Abstract: An environmentally-controlled crop storage building consisting of: a floor having a length and a width, the floor resting on compacted soil; an air-carrying plenum extending the length of the floor within the compacted soil, the plenum having a bottom, plenum side walls, and an open plenum top communicating with the building's interior; a fan adapted to force air through the plenum; a plurality of air-carrying flumes extending the width of the floor within the compacted soil and intersecting the plenum; a plurality of flume covers having a number of apertures adapted to allow air forced through the flumes by the fan to enter the building; and a plurality of plenum covers adapted to close off the plenum from the building's interior.