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Re-routing Air Ducts

2534 Views 23 Replies 6 Participants Last post by  Tedd, 
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Don't Go In My Basement HT Construction

Beginning to ready a part of my basement for a dedicated HT space. Many plans and ideas, most will involve DIY. Still designing the space, with a lot of challenges ahead. Electrical is already partially installed, with insulation in the ceiling. Floor is already sealed.

First job is to re-route my air ducts in this space so that I can fully utilize the 8.5 feet of height from the floor to the ceiling (to where the joists bottom out at in the ceiling). As you can see in the photos the air ducts are currently laid out in the middle of the ceiling. The most practical idea I see is simply extending the rectangular fiberglass duct to the wall it is pointed at, and route the flexible branch ducts along the side of the wall to build soffits around in the corner. The red lines in the second picture is where a wall will be built, so I will probably want the flexible duct that's currently running through that area to be routed around it, otherwise the wall will need to be built around it.

The fiberglass rectangular trunk duct is about a 10" x 15" size. It appears if I cut the last segmented apart that was made at the end that has the flexible branches attached, take that to the end of the wall and attach a new part of the same size duct to the two original pieces that this would fit and work well, however I have very little HVAC experience. It appears as though this might be the closest fit for the rectangular duct that I can later insulate with fiberglass sheets? https://www.menards.com/main/heating-cooling/ductwork/ductwork-pipe/rectangular-metal-duct-pipe-26-gauge/15341452lq/p-1444432236987.htm

The label on the ducting says Owens Corning Type 475 FRK. A search on this finds almost nothing commercially available that I can find.

https://www.breedinginsulation.us/products/1-x-4-x-10-type-475-frk-ductbd/

The big box stores only seem to have the flexible ducts and not the rectangular ones.

Any thoughts or suggestions? I will update this later with more information on the room and progress.

Thanks

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PreciseD
Is the garage door/parking spot staying?

Can you move the trunk line into that space and tuck the flex pipe into the joist area?

Would it be so bad to have a lower ceiling height on your screen wall and have it higher where you need it for some Atmos speakers in the seating area?
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K
PreciseD said:
Is the garage door/parking spot staying?

Can you move the trunk line into that space and tuck the flex pipe into the joist area?

Would it be so bad to have a lower ceiling height on your screen wall and have it higher where you need it for some Atmos speakers in the seating area?
Click to expand...
Yes, the garage door/parking spot is staying. I can't sacrifice my two car garage (length wise) to extend the HT unfortunately.. :) I suppose it's possible to move the trunk line, though being directly above the garage door rails and door I'm not sure it would fit. The problem is the two vents in the house above the HT area that require the duct work in the basement. Interesting idea on going into the joist...will measure the space in the joist area and see, though first thought is that the flex duct is too thick.

Lowering the entire ceiling would not be beneficial I don't think as it would reduce it from 8.5 feet to less than 7 maybe in the entire room.

Attached is a very rough drawing of where I want the acoustically transparent screen with the three channels behind it.

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BluesDaddy56
I believe what you're looking for is a junction or distribution box. You'll essentially have to cobble it together. https://www.homedepot.com/b/Heating...ting-Venting-Plenums-Air-Returns/N-5yc1vZc5he
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PreciseD
Kanob said:
Yes, the garage door/parking spot is staying. I can't sacrifice my two car garage (length wise) to extend the HT unfortunately.. :) I suppose it's possible to move the trunk line, though being directly above the garage door rails and door I'm not sure it would fit. The problem is the two vents in the house above the HT area that require the duct work in the basement. Interesting idea on going into the joist...will measure the space in the joist area and see, though first thought is that the flex duct is too thick.

Lowering the entire ceiling would not be beneficial I don't think as it would reduce it from 8.5 feet to less than 7 maybe in the entire room.

Attached is a very rough drawing of where I want the acoustically transparent screen with the three channels behind it.
Click to expand...
You could have a lower ceiling behind the AT screen to hide the trunk and just put the flex branches into the floor joists for the remainder of the theater space...

If you are not familiar with building a trunk I would have a pro do it and ask for the takeoffs to be installed into the trunk by them.. Then you can hook up the branches yourself to save a little monies.

