I just blew in some insulation into my attic space and the insulation is against the chimney pipe. Should there be some space between the insulation and the pipe? I have 14 ft double wall class A chimney. The insulation is roughly 6 ft above the stove.
Blown in insulation
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Always check the manufacturers literature, but I believe it has to have 2" CTC. I recall reading that it has to be boxed into a 1 ft box also, but am not sure on that.
I'd move it away from the pipe.
Matt
I'd move it away from the pipe.
Matt
Yes, the pipe manufacturers make attic insulation shields for the pipe for this situation. It is particularly important with cellulose blown-in insulation.
cmonSTART
Minister of Fire
This is a common issue when insulation is added. Do keep 2 inches of AIR SPACE between the insulation and the chimney.
WES999
Minister of Fire
Or like this... This is the round chimney support. The chimney is not in yet. It has a 1" clearance for the chimney. With the support shielding you see here, you only need a 1" gap between the chimney and the shield. Insulation is allowed to come in contact with the shield. As long as the chimney was installed with all of the same product line and per instructions, you should already have the shield in place. Insulation or not, it's illegal and dangerous without it. When you said you blew it up against the chimney pipe, are you sure it's the chimney pipe or the shield? If it's the shield you are good to go.
tfdchief
Minister of Fire
BeGreen said:
I have heard this and I have read this several times now but I don't think I understand why this is ... is it a matter of surface area or is there something else specifically about blown-in insulation (fiberglass) that makes it more "combustible"?
Also, I've tried to drop this question to several threads but how can I safely insulate spaces around the chimney through levels of our house? I read about rockwool, firestop caulk, firestop foam, perlite, vermiculite etc and don't know what will work best. I of course have steel insulation shields at all penetrations but there are still small areas that air can get through. I'd like to try to seal those spots with something that's safe. Thanks.
For Class A you need 2" clearance from combustibles. That means you can build your shield out of cardboard as long as it is 2" away from the outer surface of the chimney pipe. The purpose of the metal shield that all manufacturers offer is to keep any chance of anything combustible from getting within a safe distance. Even if your attic isn't insulated you must have it. Just in case a new owner comes along and does what you are doing.
Once the shield is in place you can have insulation right up against it with no worries.
Once the shield is in place you can have insulation right up against it with no worries.
turbocruiser said:
I'm sorry to bump this whole thing again but I'd still like to learn much more about these two concepts. If there are threads around that answer these already please just point me to them but my attempts at searching weren't successful.
To clarify any confusion, I have already placed all the fiberglass insulation (both bats as well as blown-in-insulation on top of the bats) right up against the metal that shields the chimney from the insulation and I know that is totally okay to do. What I'm asking about here is at minimum how to seal the little 1/8 gap between the outside of the chimney pipe and the inside of the insulation shield, or, should that small area be as it is now? And at maximum I'd like to insulate the entire area between the outside of the chimney and the inside of the shield so that I'm insulated both from air passing around that gap AND also from the heat or the cold of the attic. So ideally I'd call up ICC, ask them for a piece of their special thermoplus insulation that would be two inches thick, as tall as the shield can stretch ( i think that's 24 or 28") and about 25.13274123 inches (the circumference of outside of chimney) long. Then I'd wrap the chimney with that stuff and stuff that stuff into the space there. But, I realize that's ridiculous ... because ... ICC is never gonna sell that stuff to me that way! (That was my attempt at humor) So, short of that what would work there if anything at all?
I'm also asking more out of curiosity why blown-in-insulation is so much more of a concern with chimneys ... is it that it is more "combustible" or is it that realistically most people won't put bats between the chimney and the shield but that at any time blown-in-insulation could conceivably drop into the inside of the shield and start trouble?
Edit: I just realized I made a mistake here in misinterpreting BG's post where he was specific to cellulose blown-in-insulation and I accidentally took that further to the fiberglass blown-in-insulation which is what we have here over two big bats of regular fiberglass (we have almost an R 55 to 60 in the attic). Please pardon that but I'd still like to learn if this is the result of the material or the form, in other words, is fiberglass blown-in-insulation any more of a concern than fiberglass bat insulation? Thanks.
Thanks.
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