Cold air intake

[Booja]

A new member with my first question. I'm in the Michigan U.P. and started my first grow in the beginning of the summer but ran into a few pitfalls that I think I have managed. A long story cut short is my current grow should be ready for harvest right around October 1st, which happens to be the first normal day of frost. The grow is inside a 32x32 tent with LED lighting, but placed inside an unattached garage with no heating. I would like to start a winter grow in the same location.

Last winter temps reached as low as -34F but was usually in the low single digits for extended periods of time, ie weeks. We went months with daytime highs below freezing. I can not bring the grow into the house, so the thought is to build a roughly 4x8 grow room in the garage and heat it with an electric baseboard heater. With insulated walls I think I could regulate the inside temps without costing an arm and a leg, except for one thing.

If I need to exchange inside and outside air I would have to pull in unheated air. To me, that sounds like death to my girls and a hole in my wallet trying to fight it, or am I wrong? An alternative would be to place my existing grow tent inside the grow room and recirculate the heated air into the tent. I'd still have to recirculate the room air but would burn a hole in my wallet trying to heat it. Am I not finding winter grow info because it's just not done?

I don't smoke much and my current grow, if all goes well, should provide me plenty for the year, so I don't really need to grow in the winter. I've been smoking for 45 years and never had more than a 1/4oz at a time. This is mostly for grins n giggles because I can and find it enjoyable to grow. A winter grow just may be a pipe dream but at least the grow room could extend my season.

 

[The Bard]

First, welcome to the 420 forums!

If I understand right, you are thinking about building an insulated room inside your un-insulated garage, is that right? Just a thought... if you have a thermostat-controller on the exhaust fan in your tent, or maybe a timer, couldn't you pull air from the garage space into the grow room at short intervals? I imagine that the garage will be warmer than the outdoor air, but not as warm as the air in the tent? As long as you have good air movement inside the grow room, I don't believe that you would need to constantly refresh the air inside of it. Perhaps a short burst of the exhaust fan for a few minutes once every couple of hours? Of course, if you start running into humidity problems, you might need to refresh the air more often.

That all being said, if your only option is the garage, it might just be easier/less expensive to finish up your current grow, and then wait until spring to start over when the weather is milder?

Probably not much help, but just trying to brainstorm a bit with you.

Either way, welcome again, and good luck with the harvest!

 

[Weaselcracker]

I operate with a similar situation in that I grow inside an insulated 8x12 room and draw my fresh air from the outside world.
My winter temps aren't as cold as yours in winter but I still have stretches of freezing weather down to about -10°C.
The difference is that I’m using mainly HPS lighting. It heats my grow.

My vent fan is hooked to an inline thermostat and kicks in when the temps get up to about 80°C, pushing hot air out the top vent and and drawing fresh cool air in through a passive vent down low.
During lights out there generally isn’t any need for cooling or for air exchange and the fan doesn’t come on. Temps drop a bit during the ‘night’ but if your place is well insulated they won’t drop very much.

HID lighting is cheap these days and still grows better bud than most of the LEDs. In your situation it sounds like a good fit. You can run both at the same time and if things get hot in summer just switch to LED only.

I also have a couple quantum board LEDs in flowering. They’re good if you’re trying to avoid heating things up. But in your case HIDs will be much cheaper and more efficient than paying for both LEDs and electric heat. The HPS lights also grow bigger buds. The bud under the QBs seems a little denser, but in general I think the LEDs are a bit overrated for the high price.

 

[Booja]

First, welcome to the 420 forums!

If I understand right, you are thinking about building an insulated room inside your un-insulated garage, is that right? Just a thought... if you have a thermostat-controller on the exhaust fan in your tent, or maybe a timer, couldn't you pull air from the garage space into the grow room at short intervals? I imagine that the garage will be warmer than the outdoor air, but not as warm as the air in the tent? As long as you have good air movement inside the grow room, I don't believe that you would need to constantly refresh the air inside of it. Perhaps a short burst of the exhaust fan for a few minutes once every couple of hours? Of course, if you start running into humidity problems, you might need to refresh the air more often.

That all being said, if your only option is the garage, it might just be easier/less expensive to finish up your current grow, and then wait until spring to start over when the weather is milder?

Probably not much help, but just trying to brainstorm a bit with you.

Either way, welcome again, and good luck with the harvest!

Thanks for the welcome.

Building an insulated 4x8 room inside of an un-insulated garage is correct. The temps inside the garage would be basically the same as outside air temp. Heating the room with a thermostat controlled electric baseboard heater would be simple. Humidity in the winter historically runs in the mid 70's percent range. I wonder if entering the room twice a day to water would introduce enough fresh air to work?

I operate with a similar situation in that I grow inside an insulated 8x12 room and draw my fresh air from the outside world.
My winter temps aren't as cold as yours in winter but I still have stretches of freezing weather down to about -10°C.
The difference is that I’m using mainly HPS lighting. It heats my grow.

