I want to add a floor register to my bathroom, which has none in it now. I want to make it simple and cheap, and I was planning on using a 5" insulated flex duct into my crawlspace from furnace on main floor. Then i was going to put a damper in the duct right before it goes into the 6" inlet floor register. My questions are is this okay? The bathroom is really small, like 49 or so square feet. Thats why the damper. And how do i attach a floor boot. They dont have ears on them or anything, at least the ones at menards dont. Also, can i even get a floor register with a 4 inch inlet, to run a smaller branch and not have to use a damper?
Keep the flex as stright as possible,tight and forget about the damper you won't need it.
The boots I used had a half inch slit in each corner and I used a hammer to peen over the edge to the floor so that the flange held the boot in place.Screws work too.