There is a rising necessity concerning low energy consumption and thermal comfort, thus, new systems combining displacement ventilation and radiant heating are becoming common as a research topic. The current paper covers free, mixed, and forced convection in an experimental chamber consisting of a radiant wall heating system and a baseboard level diffuser. Air temperature in the test room is adjusted using an air blower via a novel designed baseboard level slot diffuser along with a hydronic wall heating circuit. Simultaneously; an upward direction air jet is blown through the heated or the opposite wall under two scenarios. The ranges of air inlet velocity and temperature are selected to be between 0.25 and 12.5 m/s and 14–26 °C, correspondingly. The heat transfer characteristics pertaining to the heated wall are studied with respect to the influences of wall and air temperatures, air inlet velocities, and the location of the diffuser. To derive convective heat transfer coefficient correlations valid for mixed and forced types for a radiant heated wall, acquired data have been processed. The convective, radiative, and total heat transfer coefficient intervals of 3–14.1, 5.2–5.5, and 9.3–21.7 W/m2K have been obtained for the radiant heated wall coupled with airflows, correspondingly.