Have you noticed stuffy air in your home in winter? Do you have a perfectly good air conditioner but hate using it because it makes your indoor air smell stale? If so your home may lack adequate ventilation.
Before the energy crisis of the 1970s, homes had “natural” ventilation thanks to lack of insulation and gaps around doors and windows. These days we have much better insulation so we don’t have to lose heat – but that creates a new problem: getting fresh air into our homes.