A system to condition air for an enclosed space , the system comprising: a plenum for supplying air to the enclosed space, the plenum having an outdoor air inlet , a return air inlet , and a supply air outlet in fluid communication with the enclosed space, wherein the outdoor air inlet and the return air inlet selectively open and close; a cooling unit comprising an evaporative cooler and located external to the plenum and the enclosed space, the cooling unit configured to selectively circulate a cooling fluid to reduce a temperature of the cooling fluid; a coil disposed inside the plenum and configured to selectively circulate the cooling fluid through the coil to condition air passing through the coil; a return air duct in fluid communication with the enclosed space, the return air duct configured to selectively deliver return air from the enclosed space to at least one of the return air inlet and an exhaust air outlet ; and a system controller configured to operate the system in an indirect mode wherein the return air inlet is open and the outdoor air inlet is closed and return air is cooled by the coil; and a direct mode wherein at least one of: the outdoor inlet is at least partially open and a mixture of outdoor air and return air is directly supplied to the enclosed space; and the outdoor inlet is open and the return air inlet is closed and return air is delivered from the enclosed space to the exhaust air outlet and outdoor air is directly supplied to the enclosed space. a plenum for supplying air to the enclosed space, the plenum having an outdoor air inlet , a return air inlet , and a supply air outlet in fluid communication with the enclosed space, wherein the outdoor air inlet and the return air inlet selectively open and close; a cooling unit comprising an evaporative cooler and located external to the plenum and the enclosed space, the cooling unit configured to selectively circulate a cooling fluid to reduce a temperature of the cooling fluid; a coil disposed inside the plenum and configured to selectively circulate the cooling fluid through the coil to condition air passing through the coil; a return air duct in fluid communication with the enclosed space, the return air duct configured to selectively deliver return air from the enclosed space to at least one of the return air inlet and an exhaust air outlet ; and a system controller configured to operate the system in an indirect mode wherein the return air inlet is open and the outdoor air inlet is closed and return air is cooled by the coil; and a direct mode wherein at least one of: the outdoor inlet is at least partially open and a mixture of outdoor air and return air is directly supplied to the enclosed space; and the outdoor inlet is open and the return air inlet is closed and return air is delivered from the enclosed space to the exhaust air outlet and outdoor air is directly supplied to the enclosed space. an indirect mode wherein the return air inlet is open and the outdoor air inlet is closed and return air is cooled by the coil; and a direct mode wherein at least one of: the outdoor inlet is at least partially open and a mixture of outdoor air and return air is directly supplied to the enclosed space; and the outdoor inlet is open and the return air inlet is closed and return air is delivered from the enclosed space to the exhaust air outlet and outdoor air is directly supplied to the enclosed space. the outdoor inlet is at least partially open and a mixture of outdoor air and return air is directly supplied to the enclosed space; and the outdoor inlet is open and the return air inlet is closed and return air is delivered from the enclosed space to the exhaust air outlet and outdoor air is directly supplied to the enclosed space. <EOS>