homeassistant

I built a new house last year and moved in this January. This is my first time living in a house that's air tight enough to have an air exchanger. Through the winter it was fine - I just left it run its own Eco mode and everything seemed good. I'm finding spring really frustrating though - most days are nice and warm and we open windows, most nights are cool and we close the windows. I don't like wasting electricity by running the air exchanger all day when the windows are open.

I've considered window sensors and a smart plug on the air exchanger, but I don't really want to install 13 window sensors.

Are there air quality sensors that are accurate, and reliable, enough for me to turn the air exchanger on whenever the CO2, or whatever it is that make a house feel stuffy, level gets high enough?

My air exchanger is a very basic "builder" model and won't do this itself. It has an air quality sensor and changes the fan level to what it thinks we need, but it won't turn off when we don't need it.