My vent fan is hooked to an inline thermostat and kicks in when the temps get up to about 80°C, pushing hot air out the top vent and and drawing fresh cool air in through a passive vent down low.
During lights out there generally isn’t any need for cooling or for air exchange and the fan doesn’t come on. Temps drop a bit during the ‘night’ but if your place is well insulated they won’t drop very much.

HID lighting is cheap these days and still grows better bud than most of the LEDs. In your situation it sounds like a good fit. You can run both at the same time and if things get hot in summer just switch to LED only.

I also have a couple quantum board LEDs in flowering. They’re good if you’re trying to avoid heating things up. But in your case HIDs will be much cheaper and more efficient than paying for both LEDs and electric heat. The HPS lights also grow bigger buds. The bud under the QBs seems a little denser, but in general I think the LEDs are a bit overrated for the high price.

I've been focused on extreme cold versus excessive heat. You bring up a good point about working that problem backwards. I've only used LED so heat hasn't been an issue for me. Switching to HIDs makes sense.

 

[jimbobdaz]

I have done the same as you, i converted my single skin concrete block garage into a grow room, I've only just completed my first grow in there but as weaselcracker said i don't expect any issues as I'm using hid's. How are you planning to insulate? I put up a false stud wall filled with 50mm rockwool, 9mm ply and 15mm plasterboard on top... seems to do the job nicely, no need for a tent, use the entire space to grow

 

[multiVortex]

Not sure of the height you will have to work with, but I would build the floor up about 6in off the concrete garage floor, and then insulate in that gap between. That floor is like a big heat sink, or cold sink in this case.

For insulation, it may be worth using the spray foam. More upfront, but man that stuff is very good and worth it in the long run.

Maybe you could try something like a 10x10, but then build a 5x5 or 4x4 inside that?

That would give you a buffer between, and you could exhaust the grow into the space. That heats up the surrounding area, and adds more insulation buffering to the inner grow room. Then if you still need some additional heating, you can add a small heater to the inner 4x4 and have less space to warm up.

Have you thought about adding a wood stove to the garage? Even running it low would still at least keep the inside of the garage warm enough to where the HID light should handle the rest.

While this is a pretty fun discussion, I can't say the end result will be very practical overall. Going from -34F (about -32C for our metric friends) up to normal growing temps is a big swing, even with a well insulated room. Can't say it will be very cost effective, but certainly could be a good time.

 

[TurboBucket]

Every season has it's own unique challenges. That's the name of the game. Controlling environments is not cheap the more control you want the more it will cost. A few plants in a small space with low temps won't use as much co2 as they will with warmer summer temps.

Co2 bags cost $40-50 buy one in October and another one around December January and you'll have plenty of air for plants.

I like heat mats under the containers, keep the roots above 50°f and they'll be happy even with 40° temps over night.

Get a dehumidifier to keep up with the water they breathe out.

 

[Carcass]

They're a little pricey,but they make inline heaters-you could use
one on your air intake-look up "Hotpod" on amazon
You wouldn't need the baseboard heater-just heat the tent instead of the whole room.

 

[Bush Doctor 77]

I like heat mats under the containers, keep the roots above 50°f and they'll be happy even with 40° temps over night.

^^^^This^^^^ Welcome. I'd go with HID for the heat, and run them at night when ambient temps are coolest. I've got a thermostatically controlled exhaust fan in my greenhouse, and that is the way to go. When it's that cold, RH probably won't be a problem, but not sure.

 

[TurboBucket]

Colder air holds less water. I.e. 70°air 50% Rh equals 60°air 60%rh still the same quantity of water in the air. (Only an example I don't have a psychrometric chart in front of me right now).


Before you get all out of hand selecting lighting sources for this season, are you only going to grow in the winter? Or year round?
HIDs will likely require AC in the summer.

I'd suggest an air source heat pump but you probably won't be able to use it for the coldest 4 months of the year where you're at. There are a couple available from a small company out of Canada that will run heat in your climate but they aren't cheap and require professional installation. Under the bridge we still only get about 8 months of heat with the most common ones.

 

[Booja]

Growing is an enjoyable hobby right now. The plan is to grow year round which is really kind of dumb as I'll only consume a small fraction. Like I said, it's an enjoyable hobby.

I've installed split systems, they're not that hard but way above anything I want to spend cost wise. Short of a heat wave a couple of weeks ago I haven't had any problems with the LED setup I'm using. Dealing with cold will be different.

Insulation would be owens corning ala pink panther between 1/2 inch osb and 2x4 studs. If I keep my height at 8 feet or below it not only makes material easier to fit (4x8 sheets) but gives me 2 feet of space above to store my portable ice fishing shanty.

Hotpod = $$$=bad. I'm going to throw too much money at this already. I'll pass on the wood stove, feeding the dragon and temp fluctuations don't sound appealing. A rocket mass heater would be a better alternative. I wanted to build a walapini but a high water table and lack of space kinda nixes it.

I'm thinking weaselcracker and turbobucket have the right idea. If I get this thing off the ground I'll do a journal.

Thanks