Abstract: A fireplace assembly including a direct-vent combustion system which includes an air inlet, an air outlet each sealed from the other. It includes a pre-combustion chamber for entry of a primary fuel and air mixture, a burner unit, the burner unit comprising a burner, a base plate with metered holes or slots configured to allow control of the placement, volume and flow of air flowing from the air inlet into a mixing combustion chamber from the burner unit, and an ember bed located around the burner configured to create the mixing combustion chamber in the burner unit to enhance desired flame presentation by controlling mixing of incoming air with the primary fuel and air mixture.