The Benefits of Glass: A Literature Review on the Qualitative Benefits of Glass on Building Occupants

Overview

Dated January 3, 2012, this 29-page literature review was prepared by Kathy Velikov and Julie Janiski of the University of Michigan's Taubman College of Architecture and Urban Planning for Guardian Industries, the Michigan-based glass manufacturer. It deliberately sets energy aside and asks what the research says about the non-energy benefits of glass in buildings: the image it projects, the daylight and views it admits, and the productivity and health outcomes attributed to those. The authors pulled mostly post-1999 peer-reviewed work from the university's journal database, organized it into six sections, and added an annotated bibliography.

Key Findings

• Office workers in daylight-and-view zones scored up to 20% higher on cognitive tests than the average (Wang and Boubekri, 2011).
• Occupants of newly built LEED Gold and Platinum offices reported 39 additional productive hours per person per year, about a 2.6% productivity gain (Singh et al., 2010).
• Earlier reviews cited a 15% drop in absenteeism at Lockheed Martin after moving into a daylit building, a 15% drop at an ING bank building where no desk is more than 23 feet from a window, and 6.8 extra hours of attendance per person at a VeriFone distribution center.
• Retail stores with daylight showed monthly sales gains of 0% to 6% (Heschong Mahone Group, 2003), and California students in grades 3 to 6 who spent most of their day in daylit classrooms improved test scores 21% within one school year.
• Health evidence includes light's role in maintaining the circadian system, more jaundice cases in windowless maternity units, hospital stays 2.6 days shorter for patients in sunny rooms, and 22% less pain medication used by spinal-surgery patients with sunny rooms (Ulrich, 2008).
• Focus groups of building professionals ranked proof of productivity gains, better design tools, better communication of benefits to owners, better glare-reducing windows and better controls as the top barriers to daylighting.
• Five gaps deserve more research: personal control, technology and controls, thermal comfort near glazing (south-facing window surfaces ran 2 to 10 degrees F warmer than room air), performance across climates and seasons, and how transparent buildings support community life.

Why It Matters for Daylighting

Most of the outcomes catalogued here come from daylight rather than from the view, which matters for buildings where a view is not on offer. A distribution center with a 500-foot floor plate cannot put every worker within 23 feet of a window, but it can put every aisle under a skylight. The absenteeism and attendance numbers are the ones a warehouse operator should test first, since they are already in the payroll system. The review's own gap analysis also reads as a checklist for toplighting design: glare control, thermal load at the glazing, and controls that actually dim the electric lights are exactly where prismatic skylights and daylight-harvesting sensors earn their keep, and where energy codes now set minimum requirements for large single-story spaces.

About the Source

Taubman College is the University of Michigan's architecture and planning school; lead author Kathy Velikov is an architecture professor there, and Julie Janiski was a sustainability consultant. Guardian Industries commissioned the work, so it is a manufacturer-funded review, though it is transparent about its sources and about the limits of the evidence, including studies that found no effect. The document is 29 pages including the bibliography. It has circulated through the glass industry since 2012; look for the full review and its annotated bibliography under the title above.