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Heated Garage Workshop for RV building - Ice Damming?

K

kamikaze

Well Known Member
Hopefully this is RV specific enough ... :)

So I'm having a new house built, and I've incorporated into the plans some customization to support making my garage into an RV building workshop.

Contractor calls me today asking about this, we get to talking, and he says something to the effect of:

"Well if you're going to heat your garage, you're going to have to watch for ice damming in the garage roof and the soffits just outside the door ..."

Basically, the warm air will escape from around the garage door, which is of course not sealed like normal doors usually are, and rise, and possibly (likely) freeze and cause ice damming on the soffits or whatever happens to be in its way ... (in cold Canadian winter, of course).

For those of you from cold climates and and with garage workshops ... is this something you run into? How do you solve it (easily/cheaply)?

Thanks!
 
I would have to see it to believe it. The air outside would be moving around enough that any escaping heat would dissipate long before heating your roof. I somehow doubt you're the only one wanting a heated garage.
 
I'm in N Nevada, gets -15C sometimes, average -5 to 5 C I installed drywall in the cycling with R30 laying on top that, insulated garage doors and one 1500 watt heater keeps it room temp. No problems here after 5 years.
 
I never experienced ice dams when I was working in my garage. Granted I'm a little further south in central Ohio.
 
Yup it happens

In my place in Minnesota it was a constant issue. The solution is to insulate your garage ceiling very well. The garage door should be insulated type and sealed with weather strip. Unfortunately none of this is cheap

Gary
 
see This Old House

No problem in Galveston, TX but I used to live in the mountains of PA. Ice backs up water from melting ice. Here is a pretty good explanation of the problem and some fixes from This Old House.
 
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 built both in my attached 3 car garage and in the insulated/finished pole barn I built later. You will not get ice damming in a properly insulated building with a properly ventilated roof. I used a commercial grade insulated garage door in my pole barn but had standard insulated garage doors in the attached garage.
 
JF - with all due respect, I believe your contractor does not understand what's meant by using your garage as an airplane building workshop. He may be thinking of multiple in/out actions like you were working on cars in your garage. With the RV you're going to be keeping that door closed for extended periods of time, so you're not going to be bringing in huge amounts of moisture as you would with a snow-laden car.

With respect to the door and weatherstripping, two years ago we replaced our door with an insulated one. The installer understood my requirements... "weather-tight". He did a great job in ensuring the weatherstrip fits tightly all the way around the door, and I paid a good bit of extra cash for the best weatherstrip he had. I also insisted the bottom weatherstrip be tightly crimped in place so that it wouldn't shrink at each end over the course of a summer. Of course it shrank over the first summer, so the second time around he did as I suggested and left about 1.5" extra seal material hanging out each end. Problem solved!

The net result is a door which is quite weather-tight. With this in mind, the concept of air escaping and freezing in the vented soffit seems like a very remote possibility indeed.

Of critical importance is sealing the envelope of the garage so as to minimize heat loss and vapour penetration. Think R2000 standard or better. If you get this done properly and the door well sealed, I think the contractors concerns are very unlikely to materialize.
 
Ice

I am at 7,500' in Colorado. It gets down to -20 but humidity is really low.
My garage is insulated 2"X6" frame along with the house and ceiling is R30. Garage door is insulated and seals are good. I bought a Big Buddy propane heater and run it off a small tank. On a typical day the shop starts about 45-55 and the Big Buddy runs from 1-4 hours till it comes up to 60. I shut it down at that point to conserve gas. It's comfortable for me. My CO detector has never measured any gas.
I've never seen any ice any where near the garage doors.
The biggest problem is the cold cement wears on my feet. Even with pads it makes my feet cold. Dr. Scholls gel insoles help a lot.
 
If your garage door is letting out that much heat, you will have a much bigger problem with the gas bill.

Larry
 
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!
 
kamikaze said:
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!
Click to expand...

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!
 
kamikaze said:
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!
Click to expand...

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.
 
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.
 
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.
 
rockwoodrv9 said:
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.
Click to expand...
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!:D
 
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.
 
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
 
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.
 
I've been in the same house for 23 years here in MN, and only once had a problem above the garage. It doesn't matter if the garage is perfectly insulated (or even heated, for that matter), they can still happen. I've had it happen once in those years, and, of course, the water dripped right onto the 60+ D size drawings for the RV6A I had on a desk in the garage! The garage is 900 square feet and it nailed the drawings, classic.

Deep snow drifts on the roof, especially in a valley, are the main driver. Then, the daytime sun heats up the garage attic, melting some of the snow above the drift. This runs down under the deep drift, and boom, ice dam. The key preventative measure is to pull abnormal drifts off the roof.