Most HVAC supply houses won't sell you the duct material without a license and all the tools required to do it would right would cost more than just having someone move it for you. Get a few pros in to show you what they would do and get an estimate. Then you can plan accordingly.
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BluesDaddy56 said:
I believe what you're looking for is a junction or distribution box. You'll essentially have to cobble it together. https://www.homedepot.com/b/Heating...ting-Venting-Plenums-Air-Returns/N-5yc1vZc5he
Click to expand...
Could you elaborate a bit please? How would this connect to everything else and where would it be placed?
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BIGmouthinDC
they will kerf it for you and I assume ship it to you flat.
https://www.budgetheating.com/Duct-board-Supply-Plenum-3ft-R4-R6-R8-p/148009.htm
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T
Would it be possible to transition to sheet metal ductwork right outside the theater space? Then you could do a wye at the end and top takeoffs,
and potentially go to a wider/less tall profile which might be of benefit in saving a few inches of room height under the soffit.
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T
I also wonder about where those doors go, where the stairs are, and what the circulation flow looks like in regards to the stairs. If the doors could be relocated, in conjunction with
new HVAC plus that alcove, I wonder if there's perhaps an entry lobby and a way to create some interest and it might be possible to have the alcove to allow for riser elevation
changes as part of a plan.
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BluesDaddy56
Kanob said:
Could you elaborate a bit please? How would this connect to everything else and where would it be placed?
Click to expand...
This stuff is essentially "design your own" junction. You need to design what you need in terms of inflow and outflow, cut it, put in the junctions, etc. I'm not an HVAC guy, just remember from a new unit getting installed and watching.
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T
Yes it is essentially just that. The big upside is one can potentially leverage this, to one's advantage.

You need to watch airflow and duct volume and ideally make sure there's no turbulence in the ducting. The math for the proper airflow is done so you just need smooth runs and transitions.
(But one can potentially allow for space for any turbulence to be able to smooth out over duct run, if you do find yourself going that route, for a reason. Best avoided if possible.)
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K
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Ok, looks like simply extending the fiberglass trunk and keeping the existing branches may work. Pushing the branches up in the joists looks like it may work also, so less soffit framing to build. It will require drilling holes in a few parts of the ceiling joist though, and one that appears to have a metal support beam included. A bit hesitant to start cutting into a support structure...what's the worst that could happen?? :eek:

There are possible plans for a small riser at the seating area in the middle for a back row of seating.

Will update shortly when this is done.

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T
Do not cut into that support structure!
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T
If you are up to redoing some of the HVAC ductwork, and that's 8.5' from the bottom of the joists to the floor, then you might be able to further leverage the height and that alcove.

Just a quick diagram where you could enter at one step height, and host a second row on a riser, on that one step high riser platform.

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T
If something like that above appeals to you, then you actually might be able to go to sheet metal HVAC with a Wye at the end of the run.

What is one the other side of the current entrance area? What is the purpose of the alcove added to the theater space?

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BIGmouthinDC
Tedd said:
Do not cut into that support structure!
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Until you’ve read up on the guidelines for cutting floor joists. There are codes for size and locations..
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T
The structural loads in that space are carried side to side. It's not the floor joists that represent any issue, it's that beam in the theater space by the fan,
that represents a serious barrier to embedding the HVAC.
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BIGmouthinDC
Now that I'm on my large screen I see it, yea, don't touch that mystery beam. A really odd design to begin with.
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K
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Perhaps I can route the duct mostly through the joists and around only the metal beam, shown in the first picture. I think the metal beam may have something to do with the chimney that's on the opposite side for structural reasons, but I don't know for sure. You can see where a wood furnace was placed previously that I have removed recently. It was originally hooked up to the air duct to help generate heat.

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Tedd said:
If you are up to redoing some of the HVAC ductwork, and that's 8.5' from the bottom of the joists to the floor, then you might be able to further leverage the height and that alcove.

Just a quick diagram where you could enter at one step height, and host a second row on a riser, on that one step high riser platform.
Click to expand...
I like this idea. Building a simple riser for a back row of seating is a good idea, though in practice sounds challenging. The plan for the alcove was for a bar maybe, but also where the equipment rack will go as you illustrated. The door on the right can't really be moved easily. That area is an already finished area for a workshop/weight room. Framing around it may prove a challenge as the previous owner did not build it all the way to the top, but rather left about two feet of distance from the top of the room to the floor joist. I've considered just taring it down partially to build the HT properly.

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