Analysis of the mean radiant temperature in well insulated buildings: experimental comparison between low temperature radiator and floor radiant heating system; internal reflecting solar shading effect

The paper reports the results of an experimental and analytic study on the behaviour of an internal environment characterized by high thermal insulation and alternative heating systems, low temperature radiator or floor heating system. The aims of the research are: to analyse the wintertime discomfort caused by the window in the two types of thermal plant; to verify the effectiveness of the adoption of internal reflective solar shadings to reduce the discomfort penetration depth. To that aims an experimental campaign was carried out in a full scale test room equipped with a window under controlled conditions. Wall surface temperatures, heat fluxes, globe temperature distribution, air temperature distribution and air velocity near the window were measured. Thermal discomfort was assessed by the analysis of the mean radiant temperature’s distribution (TMR). Numerical simulation were performed with a commercial code able to calculate the mean radiant temperature for different position along different axes. Experimental and numerical results were compared to check the reliability of the numerical analysis. The experimental results showed that at a distance of 1 m from the window the globe temperature was lower than 19°C. This occurs when the room was heated by floor radiant heating systems. The discomfort penetration depth decreases to 0,50 m with low temperature radiator and to 0,30 m with internal reflective solar shading. Internal reflective solar shading system reduces the variation of the mean radiant temperature near the window and the heat losses through the window.