A home is an interactive building containing thousands of individual parts and systems that need to work and perform in harmony. It is not a bunch of separate parts and systems thrown together. This can be roughly broken down into three parts: Structure, Ventilation, and Filtration.  The structure consists of the products and materials that support the home.  Ventilation is extremely important in that a home needs to be water tight, but still able to breathe at the same time.  Filtration is what maintains a high level of indoor air quality, again while still allowing the home to breathe.

The following is a diagram of a well constructed building envelope.