# Inside Wall Stack Missing



## tk3000 (Mar 30, 2016)

Hello, 

Amongst the damaged walls that I am trying to repair and refinish there are pieces of havac ductwork/stack  that seemed to having been ripped off a long time ago. The following pics depicts a missing hvac stack that should be inside this wall: 







I got some half section rectangular hvac parts (which seems to be press fitting) like the following (which seems to fit): 

http://www.homedepot.com/p/3-25-in-...Rectangular-Stack-Duct-RD3-25X10X36/100139237

but was wondering about the best approach (could not find my relevant and specific information). The stack sections seems to simply snap together by a press fitting thing, but maybe some sealant should be used as well? Once the stack is assembled in one piece, would sheet metal screw suffice to connect it to the top (angle boot) and the future rectangular stack head? 

Thks!


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## jeffmattero76 (Mar 30, 2016)

I am not an hvac guy but, if that chase is for return air, no duct is needed. The studs and drywall/plaster act as the duct and, in the basement ceiling, a joist bay


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## jeffmattero76 (Mar 30, 2016)

jeffmattero76 said:


> I am not an hvac guy but, if that chase is for return air, no duct is needed. The studs and drywall/plaster act as the duct and, in the basement ceiling, a joist bay


(hit send by accident) a joist bay likely has sheet metal across it which dumps air into the return duct.


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## nealtw (Mar 30, 2016)

:agree:....................


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## tk3000 (Mar 30, 2016)

Yeah, I got the idea. But it seems to me that this is actually part of the air delivery system (not the air return). So, assuming it is the air delivery system... How it should be approached? 

thks


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## beachguy005 (Mar 30, 2016)

Are there other air supply vents in the ceiling?


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## nealtw (Mar 30, 2016)

beachguy005 said:


> Are there other air supply vents in the ceiling?



This house has ducts in the attic.
If it is return air you mount one of these on the studs and drywall around it.
http://www.homedepot.com/p/Master-Flow-14-in-x-6-in-Cold-Air-Frame-CAF14X6/202258557

If it is supply air it should look like this. and you can buy oval ducts for 2x4 walls.


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## beachguy005 (Mar 30, 2016)

My point being that if there are supply vents in the ceilings of the rooms then the wall cavity is for the return air and doesn't need metal ducting.  The cavity alone is the plenum and a grill in the wall above the floor is the opening.


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## nealtw (Mar 30, 2016)

beachguy005 said:


> My point being that if there are supply vents in the ceilings of the rooms then the wall cavity is for the return air and doesn't need metal ducting.  The cavity alone is the plenum and a grill in the wall above the floor is the opening.



I didn't mean to imply that you didn't know  what you were talking about.


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## beachguy005 (Mar 30, 2016)

Thanks,  I just wanted to clarify my query.


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## Snoonyb (Mar 30, 2016)

tk3000 said:


> Hello,
> 
> Amongst the damaged walls that I am trying to repair and refinish there are pieces of havac ductwork/stack  that seemed to having been ripped off a long time ago. The following pics depicts a missing hvac stack that should be inside this wall:
> 
> ...



Turn the system on, if it blows it's supply, if it sucks it's return.

Return exists near the floor and can use the stud bay as the duct.

There are supply boots at HD to fit you needs, and dump in or near the ceiling.


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## tk3000 (Apr 3, 2016)

Snoonyb said:


> Turn the system on, if it blows it's supply, if it sucks it's return.
> 
> Return exists near the floor and can use the stud bay as the duct.
> 
> There are supply boots at HD to fit you needs, and dump in or near the ceiling.



The register is near the floor which also indicates that it is a force air duct since vent ducts normally would be atop. The duct going through the crawlspace really seems to be for venting since all the plenums on the two non-functional furnaces are going up to the attic (upflow). Moreover, there are other rooms which have   that same type of stack connected to a register at the bottom near the floor.


Unfortunately, I can not do turn the furnaces on right now to the test.


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## slownsteady (Apr 3, 2016)

TK is probably right about the duct being removed; why  would anybody rip up the wall so thoroughly if not to remove something big? So maybe someone here should try to answer his original question.


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## tk3000 (Apr 3, 2016)

beachguy005 said:


> Are there other air supply vents in the ceiling?



yeah, there are other wall cavities between studs which have a galvanized metal stack ductwork like the one I assume where there.


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## nealtw (Apr 4, 2016)

Stick you hand up there if the was a duct up there you will find a hole cut in sheet metal to take a boot, just measure the opening and by a boot to match.


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## tk3000 (Apr 6, 2016)

nealtw said:


> Stick you hand up there if the was a duct up there you will find a hole cut in sheet metal to take a boot, just measure the opening and by a boot to match.



There is a rounded boot up there that transition from to a rectangular stack (missing) that then goes down to provide air flow down there by registers. Below is is pic taken of the top: 






Below is some remaining of a metal support attached to the wall sole plate. 






which seems to indicate the presence of a stack there. 

