# How to extend HVAC ceiling vent through new soffit?



## ACD22

http://www.menards.com/main/plumbin...10x3-boot-extension-with-dimples/p-116809.htm


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## agreif

ACD,

How do you attach that to the HVAC to the trunk if the vent is currently just an opening cut in the main trunk with the vent then screwed in via sheet metal screws? (I was looking for the same thing this weekend, Mike)

Andrew


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## NewHomeDIYGuy

As agreif said, I have a roughly 10"x6" opening cut into the trunk, with the register that was attached straight to the rectangular trunk via sheet metal screws. Would I have to get a flat ~10"x~6" piece of metal, cut a smaller opening in that, and attach that flat piece to the trunk, and seal the edges? 

With the extensions, how do you attach them to the trunk and attach the new register to the extension? Finally tried tackling it this weekend.. Thanks.

-Mike


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## agreif

I looked at the little take home guide from Menards this morning and found a starting collar 230, that looks like it should work, but it looks like they are just a smaller size than the vent each of us probably has. I would be inclined to seal the hole I have with a piece of metal and then move it over a foot and put this in, but would love to hear about it from someone who knows.

http://www.menards.com/main/plumbin...ings/3-1-4x14-stack-start-collar/p-115673.htm


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## ACD22

The fitting I linked to assumed you already had a takeoff from the duct to the register. Since you don't have a takeoff, you need to get one. The big box stores mostly sell takeoffs that are designed to transition to round duct. Guessing that you want to keep the drywall soffit close to the existing duct, you'll need to find a sheet metal supplier in your area or online to get what you need. Check "duct register box" at this site http://www.sealtitehvac.com/product_rd.asp to give you an idea.


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## NewHomeDIYGuy

Thanks ACD that helps a lot. I didn't quite know the terminology so found it hard to find things/understand exactly what I need, when I was fiddling around with different pieces at the local big box store this weekend. The big box store has a limited selection, and for mostly round ducting. I guess I'll have to try someplace locally that sells more variety. 

After looking at different things and fiddling around, I see now that the "takeoff" has little "fingers" (that you bend inwards) which are bent into the trunk which hold it on the inside (vs. regular ducting lacks the "fingers"). I didn't quite "get it" but now that makes perfect sense. Thanks!

Edit: Oh ya.. I realize too now (might be the same for you too agreif), it might be easiest to just seal off the old 10"x6" hole made in the trunk (with a metal plate, screws, and tape) and cut a new hole a foot down the trunk. Trying to find a takeoff piece of ducting to fit that largish hole might not be possible, and perhaps it's likely more trouble than it's worth to try and make it work.


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## NewHomeDIYGuy

Are sheet metal suppliers homeowner friendly? I found a couple in my area (United Refrigeration and Johnstone Supply). Would I be best calling them up first or just driving down there and telling them I needed a "duct register box?"


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## NewHomeDIYGuy

agreif, 

You ever get your ducting all finished? Did you have a local supply store with the takoff piece and register box you needed?

-Mike


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## Marty S.

Guys/gals, Step one- get the measurement from the existing box to the drywall. Step 2- Go to a local HVAC shop that makes their own metal fittings and have them make one up. A simple extension we would knock out in 2 minutes and likely give it to you free of charge.


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## NewHomeDIYGuy

Marty,

I would gladly pay someone (and it looks like it's fairly straightforward), but what is a "local HVAC shop?" Is that the same as a "sheetmetal supplier?" I'm not sure how to find the local shop via google or the yellow pages. I've tried calling a few local shops (one was a wholesaler), but no luck finding someone short of just calling an HVAC guy and probably paying him a fortune to come out for a service call. Thanks!


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## Marty S.

HVAC = heating,ventilation and air conditioning business. The guys you use to fix the furnace and air or install a new system. Yea you'll pay through the nose to have someone come out and measure for you so call and ask if they make duct. If they do take the measurements to the shop and have it made. If they don't then call another place.


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## agreif

Marty, great point. I'm going to look into that and also see if I can just bend a square piece out of some of the sheets they have at the big boxes and attach accordingly by making some bent flanges off the ends.


