From the skyscrapers of Manhattan to the Victorian houses of San Francisco and the shopping malls of Anytown, USA, buildings in the U.S. are remarkable for their variety. Variety in the type of building (commercial warehouse, manufacturing facility, institutional and office buildings, apartment buildings, condos, single-family dwellings, mobile homes and the like) translates to variety in occupancy and use, which in turn, means differences in energy requirements and indoor air quality concerns.