I've been in the attic quite a bit before the summer, and every time I look at the duct work, I keep wondering if some crazy/lazy person did it. For example, I have a flex duct running from the main trunk that does a 180 degree turn around a roof truss simply because the register box opening faces 'away' from the trunk.

The photo below shows the way the return duct is routed, bent around a roof truss.

My question is, should I reroute it so it goes straight up? That is, where the yellow arrow is pointing.

To explain a bit further, the green rectangle is an outside corner, and there is a half wall (from the perspective of the attic) that runs in the direction of the red arrows, up to the point where the duct lies on top of the ceiling.

The diagonal red arrows also happen to point to the sad insulation job that is clinging on for dear life against the drywall. I plan to fix this at some point.

To continue the first question, if I were to run it straight up, what would be the best way to insulate the wall (and/or duct together)?

return duct image

For reference, this is a photo of the living space interior of that attic area. interior space


I think they ran the duct longer to try and avoid it collapsing coming over the edge. To me it looks to be partly collapsed going around the support. To improve the flow I would add a 90 and shorten the flex. This is not hard to do. Get a 90 and 4 zip ties long enough to go around the flex. Use a razor knife to cut the flex and a pair of pliers to cut the wire slip the inner duct on the 90 and zip tie on both sides. Now pull the insulation over the 90 and zip tie in place. If you were able to remove several feet there should be enough insulation to cover the 90. This will eliminate the possibility of the flex pinching off The air flow and with a shorter flex run less resistance so more air flow.

  • Would it be better to just run a straight metal pipe up, add a 90, and connect it to the rest of the flex? The flex pipe runs up even higher (my guess is for walkability concerns) before coming down to the air handler.
    – achao
    Aug 26 '16 at 21:44
  • There is pipe there all that is needed is a 90 many are adjustable and this would be much easier for a DIY . Unless you want to purchase cutters and crimpers. Then add insulation to the pipe. I have all these tools and would use as much as I could that is already there.
    – Ed Beal
    Aug 26 '16 at 22:01

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