roof ice/snow

[PILOON]

I am in Quebec and with cathedral ceilings this is a common problem.
For the venting to take place 3 conditions must be met.
-Sufficient space for the air to move out. 2" minimum, 4 suggested.
-Sufficient inlet air space. continous soffit venting best.
-Good outlet venting. the Maximum (brand) I consider the best.
Look at your roof ridge and I bet your little 2" high ridge vent is burried in snow and therefor the heat is trapped, snow melts, water runs down and freezes on the cold overhang and dams up, backs up and creeps under the shingles snd drips into the room.
I generally installed the Maximum vents and in fact to be shure that they'd operate I also add an extension as well as we often accumulate 3-4' of snow buildup.
That attic heat MUST be able to exhaust!

One solution that cures that is to build up a small aux roof along the ridge to create a ridge tunnel and then add a Maximum vent stack or 2 on that tunnel. Naturally you need to slit the ridge open about 2" to allow all the hot air from each rafter space to exit into that tunnel.

Now if the builder stuffed all the spaces between the rafters full up none of the above will work as the hot air just can't exhaust.
The only solution is to then lay 2 x 4's and a new deck to get that vent space.
Can tell U that around here many homes are chalets converted to all season dwellings and many were built with cathedral ceilings and rafter construction.
Today most of them now sport that second roof deck and air space technique.
You can spot them because the facia's are thicker than normal, or double facia.

 

[MossRoad]

While the rubber membrane will most likely stop the water infiltration, you will still get ice dams if you don't vent it properly.

The ice dam will still push your gutters, fascia board and soffits around and cause slow, but sure damage to your roof.

Until the spring, the best thing to do is use a roof rake and pull the snow off. You only have to go a little ways past the area over the exterior wall. No need to clear the entire roof, or even 6' back. If you have 18" eaves, 3' ought to do it. Especially on a south facing roof. The melt water will evaporate mostly before it gets to the edge and you shouldn't get to much buildup.

How do I know all this?
Because my roofer failed to install vents in the blocking between the rafters, I get ice dams each year, and I have to get up there, remove the soffits, vent the blocking, vent the rafters, re-insulate and fix it myself, but have not had the time. :laughing: So I roof rake after every significant snowfall. It takes about 20 minutes to do the whole house, except for two weeks ago when we had 3' of snow! :confused2: Then it took an hour and my arms were kinda sore! :confused3:

 

[MossRoad]

...
Look at your roof ridge and I bet your little 2" high ridge vent is burried in snow.
...

Excellent point. I have a power vent at the end of my gable that I can turn off and on manually from my kitchen if needed. It is set on a thermostat to vent when the attic gets above 85 in the summer. Saves on air conditioning.

 

[unbidden]

I don't have any experience with roof de-icing kits, but if you read the reviews they seam favorable.

Easy Heat Electric 160 Foot Roof De-Icing Cable

 

[SandburRanch]

There has been so much incorrect information published about ice dam solutions it's pathetic (including This Old House). VENT-VENT-VENT - well, let me tell those folks something. I'm not from Missouri but when you can show me cold air rises then I'll believe venting is a possible solution.

Another misconception - keep the attic the same temperature or colder than the outdoor ambient. IMPOSSIBLE. Insulation is a wonderful thing but it just won't work miracles. With no attic insulation ice dams may be a problem at 0 degrees F in a house but with excellent insulation the temperature at when it will possibly occur will be nearer 32 degrees outdoor ambient.

Ice Shield Membrane - will only be effective if the roof is completely covered and has a 100 percent seal. Ask your contractor if he will guarantee a 100 percent seal in writing. I really doubt it unless he is a complete idiot or plans to not be in business when you call.

The most workable and cost effective solution is to use heat tape at the eaves and at least one area above the building line. One heat tape straight up from the eaves edge up to the ridge will give the water a path to exit.

In post #3 the fireplace area on the roof needs to be address with heat trace tape. We can see ice in the photo and there more than likely will be water under it backing up past the building line.

