# New shingles, lots of insulation, have icicles...



## swimmer_spe (Dec 9, 2016)

I have a Mansard roof house. I bought the house in the spring. The shingles were replaced this year. When they were installed, the roof had a heating line installed.

When I had the home inspected for the purchase, I was told there was about 40 inches of insulation in the attic.

Today, I was looking out one of my windows and saw icicles. Why are they forming? What are my options, or is this normal for this type of roof?


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## nealtw (Dec 9, 2016)

Do you have rooms in the roof space, I don't think I have ever been in a mansard house.
If you have finished space up there you may not have air flow behind insulation.


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## swimmer_spe (Dec 9, 2016)

nealtw said:


> Do you have rooms in the roof space, I don't think I have ever been in a mansard house.
> If you have finished space up there you may not have air flow behind insulation.



http://i1279.photobucket.com/albums...E-D7A0-4C55-AF1F-2A2BB558D432_zpsqttptw7n.jpg

That is a picture of the offending spot. Basically, the second floor is under the roof.


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## nealtw (Dec 9, 2016)

Usually it the top of the wall that is the problem where heat escapes and as the roof is very close the heat will melt the snow in that area and the water re freezes a little lower on the roof.
This is countered by having a path for air flow just below the roof sheeting to move the heat further up the attic where it will cool and mix with cold air.
http://thehtrc.com/2013/ice-dams-icicles-attic-condensation


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## bud16415 (Dec 9, 2016)

That&#8217;s really not a roof it is a wall with shingles on the outside. It may have a pitch but is basically a wall. There wouldn&#8217;t be 40&#8221; behind that area. Some heat is being lost melting snow and the drips form the ice.


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## nealtw (Dec 9, 2016)

bud16415 said:


> That&#8217;s really not a roof it is a wall with shingles on the outside. It may have a pitch but is basically a wall. There wouldn&#8217;t be 40&#8221; behind that area. Some heat is being lost melting snow and the drips form the ice.



The problem will be at the top of the leaning wall on the low sloped roof, it likely won't cause ice dams. But dangerous at the ground.


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## nealtw (Dec 9, 2016)

In this picture they have soffet vents at the floor level but I think there should be air flow at top of wall and treat that leaning wall as a roof.


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## bud16415 (Dec 9, 2016)

I agree and then a second wall inside to hold insulation. I don&#8217;t know where the 40&#8221; of insulation is?


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## swimmer_spe (Dec 9, 2016)

bud16415 said:


> I agree and then a second wall inside to hold insulation. I dont know where the 40 of insulation is?



Above the ceiling int he attic. The sides are likely 2x4 construction, with the sloped sides.


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## swimmer_spe (Dec 9, 2016)

http://thehtrc.com/2013/ice-dams-icicles-attic-condensation

Icicles:

First let me forewarn you, just because you see icicles does not mean you have issues as this is pretty common. You see at temps above 20° with the sun shining down it still allows for snow to melt with little to no heat loss inside your attic. As the temperature starts dropping or it hits a shady area, this allows that water to refreeze before it hits the ground causing icicles to grow. Two of the biggest areas for this are on the north side of the house (coldest side) & at valleys.

That window faces almost due north. It is about -5C or 23F, so, as far as this article is concerned, I do not have a problem.


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