Infiltration Ventilation

Infiltration occurs when air comes in from the outside through cracks in the walls, openings, and around doors and windows. Infiltration will most likely not let enough air in for good ventilation, and will increase energy bills, and cause a home to feel too cold or too hot. Combustion appliances, such as gas stoves and fireplaces will burn air, and air exhausted through other means will leave only infiltration as the only way that makeup air can enter the house. Often, homes that are under negative pressure suck in air through infiltration. Negative pressure can be a problem in two ways:

Soil gases are sucked in as makeup air. These soil gases come from the ground, and can be contaminated with radon, or other contaminants, and will also draw in moisture, leading to mold, mildew, fungi, and dust mites.

Backdrafting occurs because air will take the path of least resistance and can come in through the chimney. Backdrafting can cause carbon monoxide, which is deadly, or other combustible gases to enter the home.