Passive air flow in 8x12 building. Sealed. Need a 6'' or 8'' fan with filter. Size? Where to buy? Some have said the biggest filter is the call but I really don't understand why 6'' fans are rated higher than the cfm/5 fomulas for this size and people say 8''? Want to silence whichever I buy and l will need a passive hole for intake but don't know what size hole to cut and how to stop back draft from leaving through it when fan is off? Woul a back draft damper open and close when fan is running/off? and biggest question is where can you get a back draft damper. I really could use your advice so please help.... Thanks.
Please Answer!!?
- Thread starter tonyromo
- Start date
SmokeyMcSmokester
Well-Known Member
HTGsupply will have some good prices on fan/filter combos. dont know if you would have to worry about back draft with those fans..I have the 4'' one and its awesome!
you might need the 8'' fans...8x12 is big
you might need the 8'' fans...8x12 is big
Boneman
Well-Known Member
htgsupply is a great place for just about everything. As for the back draft damper, you can go to lowes or home depot and they sell them there. I think they are near the bathroom fans but they might also be where the dryer supplies are located. Either way just ask one of the employees for a dryer damper.....Ya know what, they are where the furnace filters are. Yup, thats where the ducting is also 
Cool! But will the neg pressure when fan is on be enough to open the back draft damper since it will be in the floor with hollow bottom and about 8 feet from the fan/filter. Must open to let in air when fan is on. Will that be enough co2 from outside if it opens that is...?
htgsupply is a great place for just about everything. As for the back draft damper, you can go to lowes or home depot and they sell them there. I think they are near the bathroom fans but they might also be where the dryer supplies are located. Either way just ask one of the employees for a dryer damper.....Ya know what, they are where the furnace filters are. Yup, thats where the ducting is also
desertrat
Well-Known Member
there is no practical way you can make a back draft damper on a room that large. for that you would need an airtight seal on the whole room other than your passive intake. your problem is usually solved by keeping the fan on or using something like ona gel to kill the smell
So does that mean the back draft damper would not operated when the fan was on and close when the fan is off?? The room is almost sealed but not like a real lab would be...
desertrat
Well-Known Member
most rooms are so leaky that you don't even need a passive intake. if you can stay in the room for 12 hours and still be alive, then there is plenty of fresh air coming in.
think of it this way, in order for a damper to work there would have to be a very noticeable flow of air inside the room (think tornado) to be strong enough to pull open a hinged damper - not going to happen. dampers are designed to have air pushed through them. drawing a vacuum is a hard thing to do.
think of it this way, in order for a damper to work there would have to be a very noticeable flow of air inside the room (think tornado) to be strong enough to pull open a hinged damper - not going to happen. dampers are designed to have air pushed through them. drawing a vacuum is a hard thing to do.