Making A Case For Evidence-Based Design
Part 2: Studies Link Green Design, Occupant Productivty
Studies Link Green Design, Occupant Productivty
By Lacey Muszynski, Assistant Editor - November 2009 - Green
Many facility executives outside of health care have never heard of evidence-based design. But over the past decade, a multitude of studies has examined the impact of building design on occupants. The goal of those studies: to document the effect of green strategies on occupant performance and satisfaction.
No one labeled these studies as evidence-based design. But in their use of research and their focus on building design, those studies have much in common with evidence-based design. In fact, it's fair to say that apart from evidence-based design of health care, studies of green buildings represent the most extensive effort to evaluate the link between buildings and occupants.
"We have so much evidence about technology and the mechanics of green design, facility siting, waste water usage, and on and on," says Denise Guerin, Morse-alumni distinguished professor of interior design at the University of Minnesota. "That helps us have great predictive power on how something is going to operate, but in the interior environment, the major variable is the human."
Luckily for facility executives, there is an increasing amount of research being done on human behavior in regards to facility design. So far, the answer suggests daylighting, thermal comfort and indoor air quality all play a major role in human health and productivity.
Let the Sun Shine In
Of those factors, daylighting tends to be the most pervasive in terms of research and implementation in both sustainable and evidence-based design. Facility executives who work in green buildings are aware of the energy savings when a good daylighting strategy is used, and some even earn LEED points. Besides the green benefits, there have been a number of studies in the past decade that link exposure to daylight to productivity and increased mood in occupants of office space.
One of the most well-known daylighting studies was conducted by the Heschong Mahone Group and managed by the New Buildings Institute for the California Energy Commission in 2003. "Windows and Offices: A Study of Office Worker Performance and the Indoor Environment" examined two different study samples from the same company: 100 workers in an incoming call center, and 200 other office workers. The facilities included a range of daylighting conditions. The research measured productivity based on call center statistics and performance tests administered to the non-call center office workers. The results showed that office workers with higher levels of daylight illumination performed better in assessment tests that measured attention span and short-term memory.
The view occupants have out the window also seems to matter. Interestingly, the Heschong Mahone Group study found that better views (characterized by window size and the amount of vegetation visible) allowed call center workers to process calls 6 to 12 percent faster compared to workers with no views.
In contrast, the study warns against a potential problem with daylighting strategies: beware of glare. Simply putting as many windows in a space as possible without means to control the light coming in, such as with shades or window film, can hinder productivity.
Daylighting has also been shown to have a great effect on children in schools. Traditionally, productivity is measured in educational facilities by student test scores and absenteeism. One study, "Daylighting in Schools," completed for Pacific Gas and Electric in 1999, showed that students in classrooms with the most daylighting had 7 to 18 percent higher year-end test scores than students in classrooms with the least daylighting.
Thermal comfort can also have an effect on occupant productivity in office spaces. Good ventilation, temperatures in the comfort zones and appropriate humidity are all part of the thermal comfort equation, says Norm Miller, academic director of the Burnham-Moores Center for Real Estate at the University of San Diego. A draft paper written by Miller and Dave Pogue, national director of sustainability at CB Richard Ellis, states that worker performance increases with temperatures up to 72 degrees F, and decreases with temperatures above 73-75 degrees F.
Similarly, good IAQ measures have been shown to reduce sick building syndrome (SBS) symptoms by up to 50 percent, according to William Fisk of Lawrence Berkeley National Laboratory. Symptoms of SBS include respiratory ailments, allergies and asthma, all of which can lead to increased numbers of sick days, lower productivity and higher medical costs.
Asthma has become a real concern lately in schools, as the number of cases of childhood asthma is at an historically high level, says Katrina Shum Miller, principal, Green Building Services, a consulting firm. Besides following LEED and ASHRAE guidelines for HVAC standards, facility executives can reduce students' exposure to irritants by implementing a green cleaning program, using no-VOC paints and materials, and even instructing faculty to store art supplies in sealed areas or bins when not in use.
Studies show that simply giving occupants control over their own thermal comfort by way of adjustable diffusers — common with underfloor air systems — can go a long way to ensuring their satisfaction, whether they actually adjust the airflow or not. "When people have any degree of control, their satisfaction increases," says Guerin. "It increases their perception that their environment enhances their performance."
Besides air diffusers, Guerin also uses the example of task lighting as a small step that can make a huge difference. Many green buildings have lighting controls that balance daylight and overhead light, but when occupants need more light, switching on a task light is more energy efficient than increasing the lighting throughout the entire space. "People are just thrilled with the whole idea," says Guerin. "They feel they're being taken care of by the organization and they feel like they're saving energy."
Getting occupants involved in green efforts is often key to increasing satisfaction, research shows. A facility that they understand is one that they can be excited to work in. That makes green design a good starting point for increasing productivity. "It seems to me that most of the time, the designs for greater productivity and sustainable design will be in sync," says Miller.
Other experts agree, and recommend that facility executives who are interested in evidence-based design start by implementing green strategies. "The end goal of evidence-based design is very much in line with the goals of sustainability," says Shum Miller. "If you look at the two design strategies, they're both about making smart decisions."
Three Important Research-based Design Studies
"Designing Space To Support Knowledge Work"
Researchers at the Georgia Institute of Technology studied how a different, more open and collaborative office plan at a communication design firm affected worker productivity in terms of billable hours per project. The study found that the amount of time spent on each of five stages of a project dramatically decreased in the new office layout compared to the previous office layout, indicating huge gains in worker productivity. Read the study here: eab.sagepub.com/cgi/content/abstract/39/6/815
"Windows and Offices: A Study of Office Worker Performance and the Indoor Environment"
Two different studies by the Heschong Mahone Group looked at 100 workers in a call center and 200 other white collar workers. Researchers found that workers processed calls 6 to 12 percent faster when they had the "best possible view" vs. no view. To measure the productivity of the office workers, researchers administered tests for mental function and memory recall. Workers of performed 10 to 25 percent better when they had the "best possible views" vs. no view. Read a summary of this study, as well as another study on how daylighting affected school children, here: h-m-g.com/projects/daylighting/summaries%20on%20daylighting.htm#_ftnref1
"Building Conditions, Parental Involvement, and Student Achievement in the District of Columbia Public School System"
This landmark and oft-cited study from Georgetown researcher Maureen Berner showed a precise correlation between school condition and achievement. She concluded that raising a school condition one category — from poor to fair, for instance — resulted in a 5.5 percent increase in scores on standardized tests. The study is currently unavailable online.