Building 4 (Heating Plant)

Building 4, known as the Heating Plant, is a central heating station built in 1939 by the Air Ministry's Directorate of Works and Buildings. It features brickwork in Flemish bond, a concrete flat roof, and an asphalt finish. The building has a square plan and is entered from the south through a tall water storage tower that is set forward from the main block. At the rear, there is an extended fuel yard with various later buildings.

The entrance front showcases the slender tower, which steps in slightly in two stages at the top to a flush parapet, and reduces in plan size at the rear to form the main stack. A central door with a flat concrete canopy is set in recessed brick jambs below an extended blind brick panel, which is also repeated on the sides. The main block features three 2-light steel casements with horizontal bars on the sides and rear, positioned at mid-height, along with one casement to the left of the tower. The building is finished with a plain concrete coping on a brick soldier course, while the wall enclosing the fuel yard is rendered.

Although the interior was not inspected, the design of the Heating Plant reflects the influence of the Royal Fine Arts Commission on RAF buildings during the 1930s Expansion Period. It exhibits Art Deco characteristics and is aligned on the main axis of North Camp, which is centered on the parade ground, barracks, and Institute. Duxford is noted as the finest and best-preserved example of a fighter base from this period up to 1945 in Britain, featuring a remarkably complete group of First World War technical buildings alongside technical and domestic structures typical of both inter-war Expansion Periods of the RAF. The site also has significant associations with the Battle of Britain and the American fighter support for the Eighth Air Force. For more historical details, refer to the entry for the Officers' Mess (Building 45).