Solar and visible optical properties of glazing systems with venetian blinds: Numerical, experimental and blind control study

The increasing use of glazed areas in the building envelope can lead to high solar gains and glare problems that can strongly impact the entire building energy consumption, peak loads and indoor comfort. An important and fundamental strategy in sustainable building design for controlling solar heat gains and daylighting through fenestration is the use of shading devices. Therefore, it is recommended to use detailed models that can accurately estimate the optical properties of the different types of shading devices (such as roller blinds and venetian blinds) and include their effects in the glazing system analysis. This paper describes a net radiation method for determining both solar and visible optical properties of glazing with shading devices, particularly venetian blinds. Some numerical results were compared with in situ experimental measurements carried out in an outdoor test cell. The experimental work included the measurement of illuminance and irradiance fluxes and the determination of the visible and solar transmission properties of the fenestration system. The agreement between numerical predictions and experimental results was better for overcast than clear sky conditions. Moreover, a venetian blind control strategy that blocks direct solar radiation, whilst enabling the transmission of diffuse radiation to indoors, is implemented.