All new roofs around here also use an ice barrier under the shingles in eave and valley locations. Ask you contractor about that for your area.
 
Ice/rain barrier is required in JF's area, by mandate of the Ontario building code. A 3' strip near the eave is required, or at least that was code when I last built. Knowing how good this ice/rain barrier is, I used it across the entire roof. This barrier material will work as a roof itself for some considerable time (a few years).

Also of interest... the type of attic vent installed makes a huge difference. The most common vent one sees installed in shingle roofs looks like a plastic or metal mushroom. There's a newer and MUCH better vent on the market. It's a bit unsightly as it looks like a square pagoda up on the roof. The amount of air flowing through that vent is at least 10X what would flow through the "mushroom" vents, plus it sticks up above the snow so you get venting all year long.
 
Ice dams are a real issue in cold northern climes and have been for 100 yrs. Over my career, I was responsible for construction, maintenance and repair of some 40,000,000 sq ft of facilities for two Big Ten universities. We learned to deal with ice dams a l-o-n-g time ago ... and it entails all of: impervious underlayment along the eaves, plenty of attic insulation, and good attic ventilation. Leaky overhead doors are NOT a cause of ice dams.
Follow the recommendations of any competent, knowledgable northern-clime contractor and you'll be fine. :)
 
Thanks all! I've got the answers I was looking for ... I think I'll be OK in terms of the garage itself, and the door. I'll just try to keep an eye out around the door and just above it to see if anything abnormal develops ...

Worst case I'll work at installing better weather stripping around the door for a better seal, saw a few products and videos online with various tips ...

I didn't go into details with the contractor in terms of how I would use the garage, I just mentioned a "workshop" ... as some mentioned, it's not like I open the door constantly ...

And also as has been said also, the temperature could be kept a little cooler than the normal temperature of the rest of the house ...

Thanks again!
 
kamikaze said:
Hopefully this is RV specific enough ... :)

So I'm having a new house built, and I've incorporated into the plans some customization to support making my garage into an RV building workshop.

Contractor calls me today asking about this, we get to talking, and he says something to the effect of:

"Well if you're going to heat your garage, you're going to have to watch for ice damming in the garage roof and the soffits just outside the door ..."

Basically, the warm air will escape from around the garage door, which is of course not sealed like normal doors usually are, and rise, and possibly (likely) freeze and cause ice damming on the soffits or whatever happens to be in its way ... (in cold Canadian winter, of course).

For those of you from cold climates and and with garage workshops ... is this something you run into? How do you solve it (easily/cheaply)?

Thanks!
Click to expand...

OK, I'll bite. I moved from Ottawa back to the Vancouver area, then eventually Victoria. No ice, no snow, no problem. While Ottawa was celebrating Winterlude, we were picking daffodils. Just thought I would rub it in.
 
Canadian in Alberta Canada near Edmonton

I installed a heater which runs on natural gas and this has not been a problem. As you probably know we get temps down to - 35C and below but the air is dry! Ontario might have higher humidity.

The problem might arise with constantly open doors and the eaves becoming excessively warm and repeatedly.. the answer here might be DON DO THAT! LOL

Honestly though it isnt a problem with this 10 year old home and a natural gas heater.
 
While on the topic ...

Are infrared heaters (that heat the objects in the room first, and then the air by extension, instead of heated forced air) OK in the context of A/C building?
 
bobnoffs said:
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.
Click to expand...

My parents live in a really old but cute little cottage house in WI. Their back porch is not insulated well, and it has a large eave overhang. My dad used to deal with ice dams all the time, til he finally installed a heat cord of some kind to the exterior of the shingles. It looks like a zig zag extension cord kind of like this just above the eave.

I think insulating the door is a better idea, but these things seem to work too if the roof is sloped enough to get rid of the melted runoff. Haha, de-icing equipment on your airplane *workshop*! :D
 
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OMG

All those posts and I didn't see the right solution.
Ice is formed because the roof gets warmed from the heated space below and runs down the roof above the unseated space below the eves. The solution is to not let the roof get warm by making sure there is ventilation from the eves to the roof peak. If cold outside air is constantly flowing past the roof, the snow will not melt and run down the roof. Your contractor should know how to build with this in mind. If he doesn't, you need a new contractor.
I live in Iowa. Everybody knows this here.
 
ice dams

Kamakazie, I've been involved in the building business for a long time, the main issue as some others have mentioned, is inadequate ventilation above the attic insulation. Make sure your soffits vents are not blocked off and you have adequate sized ridge vents. Lots of info on roof ventilation on the internet. The only other possible factor might be no vapor barrier on the hot side of the insulation.
Good luck
Rick
#40956
Southampton, ont
 
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