edited and excerpted from the 1991 original 
commentary by Keith Yancey

James White

During the past 15 or 20 years, significant resources have been expended by the U.S. Department of Energy to develop new daylighting technologies, yet many of them are not sufficiently used. Factors that might affect the likely market acceptance and adoption of these technologies have largely been ignored.

In response to this lack of knowledge, an effort has been made to systematically identify, catalog, and understand architects' and engineers' perceptions of daylighting products and systems. B.F. Roberson and S.A. Harkreader at Pacific Northwest Laboratory (see References) conducted focus group discussions with these professionals to elucidate the reasons why they do or do not use daylighting systems. Insight gained from these sessions was used to develop a national survey of daylighting practices.

This article originally appeared as the Technology column in the June 1991 issue.
This article originally appeared as the Technology column in the June 1991 issue.

This survey focused on developing an accurate profile of architects' knowledge, perceptions, and use of daylighting in commercial building designs. The survey findings aimed to identify some of the barriers that exist in the commercialization or use of daylighting technologies.

In this survey, daylighting was defined as the intentional use of natural light as a partial substitute for artificially generated light.

KY: Daylighting is a difficult term to define, which may be the primary reason why the survey results in this article tend to contradict each other from one question to another. In the March 2008 issue of ARCHITECTURAL LIGHTING, Kevin Van Den Wymlenberg's article “Terminology” (bit.ly/ia68Bd) talks about a group of daylighting experts convening to discuss a particular research project, and having a lively debate on what it means for a space to be “daylit.” This discussion produced little consensus. If even a group of focused experts could not agree on the terminology in 2008, imagine a group of architects in the late 1980s. Van Den Wymlenberg's article also mentions another survey conducted in 2005 by the National Research Council of Canada that posed alternate definitions of daylighting to architects and engineers. It was no surprise that architects focused more on user benefits, while engineers cited economic and energy benefits. Today we have LEED, CHPS, Title 24, ASRAE 189.1, and soon the IGCC, all of which try to define daylighting in architecture through quantitative metrics: daylight autonomy, useful daylight illuminance, daylight saturation percentage, or even simply illuminance at a point in time. If this survey were given today, we might find that it is these metrics, for better or worse, that define “daylit architecture” for most architects and building professionals.

A phone survey of commercial design architects throughout the United States, whose names were drawn from the 1987–1988 membership directory of the American Institute of Architects (AIA), was conducted from January 11–February 8, 1989. The actual usable sample consisted of 593 architects, of which 308 responded to the survey.

Issues addressed in this survey included architects' understanding of daylighting, the major influences in the daylighting decision process, the appropriateness of specific building types for daylighting, the sources relied on by architects for technical and product information, and the design aids they prefer for the future.

Thirteen categories of daylighting benefits (Table 1) were created from the architects' responses. Ninety-four percent of the architects were able to provide at least one benefit associated with daylighting. On average, architects cited two benefits of daylighting. The most frequently mentioned advantages relate to energy conservation or efficiency, improved aesthetics or atmosphere, and reduced operation costs or monetary savings.

Table 1

When asked about the major problems associated with daylighting designs, 91 percent of architects provided at least one with an average of 1.7 problems per architect. The most frequently cited problems relate to lighting control and heat gains (Table 2).

Segmenting the problems by an architect's familiarity with daylighting showed that architects who are very familiar with daylighting cited more problems (1.78 on average) than did architects who were somewhat familiar and not very familiar with the subject (1.60 and 1.47, respectively). This finding would seem to suggest that architects who are very familiar with daylighting view it more negatively.

To avoid drawing the wrong conclusion, it is important to note that these architects cited more benefits than problems with daylighting and, therefore, appear to view daylighting positively. Indeed as one daylighting expert pointed out, daylighting's best or strongest proponents (i.e., those who have used it extensively) are more knowledgeable about this technology, and therefore, can probably cite more potential problems than the typical architect.

