I am replacing the subfloor in my turn of the century house. After ripping up the old floor, I realized that the floor register boots are huge compared to the size of the supply ducts. For example, this a picture of a 6" round duct with a 10x12" register boot.
Look at that thing! It is eating up so much floor space! I have four of these on my first floor that I'd love to make smaller. As I understand it, a 4x10 or 4x12 register boot is pretty standard for a 6" round duct. Is there any reason I can't make this change?
While I'm at it, there are three returns in the same space that are even larger. I'm talking 8x30", 6x30", and 24x30". There is no way those returns need to be so large, right? My assumption is they just used the old gravity fed registers when upgrading the HVAC system some years ago. But that is just a hunch.
So I have a couple of questions:
- Can I reduce my floor register boots for the 6" and 7" round supply lines without negative effect?
- Can I reduce my return sizes as well?
I'm well aware that I should have a Manual J/D performed to get exacting answers. I'm looking for safe rule of thumb at this point.