Shed winter ventilation

Hi everyone

I have a 9x9 shed setup and live in the northeast where temps range from 15-55 degrees in the winter.
I'm trying to figure out a venting solution to keep the room at an adequate temps and not have a fan pulling my heat out and cold air in.
Right now I have a 9k mini split to heat the room plus 2 400 watt lights to get the plants started until I install about 3000 watts of leds.
I was thinking that maybe going with 4 1k watt hps lights might be better to generate heat since I have a 12 foot ceiling but doing more research it's probably to much heat for this space with a 9k btu split.

Do you guys think I should just seal the room and use strictly C02 during veg and flowering ?

Thanks for your input

David

4x1000 watters might make enough heat that you could just vent periodically with the fan on a thermostat. Depends on insulation.

It was recently sprayed with closed cell foam so its extremely tight.
So you don't think sealing the room and using c02 for veg and flowering would be more efficient?

Now that I think about it I'm probably using the mini split to heat if I'm using the leds or using the heat of the hps lights so it could be a wash?

Thanks for your help

dalack said:

So you don't think sealing the room and using c02 for veg and flowering would be more efficient?

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It's ok but you will need to buy a bigger minisplit that will run at the low ambient temps you experience outside. Build it to run in the winter and summer.

Thanks for your advice.

Do you know how much heat cobs put out compared to hps?
In the summer I might switch over to leds

dalack said:

Thanks for your advice.

Do you know how much heat cobs put out compared to hps?
In the summer I might switch over to leds

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About 40% less heat, but no infrared so you actually need to run the room a little warmer to get the leaf surface temps up where you want them.

Thanks

What do you think about running vented 1k watt fixtures without the glass? You think that would pull out enough heat and pull in enough makeup air?
Since you have alot of experience with hps what do you recommend for de 1000 fixtures? Are gavitas the only way to go or will I get decent enough performance from generic?

This bulb seems to be ratred very high


Thank you

I have Phantoms and Sun System DE HPS ballasts that I like. Never used a gavita, I don't like my ballast above the plants where it's hot and in my setup I can't change it out mid run if it fails. Avoid Nanolux, had a LOT of failures with them, even on the warranty replacements they sent. I am using the nanolux reflectors still but the ballasts are Phantom and Sun System and they haven't had a single hiccup.

Ushio makes good lamps. Philips and Hortilux as well.

Renfro said:

It's ok but you will need to buy a bigger minisplit that will run at the low ambient temps you experience outside. Build it to run in the winter and summer.

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I am about to start on a shed build much like his with closed cell insulation throughout. Can you get away with a smaller minisplit that can cover the heat output of the equipment, or do i still need to go by the standard recommendations of btu based on size of the room + equipment? I am curious if having the more expensive and better insulation in closed cell means I can get away with a smaller minisplit meant to cover the equipment and less based on the size of the room (ie. only 3-4k watts of equipment total in a 9x20 shed)

If you don't plan to run in the summer then yeah disregard all sizing logic and do what you want.

Renfro said:

If you don't plan to run in the summer then yeah disregard all sizing logic and do what you want.

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I asked cause of all the information out their regarding the claim that a HVAC system designed for batts or similiar insulation is (according to internet sources, so validity idk) something like 40-150% oversized when placed in a SPF room. Since most of the information and advice is given based on batts/similiar and not the expensive spf options, I would assume smaller is not necessarily worse, to include running in the summer.

Hoping someone here runs a closed cell spf room and can share their experience with cooling/heating requirements

90% of your heat load is in the room, lighting, dehumidifier and such. Insulation keeps it in.

Also, it's always ok to oversize a minisplit since they only run as hard as they have to. Then you also have room to handle excess ambient heat or the addition of lighting, co2 generator or whatnot.

I found this motorized 6" vent for intake air.

Do you think 6" will be a sufficient intake for a 9x9 room?
What side would you recommend for for exaust?

Thanks
David

Assuming 8 foot ceilings you want about 1000 CFM (after any losses).

dalack said:

I found this motorized 6" vent for intake air.

MD6TU - Broan MD6TU - 6" Automatic Make-Up Air Damper w/ Pressure Sensor Kit

Broan MD6TU - 6" Automatic Make-Up Air Damper w/ Pressure Sensor Kit - Designed to provide the best technology to equalize pressure between indoors and outdoors, while providing effective ventilation for a cleaner, healthier home. Eliminate gases, smoke or particulates generated from naturally...

www.supplyhouse.com

Do you think 6" will be a sufficient intake for a 9x9 room?
What side would you recommend for for exaust?

Thanks
David

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Depends what kind of exhaust fan. An in-line 8” pulls 900cfm or so and the cheap exhausts pull way less than that.