Buildings leak water and air, which is normal and unavoidable. Therefore, designers should not fixate on preventing leakage, i.e., making buildings "airtight." Because even if all cracks were sealed, buildings have doors and windows.

Instead, the designer's goal should be to A) quantify leakage, B) reduce leakage if excessive, and C) control leakage by managing air pressures with the HVAC system. "Designer" in this case means at least two people—the architect and the HVAC engineer. It also may include the builder and building official. Until the building science engineer evolves as a separate discipline, primary responsibility for addressing building leakage will probably fall to the HVAC engineer.