Comment by malfist
8 hours ago
I find it extremely unlikely that homes are routinely at 2000-3000 ppm. That is extremely high and would mean multiple people in a small area with no air exchange for a long while.
I monitor my indoor co2, but don't take any action because it's extremely rare to be above 700 or 800. I can only remember a handful of times its reached 1k ppm. And my house should be prime candidate for co2, it was built during the era of "seal all air gaps" but before ERV or HRVs. I also use pressurized co2 to inject co2 into a planted aquarium. And my dogs are terrified of open windows so they are rarely open.
It happens a lot in efficient houses that don't cover all bases with HVAC (the vast majority of recently built houses), where the room door is closed, maybe the vents are not ideal, and there is usually no makeup air or forced air ventilation other than a furnace intake.
This change in scientific literature actually causes a ~quadrupling of recommended airflow ratios for tight homes versus ASHRAE's previous guidelines, putting strong emphasis on an ERV. Previously, ventilation needs tended to be dominated by air quality and smell, by humidity buildup, or by theoretical house parties that maxed out the system.
This ventilation adds capital expense, but it's substantially more controllable and significantly cheaper in the long run in colder climates than 'just open a window' or 'just don't build the house so tightly sealed'. Reserve the operable window for the aforementioned house party, which is out of a reasonable design envelope.
Homes in the upper midwest are well-sealed and insulated. Bedrooms can hit 2,000 ppm with two adults sleeping in them.
My bedroom regularly gets to 3000 at night, and the flat in general is around 2000. This is in the winter, when I don't open the windows for days because of the cold. The flat is very well insulated.
If we are three in my small living room in winter (around 20m2), it easily climbs above to 2000ppm in less than an hour