Heated Garage and Humidity

[bucktail]

I'm planning on building in the next year or 2. It's going to be a single story heated with PEX in the floor. I was planning on doing the heated floor in the garage as well, but I have 2 friends that have it and they both have humidity issues when they drive in with snow on the car, it melts, and evaporates.

So I'm wondering if anyone has cracked the problem with the humidity and in floor heat. I'm thinking a vented heater that draws air from the garage would help somewhat, but most of the new HVAC I've seen pulls cold air in from the outside.

 

[bearskinner]

When I was using propane heat in my shop, I had a roll around, stand alone dehumidifier. I was surprised how well it worked.

 

[OldeEnglish]

A dehumidifier, they make them in a mini split version as well. Floor drains would solve the problem but most codes require a gas/oil separator be used. And my final thought is a Modine style hot water fan coil, they do a great job of drying areas out.

 

[Grouse Feathers]

My garage is 50’ x 28’ with attic trusses for second floor storage. I finished the inside, and the walls, 2nd floor ceiling and 1st floor ceiling are insulated with fiberglass and covered with drywall. The first floor has a 9’ ceiling and I have an 18’ enclosed workshop in one end. We have about 3 miles of maintained dirt road to our home which becomes 3 miles of maintained snow road in winter. The vehicles always bring snow into the garage during the winter.
At first I only heated the workshop with an overhead propane unit heater, and in the winter the garage area remained around 32F regardless of outside temperature, even down to -37F. If I opened the garage door for a while the temperature would drop, but a couple of hours with the door closed and it would be back to 32F. I had a big moisture problem. The vehicles remained wet all winter, there was wet snow on the floor under the vehicles, and the stairway and 2nd floor had frost on the walls. I tried a vent fan, and it made little difference except to cause a problem with my workshop heater exhaust.
I then added a vented radiant propane heater to the garage area and now maintain 50F in the garage area. The vehicles are now dry, the floor is only wet under the cars, and the frost is gone from the 2nd floor walls. The floor in the garage area is sloped to a drain in the center so most of the water from the melting snow quickly drains away. I can also bring the temperature up in the garage when I have work on the vehicles or tractor. It is really nice to get all the ice and snow off the tractor for winter maintenance.
With the garage well insulated maintaining the garage and workshop at 50F (65F in the workshop for days or weeks at a time for projects) I use about ½ of a 500 gallon tank of propane

 

[OBKubota]

What do you mean when you say your friends are having humidity issues is it that bad that it's damaging the building or creating mold.I have heated double garage, and use half of it for a workshop. I have a large radiant heater running on natural gas and I don't find humidity a major problem in the winter. My heater does draw air from outside and the burner is sealed which is especially good I have no worries of fumes or dust exploding. If there is too much water on the floor I just squeegee it out, if your building from new I would suggest good drainage under where the vehicles are parked. I live in southern Ontario and I find more of a problem with humidity in the summer but I'm not going to air-conditioned my Garage and I don't think a standalone de-humidifier would do the job.


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[78Vette]

I put in a floor drain when i build my garage/shop and it's absolutely necessary, especially in the winter with the amount of water all the snow/ice/slush will generate. The humidity level absolutely has to be controlled even if you dont park in it, or all your tools will start rusting. All types of Gas have water in it (propane for me), thats why your furnace has a drain tube.....
I found that the regular run of the mill dehumidifiers are a waste of money (been there,done that) and have bought a industrial type on wheels (got 2 of them) It has a pump to eject the water it collects into a drain or into a bucket.
My model isn't listed here anymore, but are like the triton or kompact shown on this site.
http://ebacusa.com/cleaning_restoration.html
Bought mine here.....
https://www.michiganmaintenance.com/dehumidifiers

 

[OBKubota]

So to answer your questions on heated floors it seems no mater what kind of heater you got it's a matter of how you deal with the water and resulting humidity that comes with it. Good luck in your new building.


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[tthorkil]

I have an attached 30 x 40 garage with floor heat and one central drain with the floor sloped to the drain. I keep the thermostat for the floor @ 50 Fahrenheit which keeps the air temperature around 40 to 45 Fahrenheit depending on the outside temperature. The only time that I experienced excessive humidity was when I parked the Bobcat with the snowblower loaded with snow in the garage and used a fan to help melt the snow. If you intend to keep your garage warmer which will lead to more evaporation of the melted snow, you might consider installing a heat recovery ventilator like they did when they built my house. It is controlled by a humidistat that you set to the maximum humidity that you want and when that humidity is exceeded the fans exhaust the humid air through a ‘radiator’ while simultaneously drawing the less humid air from outside through a separate part of the ‘radiator’ preheating the outside air. After showering in the house and the humidity rises the heat recovery ventilator drops the humidity fairly quick. This system is hooked through my ventilation system so I don’t know what ductwork might be required but it is something that you might discuss with HVAC professionals.

 

[bucktail]

Thanks for the input. To answer some questions, they both keep their garages around 40 F and have frost on the windows that melts and makes the windowsill damp, so that it rots out. They both seem well insulated enough that nothing condenses on the sheetrock. My attached garage will tentatively be 24'X28'.

 

[Daren Todd]

My father in law has a 16x24 steel building he uses for a wood shop. Buildings not heated, but we are in a high humidity region. He was having issues with condensation developing on his ceiling. He solved it by adding in an exhaust fan near the peak of the roof to vent the warmer moist air back outside. And works just like using an exhaust fan in a bathroom while showering.

