BooMtoLate
Well-Known Member
I'm building a 5x8 grow room and I have a 6" exhaust fan... And I'm looking for ideas for an intake. I'd rather not run an intake fan just looking for idea for a light proof vent.
Passive intake
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I cut a hole for size of a cold air return louvered cover plate for a furnace I bought at Home Depot for out in my shed for passive intake, then use the carbon prefliter stuff used on those little air purifiers that I staple onto door and put cover over that. You can buy the carbon prefilter stuff by the roll as it is a cut to fit the size of what you needing, doesn't knock out all smell but it helps with any leaks and also filters the dust and crap coming in your intake to your room/space. Also use it on my boxes to cover the holes for intake/exhaust on the computer fans I use on those, not sure they block light like darkroom safe but I haven't had any issues. You could use ducting making a corner bend behind the cover if you worried about that as light don't go around corners/changes in direction in vents much (bends/changes in direction affect air flow same as your exhaust).
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BooMtoLate
Well-Known Member
Thanks that could work.
Think it's a 10'x10" square cover plate I use, they have like 800 different shapes and sizes 
Probably doesn't have to be that big but one of them. Have to change the carbon prefilter stuff every few months, amazing how much crap it filters out but then again I'm outside sorta in a shed part of a carport so not directly out in the outside world but close enough.
Probably doesn't have to be that big but one of them. Have to change the carbon prefilter stuff every few months, amazing how much crap it filters out but then again I'm outside sorta in a shed part of a carport so not directly out in the outside world but close enough.- Thread starter
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BooMtoLate
Well-Known Member
I saw at home depot they have small 6 inch round vents. If I add like 2 or 3 with ducting connected or some sort or filter over it. That should work, the room is in my garage so kinda worried about light leaks.
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BooMtoLate
Well-Known Member
Run ducting from vent cover and make a couple 45 degree bends should stop the light if you worried the prefilter stuff and louvers on cover not enough. I made a frame work for the floor and used that Foam sheet insulation stuff they sell to build a floor on top of the concrete, as concrete gets cold and transfers that cold to your plants if they sitting directly on top of it.
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BooMtoLate
Well-Known Member
I have the same idea for the floor, insulated sheets followed by some plywood. I have some white poly coming too
I used 1x4 cedar on top of the plywood as heard bugs don't like cedar, but not sure that helped any but put the sealant waterproof stuff on the cedar and helps with any water spills as plywood don't like water (and the marine grade plywood is spendy as all heck).
but put the sealant waterproof stuff on the cedar and helps with any water spills as plywood don't like water (and the marine grade plywood is spendy as all heck).
I have some little cheese cloth bags that fit just right over the End of 6” ducting. They’re excellent for pre filtering.
Vegan4life
Well-Known Member
I have a 8" exhaust fan with 8" carbon filter, I have a air filter stapled over a small window for intake air, only about 12" x 12" of filter area. I think exhaust fan has been struggling to exhaust adequate air (not enough filter area.) I just ordered a "return air filter grill" that holds a 20" x 30" pleated furnace filter. I am going to mount filter grille inside grow room on a outside wall (studs are 24" on center) and put three 14" x 4" foundation vents on the outside of building. I think the added filter area will allow exhaust fan to work a little easier and help to keep the temp down. Fingers crossed...
What temps will you be drawing from outside? Might be better to exhaust to outside, and pull air from inside? (Assuming inside is conditioned, etc.)
It's been a bit since I've done the math, but IIRC you want 2x-3x the exhaust size for intake. An exhaust duct of 8" is just over 50 square inches total (π x r2), which means you would strive for 100in2-1502.
Three intake at 14"x4" should be just fine at 56in2 each, although you may want to consider how much the filter will impede air flow. Could you go to maybe 14x6? 16x6? Not 100% sure how much the filter will impact air flow, but if it's 20%, that's "effectively" only giving you an equivalent of 120in2, which is still in the 2x-3x range, but still a hit on the overall.
