in when needed. I'd give it a shot.

 

[GarageWidget]

Here in S. FL. I run dehumidifier and keep the garage around 40% RH. Keeps the rust off the metal and the machines in good shape. It also adds about 10 degrees heat to the room averaging about 90-100 in the insulated garage.

Mine is a single car garage the DH is a 70 pint I believe. Costs about 15 bucks a month to run + the time it takes to drain it (once ever other day).

Good Luck.

 

[walrus]

Dehumidifier will raise temp in shop

 

[Dan Babb]

The temperature will go UP in the shop? Is that because of the heat generated by the unit?

I don't really have a problem with things rusting in there now...but I guess over time that could become a problem. Right now, I'm more interested in trying to feel cooler (even if the actual temperature doesn't change much).

 

[crabjoe]

The temperature will go UP in the shop? Is that because of the heat generated by the unit?

I don't really have a problem with things rusting in there now...but I guess over time that could become a problem. Right now, I'm more interested in trying to feel cooler (even if the actual temperature doesn't change much).

I would say so.. My dehumidifier definitely blows warm air.. But it pulls so much water out, it's not funny.

 

[ishiboo]

I have AC in my shop but the building is so well insulated the AC does not run enough to temper the air. Thus I am running a 70 pint dehumidifier in the Machine Shop area roughly 42 x 42 and 50 pint in the Car Shop area and that is roughly 38 x 42. The 70 pints fills a 5 gallon bucket 3/4 full every 3 days set at 40%. The Car Shop needs to be emptied every morning and every evening set at 40% also. Need to set this up on a bucket also so I can measure and see how much it is taking out.

That folks is why you do not oversize your air conditioner!

 

[manwithtools]

That folks is why you do not oversize your air conditioner!

And unfortunately the AC now has to run more frequently because the dehumidifiers raised the relative air temperature. A viscous circle of sorts.

Great point about sizing the AC properly but I know that 4 FN 27 did his research (based on what I've read in his other posts) something must not have gone as planned.

 

[4 FN 27]

And unfortunately the AC now has to run more frequently because the dehumidifiers raised the relative air temperature. A viscous circle of sorts.

Great point about sizing the AC properly but I know that 4 FN 27 did his research (based on what I've read in his other posts) something must not have gone as planned.

Thanks for the vote of confidence!!!

Sort of...my Geo guy did the sizing based on the information supplied by Morton Building Systems. To be honest their premium insulation package is better than they think it is based on the small bills for the square footage being heated and cooled.

The system basically is sized correctly if you are in and out of the building all the time (I think). But my day job keeps that from happening. It is a single unit zoned to the Machine Shop, Car Shop and Office. It also doubles to temper the air in the winter should the temp drop -2° below the set point. Helps recovery time, and it works.

Last year the AC did not even kick in until late July. I was shocked. Heck I haven't even installed the Mini Split in the Gun Vault. An isolated ICF enclosure 16 x 24 feet with a "Spancrete" Ceiling and Concrete poured on top of that. It never gets above 72° in there and the heat never runs. After 3 weeks of running the Dehumidifier in there will not even product 1 gallon of water set at 35%. It is basically a building in a building.

Basically that room is 3456 cubic feet. The Dehumidifier runs 24-7, it is a 30 pint and constantly runs the fan but it is hard to tell what the actual time of the compressor running is. But I can say the heating effect is next to nothing considering how tight the room is and it never gets above 72°.

Also Machine Shop is roughly 28224 cubic feet. I doubt the BTU's thrown off by the Dehumidifier would have any noticeable effect on increasing the temp of that room.

It is on my list of things to do/sort out...so with that said I am a novice in the Heat and Thermodynamics world, had 1 semester on it about 30 years ago I'd be interested in what a "Pro" would have to add. I am all about learning new things and applying them.

 

[aar0s]

I rarely in my garage so the doors stay sealed most of the time and I keep a fan and a small dehumidifier running, helps some but when it's super humid and raining everyday like it has been this summer there is not much you can do.

 

[Jeepster04]

Yup, I keep a dehumidifier running in my garage. Keep it at 65% since it would most likely run 24/7 otherwise. My house is down in a tight valley and it stays wet around the house, so its pretty much a have to. Stuff was getting pretty musty before I got it.

And yes, it certainly puts out warm air. I think its still more comfortable having the air a little warmer yet dry.

 

[jgregt]

Dan,

I'm over there in Raleigh. Typical suburban house with attached two-car garage. My garage is not A/C'd but I do run a humidifier. It has a humidistat and can pull a couple of gallons of water a day.

I also run a 20" floor fan to keep some air morning

This summer has been brutally humid.

 

[USAFpj]

Just bought a GE humidifier last night. Wasn't 'sure' what the RH was in the 30x50x14 shop, but when I turned it on, it was at 85%. It's now down to 65%, and I may try to get it down to 50%, but that may be asking a lot of this 70pt unit.

At what RH level are you comfortable with in a shop, for general rust and mildew free items?

 

[JMURiz]

If you can swing it, get a mini split system with a dehumidifier function. My old MrSlim unit has it and I run only that in the summer.

Makes it totally comfy even in this 95-100 deg weather and dries it out nicely

 

[crabjoe]

And unfortunately the AC now has to run more frequently because the dehumidifiers raised the relative air temperature. A viscous circle of sorts.

But if the AC is running, it's also pulling water out of the air...

 

[manwithtools]

But if the AC is running, it's also pulling water out of the air...

The significance is that the AC alone should have dehumidified the air without the need for the energy use and heat input the dehumidifier is adding to the mix.

 

[finn]

Another thing to look at if your water heater is in the garage is to upgrade to a hybrid electric heat pump water heater.

When in heat pump model they pull heat from the air and act as a dehumidifier. A bonus is that they will reduce your electric bill compared to a resistance water heater and with the rebates some power companies provide ($850 in my case) they are almost free.

It's not the same as a mini split, but every little bit helps.

 

[andybell]

Definitely worth getting a dehumidifier for your garage if you live in high humidity areas like Miami or Florida. Just don't run the humidity down too low. When you get to 40% and below you'll end up with dry and cracked leather and wood finishes. A 50 pint per day unit that accommodates a hose for continuous drain is fine. If you need to run the hose up through a window then you'll need one with a built-in pump. There are some good options here: www.knowitalllearning.com/best-garage-dehumidifier-review/

 

[mnwebb]

Yeah, does a mini-split take care of the humidity if sized correctly or does it have to be one with a dehumidifier especially built in? Isn't that what a/c units do, take water out of the air?

-W

 

[Mosby]

I have a large shop I want to look at running a dehumidifier in this summer. It is roughly 1500 sq ft, with about 2/3 of that having an 18ft ceiling, the rest a 9 ft ceiling. It haqs fully insulated ceiling, with about 1/2 of the walls fulling insulated and the remaining walls spray foam insulated, but the walls are intended to also get batt insulation eventually. So the spray foam is only an inch or two deep on the areas where that is the only insulation.

The space has one window, if I put a small window unit air conditioner in the window, knowing it won't appreciably cool the space, but would it act as a dehumidifier, enough to make a difference?

I don't anticipate using the space as a work space this summer, mostly just to store equipment. My feeling is I already own the air conditioner and this way I don't need to bother with getting the condensate out of the space, as the window unit will just dump it outside already.