Ventilation for winter - sealed room or no?

[farmari]

I'm not sure what to do here... I'd love to hear anyones opinion/advice/ideas on environmental control during cold winters.

Currently my grow area is using around 4kw (all devices) and has 1200CFM (rated, not actual) of fans exhausting into the attic. (passive intake from crawl space) The room temp stays between 55-90F.

Outdoor temps stay below freezing all winter where I live though. Last winter I was running less wattage and exhausted into the HVAC system... basically used the house as a "lung room".

But at +4kw now, (might want to add more lights as well) this doesn't seem practical for the coming winter.

My options seem to be:

1) Continue to vent into the attic. Make sure the crawl space vents don't get covered in snow.
*But will mold in the attic be a risk? (condensation due to below freezing outdoor air)
*Also, will there will be a suspicious condensation cloud at the attic vent outside?

2) Cut a hole in the wall/ceiling in the living room at the other end of the house, and route the +1000cfm grow exhaust there.
*The house would be a lung room. Dehumidifier will be in use, along with a CO2 monitor.

3) Install a mini split with heat pump and seal up the room.

Any other options? What should I do? Thanks for any help!

 

[ItGrowsHerb]

One winter I ran fresh air into a normally sealed room using a $20 attic thermostat to turn the fan on when it got above 76 or so. There seems to be something to be said for that fresh winter air because the buds were sure beautiful.
I am debating this myself. Basically you forgo CO2 enrichment and let the cycling air exchanges do that. Then an exhaust must be used that is carbon filtered to relieve overpressure.
I like the simplicity of option #3. Those are quiet too from reports.
Option #1 seems problematic. Using #2 seems the best tradeoff. I cannot tell yet if #3 is any better so hope you find a good answer.

 

[ak-51]

I run 3k and I think exhausting into the HVAC system is going to be good enough. I plan on pulling from the living area and venting back into the living area, so no scrubbing will be necessary and the pressure in the room will be neutral. It won't eliminate the need for me to use my furnace, but it will reduce the need.

I think I'll be getting a CO2 generator as well so I can run completely sealed. Venting the grow room will make the temperature swing way too wide, and I'd rather have a CO2 burner than some kind of temperature sensitive venting setup.

 

[Shafto]

If it were me in that environment I would seal the room with CO2 and a dehum, and instead of wasting power running an AC in the winter I would get a couple used car radiators with fans. Put one outside, one in the grow room, and pump antifreeze through.

Keep the room cool, stay sealed, extremely cheap to set up, use probably about 1/5th the power of an AC.

Might want to get a split system though too, to more efficiently heat the room during lights off (than an electric heater), which you could then also use in the summer to cool the room during lights on when outside temp isn't low enough for the radiator heat exchanger to work.

 

[farmari]

Thanks for the replies all.

ItGrowsHerb, that's a good idea. Did the humidity get really low?

AK-51, I decided on this method. I'm hoping noise isn't too much of an issue in the living area, with +1400cfm of air blowing in. The thinking is that if I keep the house around 70F and 50-60% RH, 500-1000ppm CO2, then the grow room should stay around 80F and 35-40% RH all year, if I'm exhausting 300cfm per 1kw. Crossing my fingers! I have concern of the house getting too warm on warmer months, but I guess that could be handled by a mini split in the living room. So it would mean stable temps/RH/CO2 all year without sealing the room, without having dehuey/AC in the room.

Shafto, now that would be nice. Too complicated for my brain to figure out how to engineer for now though. I've pondered using water chillers in a similar but far less efficient method.

 

[ItGrowsHerb]

It might have introduced swings in humidity as the fresh air kicked on once it got warm in the room, shutting off when cooled down enough. Then things would sit for a bit til the cold, fresh air kicked on again. I didnt keep track of humidity, I was just finding a solution to the inability of a window AC to cool in cool temps. This winter I see myself leaving CO2, dehuey and AC off while bringing in outside air and filtering the exhaust into the living quarters. I will track humidity then, I am a long ways from the run of winter of '10/'11

I could use a PLC to control and automate all that seasonally or get a minisplit w/inverter to keep a CO2 enriched environment year round. These seem my options so far. It may boil down to which method is most energy efficient since I am not a production grower, just personal.