The impact of venetian blind geometry and tilt angle on view, direct light transmission and interior illuminance

Venetian blinds are a common type of shading. They can reflect and transmit light efficiently into buildings by adjusting the louver angle and at the same time allow some view to the outdoors. This paper presents a systematic method for calculating projected view (or shaded) fractions for venetian blinds of any shape (flat and curved) as a function of rotation angle, taking into account edge effects and slat thickness. General analytical direct transmittance equations and charts – derived from pure geometrical characteristics – were also developed for flat slats (including thickness and edge effects) and curved slats (circle arcs) as a function of blind tilt angle and profile angle. The last part of the paper investigates the impact of slat shape and reflectance on window-blind system effective reflectance and the associated contribution to the inter-reflected component for different window areas.