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  1. #1
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    Default Relocating forced air ducts

    Background: We're working on remodeling our living room (1st floor of 2 story house), and are attempting to remove a load-bearing wall. We've got everything designed as far as structurally replacing the wall (i.e. the framing and beam - going to be a 10" LVL flush mounted, aka, recessed into the floor joists).

    Anyways, the wall we're removing is currently used to house hot and cold ducts for two upstairs bedrooms, as well as the vents for the living room itself. The living room vents are no problem, as we can just relocate them in the unfinished basement. However, I'm unsure how to best relocate the ducts for the bedrooms.

    One end of the beam is an exterior wall, but the other end is a closet. We already have to build a false back to the closet to house a drain pipe, and I can send the ducts up through that wall as well. However, there would then be about 6 or 7 floor joists between the vertical duct (going to the basement) and the horizontal ducts (going to the heat registers).

    What's the best (i.e. most hidden, least demolition required) method for building a duct from A to B?

  2. #2
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    Default Re: Relocating forced air ducts

    It's times like this sometimes a change in design is more feasible than opening a can of worms.

    Unfortunately because the beam is a flush mount there is no bulk head to reroute and run the ducting.

    Either leave the duct run and bury them in a false column or build a bulk head on the ceiling.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  3. #3
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    Default Re: Relocating forced air ducts

    We really want to avoid a column, and I'm somewhat leaning towards a bulkhead in the ceiling (depending on the height).

    I considered running the "up/down" ducts through the corresponding exterior wall (where I could then just run them parallel with the floor joists like normal), but a problem is the only wall that's an option has two windows in it - and they correspond exactly to where the heat vents are upstairs.

    Are there any other commonly-used options? If I go through the exterior wall, is there any way to go "sideways" through the studs above the window as needed?

  4. #4
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    Default Re: Relocating forced air ducts

    You don't run ducting , especially supplies in an exterior wall.
    Besides --- depending on the stud size the ducting won't fit unless you change to oval , then it would take up pretty much of the stud bay and no room for insulation , vapour barrier, etc.
    Then the transition from the vertical to horizontal would stick down beyond the ceiling

    Can of worms.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  5. #5
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    Default Re: Relocating forced air ducts

    Quote Originally Posted by canuk View Post
    You don't run ducting , especially supplies in an exterior wall.
    Good to know, so that option's out. I'm trying to envision "other" methods of getting ducting into those two bedrooms. The big problem is that there (will be) no interior walls within the footprint of those two rooms. This leaves me only a few options I can think of:

    1) Run ducts (one big hot air and one big cold air) all the way up to the attic, and then run smaller ducts down into each room. This then presents the problem of where to place the ducts within the room, as each of them have exterior walls on two sides. This then means I can't really do any "cross flow". Can I put ceiling hot-air vents above the windows, and then floor cold-air vents in the opposing wall?

    Any problems from the long (and twisty) duct trail this will leave?

    2) Run ducts into the third bedroom, right above the aforementioned closet, and then run ductwork in small "boxes" around the wall of the third bedroom. This will be an office, so it could easily be hidden in a bookshelf if needed.

    Two problems with this method I forsee: one bedroom doesn't adjoin the "third bedroom", and the other bedroom would then need to have both hot & cold ducts in the same wall.

  6. #6
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    Default Re: Relocating forced air ducts

    Any chance of bringing A and B closer together?

    IOW, would it be practical to relocate the 2nd floor registers such that you won't need to cross the joists?

  7. #7
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    Default Re: Relocating forced air ducts

    Don't worry if you need to locate supply registers on the same wall as return grilles.

    Even though it is traditional to locate them on opposite walls, this is not really necessary.

    Remember that the supplies drive the system; their velocity throws air out in a pattern that is determined by the configuration of the register, and the function of the return is actually nothing more than pressure relief of total volume of air that the supply builds up.

    If you doubt this, think of the last hotel room you were in: the A/C and heating unit sits under the window, and it has the supply within one foot of the return.

  8. #8
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    Default Re: Relocating forced air ducts

    A picture is worth 1000 words (picture shows current setup)

    Black = first floor walls
    Green = second floor walls
    Red = hot air ducting (dashed = in floor runs, x = where it goes up through the wall, empty = vent)
    Blue = cold air ducting (dashed = in floor runs, x = where it goes up through the wall, empty = vent)
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	wall.jpg 
Views:	353 
Size:	19.2 KB 
ID:	3118  

  9. #9
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    Default Re: Relocating forced air ducts

    Quote Originally Posted by rdesigns View Post
    Don't worry if you need to locate supply registers on the same wall as return grilles.

    Even though it is traditional to locate them on opposite walls, this is not really necessary.

    Remember that the supplies drive the system; their velocity throws air out in a pattern that is determined by the configuration of the register, and the function of the return is actually nothing more than pressure relief of total volume of air that the supply builds up.

    If you doubt this, think of the last hotel room you were in: the A/C and heating unit sits under the window, and it has the supply within one foot of the return.
    I would have to disagree.
    The dispersion of the supply will be severly disrupted by having the return in close proximity. You'll end up sucking supply air into the return before it has a chance to effectively disperse and reducing the heat performance.
    It's not based on tradition but rather dynamics of air flow.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  10. #10
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    Default Re: Relocating forced air ducts

    Took some measurements tonight, and there's a total 6 vents I need to move, each 2.5"x12". Conveniently the closet is just under 6 feet wide, and the beam will stick 2 inches into the room.

    Thus, I can run the ducts up the closet back wall and directly under the floor joists (in the living room ceiling). Then I can just box them into the ceiling, leaving a roughly 2.5" deep, 5' wide "depression" in the ceiling.

    Only down sides are the bump in the ceiling, and I would have to eliminate the cold air return in the one bedroom. I'm told this won't cause any problems, do you agree?

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