Building Energy Glossary

Air Conditioning generally refers to the process for cooling air in a space. It is most often achieved through a mechanical system that uses the refrigeration cycle to produce chilled air or water. The newly chilled air or water is then used for cooling a space.

An air handling unit uses blowers to circulate conditioned air and accepts returned air to be conditioned again. In addition to blowers, AHUs contain heat exchangers, which transfer heat between cool and warm materials. For example, when a space needs air conditioning, warm air from the space is returned to the AHU. This warm air is cooled by circulating a chilled liquid into the heat exchanger. This newly cooled air can then be blown back into the space.

ASHRAE (formerly, the American Society of Heating, Refrigerating, and Air-Conditioning Engineers) is the governing body which creates and releases the standards regarding indoor air quality, thermal comfort, and energy efficiency.

Buildings and facilities rely on mechanical systems and electrical systems to operate fixtures, equipment and controls; deliver a thermally comfortable space; and maintain a high level of indoor environmental quality for occupants. Building operations consume approximately 40% of the energy and 74% of the electricity produced annually in the United States, according to the U.S. Department of Energy. Any energy and electricity used in buildings that was generated through the combustion of fossil fuels also produces greenhouse gas (GHG) emissions. These GHG emissions directly contribute to air pollution and climate change. Climate change mitigation requires the reduction of GHG emissions through strategies such as building decarbonization.