A method of cooling a rack of heat dissipating components comprises cooling air, and porting the cooled air into a volume in front of the rack from above the volume. The method further comprises moving the cooled air from the volume in front of the rack to a plenum at a rear portion of the rack to pressurize the plenum. The cooled air is moved with an air mover disposed at a bottom portion of the rack, The method also comprises flowing air from the pressurized plenum past or through heat dissipating components in the rack to the volume in front of the rack, by force of pressure in the plenum through air-directing ports in the plenum. The air may be flowed through the heat dissipating components, around the heat dissipating components, or both. The method further comprises drawing warm air from an upper portion of the volume in front of the racks to cool it again.