Building a box and have some cooling questions...

[Green Reaper]

Hi there,
I am designing a 4 X 4 X 7 box for my garage. This website has been an invaluable source of knowledge to me and being so I thought I would bug you good people with a few concerns I have.

1. 7 feet high and 4 X 4. Of course, the light will take up a good foot of height, and it will be on casters so I think I'm looking at a good 5.5 - 6 vertical feet of space. My first question is weather to go with a 600 or 1000 watt light. I've got a pretty good green thumb but I've never done box / cabinet growing or any indoor MMJ growing at all. I know that they both will create a ton of heat and I would like to keep my box around 70 degrees. I'm definitely buying some sort of AC unit to duct into the box but can't decide weather to go portable or to go with a cheaper, analog window unit (I read that the digital ones do not reset in power outages).
I also need to know if a small unit would provide sufficient cooling power. I was thinking if the unit could control the heat from the 1k light, then why not just rock 1k? Would it help if I ducted the AC into the box AND into an air-cooled hood? When the AC exhausts, I've read that it can smell like ganja, and be super hot, so I was going to use insulated ducting, make a carbon filter ,and get a fan. Smell is a MAJOR concern where I am located. I know these are scattered questions haha.

2. I live in a mountainous region... There's really only four super warm months here between May and August. I'm doing this in my garage so how hard would it be to pump outside air in? How much cool air at what rate needs to be exchanged in and out of the box to deal with 1000 watts? And 600 watts?

3. I've heard if you can flower around 65 degrees, this can increase yield? Is there any truth to this?

Thanks so much dudes! As soon as I get this going I'll post pics at every step...

 

[TorturedSoul]

The 1kW fixture would better fit your square-footage, but will generate more heat.

Do you have a reflector in mind? Most that I've seen produce their light in a rectangular footprint. With smooth, flat walls and a highly reflective(sic) surface you can of course bounce the light back from the walls to the plants, but light that directly strikes the plants (or semi-direct after it reflects off of the fixture) would seem to be more productive.

DEFINITELY go with an air-cooled hood. Run ducting from outside of the box, to the light, and then outside of the box. You have just separated the vast majority of your heat from the smell of the cannabis. This, then, can be treated just like any other heat - cool it with a/c or vent it outside if you can do so in a subtle manner. I assume that your ballast will also be out of the box.

63°F-78°F seems to be a good range but cannabis will grow and flower in much warmer conditions; people have harvests from attic-grows. I don't think it's like growing peppers where production can actually stop in hot temperatures, but it will slow down as the plant has to devote some extra energy towards its own form of climate-control (transpiration). Using a highly-oxygenated DWC seems to be very helpful in such conditions by assuring that the plants have O2 available at their roots. Extra oxygenation will lead to "supersaturated" O2 levels - as the reservoir heats up, the water(sic) is able to hold less dissolved oxygen, but more is constantly being added. The roots will be much more likely to have access to the amount that they need. The DWC setup also allows the plants to uptake as much water as the plant needs for cooling action when it transpires moisture from its leaves. The warmer the environment, the more liquid is taken up by the roots. Be aware that this can cause nutrient levels in the reservoir to be more concentrated if the plant's nutrient requirements do not match their water requirements. Simple solution, add back either plain (pH-adjusted) H2O2 or a diluted solution.

With the air-cooled hood setup, you might be able to go with a venting schedule for your plants that is not continuous. This would allow you to add supplemental CO2 without worrying about it being constantly vented away. The CO2 will help the plants survive in a warmer environment, along with the somewhat elevated humidity caused by higher levels of transpiration in a sealed or semi-sealed environment. This might not give you the production boosts one normally associates with CO2 supplementation, for your lighting choices do not provide the intense levels of illumination that is often seen (lol) with such, but it will almost certainly provide you with a satisfactory harvest.

If you end up having to vent the grow box itself, yeah build a carbon scrubber. It won't need to be quite so large (capacity) since you won't be moving as much air through it as you would if not using a sealed reflector. And since the air that does pass through it will not have the (significant) heat levels that the air from the air-cooled hood will have, your carbon will be affective for longer periods between replacement.