hello all, ill try to keep it brief for security...
not a newbie here....(well maybe a little..hah)

No this is not the same question as a thread with a similar title on this forum...
heres the plan:
this will be done in a region where it could see temperatures as low as below 0degrees farenheit...which is unlikely, but quite possibly will see temps in the mid to lower teens at night...and where the average temp has been about 40, and will be about 30 for the rest of winter during the day.
I want to put a potted plant in a small cab outside...
I want to make a small plywood cab with a 250w hps bulb on the inside, and the ballast on the outside...make the box light tight and add a sealant or finish to the wood, then camoflauge it up...
I am thinking about 2.5' tall x 2'wide x 2'deep...so basically a 2 1/2 foot tall rectangle, with the housed ballast attatched to the top..the box will go about a foot into the ground and have no floor to aide in heat dissipation.. so it will be 2.5' from the ground level..
the top will also be a lid on hinges, which i will completely screw to the box and unscrew when i need to access the baby to keep in light tight...
I obviously plan on doing a lot of LST (my specialty) and will probably top her pretty young...1 month @ 18/6 veg then flip her...
I was also considering putting a small cfl in there (possibly battery powered) with a switch on the outside so i can turn off the hps before i open the box so it does not draw attention, while still alowing me to keep her "awake"
This will be in a fairly discreet location, and i can play with what hours i want it on and off...it will be located right next to an outdoor outlet.
CONCERNS: air flow and heat...
I cannot use exhaust fans for this porject because concealing light will become a huge issue...however, i was thinking possibly some sort of soil aeration or something...maybe placing towlet paper rolls in the soil around the pot or running pvc from inside underground to outside....
How big of an issue will heat be from a 250w hps in the described temperatures???? do I really need to worry that much?
Oh and for the haters- I am not expecting too much weight out of this, its really just a means of keeping a (formerly) seasonal hobby going (and i cannot grow indoors again its just not an option anymore)..
Thanks