Double skin façades performance: effects on daylight and visual comfort in office spaces

2014-07-15The demand for fully glazed, highly transparent façades has increased in recent decades as architects and clients embrace the style, and modern construction methods and materials have made them economically viable. Double‐skin façades are also becoming more common as a system that can be highly transparent and if designed appropriately more energy efficient than conventional systems. As a relatively new system, there is still limited data about energy performance and occupant comfort of the different variants of double skin façades. ❧ Designing the façade elements of the building to make a well daylit space is a challenging issue for designers. A well daylit office space will reduce the energy consumption of the building and will make a comfortable, healthier, and productive work environment for users. Too much daylight can introduce glare, heat gain, and other negative impacts. ❧ As a multi‐objective analysis, the trade‐offs between daylight quantity and visual comfort in the office spaces are complex, but it is possible for a designer to find an appropriate balance. Daylight autonomy (DA) metric of 300 lux (~30 fc) has been chosen as a target for measuring daylight quantity based on IESNA 2012 recommendation and daylight glare probability (DGP) as the metric for measuring visual comfort. ❧ Using a virtual office test cell of 27 by 12 by 9 feet, five façade parameter effects have been studied: depth of cavity; double skin façade type; façade material including different types of glass and translucent materials; shading device design considering their size, material and position in the cavity; and walkway design within the cavity. ❧ Computer simulations with Rhino, Grasshopper, and DIVA (with Radiance engine) were used to determine how the design of each façade element affects the goals in three different geographic locations: Los Angeles, New York and Houston. The results have been plotted on trade‐off charts for each city. ❧ By using the simulation results and trade‐off charts, designers will be able to find an appropriate balance between visual comfort and daylight availability while designing a double‐skin façade