Cooling grow room in winter

I have been thinking about how to cool my grow room cheaper. I’m thinking in the cooler months I can take advantage of outside air. I don’t want to just bring outside air in though because of contaminants and losing co2. I’m thinking if I pull air out of the room and run it outside through a stretch of dryer vent and reintroduce in the room it would cool a lot of air. My main concern is the condensation that would build up inside the vent and how to discharge that on it’s own without losing much air flow. I was thinking I could pull air near the floor take it outside and coil it going upwards so the condensation flows back down and somehow out then bring the air back inside and distribute above plants. Any thoughts or improvements? How could I let the condensate drip out? How long of a stretch would be efficient? Thanks for any tips

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Bringing in outside air has its challenges.

Once the cold air hits something warm and more humid, boom, moisture. Moisture causes molds and issues.

Always use a hepa filter for any outside air. This wont help with the moisture, but does for spores and bugs

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Like what @Demontrich said…use Hepa filtration for incoming fresh air and use a dehumidifier or multiple to combat extra humidity.

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Wouldn’t that cancel out the energy savings?

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What is the main thing you are trying to cool? Your lights? What is generating the heat?

If your running a sealed room…bringing in outside air seems completely counter intuitive unless it’s in a ducted system that doesn’t exchange air with the room

Edit - I misunderstood. Your wanting to chill the air. I think paying for your AC bill, assuming your unit is efficient, is the best bet.

You are proposing a lot of work for little gain. Basically making a heat exchanger with outside air.

To catch condensate, you just have a T at an elbow, creating a low spot. Pipe it to a bucket. Residential gas lines have such Ts in place to drain as such…obviously a duct is larger than a 3/4" gas pipe…but same idea

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You’re kinda talking like using the outside air like a cooling system right? Say using ducting as a cooling coil to inject cooled air back in?

If so, couldn’t you just have the duct coil dump into a bucket to keep the condensed moisture, then have the air vent back out into the grow room, hopefully dried?

Not sure if this is worth it or feasible.

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I ventilate my lights, burn propane for CO2, have a 5 ton AC unit, and still sometimes my exhaust fan comes on and I ventilate fresh air in at the same time air is taken out. HEPA in…guess outside environment is different everywhere, so it may be less humid outside where I am vs. where you are…

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For 13 years I didn’t use any HEPA intake. But now that hemp and herb are everywhere around where I live it seems there’s more fungus in the air.

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I moved from the dry west to here out east, and the difference in humidity is nuts. It’s soooo damn humid here!

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You burn propane and have heat issues, but your doing it bigger than i…so its apples to oranges. I am small so I run bottles. I have no heat problems.

I’m my mind, having to bring in outside air negates the benefits of running sealed.

Where I live, outside air is wet and full of pests.

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You could use an erv/hrv in a unconventional way

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I’m not bringing in any outside or fresh air. Yes it would basically be a heat exchanger. Maybe it would be more trouble then benefit I’m just brainstorming now. I would think 50 to 100 ft or so of dryer vent running through freezing temperatures (Michigan) would cool a lot of air?

Probably, but you would probably need a decently sized exhaust fan to pump air through that.

I think you lose roughly 50% of the pressure in an exhaust system each 90 degree bend there is, something like that anyway. So you’d want to keep the vent pipe as straight as possible with a minimal amount of bends.

But, I will say people use this type of cooling system in greenhouses for the summer. They’re doing the opposite of you, and using the ground as a heatsink to cool the air in the green house.

Check out geothermal cooling of greenhouses.

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Or, instead of flexible dryer ducting, you can get a run of metal ducting with a plenum(box) attached and the metal may help conduct the desired heat exchange better than flexible duct.

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Pickup some used water-air exchangers maybe even used radiators on Craigslist or eBay cheap. Pump antifreeze through them. Gonna take some calcs to see what the heat load is in the room and you’ll need to use an array of exchanger I’d bet.

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Do you have to heat other parts of the building?

I hate to see heat dumped in the winter.

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Exactly!!

I’ve seen basement grows used very effectively to heat the upstairs living space in winter.

It will take a tad more engineering, but the concept is pretty simple.

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All my air cooled hood air gets kicked upstairs in winter

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That was my other idea I’ve been thinking about. I have some old window AC units I could rob the exchanger out of. If I wasn’t limited on amps I would just up my ac capacity.

Not really other areas to heat. It’s in its own barn