I imagine that metal flue pipes expand and contract a great deal in length due to the hundreds of degrees of change in temperature that they experience. How can a good air seal be achieved and maintained at ceiling support boxes and attic radiation shields, where a flue passes from conditioned space to unconditioned space, while accommodating the thermal movement? Do some manufacturers' support boxes and attic radiation shields seal better than others'?
accommodating thermal movement
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Charles - are you an engineer by chance?
I appreciate your extreme thoroughness but this is not rocket science and people have been building fires in their homes since we lived in caves so most of this stuff is tested and the movement of things due to temp changes has been figured in.
Go with quality pipe and chimney and start a fire. You will be fine
I appreciate your extreme thoroughness but this is not rocket science and people have been building fires in their homes since we lived in caves so most of this stuff is tested and the movement of things due to temp changes has been figured in.
Go with quality pipe and chimney and start a fire. You will be fine
Bob, I've been in remodeling for a couple of decades, and I've seen how easy it is to create a new problem when you try to solve another.
I'd appreciate your definition of "quality pipe and chimney". Anything beyond code?
I'd appreciate your definition of "quality pipe and chimney". Anything beyond code?
Charles I have Duravent from stove to Chimney cap straight up through the house. Dbl wall pipe nd class A chimney. I do not have experience with other brands but I do like mine a lot and it came highly recommended to me.
Pro install on the chimney and I did the rest. Chimney actually is not that tough but I wanted pros to do it for insurance purposes.
You get the ting, ting, ting in the stove pipe but it has plenty of play so I don't think it moves enough to even think about if installed correctly.
Pro install on the chimney and I did the rest. Chimney actually is not that tough but I wanted pros to do it for insurance purposes.
You get the ting, ting, ting in the stove pipe but it has plenty of play so I don't think it moves enough to even think about if installed correctly.
Hopefully the screws in the slip section shear off before the top of the stove collapses.
Actually if you are worried about expansion and contraction, one could simply secure the double wall pipe at the stove and at the ceiling (not in the middle) and the slip section of the double wall could easily slip up and down with the heating and cooling, and there would be no shearing of screws to worry about. That might fix any ting, ting, tinging in the house. The flue section above the ceiling should simply be able to freely expand and grow upward out through the roof without any binding.
But as far as air seal problems being created because of thermal movement (expansion & contraction), I've never heard of that being a problem.
But as far as air seal problems being created because of thermal movement (expansion & contraction), I've never heard of that being a problem.
And there is no air seal at attic insulation shields or radiation shields The support box is sealed pretty well though. And the outer shell does not expand near as much as the inner wall. The outer wall does not get that hot
Not sure if the OP's install is all vertical but when you hook double up to a ceiling support box, it is with a ss snap lok adaptor. That connection on my simpson flues has no screws and is not good enough to hang your chimney from for the long term. Locking the slip section is often the only screws in a double wall system. I know i dont have screws at the ceiling or at the stove.
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Yeah, I don't have any screws at the ceiling or stove either, but if I was worried about thermal movement the double sleeve of the double wall pipe would seem like the logical place to allow any excessive expansion and contraction to occur because first of all it is double walled which means it probably has a slightly better air seal, and second of all I have nearly a foot of overlap, where as I only have a couple inches of overlap at the stove and ceiling. My double wall just slides into the ceiling support at the ceiling, although it does have a little extra collar that clamps over the joint.
I can't see a problem with hanging the flue pipe off the ceiling support, that ceiling support is suppose to be able to support the weight of all the insulated pipe above it. Or at least mine is designed that way. The little extra weight of half the double wall (un-insulated) pipe hanging below it would seem insignificant.
It is true that the support box can carry lots of weight from above, something like 50 feet of class a. The support box hooks to pipe below in a hokey way with a little snappy thing. I propose that the intention is to have the stove support all weight of interior chimney pipe.
My install inspections would have been failed without screws locking the slip. Screws at ceiling and at stove are either not possible, not required, or both.
kennyp2339
Minister of Fire
All quality chimney pipe has to go through testing, that's were you get the "UL" listing - it has to meet ansi & nfpa safety standards
The beauty of internet help. We each "vote" and you get to decide. Did you read the manual? There are holes prepunched in the slip for a reason.
i always secure the top and bottom because they could potentially work loose i don't see the slip coming apart unless it is barely together in which case i would secure it as well. But you should go by the instructions from the manufacturer. But i say it needs to be fastened top and bottom for sure. I could be wrong but that is how i do it. And highbeam not all slips have prepunched holes but i know some do. It is absolutely possible to screw to the stove and on the ones i have done possible to screw at the top as well
Perhaps it should be called an "Expansion Joint"???Anything with the word "slip" in its name is getting secured around here.
Interesting bit of information on this subject here http://www.woodheat.org/flue-pipe-installation.html
It seems to indicate either way may be correct, providing there is some allowance for expansion and contraction somewhere in the flue pipe.
" 8. The assembly must have allowance for expansion: elbows in assemblies allow for expansion; straight assemblies should include an inspection wrap with one end unfastened, or a telescopic section. "
It seems to indicate either way may be correct, providing there is some allowance for expansion and contraction somewhere in the flue pipe.
" 8. The assembly must have allowance for expansion: elbows in assemblies allow for expansion; straight assemblies should include an inspection wrap with one end unfastened, or a telescopic section. "
On a 2-story house (my situation) I would want the best seal at the attic insulation shield, so that's my problem.
Well they are not meant to be sealed at all seal the chase and the support box at the bottom and don't worry about it. If it worrys you that much insulate the chase and keep the entire thing outside the conditioned envelope.
If the chase is going to be cold because of the air coming down from the attic, can I insulate the chase?
If there is a firestop at the attic level there should be no cold air in the chase. Some people put vents in the chase to recover a little extra heat.
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