Growing in Southern Cali, pointers from locals?

I am having a hard time balancing temps still. I don't like drastic temp changes. What are others doing to maintain temp in the Southland? It is easier with the 1000w HPS bulb.

Room 12'x16' (Will enclose smaller after harvest)
Cooltube (Duct to attic is completely off right now to maintain temp)
1000W MH conversion bulb for HPS socket. (Runs really cool)
Box Fan in window with an A/C vent to block the light. Minimal actual pull from box fan maybe 200CFM makes it through.
House Central Heating is partially open at night.

Pointers that could tighten this up without spending a lot of $? I can put a space heater in there but what kind of $ for elec am I looking at and will I need to bring in another ext cord? Too much amps?

you haven't said how cold the room gets during its dark hours ... down to 50, don't sweat it ... cannabis likes 70-75 best, (if you are comfortable, your plant is comfortable) ... growth slows, at cold temps, but it pretty much takes a freeze to kill it ... :smokin:

Low/mid 50's on far side of room, 62F at the plant table and using an I/R gauge creatively gets me around 70 at the plant. Dirt is 63-75 across all my plants depending on location under the light. No exhaust fan running at all but intake still on. Lights out is 12pm - 6pm. These are just good guesses of what I saw this morning and middle of night I don't have my logs here.

I think a lot of my problem is the size of the room. I should have paid attention and boxed it up to begin with.

I solved the 50's on one side of the room by opening my inlet for the central air but behind a blanket. It keeps the air from crossing the room so quickly and it mixes with the intake air. Room is 65 now and raises 70 > for an hour before lights out at 12 noon.

Not scientific but... For now it works, after harvest I rebuild my intake system, add a/c for this coming summer and put my light fan on an thermo.

Changed my name to MeJuana I didn't like LAmike.