My 2-car garage is unheated. Our master bath extends partly over the garage space. Currently, the garage is only insulated where it shares a common wall with the house, plus the garage ceiling below the bathroom floor. Our bathroom is notably colder than the other rooms, and I’m considering insulating the rest of the garage (garage door, exterior walls, ceiling) in the hope that it serves as an additional buffer between the master bath and the outside.
Is this a stupid idea? I realize that I’m not heating the garage, and the great big garage door will be openned and closed a few times daily. But I’m hoping that the insulation will help capture any heat that the house gives up and perhaps keep the space below the bathroom a little warmer.
Go ahead and tell me if this is a stupid idea, but I’d appreciate an explanation (even a simple one) and perhaps even some suggestions for alternative approaches.
Almost forgot – I live in upstate NY, which has been known to get a little chilly in the winter months (from about October to June).
Best,
Rob
Edited 11/29/2005 5:25 pm ET by rsquared
Replies
I say go ahead. I don't have technical data to offer; however, I do know that my uninsulted garage is typically a few degrees warmer than the outside. As you are guessing, I guess heat escaping from the house is trapped in the garage. Insulating the garage can only help to trap a bit more.
That said, heat trasfer rates between areas of different temperatures increase as the temperature differential increases. In the winter your differential will likely be . . . say 40 or 50 and occassionally more. If you trap five more degrees, you will not change the magnitude of the differential much. So the benefit in your bedroom is likely to be small.
JMTCents.
Note that your efforts/money might be better spent adding additional insulation directly around the bathroom. First make sure that there are no (as in "zero", "none", "nada") air leaks into the existing insulation from the garage (or outside), then consider a layer of 2" foam on the garage ceiling, followed by drywall (for fire protection).
If ignorance is bliss why aren't more people
happy?
DanH,
Do you know if there is ever a problem with laying "foam" on the outside of a wall as you suggested? I am wondering if mositure could or does leak into the fiberglass batts from the bathroom and get trapped behind the foam, and therefore can't dry out?
Does it matter what kind of foam you use?
Condensation can be a problem, but not likely to be much of one for floors, since hot air doesn't tend migrate downward. (Rather, you tend to have cold outside air infiltrating upward.) Also, the temp in the garage is (as has been discussed) quite a bit warmer than the outside, so condensation in the insulation is considerably less likely. And the foam makes it even less likely that the fiberglass will get cold enough to promote condensation.Doesn't matter much what kind of foam. The polyiso or whatever they use in foam "sheathing" is about 30% better than standard white styrofoam, but that's not a major difference.
If ignorance is bliss why aren't more people
happy?
Thanks for all the great advice. I'm inclined to go Belt and Suspenders - insulate the garage for whatever benefit that might provide, and further insulate the bathroom floor (garage ceiling) and exterior bathroom walls. To add insulation to the walls, I'm thinking I could afix foamboard onto the plywood on the outside walls from the garage attic, frame an additional wall outside of that, put fiberglass batts in the "seconday wall" stud cavities and plywood over that.
Does that sound advisable?
The more the merrier!
If ignorance is bliss why aren't more people
happy?
My guess is large areas with zero insulation.
Poke some holes in the DW in the garage ceiling and see what you see.
Blow it with cells cheapest & best.
Joe H
Can't hurt. But the garage door is often a big "hole", and effectively weatherstripping it is likely to be necessary to realize any significant improvement.
happy?
My parents house had a bedroom and bath over a carport which we enclosed into a garage. They said that it made the two rooms warmer.
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The warmer the garage is, the more likely you'll be to use it (other than making a dash in from the car).
But I would try and improve the insulation directly around the BA first. You say the BA extends partly over the garage? Did they miss insulating something? A wall, part of the floor, etc? I've torn into houses and found they missed insulating a bay, or missed insulating behind a tub, etc.
And as someone else mentioned, make sure everything is sealed around the BA.
jt8
"Do not let what you cannot do interfere with what you can do."
-- John R. Wooden
If the bath doesn't extend all the way from wall to wall in the garage, I'd open up the ceiling below the bath walls and make sure there are air blocks in the stud bays.
... Oops -- make that "joist bays". I shouldn't post in a hurry, especially when I'm not quite awake yet.
If ignorance is bliss why aren't more people
happy?
