Comparison of daylight simulation methods for reflected sunlight from curtain walls

Curtain walls are more and more commonly used as building facades.They allow a better daylight availability and a direct connection to exterior environments.Meanwhile,due to the high specular reflections,they may also introduce negative impacts,such as glare and urban heat island effects,to the surround,especially in dense and urban environments.Therefore,it is important to effectively characterize the reflected sunlight from curtain walls.This study aimed to compare how different simulation methods can be used to characterize the reflected sunlight from curtain walls.It was found that the modeling of the sun and sky,ambient calculation,and the modeling of the building facade significantly affected the simulation results.A combination of forward and backward ray-tracing is recommended,with forward ray-tracing for identifying the curtain wall areas reflecting sunlight and backward ray-tracing for calculating illuminance due to reflected sunlight.A follow-up work is planned to investigate how different parameters will affect the simulation results and which method can produce similar results as field measurements.

Designerly optimization of devices(as reflectors)to improve daylight and scrutiny of the light-well’s configuration

One of the most effective ways of transmitting daylight into deep-plan buildings is to generate light-well for spaces away from the facade and window-less spaces.Among the limited methods of improving daylight efficiency in light-wells are reflectors that,as a surplus member of the wells,can aid in this improvement.A scrutiny of the light-well’s configuration can give a correct perception of the performance of the well’s walls with increasing the reflection coefficient to the designers in deciding where to install the openings,selecting the transmittance coefficient of glass,etc.In this paper,the main focus is designing and optimizing daylight assist devices on light-wells that can hierarchically reflect light from the sky to the bottom of the well(Device 1)and then emit into the desired space(Device 2).The research highlights that it is necessary to find a proper strategy for the devices regarding to the optimization process.The research design results in a comprehensive standard solution for different latitudes.The simulations were performed by Honeybee Plus version 0.0.06 and Honeybee-Ladybug version 0.0.69-0.0.66,which has the ability to simulate annual daylight performance at certain periods.Due to the maximum and minimum altitudes at any latitude,the study required time-criteria throughout the year.As a result,a cross-sectional study was carried out at two critical times:the first period(P1)and the second period(P2).Daylight metrics for analyzing configuration as well as evaluating devices are E’max,avg(illumination)and SHA(hour/m2).The DA’300 and DA’max2000 metrics were selected to measure daylight efficiency and glare risk,respectively,and the sDA is for the amount of floor area that uses enough daylight.Also,to better percept how to prepare improved-daylight at lower levels(especially for the performance of devices),the daylight autonomy has been reduced from 50%to 40%and a metric such as sDA’t40 has been created.