I'm partitioning part of my garage to make some rooms and I'd like to know what size flex duct i should go with. The bedroom im concerned about is 16 x 12 and will have 1 window. It currently has 7 inch duct feeding one vent. Should I up it to 8 or 9 inch? By the charts I'm seeing the existing 7 will be too small, but I'd like some opinions before I get in the attic to change it. Thanks.
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Duct sizing for room
- Thread starter derekeh
- Start date
I considered that, but the existing register is in the middle of the room. Going any farther to the back of the room is a near impossible task due to only inches of attic space. That leaves me with the choice of having 2 registers in the middle of the room spaced evenly across the 12ft width, or have the one in the middle and another just a few feet from it towards the front of the the room. Decisions decisions :\I always figure 1 CFM per sqft. A run of 7" flex is around 100 CFM, maybe a bit more depending on the length of the run. I would think about a second 7" run. Plus two smaller runs are easier to fit up registers.
PWC Repair
Well-known member
On a room that size, I would like to see an 8" split into 2 6" feeding 2 registers.
I know it's probably not ideal, but would having both registers in the middle of the 16 ft be ok? I think.the current one is 3ft off the wall in the 12ft.On a room that size, I would like to see an 8" split into 2 6" feeding 2 registers.
Also the main duct goes overhead here. I could just tap into it instead of splitting the 8inch duct.
isb cornbinder
Well-known member
What do you have for return air?
PWC Repair
Well-known member
Think about flow through the room. If you have ONE central return air then ideally you want supply coming in at the farthest edges of a room. It blows in.....acroos the room.....through the doorway......and heads towards the return. One register on a 12ft wall will take care of that whole wall. If there is another wall with a window, or on the North side of the house, I would probably place the second one in that area.I know it's probably not ideal, but would having both registers in the middle of the 16 ft be ok? I think.the current one is 3ft off the wall in the 12ft.
Also the main duct goes overhead here. I could just tap into it instead of splitting the 8inch duct.
Then one 8" run with a 6x10 register.I considered that, but the existing register is in the middle of the room. Going any farther to the back of the room is a near impossible task due to only inches of attic space. That leaves me with the choice of having 2 registers in the middle of the room spaced evenly across the 12ft width, or have the one in the middle and another just a few feet from it towards the front of the the room. Decisions decisions :\
Dagny
Well-known member
use metal 10 footer insulate it with a boot on it then slide it into the narrow area near the window.