Evidence-based design is a concept that has enormous instinctive appeal for those interested in clinical outcomes, performance improvement, and objective decision making, as discussed in the first in this series of three articles on evidence-based design (“The Four Levels of Evidence-Based Practice,” HEALTHCARE DESIGN 2003;3[Nov]:18-26). As that article noted, it is a deliberate attempt to base design decisions on the best available research findings. Evidence-based healthcare design has been called the natural analog of evidence-based medicine.

Evidence-based healthcare design can be used to create therapeutic environments for patient care that are supportive of family involvement, efficient for staff performance, and restorative for workers under stress. Evidence-based designers, together with informed clients, make decisions based on the best available information from research studies and evaluation of completed projects. They must use critical thinking to make rational inferences from a pool of information that will rarely fit precisely with their unique design situation. Nevertheless, an evidence-based healthcare project should result in demonstrated improvements in the organization's measures of clinical, economic, productivity, patient/staff satisfaction, and cultural success.

Describing the practice of evidence-based design is simpler than describing an evidence-based product. What, after all, qualifies as an evidence-based project? Certainly, the evidence-based ideal is not always matched by reality. A project described as a “healing environment” might be portrayed as evidence-based, but what is really meant by this? Who or what is being healed? How effectively or quickly is this occurring? Which aspects of the environment have been specifically designed to have an effect on healing? What measures indicate that healing takes place? How does the healing experience compare with that of the original setting or of an environment that isn't regarded as “healing”? In short, where is the meaningful evidence?

Scope of an Evidence-Based Project

If an interior designer selects carpet based on the flame-spread research of Underwriters Laboratories, is this an evidence-based project, or is it the “normal” research one would expect of any healthcare project? Is a serious attempt to carefully test one factor sufficient to merit the label of an evidence-based project, or must multiple issues be addressed? A project focused on a single question might be considered too simple, especially if the factor studied is not particularly complex or is resistant to study. On the other hand, addressing a single but complex question may require an exceptional but worthwhile effort.

Can a small project be described as evidence-based, or must the project be substantial in scope? Any size project, in fact, merits an evidence-based label if it addresses an important question with rigorous methodology, so long as the effort made is proportional to the project's size. Thus, an art program for a hospital based on research might be a wonderful evidence-based project, but it might be wrong to characterize the entire facility as evidence-based if few other design decisions were subjected to a research-informed process. The hospital might have rigorous data supporting the art selection, yet be a disaster from the standpoint of infection control, efficiency of nursing staff, or cleaning time between cases in the operating rooms. The evidence-based label must be applied only to the extent that research impacts the design and has sufficient scope to properly test the hypotheses.

It is equally important to note the impossibility of making every design decision on the basis of evidence from credible research. Many elements of the built environment have never been subjected to any form of research analysis. Given the current state of the art, it would be unreasonable to require that an entire project be evidence-based. Some projects must be based on hypotheses having no research support. Some of the questions encountered may be completely new or unique, and the facility will have to be designed to help answer them for the first time. These projects offer valuable contributions to the field of evidence-based design.

Does the research have to be groundbreaking, or is it just as important to develop a body of findings confirming work done in previous studies? Researchers would agree that there is real value in replicating good studies, as new evidence can either support or refute the previous conclusion. Sound methodology is more important than the choice or novelty of the study topic.

The existence of documented hypotheses associated with intended outcomes of the design interventions is a clear signal that the design is evidence-based. Such hypotheses must be stated in advance, during the design phase, and paired with sound methodology to measure observed results. Evidence-based processes should be applied to concepts or design issues that are centrally important to the project, rather than to elements only tangentially related to a client's standards of performance. They should be rigorous in their application to solving serious problems. The hypotheses should indicate how the solution will vary from routine practice, and they should identify measures to confirm the success or failure of each hypothesis. The minimum threshold for describing a project as evidence-based is the presence of hypotheses and relevant measures to confirm or refute them.

The following two projects illustrate how evidence-based design is not only beneficial in terms of problem solving, but also in terms of cost savings:

  • St. Michael Health Center, a community hospital replacement project in Texarkana, Texas, featured several design hypotheses, including downsizing unit management staff by reducing the number of patient units, while increasing the size and number of rooms on each unit. The result was a cost saving of $248,000 per year.

