I installed a used Rinnai direct vent propane gas heater I bought on craigslist for $200, it has a digital thermostat with clock and programmable if needed. I had to pay for professional installation (not diy on gas, thank you very much) so that was an added cost but living in Vermont heat is not an option. I was temporarily using an electric space heater but they terrify me, but I might use an electric oil-filled register heater if I had no other choice.
I am using the heater to heat the room, and then the tent draws heated air in by the passive intake of the inline fans. This is my first winter, so after a bit of experimentation with ventilation, I found that I need two inline fans on my 4x4 tent to control the heat without losing too much out the window.
What I found works best is I have a 4" AC Infinity fan exhausting air from the top of the tent into the room, I keep this on a low #3 setting running continuously throughout the day with lights on. This fan will shut off if the tent gets too cold but so far that is not an issue. This fan keeps the air moving and refreshing in the tent. I have a second AC Infinity 6" fan with carbon filter that exhausts the tent and vents directly outside, this fan is set to kick on at #5 when the heat gets up to 80 degrees F.
Since this fan vents outside, this keeps the room from getting too hot and also keeps the humidity down while also forcing fresh air into the room and tent (by exhausting out the window). This way, I am able to use the heat from the lights on in the tent to keep the room warm without running the propane heater, exhaust excess heat out of the building, keep fresh air passive intake and maintain continuous recirculating air without getting the tent too cold or too hot.
When the lights go out, I keep the 4" fan on #5 exhausting into the room, and the 6" fan is set to exhaust outside when the humidity in the tent gets above 60%, this keeps the room and tent from getting too humid without a constant exhaust losing heat out the tent. I set the propane heater to 72 degrees F with the lights off, and it keeps the tent at about 70 degrees F.
It might seem elaborate but it is working perfectly.
