After reading lots of these types of articles I reached the conclusion that opening (multiple) windows for a few minutes a couple times a day is a must, no matt

After reading lots of these types of articles I reached the conclusion that opening (multiple) windows for a few minutes a couple times a day is a must, no matter how cold. It also helps with CO, particulates from furniture, radon, viruses etc. Outdoor air is of course not that clean, so my solution is to run a small air purifier. It's quiet enough that I run it non-stop and rarely notice it.