Climate Control in an Outdoor Shed

I'm in the process of putting together a shed grow to supplement my annual outdoor grow here in So Cal.

Previous threads, if you care:

• https://www.rollitup.org/t/outdoor-grower-moving-indoors.912883/
• https://www.rollitup.org/t/cob-led-lights.916870/
• https://www.rollitup.org/t/building-a-grow-room-in-an-outdoor-shed.917273/

tl;dr:

• 7x7 plastic resin shed in my backyard, up against the north side of the house. 322 cu ft interior
• 8x8 pop-up over the shed
• 4x4 tray with 5x5 Scrog screen.
• 16 CREE CXB3590 COBs (800 total watts, 341 heat watts)
• 120 CFM fan on a 4" vent and a 4" chimney, both with light blocks and dampers.
• Only growing Nov-June. Too hot the rest of the year to try and keep controlled.
• I intend to run the lights when the sun is down.

Generally speaking, the months I will be running will see highs in the 70-80 range and lows in the 55-65 range which is very manageable. Here are the weather-related events that worry me:

• Early/Late heat waves: most likely in Nov and Mar, high temps can hit 90, though not for long. Generally very dry, but we can also get some monsoon-like weather if a Pacific hurricane gets too close
• Cool/moist/rainy: California coastal weather. Temps staying in the 60s all day, but very high RH. This one is my biggest concern, as we can have 6-weeks straight of this sort of thing in April-May-June.
• Cold snaps: Very dry winter desert-type conditions. Highs in low-70s but lows down to 40.

Besides the pop-up and the shade provided by the house, I figure I need insulation, a dehumidifier, a small space heater with a thermostat, and a portable A/C.

1. Insulation: Some people go hog wild here, but I think that may be overkill for So Cal. I was hoping to get away with foam-board -- EPS or XPS. EPS also has the benefit of having a nice flat-white surface to reflect and diffuse the lights. EPS is in the range of R6-R10 depending on the thickness. XPS is a little better.
2. Dehumidifier: Will a 30-pint be enough? I was looking at the Fridgidaire, but what brand would you recommend? Can I let it drain into the reservoir?
3. Space heater: Pretty straightforward but I'd appreciate any suggestions on brand/model.
4. Portable A/C: How many BTU should I be looking at for this? I don't think it will be running frequently, but we will need it for the heat snaps. Will a 5000 BTU Fridgidaire be enough or should I look at the 7000 or 8000? Seems like a lot.

My plan is to set the A/C thermostat to 82 and the heater to 78 and the dehumidifier to 50% for the lights-on cycle and 72/62/50% for lights-off cycle.

Anyway, please fire away

Better insulation is only going to help. Grab one of these. Very easy install.
http://ingramswaterandair.com/mrcool-seer-ductless-minisplit-heat-pump-wifi-p-22613.html

Two inch rigid board insulation works fine. leave an air gap between the rigid board and the exterior, air is a great insulator. maybe a 1/2" with wood shims. Tape with reflective tape and you should be good to go. Will hold the cool in and keep the heat out, and vice versa. peace going active or passive on your heat sinks for your COB's? I would go active and use the additional fans for cooling effect with a properly sized exhaust fan up high on the roof perhaps. peace

Sorry for the late reply, work is kicking my ass.

Cronik363 said:

Better insulation is only going to help. Grab one of these. Very easy install.
http://ingramswaterandair.com/mrcool-seer-ductless-minisplit-heat-pump-wifi-p-22613.html

Click to expand...

@Cronik363 that seems huge for a 322 cu ft shed. I was thinking more like a 7-8k portable unit

VegasWinner said:

Two inch rigid board insulation works fine. leave an air gap between the rigid board and the exterior, air is a great insulator. maybe a 1/2" with wood shims. Tape with reflective tape and you should be good to go. Will hold the cool in and keep the heat out, and vice versa. peace going active or passive on your heat sinks for your COB's? I would go active and use the additional fans for cooling effect with a properly sized exhaust fan up high on the roof perhaps. peace

Click to expand...

@VegasWinner

• I was thinking on going with 4" of EPS rigid (doubling up the 2" boards). Will definitely leave the air gap. Does the air gap need to be sealed or can air flow through it?
• Any reason for reflective tape over flat white? People seem to prefer flat white for diffusion.
• I'm going with the Timber kit, which comes with passive coolers. Gonna throw some small fans on the frame to move the warm air out of there
• I was going to set up the fan to blow air in from the bottom and vent out a chimney on top. Should I put the fan up with the chimney?

Thanks for the help

sheckylovejoy said:

Sorry for the late reply, work is kicking my ass.



@Cronik363 that seems huge for a 322 cu ft shed. I was thinking more like a 7-8k portable unit



@VegasWinner

• I was thinking on going with 4" of EPS rigid (doubling up the 2" boards). Will definitely leave the air gap. Does the air gap need to be sealed or can air flow through it?
• Any reason for reflective tape over flat white? People seem to prefer flat white for diffusion.
• I'm going with the Timber kit, which comes with passive coolers. Gonna throw some small fans on the frame to move the warm air out of there
• I was going to set up the fan to blow air in from the bottom and vent out a chimney on top. Should I put the fan up with the chimney?

Thanks for the help

Click to expand...

4" is better. air gap just needs to be there, not active just passive. most rigid board I see has reflective side and reflective tape seals best. Lights sound great. passive cooling means you have to remove the hot air from the space altogether and replace with cool fresh air on a constant basis. Good negative pressure in space will draw adequate fresh air from other spaces. Use fans to pull air not push air, more efficient. air is like rope. peace

VegasWinner said:

4" is better. air gap just needs to be there, not active just passive. most rigid board I see has reflective side and reflective tape seals best. Lights sound great. passive cooling means you have to remove the hot air from the space altogether and replace with cool fresh air on a constant basis. Good negative pressure in space will draw adequate fresh air from other spaces. Use fans to pull air not push air, more efficient. air is like rope. peace

Click to expand...

Thanks for the advice. The EPS rigid I see around is either plain white or white with large annoying logos. The EPX is either blue or pink depending on the brand, also with large annoying logos.

I was hoping to keep the main ventilation fan stay near the ground, as I'm already concerned with the weight the roof has to hold with the lights (~40 lbs). I was considering building a pegged frame with 2x4s and dowels that would hold up the lights and the scrog screen, but that's a different thread

sheckylovejoy said:

Thanks for the advice. The EPS rigid I see around is either plain white or white with large annoying logos. The EPX is either blue or pink depending on the brand, also with large annoying logos.

I was hoping to keep the main ventilation fan stay near the ground, as I'm already concerned with the weight the roof has to hold with the lights (~40 lbs). I was considering building a pegged frame with 2x4s and dowels that would hold up the lights and the scrog screen, but that's a different thread

Click to expand...

for lights consider using pvc lighter cheaper, and easy to change. build a frame for the fan and mount an exhaust line out the roof gable end of you have gable ends, triangles forming the roof plane. peace

Thanks. I bought a Sensorpush temp and hygro sensor/data-logger and tossed it in my existing shed. It's also a double-walled plastic resin shed, but it does get a few hrs of sun a day, so readings won't be useful estimates during those hours. I intend to get the grow shed up with lights and water but no plants for a few days in October so I can test how it the climate changes throughout the day and make my climate control purchases accordingly.