DECISION-MAKING FRAMEWORK FOR SELECTION AND DESIGN OF SHADING DEVICES BASED ON DAYLIGHTING

This research looked to improve the daylighting performance of a shading device as a window component.The paper describes the development of the decision-making framework(DMF)for the selection and design of shading devices based on daylighting.The DMF presents the process of analysis of the shading devices’daylighting performance in the selection of existing shading devices and in the design of new shading devices.The research determined the shading device daylighting performance measures(such as illuminance and daylight autonomy)as well as the variables that influence daylight performance.Interactions among the variables and the effects of these interactions on the shading device daylighting performance were explained and quantified in the DMF.The DMF also included ways of present-ing the results of testing the shading devices and the process of making the decision.A case study for three blind systems was performed to determine if the DMF provides a concept for the analysis of the daylighting performance of shading devices and for making decisions about the design/selection of the shading device.Computer simulation was used to calculate the illuminance levels and the daylight autonomies(DAs)as a result of the application of these blinds.The values of the DAs are compared for three blind systems to select the most appropriate sys-tem to be applied on a proposed building.The DMF based on daylighting can help building designers to select the most suitable shading device based on its daylighting performance,and can help shading device manufacturers in designing new shading devices with improved daylighting performance.FIGURE 2.Simplified DMF diagram.

A COMPARISON OF FOUR DAYLIGHTING METRICS IN ASSESSING THE DAYLIGHTING PERFORMANCE OF THREE SHADING SYSTEMS

The assessment of the daylighting performance of a design solution is a complex task due to the changing nature of daylight.A few quantitative metrics are available to designers to assess such a performance,among them are the mean hourly illuminance(MHI),the daylight factor(DF),the daylight autonomy(DA)and the useful daylight illuminance(UDI).Each of these metrics has a purpose,a set of criteria and limitations that affect the outcome of the evaluation.When to use one metric instead of another depends largely on the design goals to be achieved.Using Design Iterate Validate Adapt(DIVA)daylighting simulation program,we set out to examine the performance behavior of these four metrics with the changing dimensions of three shading devices:a horizontal overhang,a horizontal louver system,and a vertical fin system,and compare their performance behavior as the orientation changes of the window to which these devices are attached.The context is a typical classroom of a prototypical elementary school.Our results indicate that not all four metrics behave similarly as we vary the size of each shading device and as orientation changes.The lesson learned is that not all daylighting metrics lead to the same conclusions and that it is important to use the metric that corresponds to the specific goals and objectives of the design and of the daylighting solution.The UDI is the metric that leads to outcomes most different than the other three metrics investigated in this paper.