Evaluating Natural Light in Historic Structures through Digital Simulation
July 17, 2013, 15:30 | Centennial Room, Nebraska Union
The search for sustainable solutions to current design problems has been an ongoing focus within the architectural and interior design communities. Returning to historical uses of natural resources is one way to solve these problems. Natural light, which can be defined as light from a natural source (sun, moon, atmosphere) is a resource that has advantages and disadvantages, both aesthetically and physically, in terms of use as a valuable light source to illuminate spaces. The goal of this research was to address how past and present structures have utilized natural light as an effective lighting solution, and then apply these methods to future structures by means of digital simulation and quantifiable data. Through the analysis of exterior façade systems, fenestration design, interior spaces, and building orientation, past and present structures can help provide a complete picture of both successful and unsuccessful daylighting solutions.
Current methods to evaluate daylight prior to the design phase of a building project are wide-ranging and not standardized nor regulated. To effectively study daylighting methods, computer simulation models needed to be developed of past and present structures. Measuring the amount of light from an electric or artificial source can often be straightforward, but daylight is highly variable with many factors to consider and there is not one universal method to calculating quality or quantity. Lighting calculation tools must be able to account for these variables in order to provide an effective lighting solution that can both reduce energy and ensure adequate light levels. The methodology and procedures for this research was conducted as follows: structure selection; three-dimensional computer models of selected structures; physical site visits where applicable; daylight simulation software selection; exterior and interior lighting analysis. Autodesk Ecotect was the software chosen for this research study, which is billed as sustainable design analysis software that offers a variety of simulation and building functionalities.
Data extracted from the digital simulations focused on the amount of interior illuminance in footcandles (one footcandle is equal to the illumination produced by one candle at a distance of one foot), as well as the amount of solar radiation (sunlight) available at each site, average temperatures, and solar geometry (path of travel of the sun). The software data shows that the natural daylight within the buildings as a sole light source can provide adequate illumination levels for tasks completed within the space during daylight hours under varying sky conditions. Site visits were conducted with physical light meters to determine the accuracy of the digital simulations. The techniques employed in the historic structures to control natural light (oculus windows, clerestory windows, site orientation, roof overhangs) were then applied to a current building environment, which was additionally analyzed on daylighting implementation.
Analyzing the success of daylight as a light source before physical construction is difficult in the design industry because there are various units of measurement when dealing with lighting that pertains to different factors (such as climate, weather conditions, time of year). These types of variables can produce a large amount of data in digital simulations, which can alter the perception of the data analysis, where the lighting levels might be extremely low during a winter storm or extremely high at noon in the summer. Determining which data to use and analyze was a large portion of the research in this project. Although standards exist today to attempt to measure the quality and quantity of light within a space, such as illuminance level (footcandle) recommendations and daylight factor ratios (the amount of light available indoors verses outdoors), there is still a great deal of trial and error when designing for daylight. The results of the study were used to verify that the use of current technology, in the format of digital simulation and analysis, on existing historic structures can be reliable indicator of the success of natural lighting solutions for future buildings. From the perspective of energy savings, environmental benefit and occupant comfort, the need for additional studies and research in daylighting metrics in buildings is needed to for natural light to become a viable lighting source.