A wall plate assembly for an HVAC controller may include a rear plate including an aperture extending through the rear plate and a front plate securable to the rear plate. In some cases, the front plate may have a recessed portion that is recessed back toward the rear plate and align with the aperture in the rear plate. An air flow barrier may be secured to the recessed portion of the front plate. The air flow barrier may include a barrier surface that covers a portion of the aperture formed in the recessed portion of the front plate to reduce air infiltration. The air flow barrier may include an air flow barrier aperture that is sized to accommodate wires passing through the aperture in the recessed portion of the front plate for connection to a wire connection block of the front plate.