house is being built down the street. Every morning for several months the entire neighborhood is awakened by the sounds of constant banging from the construction site. Workers, vehicles and machinery come and go in a seemingly neverending flow. And every day, neighbors must pass the unsightly work area, where dumpsters overflow with discarded building materials.

This is the typical scenario when a house is being built stick by stick (as in typical 2 x 4 framing). But modern homebuilding is undergoing a transformation. In recent years the use of alternative building systems has become commonplace, not only because of the unsightly nature of traditional on-site construction, the waste it produces and the obvious disturbances this type of building causes to a community, but also because the use of alternative building systems results in high-quality homes, and saves time and, in many cases, money.

Simply put, building systems are construction methods that include components constructed in a factory. The words "prefabrication" or "prefab" are often used to describe these systems, and the terms "building systems" and "prefab" are often confused, but essentially they are synonymous.

There are many types of building systems available to homeowners, builders and architects. Some of the more common systems are structural insulated panels (SIPs), insulating concrete forms (ICFs), panelized construction and autoclaved aerated concrete (AAC).

But how do these building systems compare, and how do you know when to use which system? On the following pages, we'll take a closer look at four of today's most popular building systems.