All structures leak air through cracks, around pipes, under doors, and even through walls that aren't well sealed. This is an energy issue because cold air leaking in during the winter has to be heated, hot air leaking in during the summer has to be cooled. The "tightness" of a structure is specified by its air exchange rate, which is the number of times per hour that all the air in the volume of the structure is exchanged with outside hour. A typical house has an air exchange rate of 1 to 2, meaning that all the air in the house is exchanged with outdoor air once or twice an hour (every 30 to 60 minutes). Hard to believe, but true. Newer construction with better insulation and better weatherstripping should have an exchange rate a bit less than one. The EPA recommends a minimum exchange rate of 0.35 to avoid the build-up of indoor air pollution from cooking, cleaning products, and outgassing of chemicals from paints and carpets. Particleboard and plywood emit formaldehyde; carpet emits the yummy sounding 4-phenylcyclohexane. A typical house has enough air exchange to handle all this, but at the price of higher energy use.
© 2021 Randy Knight