What's up with HN and heat pumps? I've seen this multiple times over multiple years. Yes, heat pumps works when it's cold, is that really news? Why?

HN is weird when it comes to heat pumps.

Here is a fun one: You can increase the overall efficiency by using a heat pump on the exhaust air. That way heat from e.g. your PC can be used multiple times instead of just being thrown away. And yes, active ventilation is needed in well insulated houses as they are quite airtight.