AC alone wouldn’t make any difference whatsoever. You need a modern HVAC system that exchanges air with the outside with something like an ERV or HRV. And even

AC alone wouldn’t make any difference whatsoever. You need a modern HVAC system that exchanges air with the outside with something like an ERV or HRV. And even before doing that you have to make sure the building is sealed and insulated properly so the air is going where you need it to go. It’s actually a fairly complicated problem that starts with the design, building materials, and construction processes of the building itself.