Vegan4life
Well-Known Member
It is a 6' x 12' building/shed in my back yard that I built, it is insulated and is air conditioned and I have a dehumidifier. I live on the coast in So Cal temps NOW are around 70 ish outside during the day. I try to keep air exchange on to keep temps down without running up the power bill by using AC.
The three 14" x 4" vents on outside wall will not be pressing on filter, there will be approx 2.5" of air space between them and the filter, I think the only restriction will be the actual filter. I just looked up a honeywell filter 20" x 30" and it is rated for 1800 cfm, my fan is a infinity cloudline T8, 8" with a rating of 740 cfm, I believe this should solve my issue.
Ah, those “spoiled” outside conditions. 
That being the case, I think you’ll be in good shape. I know @InTheShed and @Stltoed make use of shed’s in similar climate conditions. Maybe they can offer some specific advice for that type of setup that may differ from the norm.
That being the case, I think you’ll be in good shape. I know @InTheShed and @Stltoed make use of shed’s in similar climate conditions. Maybe they can offer some specific advice for that type of setup that may differ from the norm.
Stltoed
Well-Known Member
I grow in Southern California. Temps here range from just above freezing to well over 100 degrees. I couldn't do it without AC.
I have an 8 inch Hurricane fan that pulls air in and pushes it out the roof through a "turbine" style vent.
There are a lot of variables in the equation. Fan size, duct size, and style, filter style and flow rate which will change over time. Ive used 2 filters stacked on top of each other, but i believe the filters im using now don't require that. I think youll find air throughput in the shed will take a backseat to air temp and humidity. Without AC and a dehumidifier.
Stltoed
Well-Known Member
Film is a new thing for me. The Stltoed Scorcese vision has taken hold, and now I make magic like this.I grow in Southern California. Temps here range from just above freezing to well over 100 degrees. I couldn't do it without AC.
I have an 8 inch Hurricane fan that pulls air in and pushes it out the roof through a "turbine" style vent.
See the went on top of the shed
The intake vent is 3 6 inch holes in the side of the shed, then a 3M filter a little higher up the wall inside the room. Vent is to the upper left by the AC.
I dont remember the size of the filter, but its probably 16x25". I didn't do any math on this, I just went as big as i could fit for the filter. The fan is a bit of a beast, so I didnt worry about not having enough air. The grow room takes up about half of the shed footprint. Its about 10 by 6'. The grow area is only about 4x6. The vent and fan are at opposite ends of the grow space to help fresh air get to the plants. I have another area I call the closet.
There is a 6 inch fan pulling air in and another 6 inch fan pulling the air out which also leads to the roof vent. The air in is a $20 fan. Its nothing at all special. Its always on. The exhaust fan is another Hurricane... muuuuch stronger than the first. It is only on after the room gets to 85 degrees There are no filters on either fan since its ready been taken care of. I have no issues at all with flow and have never had any issues with poorly performing plants in there.
There are a lot of variables in the equation. Fan size, duct size, and style, filter style and flow rate which will change over time. Ive used 2 filters stacked on top of each other, but i believe the filters im using now don't require that. I think youll find air throughput in the shed will take a backseat to air temp and humidity. Without AC and a dehumidifier.
Just thought it might more clear than my previous ramblings
Stltoed's got you on this one! My shed is unvented, uninsulated, and unencumbered by any HVAC products.Ah, those “spoiled” outside conditions.
That being the case, I think you’ll be in good shape. I know @InTheShed and @Stltoed make use of shed’s in similar climate conditions. Maybe they can offer some specific advice for that type of setup that may differ from the norm.
Stltoed
Well-Known Member
I want your shed...Stltoed's got you on this one! My shed is unvented, uninsulated, and unencumbered by any HVAC products.
And I want yours, if you keep paying the electric bill 
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Stltoed
Well-Known Member
Ah yes the modern, domestic, vibrating shed.And I want yours, if you keep paying the electric bill
