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  #11  
Old 04-07-2015, 03:43 PM
lr172 lr172 is offline
 
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Location: Schaumburg, IL
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If your garage door is letting out that much heat, you will have a much bigger problem with the gas bill.

Larry
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  #12  
Old 04-07-2015, 04:55 PM
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rv7boy rv7boy is offline
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Granted I'm not in Canada, but one thing I've noticed in my very well insulated garage/workshop is that I am very comfortable with the inside air temperature around 65 F. My ceiling is insulated, and I bought a very nice insulated garage door. I can't remember the R values for the walls, ceiling and door now, but a small oil radiator-type space heater usually does okay to pre-heat it and when it's really cold I run a propane radiant heater until the temp gets near 65 and then just operate the radiator type space heater.

Us folks down south probably have never experienced ice damming. If it got that cold we'd probably be in the house drinking hot chocolate by the fireplace!
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  #13  
Old 04-07-2015, 05:07 PM
BillL BillL is offline
 
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Location: Central IL
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Quote:
Originally Posted by kamikaze View Post
The garage itself will be fully insulated, including the door.

To clarify, the concern is not that heat inside the garage will warm the roof above it since above the garage is living space.

The concern is warm moist air escaping from around the poorly sealed garage door, rising, and then hitting something cold where the air would cool, the moisture would condensate, and ice dams could form over time.

The theory is sound, but if those of you who have live through the exercise report that this has never materialized into an actual problem, that works for me!
I think the other comments about a valid concern of moisture from cars is probably what he is talking about. Here we get -15, -20F with NW winds on my door, but no issues. I just installed a new insulated door and it is moderate insulation but still so much better than 20yrs ago. I imagine a well insulated door (3") would be fantastic.

Happy building, get air-conditioning too!
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  #14  
Old 04-07-2015, 05:35 PM
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chepburn chepburn is offline
 
Join Date: Apr 2006
Location: Ottawa , Canada
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Quote:
Originally Posted by kamikaze View Post
The garage itself will be fully insulated, including the door.

To clarify, the concern is not that heat inside the garage will warm the roof above it since above the garage is living space.

The concern is warm moist air escaping from around the poorly sealed garage door, rising, and then hitting something cold where the air would cool, the moisture would condensate, and ice dams could form over time.

The theory is sound, but if those of you who have live through the exercise report that this has never materialized into an actual problem, that works for me!
Being a fellow Ottawa builder, I thought I would pipe up...

My garage has a family room above it, and, my garage door is a poorly insulated one. I installed some seals above the door, but, they are not a perfect fit, so I lose a bit of heat through the door.

Its a double car garage, and the RV spent 4 winters in that garage with no issues... The heater is a gas convection style positioned in the corner of the shop.
No ice dams on the second floor roof or gables.
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  #15  
Old 04-07-2015, 07:51 PM
rockwoodrv9 rockwoodrv9 is offline
 
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Location: Meridian ID, Aspen CO, Okemos MI
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An ice dam can be formed along the eve of a roof when there is heat from the house that melts snow or ice on the roof. As it drips down the roof to the overhang - where it is not as warm, it freezes. Drips keep forming in layers and it builds up to a thick amount of ice along the edge of the roof.

On a house - no matter how well it is insulated, heats goes up and heats the roof over the heated area and the overhang gets colder so any melting on the roof freezes on the overhang. The smaller the overhang, the less problem.

The danger is ice can freeze uphill and leak between roofing and tar paper. The solution is to use that sticky underlayment called Grace Ice Shield. Im sure there are other products - that is just the brand I am familiar with. It sticks to the plywood sheeting and forms a seal that ice can't get through. It isn't cheap, about $60/square but worth it if you are in a cold area where you may get ice buildup such as overhangs and valleys.

With a heated level over the garage, there is no worry.
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  #16  
Old 04-07-2015, 08:32 PM
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Bugsy Bugsy is offline
 
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Default Ice dams in Wisconsin

I was talking to a friend of mine last week. He has ice dams that for on his soffits and he added a heated could to the rook soffit that is on a moisture and temp thermostat that melts the ice when it forms. I don't know the manufacturer but he says its is economical, only runs when necessary and has solved his ice dams problem.

