Help, please. Design of ventilation system for my closet growroom

[Guest]

I would welcome some help with the design of my growspace's ventilation. My primary concerns are of removing the heat from the grow area and keeping incoming airflow high enough to keep CO2 levels up in the normal range without a CO2 delivery system.

Grow space = 2.2' D X 8' W X 8' H - 17.6 sq ft - 140.8 cubic feet - Located in office in home. Wall in back of closet has 20'X30' den w/cathedral ceiling on the other side. Front wall and one side wall of closet are in the office.

Lighting: 1 600W HPS/MH conversion and 1 400W HPS/MH - both digital, both air cooled reflectors both have glass and the 400W has double pane glass.

Fans = 1 Can fan (265cfm) and 1 Eco Hurricane (630cfm)

Using the 630cfm, my original plan was to pull air from my office into a duct (mounted low) that was to run through both lights and then exhaust into the den (placed high on wall). This would not take any air out of the grow space. It would simply remove the majority of heat generated by the lights

My can filter was to be hooked to a 6" duct and air was to be pulled through it using the 265cfm fan also be discharged high on the wall of the den. My intakes (2-8" square light proof louvers) for this fan would be mounted low on the front walls (drawing air from my office)these would be located, just at the height of the tops of the grow containers. Another two of the same located low on the back wall would pull in air from the den.

I planned to put a speed controller on the 265cfm fan that is running through the filter and use it to control temps. Even at its lower cfm rating, it should exchange the air in my grow space 1.9 times every minute, not taking into account the lower actual cfm rate due to the restriction effect of the filter. This rate I'm thinking, combined with the fact that the vast majority of the heat from the lamps will be exhausted out of the grow space, should keep temps in the reasonable range.

I spoke with the owner of a hydro supply shop today and he suggested I just scrub the air (filter hooked to blower and blower discharged into closet) and leave it in the grow space and then vent the air from the grow space into the attic by leaving the ducting off the intake side of my first light, running ducting from the first to the second and then exhausting it into the attic. I told him I thought it was better to leave the exhausted air in the house because for every cubic foot of air I pumped out into the world, a cubic foot of air would have to come in from outside the house. That means cold air coming in through gaps in the doors and light fixtures during the winter and 95 plus degree air coming in during the summer that would have to be air conditioned.

Which idea do you think is better? Or does anyone have a better system that they have tried and had success with? I know this is a long opening to the thread, but I wanted to put all the information I could so I could give a better picture of the situation.

 

[R4st4]

hey.. i would use the 265 cfm fan to draw the air from the box thru a filter and have passive intakes(i do this)... Ideally, air needs to be replaced every three minutes (or twenty times an hour). so u would have changed air atleast 6 times every 3 mins so that fan should be more than inuf for that space also the intakes should be low and the exhaust shoud be mounted high

 

[mrgrowmez]

arent you worried about having to fans exhausting into your den? i would have thought both of em together would create a bit of noise there, maybe some silencers are in order,

i would vent the fan pulling the hot air from the lights into the den to heat it but i would probably think bout just vent the filtered air back into the office if thats a possibilty, if your running cooled hoods then hopefully the filtered air wont be too hot.

good luck
growmez

 

[Guest]

Thanks. I think I will try just using the smaller of the two fans to exhaust with. That one will probably be enough air exchange to keep it cool, I hope. If I exhaust heat from the hoods back into the office, I may need to buy the window a/c to keep the office cool enough that the intake air will be cool coming into the grow room. I'm still in the process of putting the grow room together. I was up until about 5:30 this morning putting up 4 mil thick mylar. It's a lot easier to work with than the thinner stuff I've heard but it's still a bitch if you're like me and have carpal tunnel syndrom. Plus, Ive got a really old staple gun that requires hand pressure from hell. I'm learning that if you do this right, it takes a while. I'm having surgery on my hands next week so I'd like to get it set up so I can sprout my seeds.

 

[mrgrowmez]

hey, i meant exhaust the heat from the hoods into the den, and take the cool air from the office into the grow room.

 

[Mackawber]

I agree with the hydro shop owner you spoke with---you've got the exhaust thing figured out correctly but you need an active intake fan with ducting to deliver cold fresh air/CO2 to the middle and top of the room. Buy and use a thermostatic controller to control the intake fan cycles on and off to control your room high limit temps. During night time your thermostatic control wont sense any heat so your intake fans, exhaust fans will be off (providing its really cold outside)---spring / summer the fans would be on.

