roof ice/snow

[Dutch445]

here is a question I posted in another thread, and I'm wondering
what folks around here might think also.

I get ice dams on my 70s vintage ranch house, south side, above our "living room". I usually have
to chop the ice off once a year or so to prevent interior leaks.

the living room is 26' long, and it is the warmest room in the house because i have
a floor vent coming up from the basement with heat from the stove.

the attic has ridge vent, and vented eaves (2 inch strip along the eave the entire length in the soffit)
I still get a large build up of ice , and it's concentrated over the part of the room with an 8' sliding glass door.

As i research the fixes, vent - vent- vent. Eliminate heat loss, insulate-insulate-insulate. I came
up with another possible cause and wanted to see if anybody else thinks it could be a problem.

The masonry dual flu chimney runs up thru interior walls at the end of the living room (which has
a cathedral type cieling). The chimney then continues thru the attic, before it
goes up thru the roof. My thoughts are can this "warm" chimney in the attic space be contributing
to my snow melt/ice problem on the roof? I have no inside access to the attic, but I can probably remove
a gable vent to peek in there (never have). I would imagine the chimney is warm all the way up, at least
to above the roof line. (unlike when the boiler is running occasionally in spring and fall).
Am i chasing a ghost here? or would it make sense to maybe insulate around that chimney so the heat
doesn't end up in the attic melting the snow on the roof? or just more vents?

 

[MossRoad]

here is a question I posted in another thread, and I'm wondering
what folks around here might think also.

I get ice dams on my 70s vintage ranch house, south side, above our "living room". I usually have
to chop the ice off once a year or so to prevent interior leaks.

the living room is 26' long, and it is the warmest room in the house because i have
a floor vent coming up from the basement with heat from the stove.

the attic has ridge vent, and vented eaves (2 inch strip along the eave the entire length in the soffit)
I still get a large build up of ice , and it's concentrated over the part of the room with an 8' sliding glass door.

As i research the fixes, vent - vent- vent. Eliminate heat loss, insulate-insulate-insulate. I came
up with another possible cause and wanted to see if anybody else thinks it could be a problem.

The masonry dual flu chimney runs up thru interior walls at the end of the living room (which has
a cathedral type cieling). The chimney then continues thru the attic, before it
goes up thru the roof. My thoughts are can this "warm" chimney in the attic space be contributing
to my snow melt/ice problem on the roof? I have no inside access to the attic, but I can probably remove
a gable vent to peek in there (never have). I would imagine the chimney is warm all the way up, at least
to above the roof line. (unlike when the boiler is running occasionally in spring and fall).
Am i chasing a ghost here? or would it make sense to maybe insulate around that chimney so the heat
doesn't end up in the attic melting the snow on the roof? or just more vents?

The problem is the inside of the roof is warmer than the outside of the roof. This causes the snow to melt.
The water runs downhill and freezes again when it gets to the cold part of the roof over the eaves.
Then ice backs up under your shingles and leaks in through the roof decking, usually right above the exterior wall.
Even though the eaves is vented underneath, it is not vented through the blocking between the rafters. There is no air circulation under the roof deck right in the corner where the rafters meet the joists. If there is insulation stuffed in there, it is even worse.
The solution is to make sure there are vents in the blocking between the rafters and then use a product called rafter vents to keep an open air path from the eaves to the peak of the roof, so that the underside of the roof deck stays the same as the outside air temperatures.

Do a google search for rafter baffle vents and start reading.

Here's a link to pictures of them.
rafter vent baffles - Google Search

 

[JB4310]

here is a question I posted in another thread, and I'm wondering
what folks around here might think also.

I get ice dams on my 70s vintage ranch house, south side, above our "living room". I usually have
to chop the ice off once a year or so to prevent interior leaks.

the living room is 26' long, and it is the warmest room in the house because i have
a floor vent coming up from the basement with heat from the stove.

the attic has ridge vent, and vented eaves (2 inch strip along the eave the entire length in the soffit)
I still get a large build up of ice , and it's concentrated over the part of the room with an 8' sliding glass door.

