Energy Efficiency Trends In Residential And Commercial Buildings.pdf

Population growth drove an increase in the creation of new homes from 1993 to 2005. New housing starts have averaged around 1.5 million per year from 1960 to the present, but housing is highly cyclical. Year-to-year variation is driven by mortgage interest rates and other factors including overall economic activity as measured by Gross Domestic Product (GDP). The residential housing industry is a bellwether for the economy, one of the first industries to slow and one of the last to recover from economic downturns as illustrated by the coincident troughs in residential construction and overall economic activity. Seasonally adjusted annual housing starts recently declined to less than 1 million in March 2008 after reaching a high of over 2 million houses per year during much of 2005 and 2006.

The number of U.S. buildings has increased since 1980, driven by growth in population and economic activity. A household includes all persons who occupy a housing unit, which could be a single family or townhouse, an apartment, a mobile home, or a group of rooms or single room intended as separate living quarters.

The total utility bill for energy used by U.S. buildings topped $369 billion in 2005. Energy consumption in buildings has been growing in aggregate over time. Today, the nation's 114 million households and more than 4.7 million commercial buildings consume more energy than the transportation or industry sectors, accounting for nearly 40 percent of total U.S. energy use.

The services demanded of buildings — lighting, warmth in the winter, cooling in the summer, water heating, electronic entertainment, computing, refrigeration, and cooking — require significant energy use, about 40 quadrillion Btu (quads) per year. Energy use per square foot of space is a key driver of energy consumption in buildings.