Estimation of sky and externally reflected components under various obstructed CIE skies

In many urban cities, the external obstructions may significantly reduce the amount of daylight entering to the indoor space. The estimation of daylight illuminance gained via vertical fenestration is important in energy-efficient building design and operation. Practitioners welcome simple calculation aids established via comprehensive analysis. Such methods would give building professionals and students basic and concise insight into the independency of different daylight parameters. It is also very useful in initial architectural and building façade layout stage. Computer simulations can be conducted after the design schemes have been finalized. This paper presents manual calculation procedures to predict sky and externally reflected components at the interior points under various obstructed CIE sky conditions. Performance of the proposed method was evaluated by comparing with simulated results of a sophisticated lighting program and real scale measurements. The findings showed that the predictions based on the proposed approach were in good agreements with the simulated and measured outcomes. The study can provide a reliable practice for architects and building designers to estimate the internal daylight at early design and planning stage.