[2rsf]

All new houses here have mechanical ventilation, usually with heat recovery and heat pumps but without filtering (excluding the heat pump's coarse filter for dust).

I got curious and read a little, it is generally accepted here that higher pressure in the house can actually lead to mold, maybe because there is no moisture control and it is expected that some of the moisture generated in the house will be driven into the walls, probably assuming the walls are not perfectly sealed. On the other hand air pollution in Sweden is a non-issue, except maybe for a couple of streets in Stockholm.

[valenterry]

Yeah that makes sense - if you have clean air then why would you need to filter. :)