Elsevier

Building and Environment

Volume 68, October 2013, Pages 66-76
Building and Environment

Occupant satisfaction in LEED and non-LEED certified buildings

https://doi.org/10.1016/j.buildenv.2013.06.008Get rights and content

Highlights

  • Occupant satisfaction with IEQ was analyzed in 65 LEED and 79 non-LEED buildings.

  • Results differ from literature also due to larger sample and new statistical tests.

  • The difference in satisfaction with the building and the workspace was negligible.

  • Mean satisfaction vote with indoor air quality was slightly higher in LEED offices.

  • Mean satisfaction vote with amount of light was slightly lower in LEED offices.

Abstract

Occupant satisfaction with indoor environmental quality (IEQ) in office buildings has been positively correlated to self-estimated job performance and, potentially, to overall company productivity. LEED is a voluntary, consensus-based, market-driven program that provides third-party certification of green buildings, contributing to promote sustainability into the mainstream of building design and construction. From the literature, however, it is unclear the extent to which LEED certification also improves occupant satisfaction with IEQ. The aim of this paper is to study if LEED certified buildings lead to a higher, equal or lower satisfaction with indoor environmental quality than non-LEED rated buildings. Occupant satisfaction has been evaluated on a subset of the Center for the Built Environment Occupant Indoor Environmental Quality Survey database featuring 144 buildings (65 LEED certified) and 21,477 individual occupant responses (10,129 in LEED buildings). Differently from previous studies of the CBE database, the results show that occupants of LEED certified buildings have equal satisfaction with the building overall and with the workspace than occupants of non-LEED rated buildings. The difference in mean satisfaction scores between LEED and non-LEED buildings for other 15 IEQ parameters investigated is always lower than 6% with a negligible effect size. Therefore, it can be concluded that there is not a significant influence of LEED certification on occupant satisfaction with indoor environmental quality, although the analysis of mean votes of satisfaction reveals that occupants of LEED buildings tend to be slightly more satisfied with air quality, and slightly more dissatisfied with amount of light.

Introduction

The satisfaction of occupants in office buildings is affected by thermal, acoustic and visual parameters, by air quality, and by other features of the workspace – and of the building – such as view, furniture layout, amount of privacy, cleanliness and level of personal control over the internal environment [1]. The satisfaction of occupants has been correlated to the self-estimated job performance of office workers [2], this having an effect on frequency and duration of absenteeism and intention to quit work and, potentially, to overall company productivity [3]. Therefore, occupant satisfaction is an important factor in the design, operation and management of buildings.

LEED (Leadership in Energy and Environmental Design) is a voluntary, consensus-based, market-driven program that provides third-party certification of green buildings [4]. LEED is the most popular building rating tool in the United States, and its market share is continuing to grow, both in the US and internationally [5]. Irrespective of the LEED product used for the certification, there is a general perception amongst the actors of the building industry that LEED – as well as other rating tools such as BREEAM in UK, Green Mark in Singapore, Green Star in Australia, etc. – has effectively contributed to bring sustainability into the mainstream of building design and construction [6], [7]. However, less clear from the literature is the extent to which the use of a rating tool can actually improve indoor environmental quality and workplace satisfaction for the occupants of the certified buildings. In this context, it should be mentioned that the evidence of the energy savings effectively facilitated by rating tools has also been analyzed by studies that have looked at actual energy use of LEED certified buildings versus a comparable dataset of existing commercial buildings in the US [8], [9]. The outcomes concluded that it is complex to provide a comprehensive calculation of the effective reduction in primary (source) energy use in commercial buildings certified by LEED compared to not-rated office spaces.

In the following paragraphs, this paper will introduce the LEED program, the Center for the Built Environment (CBE) Occupant Indoor Environmental Quality Survey, and will analyze the results of previous studies focusing on the relationship between indoor environmental quality, LEED/green rating and occupant satisfaction.

With the inception of the first LEED Pilot Project Program (LEED v1.0) in 1998 – and the launch of the LEED Green Building Rating System Version 2.0 (thereafter known as LEED for New Construction) in 2000 [10] – the United States Green Building Council (USGBC) has created a framework for rating new and existing buildings that encompasses to date several thousand certifications awarded across 135 countries. In February 2013, the USGBC indicated as 15,183 the number of commercial buildings having received LEED certification worldwide [11]. The USGBC defines as “green buildings” those that “significantly reduce or eliminate negative impacts on the environment and the occupants” [4]. Today, LEED consists of nine products, covering the design, construction and operation of: New Constructions & Major Renovations; Existing Buildings: Operation & Maintenance; Commercial Interiors; Core & Shell Development; Retail; Schools; Homes; Neighborhood Development; and, Healthcare. This paper only analyzes buildings certified under the first three LEED products.

