Garage Heating

September 30, 2010 8:38 AM

Most efficient way to heat an attached garage?

I have a 2 bay attached garage. It borders the house on 2 sides, one side is to the outside, one side is obviously the door. It is a brick house, but the outside wall does not seem to be insulated, at least not well. It is drywalled and has a ceiling.

Garage door is double width, metal, and does not appear to be insulated (how could I tell?) because it becomes very hot or cold to the touch based on season.

During the winter it gets quite chilly, and I am looking for a passive heating method for 3 reasons:

1. Hot water heater is in garage, and appears to labor under colder conditions, hot water does not last as long
2. House (inside) sometimes seems colder near the garage.
3. Comfort

I am near Chattanooga, TN for questions about climate.

I am considering this or something like it:

http://www.eheat.com/categories/Wall-Mounted-Electric-Panel-Heaters/

Is this a proper/reasonable/cost effective/SAFE (i.e. fire hazard) method? Are there better methods?

I don't need to warm it to 72, just maybe 50. Just defeating the chill, that's all.

posted by discountfortunecookie to Home & Garden (6 answers total)

Get insulated garage doors and a hot water heater blanket.

You'll need to insulate the exterior walls in some way. There are many options here, most people go with foam board and another layer of drywall, but to do it right, you could gut, put up rolls of fiberglass and re-drywall. This is more expensive and time consuming, but you get much better R values.

If there is an attic above your garage, insulating it will make a huge difference. You can rent the machine to blow in the insulation. Assuming it's no more than 400 s.f. area with 12/12 pitch or shallower, you should be able to do it in a weekend for a few hundred dollars. Be sure to do the attic ceiling and floors.

I'm making a couple of presumptions here: Your garage has a cement floor, you have overhangs on your roof line but they are not massive.

If the above are true, do any of your garage walls face south? If so, consider installing large windows in that wall. The sun will heat the cement floor, which holds heat well, and a well insulated garage with the thermal mass of a cement floor will stay quite warm with no additional help.

(If your floor is NOT cement, if it is in fact dirt, I'd put in radiant in floor heat and pour cement over it. You'll need a contractor for this, and another hot water heater.)

If you have no south facing wall, I'd just insulate it and get the heater you linked to, or similar.
posted by Leta at 9:00 AM on September 30, 2010

Heating the garage will be a waste of money and inefficient as a method of keeping your living area more comfortable. You would be better off investing in insulation for the main house to keep heat from leaking from the house into the garage. A blanket for the hot water heat is only about 20 bucks.
posted by JackFlash at 9:08 AM on September 30, 2010

If you have no insulation on the outside wall, a uninsulated metal garage door (a great heat conductor!), and presumably no insulation in the roof of the garage, you will be spending a lot of money to heat your garage, because the rate of heat loss will be very high. You will pump heat in and it will flow right out of the garage. Unless you want to insulate your garage and replace the door, just don't do this.

1) Your hot water heater needs an insulating blanket (or if it already has one, it needs a better one). You need to keep the heat in your hot water heater, not try to keep the heat in the garage.

2) You need to better insulate and/or air seal the walls between the garage and house (and don't neglect the weatherstripping on the door between the garage and the house). Air sealing is easy - seal around baseboards, seal electrical outlets, seal any other holes in the drywall. Insulation is a little tougher - you may be able to blow in insulation through small holes on the garage side or you may need to remove drywall. It is very common for insulation between houses and attached garages to be poor or non-existent. You may also want to consider replacing the door to the house if it is uninsulated.

3) If comfort is still worth it to you once the other factors are taken care of, then do this properly and insulate your garage so that it can be a proper heated space.
posted by ssg at 9:12 AM on September 30, 2010

Response by poster: Thanks everyone.

Attic is above and is insulated.

I called the installers and the door is not insulated, an insulating kit is being added in 2 weeks. Wish I knew this last year. I didn't know there was such a thing.

I will look into the hot water blanket. Again, no experience there so great recommendations.

Comfort is a distant 3.

I think the insulated door will help immensely, and the water heater blanket should solve #1.

Thanks again!
posted by discountfortunecookie at 10:02 AM on September 30, 2010

At the risk of being dorky, have you considered a Soda Can Solar Heater, in addition to adding insulation?
posted by adipocere at 10:43 AM on September 30, 2010

We live a few miles north of you just off of Hwy 127, so I can relate to your climate issues. I am assuming that you have electric water heating as, around here that is more economical. I would like to point out that, in the winter, the temperature of the water coming into your water heater is much lower than it is in the summer. This will make it harder for your water heater to keep up as it has a bigger job to do. We solved this by getting a much larger water heater (80 gallons). The increased mass of already hot water means that the temperature of the water in the tank does not drop as quickly. It also seems to mean that the water heater does not have to work as hard to keep the temperature up, because the mass is greater (sort of like keeping your freezer full to keep it cold). Our monthly electric bill (Volunteer Energy) was virtually unchanged with the bigger water heater. A blanket is a good idea. We went one step further and built an insulated cabinet around it. A few bucks in materials and a weekend of work did the job. This, of course, would not work well if you are using gas due to venting and combustion air issues.
posted by Old Geezer at 11:01 AM on September 30, 2010