Proper Ventilation for 400Watt HPS in Closet

So I am getting a setup underway.

I have a closed that is about 3' x 4' x 8'. It has a crawlspace opening at the top with access into the attic. I live in a very mild climate, so exterior heat really isn't an issue.

Would having a 400 watt HPS in there with the crawlspace hatch open and a couple fans blowing from the top and bottom of the closet be enough to ventilate?

Or would would having a ventilation fan at the top installed in the crawlspace hatch be a much better bet? I was thinking I could install this one here easy enough.

Room-to-Room Fan - 3031 at The Home Depot.
I would just vent it out into the attic with no ducting or anything.

try it and see, there is no way to know for sure - it will depend on things like how well the attic is vented to the outside. try without fan or plants but with the lights and measure the temp in shade under the light. if its under 85 f, you are good without the extra fan.

how do you plan on containing the smell if it isn`t a sealed room

Its a 2 story house and this closet I am using is on the second story. I think the smell will just dissipate up into the attic without stinking up the rest of the upper floor. This crawl space is the only access into the attic. This closet is also back in the corner of the house. Not too worried about the smell. If it gets bad, and I don't already have the ventilation system set up a the top of the closet, I could install it with a duct running to a vent exiting the attic.

my upstairs just did this. vented into the attic and bud man did it stink. it willl fiil the attic then come out the venting in the roof. we could smell his a block away, and they were only a foot tall.
sorry didn`t notice you had room size above. so it`s cubic footage is 96. so you need a fan that is rated probably 150 cfm. i gaurantee you will need a filter.
a 400 watt will do good. they are for ereas 3x3.
you will need the ducting or it wont be efficientr at all

It wouldn't be that hard I guess to run some ducting to the attic vent that is about 20 feet from the crawl space opening. As far as filters go, is that something that I would attach to the end of the duct by the filter? Could you recommend something that is effective but won't break the bank?

Oops, meant to say, " is that something that I would attach to the end of the duct by the attic vent?"

do you have a hood for your lights

Yes, I do have a reflector hood.

i would put the filter on the intake of the hood. then run hose from the exhaust end with hose to the attick then the fan. seal the room. then make a hole for intake in at the bottom of the room somewere. the hole needs to be at least the same size as your exhaust hole to create negative pressure to keep smells contained and provide adequate air exchange. keep the filter at the highest point of the room to catch the heat and run hose to hood if needed

bonz said:

i would put the filter on the intake of the hood. then run hose from the exhaust end with hose to the attick then the fan. seal the room. then make a hole for intake in at the bottom of the room somewere. the hole needs to be at least the same size as your exhaust hole to create negative pressure to keep smells contained and provide adequate air exchange. keep the filter at the highest point of the room to catch the heat and run hose to hood if needed

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great advice except i think the intake hole needs to be small to create negative pressure, imo.

.........nope. i also paint cars for a living and my spray booth venting works the same way. it has a damper that i cange to adjust the amount of neg pressure to keep it nutral for me so dust dont come in. if the hole is to small it will make the fan work to hard and wear out and be noisy.

bonz said:

.........nope. i also paint cars for a living and my spray booth venting works the same way. it has a damper that i cange to adjust the amount of neg pressure to keep it nutral for me so dust dont come in. if the hole is to small it will make the fan work to hard and wear out and be noisy.

Click to expand...

i think small input hole = near vaccuum = better negative pressure. and large hole = air entering and exiting = better ventilation. the answer for a grow room is a compromise. not trying to have an argument but really think it works this way. agree that too small a hole will wear out the fan. also, if you are running a spray booth aren't you running positive pressure to keep dust from coming in the room? in this case you do want a larger input.

no, dont want the fumes to exit. it needs to be nutral to a slight negative, or there is to much air movement and disturbes the dust in the room.
i have always been told to start with the same size hole and adjust it from there. yes a smaller hole = more neg pressure but it starves the fan and wont work as it should.

a half inch or so isn`t worth worrying about. i find the method i use has always worked for me, would also depend on how well the room is built or sealed up to.