  • Valley View Medical Center in Cedar City, Utah, a recently opened rural replacement hospital project, hypothesized savings in administrative costs associated with reducing the number of departments from 35 to 12. Measurement is under way.

The Process, Not the Product

The definition of evidence-based design is therefore best based on the process, not the result. It is certainly possible for a well-conceived, evidence-based project to test important concepts or hypotheses and still yield poor outcomes. Such is the nature of experimental science; not all clinical research produces the cure for cancer. Scientific research is a laborious process that proposes, tests, and rejects many ideas, combines the results of prior efforts in new ways, and continues to improve the model with each successive piece of information that emerges.


A possible anxiety for the design professional or firm associated with an evidence-based process is the prospect of producing unflattering findings. What if the predicted outcomes do not materialize or are disappointing? I understand the real fear that poor results will harm the designer's reputation, but I believe there is a moral commitment to the scientific method that requires honest reporting of any result, positive or negative. Negative results answer important questions, too, and can steer future projects to better outcomes. Moreover, healthcare itself is a world accustomed to scientific research. My clients in this field have always respected my candid admissions of lessons learned from prior misjudgments. I believe they develop a higher sense of trust when they know I'm willing to share the best and the worst of my past efforts.

If the field continues to shift further toward evidence-based models, as proposed here, all design professionals will be asked to confirm the effectiveness of their prior efforts—and those who conceal the negative will find themselves suspect. Proper use of evidence-based design will lead ultimately to far more positive than negative outcomes for clients and designers alike.

Some architects and designers may believe that evidence-based design provides an easy justification to show they're “right” about design decisions; some may view it as providing a handy “cookbook” of successful design examples. These views are simplistic. Every aspect of the designer's talent and creativity is called upon to blend the design decisions supported by research with the design decisions for which research provides no guidance. Even the available research can be full of contradictory findings that, taken to their limits, may imply polar extremes. There are few easy answers, and surface levels of almost any type of investigation or inquiry soon lead one to deeper questions and often to difficult answers.

A Bold Way Forward

While the concept of evidence-based design has been appealing to many architects and design professionals, there are elements of the process that may require acquisition of new capabilities. As the typical practitioner develops evidence-based skills, he or she also needs to develop mastery of the literature search, the use of applied research methodologies in the field, and an understanding of the intellectual rigor needed in the interpretation and reporting of findings. These efforts are worth it, because they promise higher levels of performance and superior results in the final design and development of a project. True evidence-based design offers the promise of a bright and exciting future for healthcare architecture. HD

Note: The third and final article in this series will propose a means of identifying, rating, and comparing evidence-based projects, based on standardized definitions, allowing projects of differing scopes in different locations to be compared consistently.

D. Kirk Hamilton, FAIA, FACHA, is a founding principal with Watkins Hamilton Ross Architects in Houston, and leader of Q Group Advisors, the firm's consulting division. He is a past-president of the American College of Healthcare Architects and the AIA Academy of Architecture for Health. He is a member of the board of directors of The Center for Health Design and the Coalition for Health Environments Research. He has authored and edited three books on health facility design and is currently working on a new book about evidence-based design for critical care. He recently completed a Master of Science degree in Organization Development at Pepperdine University.


Ten Steps to Positive Results

What does an evidence-based design process look like? It would most likely involve steps like these:

  1. Setting the project's design goals and objectives.

  2. Identifying the key issues suited to investigation by evidence-based techniques.

  3. Using critical thinking to explore the possibly complex implications of the research.

  4. Hypothesizing the intended result(s).

  5. Researching topics that are key to the hypothesis and benchmarking the field for relevant examples.

  6. Selecting appropriate measures to determine success or failure of the hypothesis.

  7. Testing alternative hypotheses, if necessary, and selecting the optimum solution.

  8. Constructing the environment according to the design and carefully measuring the observed results.

  9. Reporting unbiased findings from an independent viewpoint.

  10. Subjecting the findings to peer review.