LEED for New Construction (LEED-NC) v1.0 was launched in 2000 as the first LEED rating scheme geared towards the construction of new commercial buildings and major renovations [12]. LEED for Existing Buildings (LEED-EB) was released in 2002 to promote sustainable practices and the reduction of environmental impacts by addressing aspects of ongoing existing building operations [13]. LEED for Commercial Interiors (LEED-CI) was launched in 2004 to certify interior tenant spaces, i.e. targeting users that lease their space or do not occupy the entire building [14]. Following their initial releases, several versions of the various LEED products have been launched, up to the latest version 4 that was at the stage of beta testing when writing this paper [15].

All LEED products encompass five common credit categories: (a) sustainable sites; (b) water efficiency; (c) energy & atmosphere; (d) materials & resources; and, (e) indoor environmental quality (IEQ).

In the current version 2009 of the LEED products considered, credits obtainable within the IEQ category (15 credits under LEED-NC and LEED-EB, and 17 under LEED-CI) are either required or voluntary. In LEED-NC, the two mandatory IEQ credits address minimum indoor air quality performance and tobacco smoke control, while voluntary credits encompass areas such as ventilation, IAQ management plan, low-emitting materials, controllability of systems, visual and thermal comfort. In LEED-EB, three credits are required respectively for IAQ performance, tobacco smoke control and green cleaning policy, while other voluntary areas of certification include IAQ management practices, occupant surveys, controllability of lighting systems, thermal comfort monitoring, daylight and views, and green cleaning. In LEED-CI, the IEQ credit distribution is identical to LEED-NC, with the addition of one voluntary credit for low-emitting materials (systems furniture and seating) and one for daylight and views. For all the products of LEED v2009, certification is awarded according to the following scale: certified (40–49 points), silver (50–59 points), gold (60–79 points), platinum (80 points and above) [11].

To investigate occupant satisfaction and its correlation with indoor environmental quality parameters and building features, the Center for the Built Environment (CBE) at the University of California Berkeley has developed a web-based survey and online reporting tool [16]. The resulting database provides a unique opportunity to investigate the factors that drive satisfaction in the workplace from the perspective of the occupants.

The CBE survey grew out of earlier thermal comfort studies conducted at CBE, based on an established in-depth pre-testing method called ‘cognitive interviewing’, and used by the Survey Research Center at UC Berkeley to assess how well respondents were able to comprehend and accurately report answers to questions [17].

The survey is currently composed of core and optional modules, which can be added basing on specific buildings' characteristics or due to interest in particular features. The core survey appraises the satisfaction of occupants under the categories described in Table 1.

These categories are clearly not exhaustive to fully describe the satisfaction and comfort of building users, however, they are all pertinent. The survey uses 7-point ordered scale questions to evaluate occupant satisfaction with indoor environmental quality parameters, workspace and building features, ranging from ‘very satisfied’ (+3) to ‘very dissatisfied’ (−3), with a neutral midpoint (0) [1]. The survey also collects information about occupants (e.g., gender, age group, type of work, office type, distance of workspace from the window, period of time since starting work in the current building and workstation, weekly working hours, etc.) and about the building characteristics (e.g., year of construction or renovation, location, size, number of floors and occupants, shading devices and control, LEED certification, energy use, cost of construction, etc.). This latter information is provided by the building facility manager – or the survey administrator – for each building where the survey is administered. The full database currently includes in excess of 600 buildings (featuring commercial buildings, healthcare facilities, laboratories, educational buildings, libraries, etc.) and 65,000 individual occupant responses obtained over a period of more than ten years across the United States, Canada, Europe and Australia.

The CBE survey has already been applied in various research scenarios, providing the possibility of evaluating the effectiveness of a design intervention, or informing the development of design guidelines for new buildings. The survey can also be used as a benchmarking tool to compare a building's performance against other buildings from the point of view of the occupants, and can also represent a valuable diagnostic instrument to recognize specific problems and their sources [18].

A vast literature of studies has looked at the relationship between IEQ and occupant satisfaction in commercial office buildings. The following investigations were selected since they analyze more directly the connection between green rating tools (such as LEED) and users' satisfaction, health and productivity.