As i research the fixes, vent - vent- vent. Eliminate heat loss, insulate-insulate-insulate. I came
up with another possible cause and wanted to see if anybody else thinks it could be a problem.

The masonry dual flu chimney runs up thru interior walls at the end of the living room (which has
a cathedral type cieling). The chimney then continues thru the attic, before it
goes up thru the roof. My thoughts are can this "warm" chimney in the attic space be contributing
to my snow melt/ice problem on the roof? I have no inside access to the attic, but I can probably remove
a gable vent to peek in there (never have). I would imagine the chimney is warm all the way up, at least
to above the roof line. (unlike when the boiler is running occasionally in spring and fall).
Am i chasing a ghost here? or would it make sense to maybe insulate around that chimney so the heat
doesn't end up in the attic melting the snow on the roof? or just more vents?

I think your over thinking this, the best prevention is just remove the fresh snow from the edge of the roof before it has a chance to freeze. Very easy to do on a ranch house, just have to go back 2-3 feet.

You will always have some loss of heat and since you mentioned south side that means it has something to do with sun shine, both the damming and the melting above.
On masonry buildings the freeze thaw damage is often worse on the south side for that same reason.

Here in CT we have that problem less often, but every few years, like this one, conditions are ripe and my phone starts ringing (contractor) with people requesting snow removed from roof.
Did one yesterday, 3 foot drifts in the valleys.

Was LOL yesterday cause my wallet was getting so fat it was hard to close and sit on.

JB.

 

[simonds]

I would say you are both correct with what you say. Also come summer time, pull up the first 3-4' of shingles. Put down ice barrier (it's 3' wide) on the roof deck (right on the plywood) and up under the felt at the top of it. Re shingle it. The ice barrier seals around the nails and does a good job of keeping water out. If you have a problem up higher than the 3' put down 2 rows of the ice barrier. On low sloping roofs, I have done the whole roof deck with it and shingled over and have never had a problem since using it.
Good Luck
Clayton, General Contractor for 42 years

 

[Dutch445]

monday nite i did pull what snow i could reach with my
rake, i got up about 8-10', but it's snowing again today.

i'll have to try to check for the space above the soffit
vent and see if there is a restriction going up into the
attic space.

thanks

 

[Eyeshade]

I found an extremely easy fix for this recurring problem, move to a warm climate. Why do you guys live in these places? If you like the beauty of snow buy a plane ticket for $69 bucks and visit.

 

[Dutch445]

I found an extremely easy fix for this recurring problem, move to a warm climate. Why do you guys live in these places? If you like the beauty of snow buy a plane ticket for $69 bucks and visit.

don't tempt me!



(2 years ago i went to cabo in Feb, for a week,
and it was cold there, 70. not too hard to take)

 

[Egon]

There are permanent installation Heat tape systems that are made for icing roof problems. More attic venting or better ceiling insulation will also help.

 

[JB4310]

I would say you are both correct with what you say. Also come summer time, pull up the first 3-4' of shingles. Put down ice barrier (it's 3' wide) on the roof deck (right on the plywood) and up under the felt at the top of it. Re shingle it. The ice barrier seals around the nails and does a good job of keeping water out. If you have a problem up higher than the 3' put down 2 rows of the ice barrier. On low sloping roofs, I have done the whole roof deck with it and shingled over and have never had a problem since using it.
Good Luck
Clayton, General Contractor for 42 years

That's the best solution, the rubber membrane, buts it's so invassive I usually only recomend people do it at the time of reroof.

JB.

 

[Craig Clayton]

Look under (This Old House ) they have in the video sections very good information as how to help with the problem. When I watch the show and Tom Desilva takes the roof off and the first place he looks is the eves and he finds ice damming damage. When it is rotten then the sheathing must be changed. Do the research and you will know what you are doing this summer.
Craig Clayton