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## ggold

send me a picture, I can walk you thru step by step


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## NewHomeDIYGuy

I never posted back, but I got a 10"x3.5" rectangular piece of ducting from the local big box store and made it work. With tin snips, you can cut "fingers" in the metal. Then I attached it via screws and sealed it with that mastic stuff. It's solid and air tight. I only needed to bring it down 3" so it wasn't too difficult. The old opening I sealed up with a piece of sheet metal and mastic. I'll try to post a picture later.


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## ggold

That sounds perfect, did you bend a flange out at bottom (back side of drywall) so you can attach grille ? don't forget insulation wrap.


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## agreif

Bingo, that's exactly what I was thinking of making....sounds like your way is the way to go. Pics would be great


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## NewHomeDIYGuy

ggold said:


> That sounds perfect, did you bend a flange out at bottom (back side of drywall) so you can attach grille ? don't forget insulation wrap.


Yup, I bent a "flange" at the bottom, and test fitted a grille I purchased so it fits snug. 

What do I need insulation wrap for, the duct? Considering my main trunk isn't insulated, is it necessary?

I'll post pictures later.


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## ggold

I'm in south florida, we insulate everything. Is this a heating duct ?


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## NewHomeDIYGuy

ggold said:


> I'm in south florida, we insulate everything. Is this a heating duct ?


I'm in Virginia.. It's a heating/cooling trunk/duct. Seeing as how the main trunk isn't/wasn't insulated to begin with, and will be in a soffit of a finished room, is it even necessary to insulate it?


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## ggold

interesting, I would like to know the leaving air temp at unit, compared to air temp coming from vent.
Also anytime you have a cold duct in a enclosed space (non conditioned space) you normally will get condensation off duct. Is it lined ? (insulated on inside) Can you see existing duct in crawl space, do you see any signs of condensate on duct or water stains on ceiling below duct ?


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## NewHomeDIYGuy

ggold said:


> interesting, I would like to know the leaving air temp at unit, compared to air temp coming from vent.
> Also anytime you have a cold duct in a enclosed space (non conditioned space) you normally will get condensation off duct. Is it lined ? (insulated on inside) Can you see existing duct in crawl space, do you see any signs of condensate on duct or water stains on ceiling below duct ?


I'm not sure I'd call it a "non conditioned" space, as it's a soffit/duct running through a conditioned space. If it was a non-conditioned space I'd definitely insulate it, but I'm not sure it's necessary being in a conditioned space..?


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## ggold

How is the return aire getting back to unit from, where you extending the duct ?
I'm not trying to give you a hard time, just do not want you to have issue's down the road after all your work.


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## NewHomeDIYGuy

ggold said:


> How is the return aire getting back to unit from, where you extending the duct ?
> I'm not trying to give you a hard time, just do not want you to have issue's down the road after all your work.


Ggold, sorry, I'm really not sure what you're asking..? Here's the "register" I made/moved on the trunk that I was referring to, that has been frame around, and will be drywalled (soffit). I'll post a better picture later of the actual "take off register" I made.


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## ggold

When you drywall that, it will be considered non conditioned space. The ceiling beyond I notice is insulated. How does the air get back to your return air grille ?


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## NewHomeDIYGuy

ggold said:


> When you drywall that, it will be considered non conditioned space. The ceiling beyond I notice is insulated. How does the air get back to your return air grille ?


There is a return air grille in that open living area. The ceiling is only insulated for noise dampening, as this is a walk out basement. I've asked a few folks and they say insulating the trunk is not necessary..? It seems like insulating it wouldn't hurt, but not sure it'll make a difference.


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## agreif

Cool, that exactly what I'm looking for. I went to the depot and could only find a 10x4 premade rectangle. Curious where you got yours.


NewHomeDIYGuy said:


> Here's the "register" I made/moved on the trunk that I was referring to, that has been frame around, and will be drywalled (soffit). I'll post a better picture later of the actual "take off register" I made.


