The paper presents the procedure and facilities used to empirically assess the thermal performance of the window coverings subjected to the radiation from the light source. The ability of the window coverings to minimize the heat gain on the internal environment of the testing chambers is also discussed. Two identical chambers have been built whilst maintaining a recommended window to floor space ratio, one chamber has a glass pane and its replica has similar glass and a system to fit various window coverings. It was found that the thermal conductivity of window covering materials (and R-value indirectly) seemed to be less significant because the heat was reflected back to the external environment and the radiation was a major driver of the thermal performance. The entire heat transfer process is then much more influenced by the color of the window coverings, as the darker colors absorb more heat from the radiation. The lighter counterparts reflect more heat from the radiation and the
conduction and convection play a less significant role.