Abstract: A direct sidewall vent system between a fuel-burning appliance in a first space and an external atmosphere, through a wall between the first space and external atmosphere. The direct sidewall vent system has a wall assembly that defines a first passage for communicating combustion gas generated through operation of the fuel-burning appliance to a first outlet through which the combustion gas is communicated to the external atmosphere. The wall assembly further defines a second passage for communicating makeup air from the external atmosphere to the fuel-burning appliance in the first space. The direct sidewall vent system further has an external portion that is situated within the external atmosphere and at which the first outlet is located. The external portion of the direct sidewall vent system has a top, a bottom, and spaced sides.