The influence of various internal blinds on thermal comfort: A new method for calculating the mean radiant temperature in office spaces

The authors investigate the effect of the coating of various internal blinds on the operative room temperature in an office space.It is very important to correctly evaluate the impact of solar protection and daylight/glare systems on building comfort, and the resulting influence on human behaviour. Many building energy simulation programmes consider the Mean Radiant Temperature (MRT) independently of the actual emissivity of the internal surfaces. This approximation is acceptable for normal constructions with emissivity close to 1, but leads to considerable errors if low-emissivity paint or coatings are used.Starting from the theory of the net-radiation in a grey enclosure, the authors evaluate the MRT, assuming that the incoming flux and the radiated flux are the same. This method is based both on an ESP-r integrated whole-building-simulation programme and on an analytical method which allows for the correct evaluation of the thermal radiant field induced by considering the presence of surfaces with low-e coatings. The method can be used either ‘stand-alone’ for comparisons of different façade variants or within a building simulation. The simulations carried out indicate that when an ‘absorptive blind’ surface faces outwards, the summer temperature can be reduced by about 1 K at a position close to the façade.

► A new method for calculating the MRT in building simulation is presented.
► We investigate the effect of internal textile blind's coating on the operative room's temperature.
► Summer and Winter condition with high solar gains are considered.
► The textile coating has a considerable impact on the indoor temperatures.
► The reduction of the emissivity bring a reduction of the indoor temperatures.