For example, an architect might specify that an eight-inch thick poured concrete foundation contain a certain amount of fly ash in the mix. Or the architect might specify that the concrete contain fly ash in the mix and that the wall thickness be reduced to six inches. While both ideas are resource efficient, only the latter idea reducing the materials used by reducing the wall thickness is source reduction. Source reduction can result in a domino effect that may not be immediately obvious. In addition to reducing the amount of concrete used, you are now able to reduce the overall size of the building without reducing the usable square footage.
Material use is reduced in each subsequent step on the construction process.
By reducing the wall thickness you can construct a building with a smaller footprint but equivalent square footage. Smaller buildings use less material less framing material, less wiring, less sheathing, less insulation, less siding, less drywall, less paint, etc. Certain designs are inherently more resource efficient and embody source reduction principles. For example, materials used in salt-box or gambrel roof designs serve double duty. They are both roof system and wall system.