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## NewHomeDIYGuy

agreif said:


> Cool, that exactly what I'm looking for. I went to the depot and could only find a 10x4 premade rectangle. Curious where you got yours.


This is the exact piece I bought: http://www.homedepot.com/h_d1/N-25ecodZ5yc1v/R-100139382/h_d2/ProductDisplay?catalogId=10053

I basically just cut it down shorter, and made the "flange" on one end. I called around to hvac/sheetmetal shops, and came to the realization I was gonna have no luck, and something so small was gonna be a DIY ghetto rigging job. :laughing:

Here are the pictures I just snapped.


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## Doc Holliday

I'm confused, is that something you installed or removed? Every single square inch of that metal should be insulated and most trunk lines are insulated internally. 

What happens when there is no insulation is the cold dry air from the a/c meets the warmer humid air of the room and bam, condensation, water dripping from the duct onto your sheetrock. It happens all the time down here. 

If you haven't already done so, I'd strongly suggest you nip this in the bud before you go any further, while everything is accessible.


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## NewHomeDIYGuy

Doc Holliday said:


> I'm confused, is that something you installed or removed? Every single square inch of that metal should be insulated and most trunk lines are insulated internally.
> 
> What happens when there is no insulation is the cold dry air from the a/c meets the warmer humid air of the room and bam, condensation, water dripping from the duct onto your sheetrock. It happens all the time down here.
> 
> If you haven't already done so, I'd strongly suggest you nip this in the bud before you go any further, while everything is accessible.


Doc,

I installed the framing/soffit around the trunk. The basement had a partial soffit (done by the previous owner by the looks of it half assed), but I'm finishing more of the basement/refinishing parts of it, and I'm extending the soffit from one end of the room all the way to the other. If you look at the picture, you can see where the old wall stopped for the living area on the far wall (where the drywall stops on the left). The wall was L shaped and ran in front of the steel beam (as you're looking at it), and to the hallway. I knocked out the L shaped wall and pushed it back to give more room to the living room, and less to the wash room. Hope that makes sense.

I've had a contractor tell me it's "ok" to leave it non-insulated, but you're saying that I'm going to get condensation from the duct? *sigh* Big surprise I guess.. If that's the case, then I certainly will look into insulating it. Any recommendations on what to use? Here's a better picture of the soffit from the other side. It runs almost the entire length of the steel beam. Thanks for the help.


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## ggold

Go to a A/C supply house and get 1 roll of duct wrap- 1 1/2", 2 rolls silver tape, 1 can spray glue, 1 bucket white mastic. Around here the will sale to anyone for cash. I would suggest you catch an A/C guy, ask if he wants to earn money on the side. You can do this but, experienced man could knock it out in 2-3 hours. I would also have someone look at the rest of the ducts.


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## agreif

That looks just like it does around most homes here in Chicagoland. Only a hand full of home I have seen that have the ducting wrapped. Wondering if it has to do with the even more humid environment that you have in FL than in the midwest. Not saying it's a bad idea, I just haven't seen many houses with that either.



NewHomeDIYGuy said:


> I've had a contractor tell me it's "ok" to leave it non-insulated, but you're saying that I'm going to get condensation from the duct? *sigh* Big surprise I guess.. If that's the case, then I certainly will look into insulating it. Any recommendations on what to use? Here's a better picture of the soffit from the other side. It runs almost the entire length of the steel beam. Thanks for the help.


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## NewHomeDIYGuy

agreif said:


> That looks just like it does around most homes here in Chicagoland. Only a hand full of home I have seen that have the ducting wrapped. Wondering if it has to do with the even more humid environment that you have in FL than in the midwest. Not saying it's a bad idea, I just haven't seen many houses with that either.


I'm going to ask a friend of mine (GC) to get his opinion and I'll go from there. When I was doing some electrical stuff elsewhere, I saw the ducts on the 2nd level running between the joists and I don't think they were insulated either, so perhaps it's unnecessary here in the mid atlantic region? I'll have to do some digging I guess. Thanks.


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## NewHomeDIYGuy

According to another GC, insulating the ducting is unnecessary. So, I won't bother insulating it.


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