NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competences and with regard for appropriate balance.

This study was supported by a Master Services Agreement between the National Academy of Sciences and the Massachusetts Technology Collaborative (awarded November 2004); Grant 1906 between the Barr Foundation and the National Academy of Sciences (awarded September 2004); and funding from the Connecticut Clean Energy Fund (awarded April 2005); the Kendall Foundation (awarded March 2005); and the U.S. Green Building Council (awarded February 2005). Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the organizations or agencies that provided support for the project.

Copies of this report are available from the Board on Infrastructure and the Constructed Environment, National Research Council, 500 Fifth Street, N.W., Room 943, Washington, DC 20001; (202) 334-3376.