Hybrid-Model Simulations to Equilibrate Energy Demand and Daylight Autonomy as a Function of Window-to-Wall Ratio and Orientation For a Perimeter Office in Izmir

Abstract

This study is based on integrated thermal-lighting simulations to find the optimal value of the window-to-wall ratio (WWR) for a perimeter, single-zone office to equilibrate daylight autonomy and overall energy demand in the climate of Izmir, Turkey. A hybrid model approach has been adopted that combines thermal and lighting calculations in a single model via the IES <VE> software. The optimal WWRs to achieve the highest possible daylight benefit and lowest overall energy use at the same time has been found to have 30% WWR in the South and West, 40% WWR in the East and 60% WWR in the North. These WWR values trade-off daylight benefit, total energy consumption for lighting, heating, and cooling, and visual comfort compared to larger and smaller WWR options. Since the daylight use can significantly reduce artificial lighting energy consumption as long as WWR increases, the energy benefit from lighting reaches 79% as a function of daylight for the South case at 30% optimal WWR. The strongest effect of cooling demand is evident in the breakdown of energy consumption and the amount of glazing is the dominant factor defining the cooling demand. The implications of this study can help architects get feedback on how to save energy for each final energy use (heating, cooling, and lighting) reduction in window space and convey this message to their designs with suggested optimal WWR values.

Keywords

• daylight autonomy
• daylighting; energy use; visual comfort; window-to-wall ratio.