For the last few weeks, it has been warm enough to not heat our house much past noon (the sun heats it nicely!)

But I’ve been noticing a trend in our inside air quality that wasn’t previously an issue.

Our CO2 (carbon dioxide) levels are spiking in the early afternoon, and then go for an even higher spike in the evening.

By the time we go to bed, the CO2 levels in our house are poor (over 1,000 ppm). When CO2 gets too high in your house, you can feel sluggish, get headaches, have disrupted sleep, and other respiratory side effects. All because you need more oxygen!

We haven’t been able to nail down the cause. Why wasn’t it a problem when we were heating more?

We have two heat sources – a wood stove, and an oil Toyo space heater. Both have fresh air inputs into their combustion and exhaust outside.

We don’t have a modern air handler because they don’t work here in the winter.

So why were we not having high CO2 levels in the winter, but we are now?

I keep wondering if our house just breathes more when there is a bigger temperature difference between inside and outside? Were we getting more fresh air input because the gaps in our house let our warm air out and the cold in? And now that it isn’t as cold outside, this doesn’t happen as often because the temperature difference isn’t as significant?

Or is there something with the heating system I’m overlooking? Why would our air quality be worse when we aren’t heating?

Fortunately, temperatures have been -5 to -11C at night, so we can open the bedroom window a crack so we don’t have that disrupted sleep!

And during the day, if I just open a window or a door for 5 minutes, it fixes up the air quality.

The good news is our radon is consistently low! The average, since we got this Airthings detector (Amazon link), is 23 Bq/m3 so there is no need for radon mitigation for this house!