DIY DIY grow space-heat needed!

[GreeninNY]

Brand new grower! This summer I grew outdoors and this winter I’m looking to convert my disconnected garage workshop to a grow room. Odor control is not needed-only light, fan and heat. I have an idea for a few cardboard boxes lined with mylar with a 600-1000w led light as I am still researching lights. I have a small fan for the space-main issue is HEAT. Its got insulation from the 70’s. It’s roughly 12x15 with 10ft ceilings...looking for an efficient heater for the space. Not sure how much heat the light itself will produce.

any idea how much heat the lights will produce and any recommendations on efficient heaters?

 

[DCLXVI]

I'd highly suggest looking at grow tents. They make managing the environment way easier and are quite affordable unless you are really looking to pull off some massive grows. That's a really nice big space. I guess I want to not discourage you but just be realistic on the space and number of plants you want to grow.

Upstate NY? If you get typical cold NE winters you're probably going to spend quite a bit insulating the entire area to be able to maintain the right temps. On the low end 72f and 85f on the high. A big tent in a well insulated corner would probably work best. You'll also need to consider maintaining humidity levels. The winters can be really dry.

Maybe build a room within a room or wall off a corner and then mylar/paint the inside. If it's a concrete slab floor you'll need to insulate againt that too. The earth is an infinite heat sink.

 

[GreeninNY]

Not against a grow tent at all, I liked the boxes idea as I can add foam insulation and make an expandable & insulated space-pretty much building an expandable room within a room. The workshop itself is insulated, but it was last insulated in the 70’s as a small sculpture studio. As I understand it, grow tents are great at controlling odor, but I haven’t seen a tent that has insulation etc, I originally was going to use a tent in our house but storage space is precious. The expandable room made more sense when odor control isn’t a major issue. If tents are great at temp control in cold environments I’m all ears!

 

[yak22]

I think the idea of a grow tent is just to allow you to only have to try to heat a smaller area. They really aren’t insulated per se, but they could help keep whatever heat you generate in the right place if that makes any sense.
for me, I have a tent in an insulated garage where I keep a gas furnace on all winter at 40 degrees. Just to keep the area from freezing. Then I’ll plan to put a small oil filled electric heater in the tent itself to make up the extra heat that may be required. Not sure if that helps.

 

[GreeninNY]

I think the idea of a grow tent is just to allow you to only have to try to heat a smaller area. They really aren’t insulated per se, but they could help keep whatever heat you generate in the right place if that makes any sense.
for me, I have a tent in an insulated garage where I keep a gas furnace on all winter at 40 degrees. Just to keep the area from freezing. Then I’ll plan to put a small oil filled electric heater in the tent itself to make up the extra heat that may be required. Not sure if that helps.

I have a make-shift tent idea with an ikea shelf and some emergency blankets I have from boating safety kits.

that said, a tent is less than a light! No issues buying one if needed. Already have an oil radiator to heat the space.

 

[Bob's Auto's]

Wouldn't you be better of with building something yourself which you can isolate? I guess the better it's isolated the less $$ you're putting in your grow keeping it up to temperature.

 

[GreeninNY]

Wouldn't you be better of with building something yourself which you can isolate? I guess the better it's isolated the less $$ you're putting in your grow keeping it up to temperature.

I use the shop during winter for other things. It’s already heated intermittently-not a leap to make things more permanent over winter.

 

[Rapha El]

here's not a solution but an additional trick for your arsenal for the fall:
* get yourself a temperature controlled fan and use that as extraction for your growspace, be it a tent self built box or whatever.
* set your threshold temp to 80 and have the fan running at 0rpm otherwise
* set your light shedule so they are off during the warmest part of the day and are on at night
* add a oscilating fan that circulates the air inside the growspace, must have

now you're heating your tent with your lights, only extracting (taking in new, cold air) when it gets too warm and using the internal fan to diffuse any temperature cold/hotspots resulting from intake/extraction.
plus it'll smooth out any additional heating you might be throwing into the shop.

 

[Olderfart]

here's not a solution but an additional trick for your arsenal for the fall:
* get yourself a temperature controlled fan and use that as extraction for your growspace, be it a tent self built box or whatever.
* set your threshold temp to 80 and have the fan running at 0rpm otherwise
* set your light shedule so they are off during the warmest part of the day and are on at night
* add a oscilating fan that circulates the air inside the growspace, must have

now you're heating your tent with your lights, only extracting (taking in new, cold air) when it gets too warm and using the internal fan to diffuse any temperature cold/hotspots resulting from intake/extraction.
plus it'll smooth out any additional heating you might be throwing into the shop.

Those plants need their CO2 though, so if the extraction fan is off for too long, they will be starving.

I have puzzled a lot over this. I have not been able to find a decent reference as to exactly how much air exchange is needed. Too many of the "guidelines" are from the fan companies, who obviously have an axe to grind in the air exchange department. The suggestion at Royal Queen Seeds is to fully replace air in the growdrobe once per minute. I find it abidingly unlikely that plants would substantially reduce available CO2 in one minute, but am still looking for test results to document measured changes during different exchange rates. If anyone has a link, my finger is poised.

 

[Bruce Campbell]

Those plants need their CO2 though, so if the extraction fan is off for too long, they will be starving.

I worked through the numbers, but doesn't seem like you'd need much ventilation to provide the necessary CO2. From what I could google, most of plant water use is for transpiration and not photosynthesis. Humidity control may actually end up still governing your ventilation flow (and the associated heating needed for the incoming air).

Details are below for estimating CO2, and you can adjust them for your number of plants, etc. I haven't looked at ventilation needed for humidity control, though.

Estimating Air Flow for CO2 needs:

You can ballpark CO2 needed if you know your water consumption rate and the transpiration ratio for the plant species. The transpiration ratio is basically the ratio of water lost to transpiration (to move nutrients through the plant) vs. the water consumed in photosynthesis (i.e., combined with CO2).

I haven't found those ratios specific for cannabis, but they can be pretty high for some plant species - google says usually around 99% of water is transpired, only 1% is actually used in photosynthesis and combined with CO2.

(If anyone can find those ratios for cannabis, let me know.)

But, the equation basically works out to be:

(122 CFM of air) x (% water used for photosynthesis) x (L/day of total water that you use).

Let's say you have 6 plants using 1 L (each) every 3 days, and assume 10% goes to photosynthesis.

Then, they would be using 122 x (10%) x (1 / 3) x 6 = 24 cfm of total air, which isn't all that much.

Heating dry air is basically:

0.321 W per CFM per °F (difference between intake and exhaust air.

So, lets say 30 CFM, 30 °F outside air, 80 °F in tent:

0.321 x 30 x (80-30) = 481 W heating needed for the incoming air.