Table 2

The payback period is the number of years required for the savings from a new product to pay back its higher initial cost. Architects generally felt that the longest payback period a client would accept is seven years. The architects were then asked what they thought the payback period for daylighting was; again, their average response was seven years.

Familiarity with daylighting appears to influence architects' estimates of payback periods. The results indicate that architects who are very familiar with daylighting estimate a shorter payback than do those who are less familiar with daylighting. The average estimate from those who are very familiar was six years; those who are somewhat familiar estimated seven years; and those who are not very familiar estimated eight years.

KY: Payback periods have been shortened in more recent years probably due to the availability of less expensive dimming ballasts, photocells, and controls, along with increased energy costs.

  The surveyed architects were asked whether they agreed or disagreed with 10 different statements about daylighting. Six of the statements are positive; four are negative. The six positive statements listed in order of agreement (strongest agreement first) are that daylighting systems:

  • Improve the satisfaction of building occupants
  • Make a building more attractive
  • Improve the productivity of building occupants
  • Are a good value
  • Are reliable
  • Save energy

  • These results clearly illustrate that architects do not consider energy savings to be the primary or major benefit of daylighting. Rather, visual appeal, which improves aesthetics and worker satisfaction, is the primary benefit of daylighting. This finding has implications for those who are trying to increase the use of daylighting systems. The impact of daylighting systems on aesthetics or their visual appeal should be emphasized more than energy consumption if they are to appeal to architects. Though this might appear to contradict the results in Table 1 [see next page], closer examination of that table reveals that most responses relate to visual effects rather than to energy efficiency.

    KY: A contradiction at the time, most likely due to the lack of readily available energy-modeling and daylight-prediction software. Another interesting result is that occupant productivity is ranked third, when in fact several studies such as those by the Lighting Research Center and Heschong Mahone Group show a connection between user satisfaction and productivity or performance. It's difficult to separate the statements (energy savings vs. visual effects), which also lead to the “good value” statement. A story in The Wall Street Journal, “See the Light About Daylight,” from Oct. 19, 2004, cited studies showing the positive attributes of daylighting and views, from reduced absenteeism to improved worker productivity. I think it would be difficult, if the survey were given today, for architects to ignore these connections. With all of the available data from these human-environment studies, my guess is that architects would rank energy savings first and good value second, since there is such pressure to defend sustainable design beyond simple building aesthetics.

      The four negative statements listed in order of disagreement (strongest disagreement first) are that daylighting systems:

  • Introduce more problems than they solve
  • Are difficult to integrate with other systems
  • Increase building maintenance costs
  • Are expensive to purchase and install

  • Over 80 percent of the architectural industry disagreed with the statement that daylighting systems introduce more problems than they solve, and nearly 60 percent disagreed with the statement that they are difficult to integrate with other systems.

    The industry seemed uncertain about the costs associated with daylighting systems. Statements that daylighting systems are expensive to purchase and install, and that they increase building maintenance costs met with agreement from 57 percent and 53 percent of the industry, respectively. These concerns need to be addressed in educational programs about daylighting offered to architects.

    Fifty-five percent of the architects thought that architects have the most influence on the decision to use daylighting; 36 percent said that clients have the most influence; and only 9 percent said that lighting engineers have the most influence. As to who is the second-most influential, 39 percent thought clients were; 37 percent chose architects; and 24 percent picked lighting engineers. Just over two-thirds of the architects surveyed thought that lighting engineers have the least amount of influence on the decision. More than 25 percent thought clients, and only 8 percent thought that architects have the least amount of influence on the daylighting decision.

    The architects were also asked to rate six situational factors that can influence the decision to use daylighting in a commercial building design as very important, somewhat important, somewhat unimportant, or very unimportant.

