Title: The Commonwealth Building: Groundbreaking history with a groundwater heat pump

In 1946, following a wartime moratorium on the construction of commercial buildings, a savings and loan in Portland, Oregon, was granted the first permit to build a new commercial office building. The Equitable Building -- known today as the Commonwealth Building -- was subsequently designed and constructed, incorporating many other ``firsts`` in the architectural, mechanical, and electrical design of commercial buildings. For example, the groundwater heat pump plant, designed by J. Donald Kroeker, has become known as the first major commercial installation of a central ground-coupled heat pump in the US. In addition to being the first large commercial groundwater source heat pump installation, the Commonwealth Building was the first building designed in an architectural style that was to become the standard for many decades. The architect, Pietro Belluschi, was a nationally recognized Portland architect. The building has become something of a legend in its use of innovative building systems technology. Throughout the intervening years, the Commonwealth Building has received credit as: (1) The first building to use a central heat pump system, coupled to the earth, in the form of well water, for both heating and cooling. (2) The first building in the United States to be constructed with fixed double-paned glazing. (3) The first building to recover heat from toilet exhaust for use in pre-heating fresh air. (4) The first building to use an exterior building system composed of aluminum sheathing. (5) The first building to make significant use of cold cathode fluorescent lighting for flexibility in tenant space layout. Within the building engineering community, the central, well-coupled heat pump system in the Commonwealth Building has received the greatest acclaim. The building was recognized by the ASME as a National Historical Mechanical Engineering Landmark in 1980. The central heat pump plant has many unique features and an intriguing operational history.