Daylight harvesting is now attracting attention not only from energy saving but also from the viewpoint of improving the health and comfort of people working in the building. Daylighting standards, such as EN 17037:2018, provides the target values to obtain sufficient daylight, and also prescribe the evaluation criteria for view and glare.
We used a Meta_Simulation platform that combined Radiance and NewHASP to evaluate lighting and air conditioning energy of exterior and interior sun shading devices. We confirmed the behaviour of basic parameters by combining glare and view evaluations from Radiance and using the graphical algorithm editor Grasshopper to calculate air conditioning/lighting energy, glare index and view. By utilizing the plug-in software OCTOPUS, we evaluated air conditioning/lighting energy usage, glare, and view based on four variables of exterior and interior sun shading devices and the optimal solution for Tokyo (Hyakuri) was confirmed.
For glare, the vertical illuminance of the viewpoint was not high in the building targeted by our simulation, and because no cases exceeded the allowable simplified DGP value of 0.35, the threshold was lowered to evaluate glare in the multi-objective optimization calculation.
Under the European Standard, view is evaluated based upon the horizontal angle of the window, the distance to adjacent buildings, and the number of layers for sky, landscape, and ground that can be seen (European committee for standardization, 2019). We used a simple evaluation based upon the ratio of sky that could be seen from a sample point, however it is possible to incorporate the view metrics of the EN 17037:2018 into our new module using Radiance.
We conducted a multi-objective optimization calculation for the annual fixed angle of vertical louvers and of blinds typically used in the sun shading devices. In the future, we plan to apply optimization calculations to complex sun shading devices such as slat cut-off angle controls for blinds, moveable or curved surfaces for exterior sun shading.
