Indoor Environmental Quality in LEED-Certified Buildings in the U.S.

Abstract

The purpose of this study was to evaluate the indoor environmental quality (IEQ) of workplaces in the LEED-certified buildings in the United States. LEED ® , standing for the Leadership in Energy and Environmental Design, is a U.S. national sustainable building benchmark as well as green building rating system adopted nationally and internationally. The study compared seven IEQ criteria in relation to occupant's satisfaction and performance between LEED-certified buildings and non-LEED-certified buildings. The seven IEQ criteria included qualities of office layout, office furnishings, thermal comfort, indoor air quality (IAQ), lighting, acoustics, and cleanliness and maintenance. The study found that LEEDcertified buildings showed higher occupant satisfaction with office furnishings quality, IAQ, and cleanliness and maintenance quality than non-LEED-certified buildings. However, non-LEED-certified buildings presented higher occupant satisfaction with office layout quality, lighting quality, and acoustic quality than LEED-certified buildings. LEED-certified buildings had higher occupant performance in office furnishings quality, thermal comfort quality, IAQ, and cleanliness and maintenance quality than non-LEED-certified buildings. But non-LEED-certified buildings showed higher occupant performance in office layout quality, lighting quality, and acoustic quality. The implementations of the study include emphasis on various issues of IEQ in workplace design when complying with LEED and refinement of current LEED IEQ criteria.

Occupant satisfaction in LEED and non-LEED certified buildings

“…The findings of our study in terms of mean values of occupant satisfaction with indoor environmental quality in commercial office buildings -both LEED and non-LEED rated -are also broadly consistent with those of other earlier studies on the CBE database (e.g., [1,21,22,36,37]), that reported low satisfaction particularly with their thermal and acoustic environment. As previously mentioned -in both LEED and non-LEED certified buildings -the lowest mean score of satisfaction was observed with sound privacy (LEED: M= -0.96; non-LEED: M= -0.88).…”

“…The conclusions of our study in terms of comparison between occupant satisfaction in LEED and non-LEED certified buildings are considerably different from previous analysis of data extrapolated from the CBE survey database [16][17][18][19][20][21][22]. In fact, earlier studies had concluded that LEED rated/green buildings were generally characterized by higher occupant satisfaction with the building, the workspace, air quality, cleaning and maintenance, and thermal comfort.…”

“…The difference between satisfaction votes in LEED/green buildings and the all-age inclusive rest of the database was found to be, on average, small and not statistically significant for: office layout, lighting, and acoustics. An analysis of the same subset of the CBE database was also presented in Lee and Kim [21] and in Lee and Guerin [22], which analyzed the IEQ parameters that mostly affect occupant satisfaction and self-estimated job performance in LEED buildings, and compared the results obtained with non-LEED certified buildings. The studies concluded that LEED certified buildings showed higher occupant satisfaction and perceived job performance with office furnishings, indoor air quality, cleanliness and maintenance.…”

“…Finally, to be noted that where the number of individual responses considered for each 'nonenvironmental' factor differs from the total number of occupants' responses available in the dataset (21,477), it means that some of the respondents to the survey did not provide that specific information.…”

“…Although the results of these studies of the CBE survey database provide important advance in the exploration of the relationship between LEED/green certification and occupant satisfaction with the indoor environment, in interpreting their outcomes the following limitations must be taken into account: these investigations were based on a relatively small sample of buildings (particularly in terms of buildings with LEED certification) and, in some cases [21,22], they were only using secondary data (i.e. without consideration and /or verification of building size, year of construction, etc.…”