Will I create Ice Dams?

[PeteD]

So, I had some ice dams a couple of weeks ago on the north side of my house (this is also where my internal chase penetrates my roof). Not too bad, just enough to drip through soffet vent strip, not inside walls. A combination of two things caused this:

1. A really cold snowy winter (for my house)
2. Having my fireplace chase (which is internal and goes through my attic) allow hot air into my attic during a few days of construction to frame the opening for my new install.

So my question is, although my attic is normally very cold and well vented, will the 2 or 3 feet of Class A pipe that is going to extend through my attic create ice dam issues in the future?

It seems to me that burning my fireplace may add as much heat (or more) to the attic as having an opening to the heated space below over a weekend that caused my recent ice dams.

How hot does the exterior of Class A pipe get??

The attic floor will be about 14 feet above the top of my Lennox Brentwood when installed.

Thoughts?

Thanks,
Pete

 

[LLigetfa]

I ran radiation shield all the way from the firestop at the ceiling to the flashing on the roof. It serves to hold the heat in so the chimney drafts better and stays cleaner.

 

[burntime]

I had to insulate my liner and run a block off plate on my masonary chimney because it was heating the attic and causing ice damning. Insulate what you can and increase airflow.

 

[Hogwildz]

Keep in mind, even normal melt on sunny days will re-freeze and cause Ice dams if the gutter is full of ice already. No getting around that unless you tear all your gutters off.

 

[mouchey]

How do you safely insulate your class A chimney pipe to prevent the ice daming heat loss into the attic with the internal chase. I have the same issue. Not huge ice dams just happen to notice it's more obvious on the side with the chimney pipe.
MJ

 

[fraxinus]

I'm not at all sure if your chimney has very much to do with the ice dams. For many reasons, this has been a particularly bad winter throughout the Northeast for ice dams and ice stalactites. Raking snow off the roof can help a great deal as a preventative measure, but as another poster mentioned, full frozen gutters create dams and there is little you can do about it except pray for spring.

 

[PunKid8888]

My roof peak is along the north south with the back of my house on the north. I have noticed that my Ice dams have been minimal compared to some of my neighbors. I have gutters on the east side, and not the west.

I think most ice dams are just from heat getting into the attic, anyway it can, I keep my house pretty cool, (current 62F) and I think that helps to minimize the heat in the attic.

My garage (runs parallel) has no ice dam what so ever (but no gutter) But it temp is almost always below freezing except for the weekends I am out there working on something.

 

[PeteD]

Having the chase open did make the dams worse in my case. It was 10 F outside, but my attic was getting heat from me working on my chase. Water soaked through the plywood - only the bottom six inches of the roof line (I could see this from the chase opening). I do not have gutters on the back of the house anyway, but still had the dam occurring on the soffit portion of the roof, and worse towards the end where my chase was open for about 48 hours. The overhang is about 1 foot, so no water got inside the walls, but rather formed icicles through my soffit vent.

Within a few hours of sealing the chase - no more drips.

I do agree I have seen more icicles this year on peoples houses in eastern MA than in the last 10 combined, so I am not too worried about it. I do not have icicles on the back now, since I sealed the chase temporarily with plywood to keep the attic cold.

I am a little concerned that the Class A will heat the attic (locally) to some extent. I guess I will just have to watch it and do snow removal as needed - this will keep the area available for sweeping also.

The calcium chloride in a stocking (from another thread) sounds like a good idea for controlling the dams, also.

Like someone else said, short of building a chase in the attic around my Class A, I do not see how else I could insulate the Class A from the rest of the attic. I have a lofted ceiling next to the area of the chase, though, so I do not have access to the attic in this area, aside from inside the chase on the second floor currently exposed.

Pete

 

[PeteD]

I ran radiation shield all the way from the firestop at the ceiling to the flashing on the roof. It serves to hold the heat in so the chimney drafts better and stays cleaner.

Actually, missed this the first time - sounds reasonable. Just sheet metal, right?

My wooden chase extends above the roof, so the heat will have room to rise locally above the roof level. I was also wondering if I could vent the chase somehow...this is the old setup.

 

[LLigetfa]

Yes, just sheet metal. You often see short lengths used to go between joists and rafters and to hold the insulation back from touching the chimney. It is 4 inches larger diameter than the chimney so you have a 2 inch space on all sides. It is safe to put glass insulation against the shield. It could be vented but I didn't because I like to keep the chimney as warm as possible without insulation touching the chimney. In your case, you could just stub it up into the chase and insulate the attic portion up to the bottom of the chase.