Ventilation refers to the exchange of indoor and outdoor air. Without proper ventilation, an otherwise insulated and airtight house will seal in harmful pollutants, such as carbon monoxide, and moisture that can damage a house.
To start, gases from combustion appliances, like your stove and fireplace, can accumulate in a poorly ventilated home, threatening your health and safety. Elevated levels of humidity can make cooling equipment work harder too, resulting in more costly energy bills. Most notably, excessive moisture in a home can lead to mold growth, ruined insulation, and even structural damage.