Am I overthinking garage heat and insulation?

[dtbingle]

Just put an offer down on a house with the following layout. Garage is technically "attached", but not really. The house is otherwise dead on for what my gf and I want minus the garage situation.

I was dead set on having an attached garage because when properly insulated, the radiant heat off of the house should be enough to keep the temps a bit warmer in the garage which would allow me to keep tool batteries, paints, chemicals, etc out there instead of having to lug them inside during the winter to avoid freezing. Also, having this slight temperature bump would decrease the amount of condensation that forms on tools, equipment, and cars.

My current garage situation is a detached, uninsulated, unheated, poorly sealed door, etc. I have problems with the concrete becoming wet, condensation on tools, and rust on things just sitting there. I'm trying to avoid this happening at the new place assuming our offer is accepted.

What would be the best solution to manage heat and moisture in this detached "attached" garage layout? Am I just overthinking this and insulating and sealing it properly will take care of most of the moisture worry? Then just keep "freezables" downstairs and use a heater when needed?

 

[yeldogt]

I never had an attached garage that gained much heat from the house -- if any.

The more you can close it up the better -- without heat .. if you drive a wet car into a garage the humidity goes way up.

 

[Showkey]

My attached garage never ever freezes, water on the floor and temperature hoovers at about 32* to 40* most of the winter months. Even when outside temps are -25*. Park two cars in the garage every day with out fail. I do not leave the doors open other than to come and go.

The garage 28X36' is insulated both in the walls, doors, double pane windows, insulated doors and ceiling. The 36' length touches the home. The home is very well insulated.

In the opposite .........I have a detached shop/ garage in the woods very well insulated in the summer the temps never raise above 70-75* in the heat of summer. I do have run a dehumidifier to control the humidity. I heat this shop during the winter at all times to 50* and when working 60-65*. Humidity in the winter is not a concern.

 

[bzinsky]

My attached garage never ever freezes, water on the floor and temperature hoovers at about 32* to 40* most of the winter months. Even when outside temps are -25*. Park two cars in the garage every day with out fail. I do not leave the doors open other than to come and go.

My detached garage does the same thing, no insulation, lowest temps are single digits.

I guess just a few windows and a little geothermal effect is enough to keep the temperature above freezing

 

[dtbingle]

My attached garage never ever freezes, water on the floor and temperature hoovers at about 32* to 40* most of the winter months. Even when outside temps are -25*. Park two cars in the garage every day with out fail. I do not leave the doors open other than to come and go.

The garage 28X36' is insulated both in the walls, doors, double pane windows, insulated doors and ceiling. The 36' length touches the home. The home is very well insulated.

In the opposite .........I have a detached shop/ garage in the woods very well insulated in the summer the temps never raise above 70-75* in the heat of summer. I do have run a dehumidifier to control the humidity. I heat this shop during the winter at all times to 50* and when working 60-65*. Humidity in the winter is not a concern.

Agreed, the problematic time though is the winter -> spring transition where temp and humidity vary day-to-day. Seems like you have the temperature and humidity situation well controlled - even in your detached. What do you use to keep your detached shop heated at all times?

 

[theoldwizard1]

What would be the best solution to manage heat and moisture in this detached "attached" garage layout? Am I just overthinking this and insulating and sealing it properly will take care of most of the moisture worry? Then just keep "freezables" downstairs and use a heater when needed?

Yes, you are over thinking it. The sad thing is, you'll likely never achieve your goal. A previously built garage WITHOUT vapor barrier and insulation under the concrete floor and with "typical" garage doors, will "leak" a lot of heat and moisture. Spray foam insulation ($$$$) will do the best at sealing the walls and roof, but it will really won't be "dry". Any unvented, non-electric heat source will ADD moisture.

I was in the same situation when I bought my house 40 years ago. Surprising only a few tools have some rust, and even those are not too bad.

If you have to have a well insulated/heat garage, tear it down and start over.

 

[Showkey]

^^^^^^^^^^Nat gas Beacon Morris 45k btu ceiling mounted heater.

The attached garage floor will sweat on humid days for several months in the season change until the thermal mass comes up in temp. Basicly the floor acts just like a giant ice tea glass on hot humid day...........same in fall to winter the slab takes a long time to drop in temp.

 

[toyotadriver]

The house is built. Can't control what's under the concrete.

You can control the moisture to some extent. Insulate the garage as best you can. Then, install a gas VENTED heater. You don't want to be putting extra moisture into your garage. Then, as the temps warm up in the spring, run the heater some even when you don't need to. Run a fan pointed up to the rafters to help circulate the heat off the ceiling and onto the floor. The warmer you keep the garage throughout the winter and especially in the spring will help prevent too much condensation on your garage floor.

With your cold climate you'll still probably get some condensation but the more you can run a VENTED gas heater, the less it'll sweat.

You might also need to run a dehumidifier as well to help keep the humidity level down.

I live in a warmer climate but this winter is the first one where I ran the heater regularly throughout the winter. I had sweating last few years but none this year. The concrete temp is much higher than last year at this time due to my running the heater.

 

[engineer2]

Insulate, seal it as best you can. 20,000 BTU is the minimum that should do it. 36,000 BTU will heat it up faster.
Agree that the floor will sweat in the springtime for a week or so.
Agree that Vented is the only way to go.

 

[75gmck25]

For an existing poured floor (probably minimal insulation under it), would it help to reduce moisture and sweating if you sealed it with good cement paint, put down thick poly, and then covered that with Racedeck as a work surface to protect the poly? Or would you be fighting a losing battle?

Just wondering.

Bruce

 

[toyotadriver]

For an existing poured floor (probably minimal insulation under it), would it help to reduce moisture and sweating if you sealed it with good cement paint, put down thick poly, and then covered that with Racedeck as a work surface to protect the poly? Or would you be fighting a losing battle?

Just wondering.

Bruce

I wouldn't. Secret is to keep the concrete warmer than the dew point. It doesn't have to be warm....just warmer than the dew point.

OP might want to consider a radiant tube heater if he has enough overhead clearance. It'll do even more to keep the the concrete above the dew point.

 

[dtbingle]

I was holding off a bit to reply until we heard back.....we got the house! It seems like the general recommended method would be insulate and install vented heater.

What's recommended for insulation? Any moisture liner on inside between studs? Spray, standard fiberglass, rockwool, etc?

Considering it's older, it probably doesn't have a moisture barrier under the concrete floor, meaning any coating (ie. epoxy) would not be worth it because it likely wouldn't hold up. A better solution is to put in some type of heater as you guys have mentioned to keep the concrete slightly warmer than dew point. Unfortunately not enough overhead clearance for radiant heat, so it's looking like a vented electric or gas are the better options.

 

[86turbodsl]

If it's a typical dearborn house, built in the early 1900s, there will be just studs in the garage, insulate with dense pack cellulose or spray foam, use a vapor barrier across the studs on inside, then sheetrock or osb, and use a vented natural gas hanging heater. They occasionally come up for auction at RJM in plymouth. At least i've seen a few there. Or go new. Not hard to install really.

 

[theoldwizard1]

What's recommended for insulation? Any moisture liner on inside between studs? Spray, standard fiberglass, rockwool, etc?

1"-2" of spray foam (vapor barrier and crack filler) and fiberglass.

You will need a ceiling and 6"-12" of blown fiberglass or cellulose if you want to keep the heat in. Forget electric heat. Cheap to install, expensive to operate.

If the floor has a lot of cracks, you should start saving for a replacement at which time you can add a vapor barrier and insulation.