fresh air

if i built a grow room outdoors and its cold out and i want to keep temp up how to i pump in fresh air thats not cold air and same as summer when i want temps down do i keep from pumping in hot air. it gets real hot here and real cold here. thanks for any suggestions

a vent with an flap to open/close(never fully closed) + heater or small ac.

a vent with an flap to open/close(never fully closed) + heater or small ac.
also insulate.

cooltube with splitter that puts heat into the room - if too much open the splitter more to dump more outside.

Run your lights at night when temps are lowest and get a mini space heater. Set the thermostat on the heater to click off when temps are where you want them. The heater will keep temps from going below where you set it. For summer you can use a 5000 btu window a/c that has the nob controls not digital. This way when you hook a timer up it will come back on.