What do they mean by the house has to “breath”.

Usually that means that the house leaks so much air that it runs up utility bills.

Now with a tight house you might need ventatation systems and ideal a EVR (energy ventalation recovery system).

But those are CONTROL ventalation has needed. But excess from a pooring constructed house.

See buildingscience.com.

It will take you a while to find the right parts, but it has a ton of information about this.