Exhausting air from room during lights off

Bookush34 said:

I have a 6” duct booster that runs during my lights off. It keeps my humidity in check at night. Also stops cold winter air from coming back down my ducting.
But this is in a tent not a big room

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How has it been working are your plants still thriving? I was thinking about having vent in during dark period also to remove some unwanted humidity. Temperature is in check my dehu just isn’t dropping humidity enough for me. I was just thinking that venting too much air out the room would cause maybe like not enough oxygen in the room or something?

that's what the air in is for right? if your pulling air out what more is it to pull air in? you'll need to do it via fan so it's not passively leaking.

I run my fans 24/7 but I don't use co2.

Streetdoctor3 said:

How has it been working are your plants still thriving? I was thinking about having vent in during dark period also to remove some unwanted humidity. Temperature is in check my dehu just isn’t dropping humidity enough for me. I was just thinking that venting too much air out the room would cause maybe like not enough oxygen in the room or something?

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If you only want to vent at night you would need to have a passive intake as well. To lower your humidity you need to replace the it with less humid air.
My plants do fine. If I have no exhausting at night I will see humidity in the 70%+.

I run a 6” inline fan on the same ducting as the duct booster. The inline runs on a t-stat and the booster is on all the time. Helps keep a slight negative pressure on the tent.

Yes you can hook up exhaust. Which way you are wanting to exhaust will alter your wanted results. Positive pressure? or Negative Pressure? Co2 is a heavier gas molecule, therefore settles lower than oxygen. Cold water/cold humidity holds more CO2 and cannot vaporize. But hot air=less oxygen.. Does your quest have a defrost compressor? Not too familiar with them. I would say you have a VPD issue... regarding your air exchanger...Which room is this problem occurring in? upper floor?

Monster_of_Au said:

that's what the air in is for right? if your pulling air out what more is it to pull air in? you'll need to do it via fan so it's not passively leaking.

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Maybe I've misinterpreted?
To be pulling it has to be drawing through the passive vents or somewhere?

Passive leaking is certainly a problem but ime a fan won't prevent it unless it's running constant during the dark period, it would then cost a fortune to heat and blow it away.

A back draught shutter is a more economical method coupled with a humidistat/ink bird

Streetdoctor3 said:

Can I exhaust air from the room with lights off to reduce co2 levels at night and lower humidity? Turn off the exhaust during lights on? With co2 burner running with lights on and semi sealed room.
Co2 is kind of high during lights off and humidity is high.

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yes of course you can.
I build sealed growrooms with the ability to also ventilate. Put dampers on both intake and exhaust ducting.
I “dump” my rooms 3 times when lights are on and as often as I want at night. Whatever is clever for the time of year

I’ve found that by dumping a sealed room every 3-4 hrs with lights on makes for a more healthy room especially when using a co2 generator.

just a thought...when you are dumping all this air outside, where are you getting the makeup air from ? hopefully not from your furnace or water heater exhaust. some of these exhaust fans will suck enough cfm to overcome many combustion blower motors and cause a back draft. infiltration is more so in older houses compared to the airtight newer more efficient homes. you want your house on a slight positive pressure to stop infiltration in the winter.

kahoona said:

just a thought...when you are dumping all this air outside, where are you getting the makeup air from ? hopefully not from your furnace or water heater exhaust. some of these exhaust fans will suck enough cfm to overcome many combustion blower motors and cause a back draft. infiltration is more so in older houses compared to the airtight newer more efficient homes. you want your house on a slight positive pressure to stop infiltration in the winter.

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I pull from wherever is clever.
My most recent setup, i pull through a cold air return grill with filter that I installed, sucking from an adjoining room with the window cracked a bit.

kahoona said:

you want your house on a slight positive pressure to stop infiltration in the winter.

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Haha!
Yeah, evidently not here in California where we deal with title 24.
They now say our new homes are built too enclosed and have to have an IAQ(indoor air quality) fan running non-stop creating a negative air pressure situation. It’s lame and bullshit.
I’m wiring mine up so i can control it with a switch after the final inspection.

My air is cleaned thru filters and recirculated throughout the house. Every time I open the front door air is exchanged and replaced. I never have to blow air outside