Garage Dehumidifier in Winter

[RamFan]

Hi All-

Forgive me if this isn't the best forum for this question, please move to a more appropriate one if needed.

I've been countlessly reading, as I do every winter, on the best preventative methods for combating rust. As most of us know, the go to tips are; proper washing/sealing, underbody wash, professional rust proofing and dry air.

The last tip is the point of my inquiry. I have standard two car (attached) garage where both vehicles are parked. I've been thinking about getting a dehumidifier, but I'm not sure if it would be beneficial in my case. Since we park the cars in there, we open the door throughout the day. Typically we have the door open 3-4 times in a day. I leave for work around 7a, wife leaves around 12p, I get back around 6p and then she gets back around between 6p and 9p.

Would a dehumidifier even be able to actually keep the humidity low enough with the door being opened to help? Also, the garage isn't heated, typically it stays around 15-20 degrees warmer than the outside temp in winter. I don't ever recall seeing it get below 25 degrees in there, I think the houses heat and insulation must make that the bottom out point.

What are your thoughts?

 

[2heeldrive]

Dehumidifier's don't work in cold temperatures because the coils freeze up. 60F is about the minimum temperature where they will be effective.

I would think about putting in a garage heater. They have electric ones that are suspended form the ceiling. That should work well to dry out the air in your garage.

The flip side though, heating your garage may actually cause more rust. Rust happens more rapidly as the temperature rises. I seem to recall that rust almost stops at temperatures below 40F.

 

[silveravant]

Humidity is usually low in the winter so I don't think a dehumidifier would be of any help. I don't think it would even work in the cold.

I do think you could save quite a bit on your heat bill by keeping the door closed because it seems like the insulation between the garage and house is lacking. A garage door opener may pay for itself as well as adding convenience.

 

[64bawagon]

I painted my floor and the one concrete wall in my attached, unheated garage, hoping that helps with dampness this year

 

[KrisZ]

My previous house had a built in garage like yours. It was quite well insulated, but not heated and the temperature inside always stayed above freezing, even during the coldest months.

I had to park my car there all the time and kept my motorcycle there as well. The moisture would freeze on the inside of the garage door and the slush from the car would melt and pool at the door (the floor was sloped), but overall there was no problem with rust. My motorcycle brakes and other parts never showed any rust. There wasn't even any dew accumulation on it. Same thing with my car parked there.

I think that if the vehicles inside stay dry, with no dew or frost accumulation, then the air inside is dry enough to be a no problem.

 

[bullwinkle]

Normal IL winter air is going to always have a low dew point, no higher than 40F or so. You don't want to heat the garage & then put a salty vehicle (or trailer) in it-my company branch here & the one in Columbus had identical steel frame enclosed trailers, bought at the same time, but they had room to keep theirs inside in winter & we didn't. Theirs rusted out the A-frame of the trailer, ours was still perfect 5 years later when we finally retired it.

 

[Donald]

Start with getting a RH meter/gauge. Heat will make it worse since rust is a chemical reaction. Cool it to -273K and you can be assured of no rust and not much else either.

The best protection is a place that sprays one of a number of rust preventive sprays like CarWell or Krown or Fluid Film. There are other similar ones. No wax ones or Ziebart.

If its not treated then a car wash with undercarriage spray every week or two when it gets a little warm in March or April.

If its treated then no undercarriage spray until its ready to be re-sprayed.

 

[WyrTwister]

Originally Posted by twoheeldrive
Dehumidifier's don't work in cold temperatures because the coils freeze up. 60F is about the minimum temperature where they will be effective.

I would think about putting in a garage heater. They have electric ones that are suspended form the ceiling. That should work well to dry out the air in your garage.

The flip side though, heating your garage may actually cause more rust. Rust happens more rapidly as the temperature rises. I seem to recall that rust almost stops at temperatures below 40F.


If it is not too cols outside , a mini split heat pump may be more cost effective to operate than electric resistance heat .

 

[PimTac]

It sounds like you need air movement. A small ventilation fan could do the job.

 

[RamFan]

Originally Posted by twoheeldrive
Dehumidifier's don't work in cold temperatures because the coils freeze up. 60F is about the minimum temperature where they will be effective.

The flip side though, heating your garage may actually cause more rust. Rust happens more rapidly as the temperature rises. I seem to recall that rust almost stops at temperatures below 40F.

They have low temp dehumidifiers, the ones I've looked at function down to the mid-30s. Yup, not looking to add heat to the garage for that very reason. If I had a workshop only garage it would definitely be heated but not for a daily use garage.
Originally Posted by silveravant

I do think you could save quite a bit on your heat bill by keeping the door closed because it seems like the insulation between the garage and house is lacking. A garage door opener may pay for itself as well as adding convenience.

We own a raised ranch townhome. Garage is under our living room, stairs go from the garage straight up into the living area. They definitely didn't insulate from about halfway up the staircase, down. I wish there was something I could do to increase the insulation but unfortunately I'm limited in options. I'm confused by your garage door comment.
Originally Posted by KrisZ

I think that if the vehicles inside stay dry, with no dew or frost accumulation, then the air inside is dry enough to be a no problem.

