Freezer grow- help with temperature control

My setup-
20"D x 27"W x 60"H vertical freezer
6" Vortex S-line 347cfm inline exhaust fan
Titan controls zephyr1 temp controller
Currently 1 3" Passive intake
CAN33 carbon filter
4" ducting throughout
5- 2ft HO T5 6500k grow lights
Will add clamp on 2 or 4 CFL bulbs in flowering (Possibly LEDs down the road)


I'm about ready to start my first grow in my brand new used rebuilt freezer grow box. I have a few questions regarding ventilation. I realize my exhaust fan and carbon filter is probably overkill

The freezer is in my garage which is currently not tempeture controlled. So it will be using the ambient air in the garage
at this time it's not ideal to run ducting from house to garage) The next few months will range anywhere between 50° highs 0° lows. So I'm afraid I will he fighting to keep my box warm enough all winter. I'm open to suggestions to combat this problem.

Does my exhaust fan need to run 24/7 to constantly exchange the air inside the freezer? Or can I use a thermostat that will control the exhaust to turn on when the temp hits say 80 degrees? I would have a small desk fan running to circulate the air inside. My concern is when my lights are off the temp will either drop too low and damage my plants or the exhaust fan would not turn on and my plants would not receive enough fresh air. Any suggestions or helpful tips would be appreciated. Thanks.

If you can't temperature control the new air coming in.. it may have to be a sealed system for this box to work in a cold garage. The best place I recommend is a closet as long as the room is warm and relatively dry. The problem with mixing cold air into the garden is mold and slower plant growth. The vegetative closet I built used a box fan to circulate air from a room heated via HVAC system. The video below explains the break down of my vegetative closet if you skip to 5:05. Hope this helps and good luck!

Damn, that's a killer set up

Would a seedling mat keep the roots warm enough when the lights are off?

Cmon I can't be the only one that grows in the cold. Any help would be appreciated.

Your problem is not going to be your exhaust, your problem will be bringing in cold air on the intake and that will be the key to dialing it in. You'll need to play with it as temps drop but I'd either go passive intake or active with a variable controller then a timer or thermostat + damper on the intake fan, that way unless the fan is on and strong enough to bring air in (triggered by the thermostat), it won't.

I use a wall heater to warm the room my plants are in.. When I let my room get too cold.. I started to get powdery mildew.. which didn't stop until I kept my room warm and dry. I think seedling heat mats will work well with a setup like yours.. I would hook up a voltage regulator to the exhaust.. then hook the regulator on a timer. In the cold parts of the day.. I would keep the system sealed.. then run the exhaust when the garage warms up. Just like GroErr said.. controlling temperature via the cold air that is pulled into your grow space will make your plants much happier. Good luck man!

OK that makes more sense now. Thanks a lot fellas!

Solar I like that idea and this might be a noob question but by doing that would the air inside the box become stale? Or would the small oscillating fan be enough to prevent that?

I really need to figure a way get some ducting from inside the house soon and prevent this whole issue... We are currently looking for a new place so everything may work out in the end. But my buddy has clones ready to go and I'm ready to get started after months of planning and building.

I think that a small oscillating fan would help with air circulation within the grow space for sure. Taking that first plunge can be sometimes be a doozy.. but with good environmental control.. you should be set for sure. I have been one of the idiot growers that has ruined a fresh batch of cuttings within 10 days.. but they were still in the cloning phase. However, that was because I let the ez-cloner get too warm during a heat wave.

In regards to the stale air issue.. I think it would be technically possible to run a completely sealed system inside of a refrigerator as long as you have a co2 monitor inside. However, you can also poison plants with too much co2.. as the roots need oxygen to breathe. However, even with fresh warm air inside the system.. Personally, I still view relative humidity as the main priority compared to air exchange. If you draw in warm.. but moist air.. ie: air exhausting form a clothes dryer outlet vent.. then still mold can still have a much easier chance to take hold on fan leaves.. as rH is only relative to the current temperature.

Two items I recommended.. First, a good digital hygrometer/thermometer that will save maximum and minumum humidity and temperature. When I was dialing my temperatures I was using a Honeywell unit very similar to Meade Instruments hygrometer/thermometer on amazon.com for about 25 dollars. With my closet grow setup.. I used 24/7 air intake to prevent risking humidity spikes via pulling air from a room with low rH and warm temps.

However, you might want to exhaust the air back in the same air the the intakes is drawing air.. This is prevent heat from pouring into the garage.. which can be picked up via infrared if anybody scans your house for grow hot spots at night and in the morning. Second item is if you choose to use ducting.. I recommend 4 inch insulated ducting from Lowes or Home Depot.. then you can you pull/push air with minimizing the heat leaks. Might be a bit of a challenge to dial things in.. but that's half the fun!