Thread: Northern state residents with roofing knowledge....

I'll give a narrative of the problem and then ask my question to anyone who may offer their advice. Much appreciation in advance:

Here in Minnesota we had a brutal winter last year. Speculation is we're in for another. The snow was well past my waist on our roof this last winter and caused some ice damming before I could remove the snow. The ice dams caused some water damage inside. The ice dams were a result of inadequate venting and warm air passage from a room with a 10' high ceiling in which we have a wood stove that heats that room (an addition). The main home runs West/East. The addition runs North/South forming a "T". Where the roof line of the main home and the roof line of the addition meet, the two valleys are where the ice damming occurred.

I'm not the original owner so I've inherited these problems. Here are the reasons why the ice damming occurred:

1) The space below the peak of the roof of the addition, the "attic" area was completely uninsulated. I mentioned the 10' walls in that addition; there is a shared wall separating that addition and the main home. On the other side of that shared wall above the doorway is that uninsulated attic area.
2) There were two small (2'x2') access doors near the ceiling of the addition on the inside wall of that finished room leading to that uninsulated area. Using a ladder, you could peek your head inside each of those doors. The original shingles of the main part of the home serve as the "floor" in that uninsulated space since the addition's roof was just tied into or roofed over/above that portion of the main part of the house. The previous owners had just cut some rigid pink styrofoam as an air barrier behind those access doors which did not create an airtight seal in any way.
3) The wood stove used to heat the addition (approx 26' x 26') burns day and most of the night. The air temp at the ceiling level is about 105 degrees. That hot air was leaking into that uninsulated air space under the roof of that part of the addition through those two little access doors and creating the ice dams.

SOLUTIONS:

1) Contractor added four roof vents three on one side of the peak and one on the other in that roof area of the addition directly above what was that uninsulated space. There was a ridge vent running the length of that addition, but not effective.
2) He insulated that air space with cellulose insulation.
3) He also sprayed the entire backside of that shared wall with about 3"-4" of closed cell polyurethane foam and permanently sealed those two access doors, foaming the cavity for each then sheet rocking. This was done to stop any warm ceiling air from making its way into that airspace and to serve as a vapor barrier to prevent any condensation from the hot side of the wall to the cold side of that wall inside that roof airspace.

Here's my question:

I'm glad the four roof vents are there. When I have snow cover on the roof though, the venting capabilities of those vents will be rendered virtually useless, won't they? Is there some product made that you can put over roof vents to shield them from the snow? I thought about tipping metal garbage cans upside down and cutting a few holes in the bottoms (which would then be the tops) but that idea seems lame. It would allow the top of the can to be above the snow cover maintaining the venting capabilities of the vents.

Any thoughts?

Not burning the wood stove is not an option...

There are two ceiling fans in the addition and I plan on running those clockwise during the winter to redistribute that warm ceiling air the best I can.

Thanks!

ChrisL

First thought is a alternative to the upside down Garbage Can idea

Could you buy/make some Roof Crickets to make sure that the vents stay clear..

Also what is the roofing material ???

ps: When our roofer here thought we were having an Ice Damming issue he was going to insert some foam with small holes under the roof cap to stop the ice from moving upward under the cap,, We have a metal roof, and it turned out we were not having an Ice Dam problem rather a busted Cricket and Stand Pipe

Thanks Glen. Roofing material - asphalt shingles. New in 2012.

I googled that cricket idea. some images seem like a better idea. One image was a triangle made out of OSB. I could just cut the top of the triangle off allowing for venting maybe. It gives me ideas anyway. Thanks for the suggestion.

ChrisL

Let me just try to wrap my head around it. Are you saying you are getting some melting snow on your roof and the resulting water is freezing back and the water which does not freeze is running back into your vents? As a mason contractor we have to defend ourselves from the roofer when a water issue comes about on a project, so I may be able to offer a different perspective?

I meant roof vents.

The insulation should stop it entirely from happening again. That heat lose through the ceiling is a major problem with ice damming. I suspect that if you've had the place properly insulated since last winter, you wont have a problem with it this year.

As for the roof vents, really they're there to let the heat out of the attic. That' s why they are always at the highest part of the roof. Vented soffit is all we install in our houses anymore too, along with moore vents which allows the air to blow up through the soffit, into the attic and drive that hot air out through the roof vents. I wouldn't worry about them through the winter.

Chris, I am pretty sure you have already looked into the heated roof wire, to bust the dams, but just want to toss it on here to confirm it has been mentioned

https://www.youtube.com/watch?v=JStM3jmWclY

Are the style/type of roof vents used common in your area? If so they are likely a good design.

If only a few have this style go talk to the home owners and ask if they have had any issues.

Jonathan

Originally Posted by JazzWillie

Let me just try to wrap my head around it. Are you saying you are getting some melting snow on your roof and the resulting water is freezing back and the water which does not freeze is running back into your vents? As a mason contractor we have to defend ourselves from the roofer when a water issue comes about on a project, so I may be able to offer a different perspective?

No, the water leaked under the shingles in the two valleys. There were no roof vents last winter. The large snow load acted as a blanket. The roof heated from that hot air melted the snow on the roof surface creating about 3-6" of ice. The ice where it contacted the shingles melted and found its way into the interior.

Originally Posted by gssixgun

Chris, I am pretty sure you have already looked into the heated roof wire, to bust the dams, but just want to toss it on here to confirm it has been mentioned

I did think of that as an option, Glen, but we get so much snow up here, the issue is not only the ice dam potential, it's the weight of the snow on the roof. I can't imagine how many tons of weight was up there last year when the snow was over my waist in some areas. After shoveling the roof off, the mountains of snow from the roof were higher than the roof edge itself. Since I may have to shovel off again, the heat cable would get in the way of shoveling off the snow above the heat cable.

https://www.youtube.com/watch?v=JStM3jmWclY

ChrisL

Glen:

I thought about the heat cables. However, a problem we have in addition to ice dam potential is the sheer weight of the snow loads. I can't imagine how many tons of weight were up on our roof last year. We had quite a few buildings, mostly outbuildings collapse last winter due to snow load. The heat cable would help by melting the snow at the roof edges or in valleys, but I'd need to get the snow off the roof above the heat cable. The cable would make it difficult to push off the snow without messing with the heat cable.

Chris L