This problem is sneaky and secretive unless you see water dripping from upper window areas.

The quickest way to have water enter is freezing rain followed by a few to several several inches of insulating snow. In this case you won't even see the thick ugly ice dam depicted in drawings because it doesn't need be there. The 1/8 inch of freezing rain is sufficient and the total roof will be under water except for the eaves.

 

[wdchyd]

I have a neighbor that had repeated trouble with this same problem....after membrane under shingles and adding ventilation/insulation the thing that did the trick for getting rid of the heat (winter and summer) was one od these....

Roof Turbine Vents

He mounted it on the back side of house on roof (ugly to see from street) and the thing draws air out year round from his attic....he loves it and the ice buildup vanished....no electricity needed and quiet......

 

[wdchyd]

Look at your roof ridge and I bet your little 2" high ridge vent is burried in snow and therefor the heat is trapped

I've had this conversation with friends with new houses with only ridge vents......They complain of the ice buildup and claim they HAVE enough ventilation.......

My reply to them "If you only have a roof ridge vent and no side eve vents then you have NO ventilation when covered up with snow"......

 

[Duffster]

There has been so much incorrect information published about ice dam solutions it's pathetic (including This Old House). VENT-VENT-VENT - well, let me tell those folks something. I'm not from Missouri but when you can show me cold air rises then I'll believe venting is a possible solution.

Another misconception - keep the attic the same temperature or colder than the outdoor ambient. IMPOSSIBLE. Insulation is a wonderful thing but it just won't work miracles. With no attic insulation ice dams may be a problem at 0 degrees F in a house but with excellent insulation the temperature at when it will possibly occur will be nearer 32 degrees outdoor ambient.

Ice Shield Membrane - will only be effective if the roof is completely covered and has a 100 percent seal. Ask your contractor if he will guarantee a 100 percent seal in writing. I really doubt it unless he is a complete idiot or plans to not be in business when you call.

The most workable and cost effective solution is to use heat tape at the eaves and at least one area above the building line. One heat tape straight up from the eaves edge up to the ridge will give the water a path to exit.

In post #3 the fireplace area on the roof needs to be address with heat trace tape. We can see ice in the photo and there more than likely will be water under it backing up past the building line.

This problem is sneaky and secretive unless you see water dripping from upper window areas.

The quickest way to have water enter is freezing rain followed by a few to several several inches of insulating snow. In this case you won't even see the thick ugly ice dam depicted in drawings because it doesn't need be there. The 1/8 inch of freezing rain is sufficient and the total roof will be under water except for the eaves.

Insulation and ventilation works and I can prove it. Just come on over any time and I will show you some new houses I built that dont have a lick of ice on them and then I will show show you any number of older house that do have ice dams on them.

 

[SandburRanch]

Insulation and ventilation works and I can prove it. Just come on over any time and I will show you some new houses I built that dont have a lick of ice on them and then I will show show you any number of older house that do have ice dams on them.

--------------------------------------------------------------------
Read this part again.

"Another misconception - keep the attic the same temperature or colder than the outdoor ambient. IMPOSSIBLE. Insulation is a wonderful thing but it just won't work miracles. With no attic insulation ice dams may be a problem at 0 degrees F in a house but with excellent insulation the temperature at when it will possibly occur will be nearer 32 degrees outdoor ambient".

 

[Duffster]

--------------------------------------------------------------------
Read this part again.

"Another misconception - keep the attic the same temperature or colder than the outdoor ambient. IMPOSSIBLE. Insulation is a wonderful thing but it just won't work miracles. With no attic insulation ice dams may be a problem at 0 degrees F in a house but with excellent insulation the temperature at when it will possibly occur will be nearer 32 degrees outdoor ambient".

Attic temp doesn't have to be kept at or below ambient temps.

The roof deck sheathing is another insulation so as long as the minor amount heat is ventilated from underneath the roof deck melting will be eliminated.

Like I said it works and I can prove it.