Edited 11/30/2005 9:58 am by DanH
One thing to consider is that you may have too much heat in your garage. Insulating and sealing up the garage may result in the more humid air that escapes from your house condensing inside the cooler garage. Also during the winter months ice and snow on your cars will melt off in the warmer temps and add to the overall moisture present. Do you have a floor drain? All the water from the ice melting off the cars has to go somewhere. I know this may sound kind of far fetched but I can claim first hand experience. I live in northern Wisonsin and we get a lot of snow. Over the years I have seen folks insulate their attached garages without taking everything into consideration and end up with a cool damp garage. Excess moisture will cause many expensive problems. Moisture control is the big thing. Unless you take this all the way I think your efforts would be better spent insulating the existing space. Now that said, I think a heated garage is the best thing since sliced bread, particularly for those of us who live in the far north. I have enjoyed getting into a dry warm car each morning for many years. Roger
Ah, there's always more to the issue than meets the eye.
Roger, how do you heat your garage, and to what temp? It would seem to me that the concrete garage floor would complicate matters as a thermal bridge. Re the moisture, there is no floor drain - currently the icemelt just drains down through the gaps at the bottom of the garage door, but those gaps would be sealed better after
Dan, the Bath does not extend from wall to wall. What would air-blocks look like? Just additional batts stuffed in the joists, or a more impermiable barrier?
Rob
Air blocks would be something REALLY airtight -- a piece of wood blocking with foam in the cracks, eg, or you could put to use those old political signs in the garage (the ones made out of plastic "cardboard") and cut a piece to fit tight with flaps that can be stapled to the joists and the floor sheating, and another flap on the bottom edge that will hug the drywall once that's restored. Some sheathing tape along the joints would provide additional insurance.Even a small amount of airflow through what is likely regular fiberglass batts in there will pretty much destroy the effectiveness of the insulation.
If ignorance is bliss why aren't more people
happy?
Rob, I use a propane fired (natural gas would also work) unit heater with fan induced draft. The unit vents out the side wall and has a condensate drain line. In addition to exhausting combustion gases it also vents the moist air out of the garage. The inside temperature is adjusted relative to the exterior temperature. When its in the 40's outstide, the garage is probably 60 degrees. During the summer and fall I just leave the windows open and turn the heater off. As the temperatures cool off I lower the inside temperature to about 50. The whole idea is to stay above the dew point. I also have fresh air vent set above the floor on the opposite side of the garage from the heater for make up air. There is a flapper in the vent that I have propped open with a clothes pin when the temperature is above 0 degrees F. Below zero I remove the clothes pin and let the vent open and close with the heater. I could incorporate a power operated damper that would open and close with the unit heater or a humidistat but the clothes pin works quite well. If we are out of town for afew days I just remove the clothes pin. I have actually thought about incorporating a humidistat into the control scheme with a min-max thermostat. But then that is starting to complicate things more than I would like. I have always tried to keep the critical technolgy in my house to a level that my local plumbing and heating guy can handle if it breaks when I am out of town. I Hope this answers your question. Roger
Thanks for the detail Roger. Do you use your garage as a workspace, or do you just like your vehicles warm in the morning? Have you ever tried to calculate the operating cost of your set-up?
Rob
More detail - I estimate that it would cost roughly $300 for the insulation (R13 walls between 2X4 studs, R25 ceiling between 2X8 joists). I need a new garage door anyway, and an insulated door at R17 is a few hundred dollars more than uninsulated. So all together I'm looking at $500 to $600 to insulate the unheated garage space. Worth it?
Of course, as I slide down the home improvement slippery slope, I'm thinking that adding a heat source as Roger describes above sounds nice too...
Rob
I think he's trying to keep his bathroom warm, not the garage.
I think he's trying to keep his bathroom warm, not the garage.
rsquared was the original poster. Sounds like he wouldn't mind having both warm. The BA is probably higher on the list though.
jt8
"With Congress, every time they make a joke it's a law, and every time they make a law it's a joke." -- Will Rogers
Rob, I don't really know how much it costs to heat the area. If I had to guess it would be about 100-150 gallons of propane. Like all heating costs really dependent on the weather. I have water and drain lines installed. I use part of the garage as a prep area for my BBQ grilling. I guess you could call this area my outdoor kitchen! Works good for that and I have a warm car to boot. Roger
Would a radiant heat system under the bathroom floor be an option?
what dan said foam and rock over