Basement, Open-loop grow room, negative pressure intake heater

Hello gentlemen.
I am trying to solve a design problem of my grow room which I am going to build.
The grow room will be situated in the basement where is a constant temperature between 60 and 64 Fahrenheit and humidity around 40%.
My plan is to use the Open-loop concept, where exhaust fan with carbon filter is inside grow room and without any intake fan, just a hole.
Probably the problem will be the intake air temperature, which is too cold isn't it ?

To solve the problem, I was thinking about using Circular duct heater which would be connected to the intake hole from outside of grow room and cable connected to thermostat inside the grow room. So the duct heater would be switching on/off depends on the temperature inside grow room.

For example it looks like this:


My grow room planned dimensions: 23ft x 23ft x 10ft = 5290 cubic feet.

The Circular duct heater have parameter like this: "A minimum air speed of 1,5m/s is necessary for the battery. " - source: Circular duct heater
So for instance that I will use exhaust fan with minimum 5290 CFM performance, is it possible to reach the minimum air speed of 1.5m/s as required by the Circular duct heater through the intake hole ? Will be even ok to intake warm/hot air inside the grow room ?

I have a little bit of headache about temperature control. I was thinking about AC unit which would solve the problem but I don't like the fact that there will not be fresh air exchange and I think I don't want to use Closed-loop concept and CO2 although the grow room will be air sealed.

Thank you very much in advance for your help.


P.S. I apologize for my English, it's not my first language.

Just put your exhaust fan on a temperature controller like a sonoff th10 or th16. Then the fan will only run when the temperature rises and turn off when the room is cool enough.


that's a huge room can't wait to see what you do.

in cold climate with very cold intake air the problem can be co2 depletion ..
plus its a big waste to heat the room to dump the hot air outside

sealed with a small burner would do the trick better

MidnightSun72 said:

Just put your exhaust fan on a temperature controller like a sonoff th10 or th16. Then the fan will only run when the temperature rises and turn off when the room is cool enough.


that's a huge room can't wait to see what you do.

Click to expand...

Thank you for answer.
Understand, but will be the air exchange enough in case of CO2 ?

Philip0407 said:

Thank you for answer.
Understand, but will be the air exchange enough in case of CO2 ?

Click to expand...

Ya I mean a 23x23 room. If you are filling that with 1000W lights I bet that fan will run 12h a day solid.

If you use a fan you will be pulling in new CO2 all the time.

Or you can do like the other use mentioned as well and a burner if needed. But I mean silly to cool a room to just go and heat it back up.

kingromano said:

in cold climate with very cold intake air the problem can be co2 depletion ..
plus its a big waste to heat the room to dump the hot air outside

sealed with a small burner would do the trick better

Click to expand...

Thank you for answer.
Yes, maybe you are right, it looks like it will be a huge waste of hot air and electricity. So do you suggest Closed-loop concept and AC unit instead ? or what do you mean by the small burner ? like propane burner inside the grow room with Open-loop concept ?

How big of a fan are you using? The room is 23x23x10 = 5290 cubic feet.

You should be able to empty that volume once every couple minutes. So you can size your fan or multiple fans accordingly.

MidnightSun72 said:

Ya I mean a 23x23 room. If you are filling that with 1000W lights I bet that fan will run 12h a day solid.

If you use a fan you will be pulling in new CO2 all the time.

Or you can do like the other use mentioned as well and a burner if needed. But I mean silly to cool a room to just go and heat it back up.

Click to expand...

Actually that sounds good, I would not need any heater in that case right ? I am wondering how would the equation change if I incorporate a humidity control with humidifier. Does it change anything ?

Philip0407 said:

Thank you for answer.
Understand, but will be the air exchange enough in case of CO2 ?

Click to expand...

a propane/NG burner with pilot flame would be perfect
your room is pretty big you will also need to cycle on/off the main burner
will also heat the room a bit which is a good thing sometimes

no need to vent with it. at all

but you will need a good dehumidifier or two for sure ..