Designing 'healthy' homes can be a bit more complicated than we think. In our endeavour to seal our homes so tightly that air conditioned air cannot escape, we may be creating 'unhealthy', smelly spaces... see this article written by Courtney Humphries for Politico. 

As with most things there is no definitive rule or answer but some kind of balance which takes into account many more aspects than is initially considered. A bit of leakage to allow fresh air is essential - the key is to maintain how much each inhabitant can tolerate without cranking up the air con too much to compensate. 

Cheers, F.