Heating, Cooling, And Ventilation

I may just answer My own question here so bare with me..


I just build a new grow room that has 2 chambers separated by a half wall and curtain. One room veg, the other flower.

I live in an area where in the winter - its COLD. the grow room is surrounded on 4 sides by outside walls.

I currently suck air through a carbon filter, through my 600watt hps and out a vent on the flower side. The flower side is connected to the veg side when the curtain is closed by an 8 inch pipe with indirect chambers to keep out light leaks.

Air comes in through a port on the floor in the veg side which is in use right now by a portable air conditioner.

My concern is winter. I really do not want to run an electric heater and still vent out the heated clean smelling air through the light. I would like to use the light heat to keep the 99% air tight room heated.
What is my best choice for retaining as much energy as possible , yet, still having enough air circulation for the plants?
When I say cold, I mean 10 deg far. for at least a month then 20-30s for 3-4 months.

Room is 8 ft L * 8Ft H * 4ft w

thanks

a couple Oil filled rads with therometers - if your referring to night time temps being cold - put your lights on during night and lights off in the day.

I have my lights on at night.
I just think it is a shame to waste that nice hot dry air going out my vent
How much new air do I actually need>?

its called a thermostat. https://www.rollitup.org/grow-room-design-setup/249275-exhaust-fan-timed-temp-controlled-2.html that should help

and here https://www.rollitup.org/newbie-central/200093-fans-making-my-head-spin.html