The whole-house approach looks at the entire house as an energy system with interdependent parts. Like a human body, when one part functions poorly it affects the performance of the entire system. For instance, the benefits of an energy-efficient air conditioner are lessened when a duct system leaks, windows don’t close tightly, attic insulation is insufficient, and humid summer breezes are drifting in under the door.

The systems approach recognizes the interaction of windows, attics, foundations, mechanical equipment, and all other components and assemblies within the home. Changes in one or a few of these components can cause changes in how other components perform. If you recognize and take advantage of this fact, and apply appropriate advances in technology to the components, you can reduce your energy costs while improving your comfort. From a builder’s or seller’s perspective, an energy-efficient home is likely to be more marketable— especially if you can show the prospective buyers your low energy bills.