    Even though building codes had the lowest mean score, 40 percent of the architects still said this factor was very important. A possible explanation for this is that the impact (positive or negative) of building codes on the use of daylighting varies from area to area in the United States. Roberson and Harkreader found that focus group participants in Los Angeles encountered problems meeting building codes when using daylighting design features, while architects in Chicago encountered no problems with building codes. Although assessing the impact of building codes is beyond the scope of this study, future research to explore this area would be beneficial.

    Architects felt that schools were the most appropriate place to use daylighting designs (80 percent). Low-rise office buildings and libraries ranked next (just over 50 percent). Roberson and Harkreader found that the focus group participants also thought that daylighting was appropriate for low-rise office buildings and libraries.

      “Twenty years ago, architects cited aesthetics as the most important consideration for introducing daylighting into architecture. Today, architects are mostly identifying sustainability and energy savings as the number-one reason for daylighting. What's changed? Are we that much better at it? Are we able to save more energy today than 20 years ago? Or are we simply a product of the times?” — Keith Yancey

    The focus group participants felt that warehouses, hospitals, and museums were among the more appropriate building types for daylighting; and high-rise office buildings the least appropriate. These findings are not supported by the results from this survey, which are shown in Table 3 [not shown here].
    High-rise office buildings were the fourth-most appropriate building type. This is an intriguing result, as previous research found that high-rises were viewed as inappropriate. Apartment complexes rank fifth, followed by hospitals, hotels/motels, restaurants, museums, warehouses, and retail stores.

    The view that retail stores are the least appropriate for daylighting should also be evaluated in future research. It would be useful to know what features associated with retail stores, warehouses, museums, etc., make them less appropriate for daylighting.

    The architects' responses were segmented by familiarity with daylighting. Architects considered very familiar with daylighting are thought to have the most accurate knowledge of its use. In general, the architects in this group have stronger positive opinions than the other groups on the appropriateness of daylighting for each of the building types except libraries, museums, and warehouses.

    The most interesting observation resulting from the segmentation was that libraries, ranked third by the entire sample, dropped to seventh among the architects who are very familiar with daylighting. This result is especially interesting because libraries were viewed by the architects in the focus groups, and most of the architects in this survey, as being appropriate buildings for daylighting.

    Architects very familiar with daylighting ranked apartment complexes and hotels/motels higher (relative to other building types) than did other architects. Sixty percent of the architects who are very familiar with daylighting felt that apartment complexes were very appropriate, while less than 40 percent of the architects who were less familiar felt this way. More than 50 percent of those very familiar with daylighting also thought hotels/motels very appropriate; only 34 percent of those somewhat familiar and 14 percent of those not familiar with daylighting felt this way.

    Survey results suggest that a major barrier to the use of daylight is simply that most architects do not have a basic understanding of daylighting. Programs aimed at educating practicing architects about the correct application of daylighting should be developed.

    Roberson and Harkreader found that none of the architects in the focus groups had tried to convince their clients to use daylighting features to reduce energy costs. Rather, the primary advantage that they presented to clients was the aesthetic effect. The survey results indicate this is common throughout the industry. Although positive energy effects were mentioned a number of times as benefits, the underlying theme of the benefits mentioned had to do with different aspects of daylighting's aesthetic effects.

    The results suggest that any education campaign should emphasize the positive impacts that daylighting can have on a structure's total energy use. To change architects' perceptions of daylighting's performance, there appears to be a need for additional and clearer evidence regarding daylighting's operational effectiveness.

    Until precise, credible performance information is available and architects know about it, most will continue to be apprehensive about promoting the use of daylighting. Information on the payback period, the costs and energy savings, and the most appropriate building types for daylighting should also be included in any educational program.

    Based on the survey results, it is apparent that educational information should be written up in professional journals and publications, which were cited as the most important source of information for architects. The second most used channel of communication, or source of information, is informal discussion among architects. This suggests that another possible way to communicate daylighting information is identifying key experts in each state or in major communities. It might also be feasible to recruit architects to become daylighting design experts for their home community, and as such, serve as information sources for fellow architects in the community. These community or regional daylighting experts could also receive training in the use of the latest computer-based design aids being developed by government and private industry. It might even be possible to fund their time when they help other architects with daylighting design.

