HRV ducting question
I live in Alaska and am in the process of hooking up my HRV system. I’m running all 6″ rigid ducts and fittings in the unconditioned attic space, using 3 screws & mastic duct seal on all joints and then insulating the ducts with R-8. After already securing and putting together two far ends of a duct run, a 90 degree elbow I had in the middle broke in half. The screws and mastic that secured this connection have already fully dried. I’m wondering if there’s an easier, proper solution than to cut out this bend and reinstall a new elbow. Would it work to seal this gap with mastic and then cover this portion of the 90 with an insulated 7″ flex duct? Or is it best to just cut this connection out and re-install it? I have tried to put the pieces back together but am not able to do so. Thank you!
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You can seam it together with a sheet metal strip and cover with mastic but I would replace the elbow. Just cut the duct after the elbow and install a small extension with the new elbow. It looks like the angle was not right there anyways.
Unless these are the outdoor supply and returns on the HRV, R8 insulation is not much for cold climate. If you can't bury them in attic insulation, go for at leas the R12 stuff, even better another layer of R8 insulation for 10" duct over it.
Thanks Akos, I appreciate the advice. This duct here is for the HRV exhaust in the building. It goes to 3 bathrooms and the laundry room. The ducting rests on top of the trusses and I will be blowing in 20" of pink fiberglass in the attic. I will also add an additional few inches blown over where all the ducts lay. R8 is the highest R rating duct insulation I can find in my area. I assumed if it were completely covered in blown in pink fiberglass, it should be adequate but I welcome your input on this as well. Thanks again.