Installing extended eaves shades the exterior wall and reduces the energy needed for cooling the home. The rule of thumb calls for a total eave length (including extension) of 18 to 24 inches. Installing extended eaves also provides weather protection.

Installing extended eaves shades the exterior wall and reduces the energy needed for cooling the home. The rule of thumb calls for a total eave length (including extension) of 18 to 24 inches. Installing extended eaves also provides weather protection.

Application: From a resource-efficiency standpoint, extended eaves protect the exterior walls of the home from rot and decay, extending their life. This in turn lowers pressure on limited sources of raw materials because replacement materials will not be needed. Similarly, not having to dispose of ruined building materials lowers the pressure on local landfills, as well as the embodied energy of the home.

From an environmental-responsibility standpoint, extending the life of the building materials made of wood protects the environmental services forests provide. A similar environmental benefit is gained by avoiding the production of stains, sealants, and other toxic applications to retard the growth of mold, rot, and other forms of decay. This leads to benefits in a healthier living environment. Mold and mildew can contribute to poor indoor air quality. Unfortunately, many of the applications and chemical treatments used to prevent mold and mildew also threaten indoor air quality.

Lastly, properly designed extended eaves improve the energy efficiency of a home by blocking the high summer sun from entering the windows, while allowing lower winter sun to enter and provide free heating.

Benefits: Extended eaves save on air-conditioning bills. Extended eaves block summer sun, reducing the need for mechanical cooling (fans or air conditioners). They shield furnishings and building materials from exposure to the sun's ultraviolet rays. Extended eaves protect the home's exterior from the elements, lengthening its service life while also reducing the potential for health risks caused by unwanted moisture.

Challenges: Extended eaves cost more and use more material than conventional ones. To be effective, the roof design must take into account the solar path.

On the 'Net: www.susdesign.com/overhang/index.html

Information provided by Earth Advantage, an Oregon-based nonprofit organization that specializes in green building. Info: www.earthadvantage.com