    In some regions of the United States, utility programs are available to provide technical design assistance to encourage the construction of energy-efficient commercial and industrial buildings. One example is the Energy Smart Design Assistance program sponsored by Bonneville Power Administration. Daylighting design could be incorporated into these utility programs to encourage its use.

    The survey results show that while architects want future design aids to be computer-based, they do not want to devote much time to generating computer simulations of illumination levels or energy usage. Access to a recognized local expert or a toll-free technical-support line for help in the application of the software (much like the support lines offered by makers of word processing software) might encourage architects to use the software more extensively. If the software is used more often, it follows that daylighting systems would like be included in building designs more often.

    The survey results suggest that 49 percent of the buildings designed by survey respondents in the past two years included a daylighting component. Several daylighting experts who reviewed the survey results felt that this number was very high and had to do with how daylighting was defined. They felt that the usage of the more complex “active” daylighting systems, which employed the newer daylighting technologies and controls, was much lower. Experts tend to define an “active” daylighting design as any aperture that has fenestration controls designed in conjunction with a photoelectric system, which will control electric lights to reduce energy consumption. The experts were certain that the 49 percent of the buildings designed by survey respondents in the past two years had to include “passive” systems, which simply allow natural light in, but do not use the more complex daylighting technologies and controls.

    KY: Since this article was written, there has been a reversal of architects' perceptions of daylighting. Twenty years ago, architects cited aesthetics as the most important consideration for introducing daylighting into architecture. Today, architects are mostly identifying sustainability and energy savings as the number-one reason for daylighting. What's changed? Are we that much better at it? Are we able to save more energy today than 20 years ago? Or are we simply a product of the times? This energy claim can be good and bad. Good, in that we apparently have more information and tools available for predicting energy savings, but bad in that we may be starting with energy as the primary reason for daylighting, instead of simply creating great spaces for humans. Are we abandoning our principles or merely using energy and sustainability as a crutch to bolster what we always knew as truth: Daylight is good for people and they like it, therefore we should keep it in our architecture. Resting simply on energy savings is shaky ground, especially as electric light sources get more and more efficient. We're seeing power densities of less than 0.5W per square foot in some ambient lighting situations. It's hard to tout daylighting as more efficient in some climates and programs where cooling loads are prominent. It's a good idea to try and understand the reasons why architects were not embracing current daylighting technologies at the time. Daylighting, as design itself, continues to be an elusive entity to define. You know it when you see it. It works well. It's poetic, harmonious, inspiring, beautiful—and, oh yeah, it's sustainable.

    The American Institute of Architects (AIA), 1989. “The American Institute of Architects 1989 AIA Firm Survey Report,” AIA, Washington, D.C.

    B.F. Roberson and S.A. Harkreader, 1988. “Focus Group Discussions of Daylighting Practices,” PNL-67 40, Pacific Northwest Laboratory, Richland, WA.

    Booz-Allen & Hamilton Inc., 1987. “Daylighting Program Evaluation Volume II: Report Prepared for Southern California Edison.”

    S.E. Selkowitz and J.W. Griffith, 1986. “Effective Daylighting Buildings—Revisited,” Lighting Design + Application, pages 34–47.

    Keith Yancey, a principal at Lam Partners in Cambridge, Mass., is a registered architect and professional engineer with 25 years experience in the architectural, lighting, and engineering fields. His experience includes daylighting and electric lighting design for a multitude of projects throughout the world. He also teaches and lectures extensively and has served on several design juries.

    Given the change in architects' perception of daylighting, ARCHITECTURAL LIGHTING thought it would be interesting to conduct a new survey. With the help of Keith Yancey, AL has prepared new questions and the survey can be found at archlighting.com.