Thanks guys,
As far as the intake/exhaust I really don't have one because the whole front of my grow has been open. I have just been sliding a large piece of styrofoam in front of it for reflective purposes. But now that I will be flowering I will need to seal for light of course so it gets a little tricky. I have had a computer fan hanging in there blowing on the plants continuously and since the top has been open they've gotten plenty of fresh air.

Not sure how I will cover the front which is actually more like 6 feet tall by 18" wide. Any ideas? A tarp with hooks ? Velcro?

Also, if I leave a hole at the top of my grow and have one at the bottom too will that be enough to draw new air by letting the heat rise and pull new air in from bottom? I would still leave the fan in there to move the air around of course, but if I SUCK air in then it will get very cold in there very quickly 'cuz the space is so small.
I also thought about sucking the air out from the bottom of the grow and in from the top. Figured maybe this would pull the warm air from the lights down to warm the plants and the soil?
The space is too small for an actual heater and if I have to heat my whole shed then it becomes REALLY expensive.

So in summary, I figured I will line the grow with reflective insulation material, and then try to just let the heat draw new air from bottom and out the top... or the reversed fan option I mentioned above... not sure which would keep it warmer?

Lastly, I thought about wrapping my pots in like a 20 or 30 watt propagation heating mat as I hear that if I keep the roots warmer then the plants can handle more cold.

Sorry to be so long winded.... any thoughts from you guys are really appreciated.
Bulster Reviewed by Bulster on . Flowering advice please... OK, got a few questions for the next stage of my grow. Feel free to just answer the ones you are knowledgeable in. I am growing two MK-Ultra's and Two Sour Diesels in soil for personal medicinal use in a space that's roughly 18" by 24" but with 5 feet of vertical space. Will be using only 200 watts of CFL for flowering (~12000 usable lumens) Plants look kind of like a SOG since I have been doing LST from early on. I'd say I have about 15-20 grow tips that are all about 8" tall. 1. At Rating: 5