In past building practices, each part of a building was considered to be an individual component. Buildings were not built to work together as a single system, and this caused problems.

In todays building practices, each component needs to work with all the other components of the building. Building a house with the house-as-a-system approach builds a more durable, more comfortable, and more energy efficient house. The major component categories of the house-as-a-system approach are:

• The Building Envelope
• The Mechanical Systems
• The Occupants

Each individual component can influence the performance of the system as a whole.