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Community and Q&A

Should truss builders include duct chases?

user-2310254 | Posted in Mechanicals on

I specified open-web trusses for my new house in part to simplify the installation of mechanical systems. Recently, I discovered that the truss system would not support metal ducts. There simply wasn’t a way to get from the mechanical room to the other end of each floor using metal.

I was annoyed that the truss company had not included a clear path for running metal ducts. My builder defended the truss designer by saying we did not include a duct design (for long and complicated reasons I won’t get into here).

I could see where it would have been helpful to have a duct plan but still could not understand why they didn’t provide a default path for HVAC. They had some framed in square openings here and there, but these were pretty much worthless for running metal. Now, we have to use flex duct for the horizontal runs, and I absolutely hate this material.

What does the community think?

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Replies

  1. GBA Editor
    Martin Holladay | | #1

    Steven,
    The term "open-web trusses" is not enough. Trunk ducts come in different sizes -- not all of which fit in some truss openings.

    If you ordered "open-web trusses," and that's what you got, you can't complain to the truss company. If you didn't provide a duct plan, they can't read your mind.

  2. user-2310254 | | #2

    Hi Martin.

    I take your point, really I do. But we are in the land of suffocating humidy. Virtually every home, from the most modest tract home to the most wildly overdone mc-palace, has forced air heating and cooling. It just seems weird that they wouldn't anticipate the need for a duct run.

    Okay. Rant over.

  3. GBA Editor
    Martin Holladay | | #3

    Steven,
    Leaving aside the current question, which sounds settled, I'd like to make a plea to all designers and architects reading this thread: please establish an HVAC plan early in the design process.

    It is unfair to HVAC contractors to show them a plan that is almost complete and ask the contractor for an HVAC plan at that point. Even worse is the case where the HVAC contractor is called after the roof is on and the house is dried in.

    Trust me: if you wait until the last minute, the mechanical room will definitely be too small. And there will definitely be nowhere to run the ducts.

  4. Expert Member
    MALCOLM TAYLOR | | #4

    Steven, did you have an architect, GC or other professional coordinating the design?

  5. user-2310254 | | #5

    Hi Malcolm.

    I had an architect develop the plans. The GCI is building to those plans. And I hired an environmental engineer to create the HVAC design. He advised against doing a complete duct design. This situation probably wouldn't have come about except we had to shift from mini splits to a more conventional strategy.

  6. Expert Member
    MALCOLM TAYLOR | | #6

    Steve, that's too bad. You can usually just assume that the location of the truss cords will be similar but I guess circumstances didn't turn out that way. Good luck with the rest of your build.

    Martin, another very common one I run up against is no forethought as to where the 3"and 4" plumbing drains will run. If bulkheads are necessary it's aways so much better that they be integrated into the design not just dictated by unforeseen circumstances.

  7. GBA Editor
    Martin Holladay | | #7

    Malcolm,
    Architects and designers need to invite plumbers and HVAC contractors to the table -- early in the process. You're right.

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