Indoor air quality is not a vapor barrier or insulation issue. The concept the "the house needs to breath, at least in the context of allowing breathing from your indoor air-space into & through the structure is, well quite simply, a very persistant myth. If there is an air quality problem, this needs to by managed by an air management system.
remmeber, the tighter the better, but you also need to actively manage you indoor air quality. Also, if air can move into your structure from your livivg space, it can also move in reverse, carrying with it whatever has grow from the moisture that was allowed into the structure (as well as other pollutants.