Ventilation question

Since ventilation happens as a result of the theromostat/hygrostat telling the exhaust fan to cool/dehumidify the grow area, what happens if the area stays below the set temperature and humidity levels based on environmental factors? I could see this happening when the weather is cooler.

Wouldn't ventilation be inadequate if the room isn't getting too hot or humid?

Do folks run constant air intake, or an additional meter to trigger the fan when CO2 drops below a certain level?

That's a problem I've been dealing with for almost 20 years,

My grow room is in a very cool and much larger underground basement/crawl space and my exhaust fan is controlled by a temp/RH unit that won't come on at all unless I'm running at least 2 - 400W HIDs in there. My heater even has to kick in sometimes during their day. Eventually the plants run low on CO2 and just quit growing so I'll burn an alcohol lamp in there to add some. Even a candle makes enough CO2 to keep it up to 1000+ ppm. My RH is always low so the humidistat never kicks the exhaust fan on.

I'm planning on a sealed grow room as soon as I can afford a portable AC unit and a tank of CO2 to keep things right where they need to be.

It's not uncommon to exchange the room air on a regular basis. Including sealed rooms with Co2.

One way....as an example.
Use a cycle timer to turn the fans on for 5 minutes, every 3 hours.

TintEastwood said:

It's not uncommon to exchange the room air on a regular basis. Including sealed rooms with Co2.

One way....as an example.
Use a cycle timer to turn the fans on for 5 minutes, every 3 hours.

Click to expand...

The whole idea of having a sealed room is so you don't have to ventilate and flush all your CO2 out then replenish it.

Tempted to slap the VISA card down and grab an 8000 BTU 3-in-1 portable AC now on sale at the local Home Hardware store. Plenty big enough to work with my grow space and comes with the exhaust line kit.

Decisions, decisions.

OldMedUser said:

The whole idea of having a sealed room is so you don't have to ventilate and flush all your CO2 out then replenish it.

Tempted to slap the VISA card down and grab an 8000 BTU 3-in-1 portable AC now on sale at the local Home Hardware store. Plenty big enough to work with my grow space and comes with the exhaust line kit.

Decisions, decisions.

Click to expand...

Agreed. Unsealed it's more common. Guys that run burners to generate Co2 would be candidates to dump occasionally.

I run Co2 off a bottle, I only dump at lights out, and lights on.

I'm still learning myself.
https://www.cannabisbusinesstimes.com/article/bad-gas/

TintEastwood said:

Agreed. Unsealed it's more common. Guys that run burners to generate Co2 would be candidates to dump occasionally.

I run Co2 off a bottle, I only dump at lights out, and lights on.

I'm still learning myself.
https://www.cannabisbusinesstimes.com/article/bad-gas/

Click to expand...

I'm running open too but have a temp/rh controller on my exhaust fan and with chronically low RH and a cool grow room the fan can go all day without dumping so my plants become starved of CO2.

The only solution I can come up with is running sealed with more control over the environment so I can keep the rh up to a proper level and maintain all the other grow parameters at optimal.

Another learning curve to climb. lol

For my 4x8x8, a 5 head mister will raise RH as high as needed.

From "House of Hydro"

https://www.rollitup.org/t/dual-duct-portable-acs-inside-vs-outside-tent.990142/#post-14918392

Use near zero ppm RO water.

OldMedUser said:

The whole idea of having a sealed room is so you don't have to ventilate and flush all your CO2 out then replenish it.

Tempted to slap the VISA card down and grab an 8000 BTU 3-in-1 portable AC now on sale at the local Home Hardware store. Plenty big enough to work with my grow space and comes with the exhaust line kit.

Decisions, decisions.

Click to expand...

Make sure it has intake and out put hoses. The single hose models take air from the room and expel the hot air. You don't want that. I use a 5000 BTU and would go smaller if they made for a 4x6x8 room but it's the window style. They do not provide air exchange which is desirable in a sealed room.

I also run my heat and AC off a controller so if you do that they both need to have an auto restart after power outage feature. Heaters usually no problem but not all AC have this