These are our DDs so unfortunately they see the elements before being parked for the night.
Originally Posted by Donald

The best protection is a place that sprays one of a number of rust preventive sprays like CarWell or Krown or Fluid Film. There are other similar ones. No wax ones or Ziebart.

Ziebart is the local option, I've looked into them a time or two but the mixed opinions keep me away. Why do you not recommend them?
Originally Posted by PimTac
It sounds like you need air movement. A small ventilation fan could do the job.

Why is that?

 

[Donald]

Originally Posted by RamFan
Originally Posted by twoheeldrive
Dehumidifier's don't work in cold temperatures because the coils freeze up. 60F is about the minimum temperature where they will be effective.

The flip side though, heating your garage may actually cause more rust. Rust happens more rapidly as the temperature rises. I seem to recall that rust almost stops at temperatures below 40F.

They have low temp dehumidifiers, the ones I've looked at function down to the mid-30s. Yup, not looking to add heat to the garage for that very reason. If I had a workshop only garage it would definitely be heated but not for a daily use garage.
Originally Posted by silveravant

I do think you could save quite a bit on your heat bill by keeping the door closed because it seems like the insulation between the garage and house is lacking. A garage door opener may pay for itself as well as adding convenience.

We own a raised ranch townhome. Garage is under our living room, stairs go from the garage straight up into the living area. They definitely didn't insulate from about halfway up the staircase, down. I wish there was something I could do to increase the insulation but unfortunately I'm limited in options. I'm confused by your garage door comment.
Originally Posted by KrisZ

I think that if the vehicles inside stay dry, with no dew or frost accumulation, then the air inside is dry enough to be a no problem.

These are our DDs so unfortunately they see the elements before being parked for the night.
Originally Posted by Donald

The best protection is a place that sprays one of a number of rust preventive sprays like CarWell or Krown or Fluid Film. There are other similar ones. No wax ones or Ziebart.

Ziebart is the local option, I've looked into them a time or two but the mixed opinions keep me away. Why do you not recommend them?
Originally Posted by PimTac
It sounds like you need air movement. A small ventilation fan could do the job.

Why is that?


Ziebart sprays a rubberized undercoating last I heard. It looks good until a chunk falls off and you see all the rust it was hiding. Some places do not want to work on cars with the rubberized undercoating. The places I suggest are much less money but it needs to be treated yearly. Its kind of an oily based product that creeps.

Ziebart could have changed but I think they want a sale of $800 to $1000, get all the money up front. The Krown and similar places are much less but you need to get it done yearly. Krown does not just inspect it yearly, they respray the entire vehicle yearly.

 

[MasterSolenoid]

I vote for some type of Oil Undercoating.
Don't waste your time/money with a dehumidifier.

Do an Internet search for Fluid Film undercoating / be informed.
Start asking around for anyone in your area that does 'oil' undercoating.
I also agree to stay away from Ziebart / tar spray.

What I do when there is a lot of slush under my vehicle is: park outside until it melts.
Get one of those Snow Brushes that they use at Car Dealerships.

 

[RamFan]

Wanted to follow up on this thread. Got a thermometer with humidity reader and these are the results after a week. Picture was taken this morning at 7am after the garage door had been closed for 13 hours, outside temperature was 23*F.

Small numbers are the respective record highs and lows for both temp and humidity.

 

[MasterSolenoid]

I still say, "you can't fight Mother Nature"
Forget your original thought of using a dehumidifier in your garage.
I have a dehumidifier in my basement for the Summer time and my electric bill doubles.

Do what everyone else does and get the vehicle OIL undercoated.

Good luck.

 

[demarpaint]

I open the door about a foot during the day for a few hours if someone is home. I get airflow from the top and bottom of the garage door. No problems with anything rusting in close to 40 years of owning a house and parking in the garage in the Northeast.

 

[JTK]

I think the key is like said above. You want to keep a salty vehicle as cold as possible. Maybe it's a good thing my ~2.5 car garage has too much khrap in it to easily fit a car?

 

[MechanicGuy]

Originally Posted by demarpaint
I open the door about a foot during the day for a few hours if someone is home. I get airflow from the top and bottom of the garage door. No problems with anything rusting in close to 40 years of owning a house and parking in the garage in the Northeast.

I'm using the same method with demarpaint and it's working great. Also, I put some carpet remnants under where I park to keep my floor dry.

 

[garrettporter]

I know I'm a bit late to the party on this topic, but I thought I'd add my two cents in. Without my dehumidifier running, I've seen RH up to 90% in my garage (single brick walls, no insulation).
The dehumidifier I currently use (Meaco 8L) is run 24/7 on the laundry mode and that brings it down to 45-55% most of the time and it turns itself off when it gets to 45% anyway, to save power.
I think 45-50% RH is fine. The heat it puts out keeps the garage couple of degrees above outside air temperature, so that helps too.
You don't need to reduce RH to zero and it would be quite difficult to get it below 30% in most brick-built detached garages unless you used an industrial dehumidifier.
And here's how you can choose a proper dehumidifier and how to prolong it's lifetime.