General ventilation advice please - Pics included

[ChefKimbo]

I'm having heat issues with my 24cft grow box. The box is in an unconditioned shed which is 1260 cubic feet(14'L x 10'W x9'H), with a stucco exterior, all wood interior framing, slanted roof, and two windows. For ventilation there is an 8 inch roof vent

, about an 6 foot long opening on the back wall(my box right on the other side of the wall), and a 2 inch gap at the bottom of the door.

IF the door is kept closed, temp slowly creeps up to about 88-90F at about 3pm EST. Of course this is with no equipment on. Last time I ran test the box got up to 101F, but those test were with different equipment. I had an Axial fan rated at 200cfm mounted on the 4 1/2 exhaust hole pulling from the box, but no ducting to pump hot air out. I got rid of the fan, even with ducting I don't think it was going to keep up long term. So first I researched duct fans and was convinced to buy a ACMEMiami 6" inline duct fan rated at 240cfm. I also have about 20ft of 6" insulated ducting to use for exhaust. For some reason I decided I'm not going to waste my time installing this fan for exhaust from the box. I plan on installing 8" filter and I just don't think its going to be the answer. Yesterday I ordered a 6" Hurricane 435cfm for the box exhaust/filter issue. I thought I would keep the duct fan and possibly run additional ducting to help pump hot air up and out of the shed and increase the air movement inside the building altogether, routed to either the 8" roof vent, or the opening above my grow box. Any ideas?

 

[Cultivator]

what are your outdoor temps? bearing in mind the room will always run a few more degrees than outside temp with lights on.

for a space that size id be running a 10 or 12" 2000-2500cfm fan extracting straight outdoors.

That will air exchange the room twice per hour keeping temps alot lower than running a 450cfm.

Ofcourse it depend on how many lights you intend to run.

 

[ChefKimbo]

Temps? Depends on who you ask lol. Supposedly its only 88F but my thermometer/hygrometer says its 122F outside after a 30 minute visit.

I hope the recommendation for a 10-12" fan isn't for my box, its only 24 cubic feet. The shed its in is 1260 cubic feet. Average temp in the shed this time of day is in the lower to mid 90's. The PC fan I used for exhaust worked out, but it was already working at a high speed and would have been useless when I add the filter and ducting. My goal is just to move more hot air near the already established venting areas, and pull cooler air in from outside. Eventually I will be running the lights at night, my plants are outdoors right now and eventually I will be pulling the plants indoors for security and automation. I'm a noob grower so I'm starting off cheap and simple with a 10 bulb CFL fixture overhead and will be installing 4-6 more sockets on the side panels for late stage flower/bloom. I will be upgrading to HPS at some point as I am interested in building my own fixture, till then I want to be prepared for the heat increase. A small 6-8,000 BTU window unit isn't out of the question, just not at the moment. I may have to upgrade the circuit for the AC.

 

[Cultivator]

i thought the shed was the space. if its that hot outside you are fighting a losing battle trying to cool the room with an exhaust fan. but if you want air to go out of vents you must run duct work too it. i would def only run lights at night if that is the day temps, that is when you bring them indoors of course.

 

[ChefKimbo]

Yes its really a battle, but if I ran the lights at night I think it can be done. Ran a test with the 120mm fan a week ago and the temp stayed near 85-86 with 10 lights on. But that's without adequate ducting for ventilation. The intake air is actually pretty cool at night, coming from an small windy alley covered by trees. During the day that are gets a lot of sun and temps sky rocket. IF I ran ducting the straight up from the box to the 8 inch vent, how would that effect the ventilation of the rest of the room? At some point I plan to install an 8 inch filter, should the filter be installed directly under the vent?

 

[Cultivator]

you could cut a few small holes at ground level in the shed to use as intake. its better to take air in at ground level as its cooler and will be pulled up through the plants. ideally you want your filter above your plants so that it pulls air up and through them and also scrubs the air in that room.

 

[ChefKimbo]

After running a couple of primitive ventilation test I realized that the gap under the door is the only intake in the whole shed. Very strong air current cant hold a flame upto the gap. Is this evidence that more intake capacity is needed? If added holes vents where should they be and how big?

 

[Mountainman80]

I'm having heat issues with my 24cft grow box. The box is in an unconditioned shed which is 1260 cubic feet(14'L x 10'W x9'H), with a stucco exterior, all wood interior framing, slanted roof, and two windows. For ventilation there is an 8 inch roof vent

, about an 6 foot long opening on the back wall(my box right on the other side of the wall), and a 2 inch gap at the bottom of the door.

IF the door is kept closed, temp slowly creeps up to about 88-90F at about 3pm EST. Of course this is with no equipment on. Last time I ran test the box got up to 101F, but those test were with different equipment. I had an Axial fan rated at 200cfm mounted on the 4 1/2 exhaust hole pulling from the box, but no ducting to pump hot air out. I got rid of the fan, even with ducting I don't think it was going to keep up long term. So first I researched duct fans and was convinced to buy a ACMEMiami 6" inline duct fan rated at 240cfm. I also have about 20ft of 6" insulated ducting to use for exhaust. For some reason I decided I'm not going to waste my time installing this fan for exhaust from the box. I plan on installing 8" filter and I just don't think its going to be the answer. Yesterday I ordered a 6" Hurricane 435cfm for the box exhaust/filter issue. I thought I would keep the duct fan and possibly run additional ducting to help pump hot air up and out of the shed and increase the air movement inside the building altogether, routed to either the 8" roof vent, or the opening above my grow box. Any ideas?

Get u a small ac.unit problem solved it will work I seen several. Using them.