I'd press with your desire to heat the garage and then solve the ice dams problem if it occurs. Steepen the riff pitch over the garage is another solution if in the design phase. I'd press with heated garage.
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  #17  
Old 04-07-2015, 08:34 PM
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ppilotmike ppilotmike is offline
 
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Location: Denver, CO
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Quote:
Originally Posted by rockwoodrv9 View Post
An ice dam can be formed along the eve of a roof when there is heat from the house that melts snow or ice on the roof. As it drips down the roof to the overhang - where it is not as warm, it freezes. Drips keep forming in layers and it builds up to a thick amount of ice along the edge of the roof.

On a house - no matter how well it is insulated, heats goes up and heats the roof over the heated area and the overhang gets colder so any melting on the roof freezes on the overhang. The smaller the overhang, the less problem.

The danger is ice can freeze uphill and leak between roofing and tar paper. The solution is to use that sticky underlayment called Grace Ice Shield. Im sure there are other products - that is just the brand I am familiar with. It sticks to the plywood sheeting and forms a seal that ice can't get through. It isn't cheap, about $60/square but worth it if you are in a cold area where you may get ice buildup such as overhangs and valleys.

With a heated level over the garage, there is no worry.
I've heard of this too, but I would bet it's rarely an issue. The only ice damming I've heard of is my neighbor across the street, whose driveway is on the north side. In the winter, I hear him "damning the ice" all the time!
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  #18  
Old 04-08-2015, 05:15 AM
bobnoffs bobnoffs is offline
 
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i am surprised more don't know about ice dams. they are very real in cold climates and can do a lot of water damage. as someone said the warm roof above the heated area melts snow on the roof. it melts and the water refreezes when it gets to the overhang with no heat under it. the cycle continues until a ''dam'' of ice has built up. it continues to move up the roof until water runs into it and then gets behind the top edge of a row of shingles. then the water makes its path into your houses structure, eventually causing a lot of damage.
amazing how few contractors really know how much warmer an attic , even well insulated, is than the outside air. when i built my house i finally ended running an inside/outside thermometer thru the ceiling in my hallway.i have a well insulated house and my attic is 10-15 warmer than outside air. so above 20 deg i am making ice dams.
i live in n. wi. with 20 to 30 deg. below zero and 2 foot of snow on the roof. ice dams don't form in the real cold, only above 20 deg.
2 solutions........you can ''rake'' the snow off the edge of the roof or put electric heat tapes in . i have had the tapes in for 15 yrs. and have never had water damage. they are only needed a few days a year and the they keep the dam melted when the conditions are right.
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  #19  
Old 04-08-2015, 05:38 AM
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robertahegy robertahegy is offline
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We keep our attached garage/hangar heated all winter to about 64 deg. F. The important thing is to have adequate soffit vents and either a ridge vent or gabel vent to keep the air above the insulation cool and vented to release moisture and keep the insulation dry. We have never had a problem with ice damming in 15 years.

Roberta
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  #20  
Old 04-08-2015, 07:03 AM
bunkie bunkie is offline
 
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As others have mentioned, heat meeting the underside of the roof melts snow which then re-freezes, which prevents liquid water from draining off the roof, allowing it to get under the shingles.

The way to prevent ice dams is to keep the underside of the roof from becoming warmer than the outside air. This is why there are soffit and roof vents on many peaked roofs. The insulation is held away from the underside of the roof which is open to the outside air which flows underneath it. If you create an envelope of heated space within the larger cold structure, you will be fine. There are a number of ways to do this. The easiest is to insulate above the ceiling, leaving the attic space uninsulated and vented to the outside. If you want to heat the attic space, there are forms that can be stapled between the roof rafters that hold the insulation away and provide an under-roof path for the cold air.

In some places, neither of these are possible and for that there is special material called ice shield that goes on under the roof shingles. It provides a (mostly) waterproof barrier and is applied on the bottom 4 to 8 feet of the roof. Best practice is to combine the ice dam with proper roof venting.
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