Cutting Into Existing Duct Work Question

Posted by Jared Murray on 12th Mar 2015


Q: I saw some of your videos on youtube. I have an old vent fan that vents my kitchen. It's not a hood, just a grate on the ceiling and a box in the attic similar to a bathroom vent fan. The fan box has a rectangular damper on the side which then turns into 8" hard metal duct that turns 90 degrees and goes up and out through the roof. This existing vent fan is old and noisy and needs to be replaced. I'm a big fan of the new "mixed flow" technology for inline fans and I'd like to install an 8" inline fan in the attic. I'm thinking of leaving the existing fan box and damper and cutting a section out of the existing vertical 8" round duct work so that I can mount the inline fan to a rafter and running flexible duct from existing 8" hard round duct to the inline fan an back. My question is that I was watching one of your videos on cutting the sheet metal and you suggested punching a hold with a screwdriver. Can I do that sort of thing with installed ducting or is there a better way to cut installed duct?

A: That works. Or use a unit if you have one.