Recently, I've been measuring the CO₂ concentration during multiple nights and the levels in the bedroom where I sleep are very high and unhealthy (over 1600 ppm).
I get a high concentration only when I'm sleeping, so I assume that the CO₂ comes from me. Since the windows are shut and the door closed, the CO₂ gets trapped.
The problem is that during the summer, the temperatures outdoor are over 95 F (35 C) with high humidity, and I have the airconditioning running inside. If I open the window, the heat comes in very fast and then the AC has to do extra work, which means waste of money and resources. And it's the same situation during the night.
How do I get rid of CO₂ inside the house without opening the windows when the weather is hot?
EDIT: After reading all the great suggestions, I have tried a new measurement with the device far away from my bed, so it will not be affected by my breath. I also checked for timers and couldn't find any. Last night I closed the window and the door at around 11 PM and the concentration started to slowly increase. During the night, the CO2 levels increased significantly (see graph below). In the morning, I opened the window and it slowly started decreasing. I have no doubt that there is a lot of CO2 in the room. So my question stands. How to get rid of CO2 or any other gases/vapors for that matter, in a hot, humid climate. Is HRV the only solution?