Modern construction standards like Passive House call for an extremely well insulated and air tight building envelope. Because you're no longer losing conditioned air to drafts, they then use a system that constantly brings fresh air from outside, runs it through a heat exchanger to extract most of the heat (or cool, and in some cases moisture) from the conditioned air before it's exhausted. Generally you constantly pump fresh air into the living areas and bedrooms and exhaust air from the bathrooms and kitchen (places with lots of moisture and smells).