 

[Guest]

I think I've decided to go with a closed system. I'll use the smaller Can Fan (265 cfm) to exhaust the air in the grow closet back into the office. When odor becomes a problem, I'll hook that fan to the filter and scrub the air when it becomes necessary and still exhaust it into the office/extra bedroom where the closet is located. I'll also pull air through an intake with duct hooked to it from the office, through the lights and exhaust back into the office, using that (closed system, no air pulled from grow closet) air to only cool the ligts. I'll buy a window a/c unit and open the exhaust on it so it will exhaust the office air to the outside while pulling in fresh air with CO2 from the outside. When and if I ever decide to hook up a CO2 system to the closet, this system should also help me keep CO2 levels where they need to be and I'll close the exhaust on the a/c to have it just recirculate air in the office. Sort of a closed environment within a closed environment.

I am going to wire the timer to a receptacle so that both lights and the can fan come on together (timer's rated at 1750W, so I won't even be close to max on it). I'm also going to wire a fan speed controller to the fan so that I can adjust the temp where it needs to be. When the temp in the office stabilizes at a particular setting on the a/c and I find the proper fan speed setting, then whenever the lights come on, there shouldn't need to be any further adjusting.

By using the window a/c I also keep humidity low. I know to keep the passive air intakes for circulation in the grow closet at top of plant pot height and exhaust high. I think this sounds like the best way to have control over temps. No sound or odor to the rest of the house and my office door is always locked.

 

[Mackawber]

Thats a bad decision. You need fresh air for those plants, not a closed system recycling and reguritating the stale air! What are you thinking (smoking) and do share some with the rest of us!

You might want to reconsider.

 

[Guest]

Thats a bad decision. You need fresh air for those plants, not a closed system recycling and reguritating the stale air! What are you thinking (smoking) and do share some with the rest of us!

You might want to reconsider.

Mackawber, thanks for the advice man, but I think you may have missed the part in my post about the window a/c unit taking in air from the outside of the home and exhausting the stale air from the office, which is where the air from the grow closet is coming from, back outside the home. So in fact, it won't be circulating air in just this one room but rather it will be circulating air from outside the home into my office and returning it outside the home through the a/c unit after the air has gone through the grow closet. The grow closet will take in its air from the office through passive, light proof intake vents, and exhaust that air through a cabon filter back into the office. Office air will be exchanged with outside air on a continual basis with air outside the home via the air conditioning unit which will be set to take in fresh, outside air. When I spoke of a closed system, I was speaking about it being closed from the rest of the home. No odor, no noise, no visible signs of my growing efforts to the rest of the home, and no heat plume visible coming from the roof or side of the house the way I plan to do it.

What I'm proposing doing is no different from exhausting air back into another part of the home and other growers do that frequently. I'm just doing it from one room, not the whole house! The lights will be cooled by pulling air from the office, through intake ducts, pulling that air through the reflector hoods, and then exhausting that air back into the office. The cooling of the lights will not draw air from inside the grow room.

By using the a/c to cool the office, which is where the grow room will be getting its air, I should be able have tighter (and more immediate btw) control over temps in the grow room.

In summary, two fans will be used. The first fan is a 275cfm CanFan (brand name) that will change the air in the grow room at the rate of 1.88 times per minute. This fan will draw in air from the office via passive, light proof intake vents, scrub it with a carbon filter and exhaust it back into the office. This fan cools the grow room and replenishes its supply of CO2. The second fan is a 440cfm inline fan that will pull air from the office, pass it through a system that is closed from the air in the grow room, and exhaust it back into the office. This fan's only function is to cool the lights, thereby helping to cool the grow room. The air from both the grow closet and the office will all be freshened by the a/c unit as it takes in and exhausts air from outside the home.

It is intended that this system will also be CO2 system ready, if and when I decide to use it, by simply closing the intake vent on the window a/c that pulls in fresh air from outside the home. This will cause the a/c to only circulate the air from inside my office, which is where the grow room will be getting its supply of air. This should help my CO2 levels stay more constant.

If I've left something out or am unclear about expressing any part of this, someone let me know! If anyone fully understands my concept and can find any flaw in my reasoning, please let me know. I'm new to growing but I'm not unintelligent, so I need to hear constructive conversation about whether or not this should work.