We're in the middle of a gut reno of our house, and we're putting a ventilation fan in the ground floor, interior bathroom (there was no fan in the previous bathroom). That's good because it means we can install the duct ourselves. There's a long run to the outside of the house (25 feet or so) and so we got a pretty powerful fan, and it has a six inch duct. We bought 6 inch flexible aluminum duct, but the actual diameter seems to be 6 1/4 -- it's kind of baggy when we put it around the fan, and tightening it down with the collar still doesn't seem that secure. Is that really all we do? I've seen some recommendations for attaching it with sheet metal screws and/or foil tape, but it's so baggy around the attachment spot, that seems weird to me. And wouldn't the sheet metal screws puncturing there lead to leaks? What are we doing wrong?

Hi, I just added an 18' x 20' room off the back of my house which has 3 floor registers for heat/ac. My contractor has not finished yet and there is no cold air return. This summer I noticed a lot of hot air up in the tray ceiling that you would feel when you turned on the ceiling fan. I want to add a cold air return high on the wall but getting duct work to it is difficult. I can't easily go up the walls on either side of the room. I live in a split, so there are basically three levels with a return on each level. Two of the returns (middle floor and upper floor) terminate at the attic. Is it OK to tap into one of the two cold air returns that end at the attic and run duct work through the attic to the new vent? My contractor doesn't seem to want to do this. (too much work?) He seems to want to put in a return low on a wall or in the floor, which I do not like at all. Sorry to ramble, but I wanted to provide as much info as possible. Thanks, John H.