A modular animal enclosure includes a housing comprising a top portion affixed to a base portion to form a sheltered interior. The housing includes a door aperture and a climate conditioning aperture. A remove ably attachable climate conditioning unit is installed over the climate conditioning aperture to facilitate a flow of atmospheric air from the exterior environment into the interior of the housing. The climate conditioning unit can variously comprise a cover assembly, a heating unit, a cooling unit and a forced air unit, and different types of units can be installed at different times. In another aspect, the bottom portion can be selectively hinged to the top portion on opposing sides of the housing to allow pivotal movement of the top portion in two opposite directions, as desired to permit access to the interior of the housing for inspection, maintenance and cleaning of the interior.