I am not not all that familiar with these ducts and how they changed other time. Not sure how old it is and what the spcecs. It seems that it is 10inches size. Most of the new stuff are press fitting (parts often snaps in). To connect the new stack to the upper boot there is also no much clearance there: it should fit without any sealant or anything else?

Also, it seems that this stack would provide air flow for two rooms, so at the bottom it must split into two for two registers. 

thks


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## nealtw (Apr 6, 2016)

I would not like two rooms fed like that as a fire in one room will have instant access to the next.
There is a guy near where you live that makes this stuff, I would take all this info to that guy and have him come up with the best solution. You just have to find him. He is the guy that makes it for the furnace installers.
I would also dig it out in the attic to see what  exactly you have there and get measurements.
I would want two oval ducts with two offset boots for the registers.


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## tk3000 (Apr 7, 2016)

nealtw said:


> I would not like two rooms fed like that as a fire in one room will have instant access to the next.
> There is a guy near where you live that makes this stuff, I would take all this info to that guy and have him come up with the best solution. You just have to find him. He is the guy that makes it for the furnace installers.
> I would also dig it out in the attic to see what  exactly you have there and get measurements.
> I would want two oval ducts with two offset boots for the registers.



The boot  above has cleats in two sides. It seems that it would fit a 12 stack. 

So, I can not simply buy this thing in store but have to make some type of special order or pay someone to do it. 

I will look into the attic, there is just so much insulation there. 

thks


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## nealtw (Apr 7, 2016)

The last thing you want is an air leak from the house or duct into the attic, You would have to start with a starter piece so you could do it from below and find some way to seal it. Never say never but just finding something off the shelf that fits will be hard.
This will show you some of what you will be up against. 
[ame]https://www.youtube.com/watch?v=YLVAsSJFZac&ebc=ANyPxKqIrGt4EEKxMFTIRhkFwZadCp1v-FJh9iuvIjx5QpvPDspm50Xge46pO91I3ddiPk8vCJ2gFh81pS5y9t6c1wzD4bnlig&nohtml5=False[/ame]


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## slownsteady (Apr 7, 2016)

It may be easier to replace the old pieces than to find new pieces that fit it.


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## nealtw (Apr 7, 2016)

So in the picture we can see the end of an electrical cable so some more work might be done with that. In the same picture we can see some very dirty insulation. That says some dirty air from the house has been leaking there and that wants to be stopped. You might find it easier to fix from upstairs or even working thru the duct from above and that way you might find ready made parts that you can make work.
I would think after you have something started down you want to fill all the gaps around the new duct work with a fire rated foam to stop all air leaks from the house to the attic.
Then you have other heat registers that should be tighten up too.
I know all this sound like ugly work and it probably is but warm moist air leaking into attic is food for mold it will certainly destroy a house but can be deadly for people too. And there will never be a better time to fix it than when you have things already under way.


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## tk3000 (Apr 13, 2016)

slownsteady said:


> It may be easier to replace the old pieces than to find new pieces that fit it.



Yep, I was concerned about the thing being very old or maybe custom made. But after  looking in the attic, it seems to be a relative new installation and all the duct works work over there is covered with insulation, etc. It seems that the one in the pics measures 2 1/4 x 12". There is a similar situation at other end of the house (this house is a duplex, and I have done almost nothing at the  other unit), but there it seems that it seems that the the is 3 /14 x 10"

thks!


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## tk3000 (Apr 13, 2016)

nealtw said:


> So in the picture we can see the end of an electrical cable so some more work might be done with that. In the same picture we can see some very dirty insulation. That says some dirty air from the house has been leaking there and that wants to be stopped. You might find it easier to fix from upstairs or even working thru the duct from above and that way you might find ready made parts that you can make work.
> I would think after you have something started down you want to fill all the gaps around the new duct work with a fire rated foam to stop all air leaks from the house to the attic.
> Then you have other heat registers that should be tighten up too.
> I know all this sound like ugly work and it probably is but warm moist air leaking into attic is food for mold it will certainly destroy a house but can be deadly for people too. And there will never be a better time to fix it than when you have things already under way.



I confess that I did not pay much attention to the fact that air is leaking from the house to the attic. I will address this issue with expandable foam insulation as you suggested. But most houses I have seen do not seem to have air tight sealed air connections with the hvac, so I would assume that most of the time there would air leaking to the attic which is probably more true during the winter with the low pressure zones created by the heat.

Apparently the attic has several layers of insulation that were added over time which makes difficult to find or track anything

The wire shown in the pic seems to be a phone wire.Apparenlty they did not care about affixing the wires anywhere.


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## nealtw (Apr 13, 2016)

We don't have heat in the attic but we do have ac up there. Our house are completely sealed with poly behind the drywall on exterior walls and sealing, they are so tight that they have a fan to extract air and a vent to allow air in.
We have special plastic wraps for light boxes and outlets, we seal every hole everywhere, But then we drill holes in the outside sheeting so the walls can breath to the outside.
You would have to be a fanatic to do that unless you were pulling insulation anyway, I would still attempt to block what I could anyway, what ever you trip over. Keeping moisture out of the attic is the game.


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