Daylighting is one of the oldest and most treasured aspects of architectural design. Perhaps its history is why designers treat it more like fine art than building technology. In the title of his quintessential book, legendary lighting designer and educator William Lam describes daylight in profound terms, calling it a 'formgiver' to architecture (Perception and Lighting as Formgivers for Architecture, 1977). Indeed, for us mere lighting designers, it is hard to compete with the Almighty-or for that matter, with Aalto or Foster.
But here, in the twenty-first century, design professionals are increasingly expected to create buildings that perform significantly better than buildings ever have before. At first, this awareness was driven by a surging interest in energy efficiency, rising fuel costs, and the environmental movement, but that only had a modest effect on design and on public expectations for it. The real impetus has come from the US Green Buildings Council's LEED system, launched in 1998; this program has finally raised building science and engineering to its rightful level of importance in the design behind a 'green' building. Daylighting-especially if it provides energy efficiency and reaches most interior spaces-is the potential star of the sustainability show.
The problem is the modern architect is generally ill equipped to evaluate the performance of daylighting design. Crucial decisions concerning daylighting are made in the schematic design phase, but most architects have no tools, other than common sense and experience, to measure the final effect. During early schematics, for example, it is hard-or even impossible-to thoroughly compare the ultimate performance of alternative fenestration proposals. Yet this very aspect is often the difference between one LEED level and another, with up to 12 precious LEED points at stake.
'Mainstream practitioners think they are doing daylighting, just because their building has windows. They have such a simple view of daylight that they don't know how to think about it usefully,' says Lisa Heschong, architect and principal of the Heschong Mahone Group, a Sacramento-area firm specializing in building science research. The group has researched daylighting equipment and practices for 15 years, with a focus on California.
In order to truly expand the application of informed daylighting design practices, certain issues must be addressed. Today, the problems with this design approach include:
a small body of knowledge. Most literature in the field is artistic, conceptual, or trend and fashion. Worse, some current architectural textbooks provide inaccurate information, extorting the artistic virtues of famous daylighting designs that are technically so bad they would cause a building to fail to qualify for LEED at all.
limited educational opportunities. Few colleges of architecture have faculty with genuine daylighting expertise; and even fewer have artificial skies, helidons, and other systems for scale modeling and measuring daylighting performance. There is a tenuous acceptance of computer analysis and an unfortunate scale-modeling-versus-computer-modeling controversy brewing.
no established standards of practice. Exceptional architects have learned to identify and employ daylighting consultants in a consistent manner, but for most architects, each project is a new experience where daylighting is concerned. Many design decisions are based on the architect's intuition or artistic sense, rather than on serious analysis. For instance, how many new buildings in this hemisphere have light shelves on the north façade? (Answer: One is probably too many.)
no established standards for 'how much' daylight. LEED 2.1 took a courageous step in requiring 'a daylight factor of 2 percent for 75 percent of all space occupied for crucial visual tasks.' Yet 'daylight factor,' according to the IESNA, is a 'low-precision procedure ... generally used with overcast skies ... especially in Europe.' It is the wrong method for assessing daylighting under sunny skies and has only 'some application in North America.' (Fortunately, LEED's requirement for mechanical analysis ensures climatologic considerations, and the daylight factor requirement is unpopular and slated for change with the next LEED release.)
limited access to the appropriate tools. Architects have little access to daylighting design and analysis tools. For example, there are less than 20 artificial skies in North America.
no common lexicon. There is no broadly accepted terminology for discussing daylight glare; and no accepted numerical system for predicting and evaluating it.
inability of architectural reviewers to judge daylighting designs on performance. Some recently published 'green' buildings employ exceptional daylighting, but in many it is a fantasy of architectural design and the gullibility of the writer.
Most of these failings are holdovers from twentieth-century daylighting design, in which glass became a new tool for architectural expression. Like most fellow lighting designers, I am an admirer of architecture and have often been thrilled by buildings using the medium as skin, roof and form. But I have also wondered how an architect could have chosen a particular fenestration treatment given the climatology of the site. Even the most famous 'green' architects have designed a solar oven or two.
In twenty-first-century daylighting, we will rapidly resolve these issues and learn to design-and teach-daylighting solutions better. And many of the tools of the future will come from the field of architectural lighting. The most important current advances include:
• Next-generation lighting software that includes ray-tracing and radiosity methods to produce acceptably accurate calculations and compelling visuals with a fast-and comparatively easy-user interface.
• Photometric testing of high-performance skylighting systems to permit direct use of that data in lighting software in order to produce exacting results.
• Ongoing development of a glare metric that can be calculated along with illumination and other quantities.
• A methodology for predicting daylighting energy performance by predicting daylighting illumination performance.
There are, of course, a few good resources and expert practitioners out there, many of whom will be at Lightfair International's inaugural Daylighting Institute in Las Vegas this March. This is the first major North American daylighting program since 1986, and Lightfair organizers hope it will become the premier annual event in its field.
Owing to the Daylighting Institute, LEED, and other initiatives such as California's CHPS (Collaborative for High Performance Schools) and the Wisconsin Daylighting Collaborative, I expect that daylighting design technology will advance very rapidly in the next ten years. But until we get twenty-first-century daylighting, we need to be especially critical of buildings where technical measures are not used to objectively assess the design. Because we are still working with twentieth-century daylighting, there will continue to be buildings whose daylighting design story makes claims that won't stand up to the light of day.
James Benya is a professional lighting designer and principal of Benya Lighting Design, West Linn, Oregon. He serves on the editorial advisory board of A|L.