An electric space heater does not give off CO2. People do!
What is happening is that you are closing up all the windows, and the CO2 you generate is getting stuck in the house.
One thing that really helped me on PH was putting an air-stone in the sump, where the input is from the outside or garage,
not from the main house.
I used a kill-a-watt measuring tool and in the winter, it was definitely almost all heaters.
I have an insulated acrylic tank already, so hard to improve that.
There are some fun solar heater ideas, but the usual fix is a gas heater or electric heat pump.
What is happening is that you are closing up all the windows, and the CO2 you generate is getting stuck in the house.
One thing that really helped me on PH was putting an air-stone in the sump, where the input is from the outside or garage,
not from the main house.
I used a kill-a-watt measuring tool and in the winter, it was definitely almost all heaters.
I have an insulated acrylic tank already, so hard to improve that.
There are some fun solar heater ideas, but the usual fix is a gas heater or electric heat pump.