His issues more spring through fall in his shop, so he hooked his to a thermostat so it only kicks on over a certain temperature. He also hooked it up with a bypass for the thermostat via a switch so he can turn it on manually to vent dust or fumes when needed.

 

[Daren Todd]

After reading your reply on the widows, that brings up questions My question for your friends is what type of windows they have and how old?

We had issues with all of the windows in our house with condensation. But they were 30 years old with the old aluminum frames.

The old double pains used gaskets to seal in the argon gas. After 30 years, the gaskets were toast. Updating the windows to new double pane widows, that were manufactured under the new guidelines took care of the issue. New windows are made in an argon filled room instead, and dont use gaskets. Along with the frames being vinyl instead oof aluminum. Garage isn't heated, but very rarely drops below freezing inside, even when we get a cold spell. Haven't had issues since we installed the new windows in the house

On the new windows, with a infrared temp gun, the outside pain shows the outside temp. Inside pain registers the inside temp The old ones would register the outside temp on the inside window pane

 

[tthorkil]

So far I am quite pleased with my selection of the Marvin Integrity Ultrex windows. In the house I have the Marvin INTEGRITY WOOD-ULTREX DOUBLE HUNG and in the garage I have the INTEGRITY ALL ULTREX DOUBLE HUNG to alleviate any moisture problems. The all-ultrex is a fiberglass frame.
http://www.marvin.com/our-products/windows/double-hung

 

[OldeEnglish]

Daren,

As well as how good of condition the gaskets between the sahes of glass are and condition of your windows themselves you have to take account for negative air pressure within the home. Newer houses today are built very tight as far as air flow goes. Old home were built to breath because most people heated with wood or coal. There can be a number of appliances removing the make up air within the home like a bathroom fan, boilers/furnaces that do not draw their own outside combustion air, kitchen exhaust fans, clothes dryers, and fireplaces or wood stoves. If there isn't any air coming back into the home to replace what is lost it creates a negative air pressure. No house is completely air tight so like water, air will enter in the path of least resistance.

I find that air like to come in between the two sashes of windows and it's enough to cool that glass off enough to create condensation. It will basically tell you where the air is coming in, the windows themselves may be fine and just need the gaskets replaced.

A lot of new homes, especially ones spray foam insulated, have a HRV unit installed. Basically it will recirculate the return air with fresh air when needed and also heat that cold fresh air with an electric coil so it doesn't shock the furnace or freeze a hot water coil.

Humidity is never a bad thing during the winter, it makes the home feel warmer and it's good for the sinuses. A lot of force hot air systems have humidifiers installed, especially the new "green homes" heavily insulated. Too much where it is collecting condensation somewhere and growing mold is not so you just need to find that happy medium. Most of the time if the windows are in good shape to fix that problem you need a fresh air intake into the home.

 

[bucktail]

One of them is a modular house bolted together 05'ish. The other is a mid 80's house bought off of a lot and moved on in 09, I think. It got new windows and siding on the house, and the patio door is new, but I'm not sure about the other windows in the garage.

 

[North Idaho Wolfman]

I'm getting ready to build our home and we too are doing hydronic (PEX) heating, house, garage, and side walks ,garage apron on separate glycol system (RV antifreeze) to melt snow and ice.

Insulation and vapor barrier in the floor is very very critical for a good working system as is floor drains in the garage.

Treat the garage just like the home, good insulation in walls and ceiling and a good insulated garage door.

 

[OBKubota]

Wolfman if heat the drive way you won't have a reason to use kubota all winter [emoji853]


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[SLIMSHADIE]

Wolfman, my boss built his retirement home in 2000. He said he tried to think of everything. It ended up really nice and he was just 60. Double wide hallways for 2 wheelchairs, extra wide doors, laundry at both ends of the house, 2 dishwashers, tile floors thru out, 2 boilers for floor heat, 2 a/c units, whole house generator, ..... also heated his rear/front sidewalks and the front driveway. He had 2 sensors, 1 for moisture and 1 for temperature. It would snow and melt the driveway. After the first winter month and the wife got the energy bill(over $1k)
needless to say she said to never turn the outside heat on again, that was in 2001

 

[D2Cat]

SLIMSHADIE, sounds like he built his personal Nursing Home, hallways wide enough for two wheel chairs to begin with.

 

[bucktail]

Wolfman, what are you going with for AC? I'm thinking ductless for mine. Current plan is stained concrete on most of the house, epoxy in the mechanical room. Oversize the mechanical room to make room for a chest freezer and a small reloading bench. At least one bathroom will get the tall toilet, a shower with a bench, and room to move a walker or wheelchair. Open design between kitchen and living/dining room. Pedestal fireplace as close to the majority of the plumbing as it will fit without looking stupid.

 

[Tooljunkie]

Most economy brand dehuies work above 65 degrees. The ones with defrosters work in lower temps.
I had a heated slab years ago, no floor drain and water ran everywhere. Tried a squeegee out the door but made a ridge of ice. Shop vac did the best.
Want to rot a vehicle from the inside out, park it in a damp garage.

My shop has a floor drain, at night it gets to 45,daytime working temp is 70.
When its -20 or colder i have moisture starting on windows. Exhaust fan would be a great benefit to moisture control,hrv would be better, but dust reduces the efficiency.
I heat electric at night, pellets during the day.