Quick lay of the land. We opened up our bathroom for a reno and discovered some poor ductwork for the pre-existing kitchen chimney style hood fan - (they share a wall. one side bathroom, other kitchen - hood fan side). Previous owner/builder had used corrugated 4.25" flexi duct, much like that dryer vent stuff. Obviously a serious grease trap. The hood fan that was installed was "custom" and wasn't sucking up much air at all - so we've decided to replace.
Now we have the duct to deal with. We can't run it tight to ceiling between the floor joists if we upgrade to 6" duct because there's only 5 3/8" height on the joists. So that means lowering the ceiling - which would be fine if we could just frame it out with 2x4's, dropping the ceiling by only that 3.5" amount. But I think I discovered a hiccup.
As you can see from these photos. The pipe exits the kitchen under a brace in the stud wall. It used to cross above this oddball portal shower to exit the house.
For this particular section of the stud wall there isn't a top plate - there's a brace there, a 2x4 on it's side and it looks to be load bearing. If you look closely you can see that they've sistered one of the floor joists that's running through the space. And then notched out two of the wall studs on either side, setting that 2 x 4 into place to help brace that sistered joist.
And therein lies the problem. I don't know if it's a great idea to notch out a load bearing brace. We'd need to notch it a half inch or so to run a 6" duct above the brace. And we'd still need to drop the ceiling by 3.5". If we run the duct below, we'll need to drop the ceiling a lot more, by about 10". Making it 8ft before drywall.
My contractor seemed to be keen on running 4" straight galvanized to keep the ceilings nice and high throughout. And avoid the extra $1400 or so to drop the ceiling. He seemed to think it was fine for a 400 cfm max fan with one elbow and a straight run of about 5.5-6ft.
My HVAC friend suggested using 3x10" square duct in the ceiling - with a 6" round universal boot adapter to connect it to the 6" round that exits the hood fan. To allow for more airflow. But my contractor thinks those transitions will catch grease. So he doesn't see it as an advantage over the 4" round.
The other option is splitting the difference - using a 5" round duct. That can go over the brace and fit in the ceiling without dropping.
And the final option is just to drop the ceiling 10" only above the shower area, but it creates an uneven look to the ceiling that's less attractive.
If anyone has advice here, that'd be great! I kinda feel like the 5" round duct or the 6" round to 10x3" duct if it doesn't actually act as a grease trap (not sure my contractor is right there) - are the best options for my new 400 cfm fan.
Now we have the duct to deal with. We can't run it tight to ceiling between the floor joists if we upgrade to 6" duct because there's only 5 3/8" height on the joists. So that means lowering the ceiling - which would be fine if we could just frame it out with 2x4's, dropping the ceiling by only that 3.5" amount. But I think I discovered a hiccup.
As you can see from these photos. The pipe exits the kitchen under a brace in the stud wall. It used to cross above this oddball portal shower to exit the house.
For this particular section of the stud wall there isn't a top plate - there's a brace there, a 2x4 on it's side and it looks to be load bearing. If you look closely you can see that they've sistered one of the floor joists that's running through the space. And then notched out two of the wall studs on either side, setting that 2 x 4 into place to help brace that sistered joist.
And therein lies the problem. I don't know if it's a great idea to notch out a load bearing brace. We'd need to notch it a half inch or so to run a 6" duct above the brace. And we'd still need to drop the ceiling by 3.5". If we run the duct below, we'll need to drop the ceiling a lot more, by about 10". Making it 8ft before drywall.
My contractor seemed to be keen on running 4" straight galvanized to keep the ceilings nice and high throughout. And avoid the extra $1400 or so to drop the ceiling. He seemed to think it was fine for a 400 cfm max fan with one elbow and a straight run of about 5.5-6ft.
My HVAC friend suggested using 3x10" square duct in the ceiling - with a 6" round universal boot adapter to connect it to the 6" round that exits the hood fan. To allow for more airflow. But my contractor thinks those transitions will catch grease. So he doesn't see it as an advantage over the 4" round.
The other option is splitting the difference - using a 5" round duct. That can go over the brace and fit in the ceiling without dropping.
And the final option is just to drop the ceiling 10" only above the shower area, but it creates an uneven look to the ceiling that's less attractive.
If anyone has advice here, that'd be great! I kinda feel like the 5" round duct or the 6" round to 10x3" duct if it doesn't actually act as a grease trap (not sure my contractor is right there) - are the best options for my new 400 cfm fan.