Data from the CBE survey have been utilized in several studies. An early work by Huizenga et al. [17] analyzed and compared the responses obtained in three LEED certified buildings against the rest of the CBE database, comprising at the time of the study of 45 buildings in US and Europe. Although based on a very limited sample, these preliminary results showed that green-rated buildings are characterized by higher occupant satisfaction particularly for indoor air quality. A larger sample of 16 LEED rated and 9 self-nominated ‘green’ buildings (i.e., buildings having received awards for their sustainable credentials) was used by Huizenga et al. [19] to examine occupants' responses in ‘sustainable’ buildings within the CBE database. The research revealed that green buildings received statistically significant higher votes of satisfaction with the building and the workspace, indoor air quality, cleaning and maintenance, and thermal comfort. However, LEED and self-nominated green buildings did not perform better for lighting and for acoustics. The study did not find a clear relationship between LEED credits and occupant satisfaction with IEQ parameters, therefore suggesting that LEED certification per se may not guarantee a better perception of indoor environmental quality by its occupants. Based on a similar subset of the CBE database, Abbaszadeh et al. [20] analyzed 33,285 responses from 181 buildings, of which 15 had been certified by LEED and 6 had been indicated by their designer/owner as designed or operated in a sustainable way. The results revealed that, on average, occupants of green buildings showed statistically significant higher satisfaction in comparison with the rest of the CBE database in the following areas: office furnishing, thermal comfort, air quality, cleaning and maintenance, workspace, and building overall. Higher mean scores of satisfaction with these parameters were obtained in LEED/green buildings also when including in the comparison only ‘non-green’ buildings newer than 15 years – and thus chronologically similar to the LEED/green group – although in this case these relationships were found to be not statistically significant (with the exception of satisfaction with air quality). 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 Refs. [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. Conversely, lower mean scores of satisfaction were obtained with office layout, lighting, and acoustic quality. Finally, in terms of the influence of subjectively evaluated indoor environmental parameters and building features on occupant satisfaction, Frontczak et al. [1] analyzed the responses from 350 buildings of the CBE database, showing that, in average, building occupants were satisfied with their workspace and the building, and with all the IEQ parameters of the CBE survey. The study also indicated that, amongst all the parameters included in the database, satisfaction with the amount of space available for individual work and storage was the most important factor affecting workspace and overall building satisfaction, followed by noise level and visual privacy.

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.); the comparisons were made between buildings and not between individual occupants' responses; no selection of the responses available in the CBE database was made so as to compare only those obtained in buildings of similar size and age; the results were based mostly on the analysis of mean and median, without consideration of other statistical measures such as the effect size.

As far as occupants' perception of health and productivity is concerned, Baird et al. [23] studied whether users perceive the performance of green buildings differently from conventional ones. To this aim, a comparison with respect to 44 factors related to operational, environmental, personal control and satisfaction between two sets of buildings was performed. The two groups featured, on the one side, 31 ‘green’ commercial or institutional buildings located in 11 countries, and, on the other, 109 buildings chosen within a larger database (although not representative of a random statistical sample). The results indicated that green buildings were perceived by occupants as performing better in terms of operation and satisfaction scores, with significant improvement particularly in perceived productivity. However, modest improvements were found in thermal conditions and lighting, and no significant difference was observed for perception of noise and personal control. Singh et al. [24] investigated the role of improved IEQ in two pre-and post case studies of occupants moving from conventional to LEED certified office buildings. They found that improvements in IEQ contributed to the reduction in occurrence of absenteeism as perceived by the employees, and to the decrease of self-assessed number of hours of work affected by asthma, respiratory allergies, depression and stress. Following the move, employees also reported a perception of enhanced productivity. However, these results may have been biased by the fact that, for the first study, the pre-move survey was conducted 4–6 weeks after the move, hence bringing the risk of a recollection bias. Another limitation may have been represented by the fact that pre- and post-move surveys were taken at different times of the year, so asthma and allergy symptoms may have been affected by seasonal factors.

To inform a comparative analysis of conventional and green buildings from the point of view of the users, Leaman et al. [25] performed a post-occupancy evaluation in 22 ‘green-design intent’ and 23 conventional buildings in Australia. The study revealed that most green buildings outperformed conventional ones particularly for occupant satisfaction with ‘soft’ parameters such as design, needs, image and health. However, due to their relative infancy, the first generation of Australian green buildings showed a wider spectrum of performances and may be underperforming in terms of perception of ‘physical’ variables (e.g., noise and, in particular, temperature). A further study by Leaman and Bordass [26] in United Kingdom confirmed these results, analyzing and comparing occupants' surveys from 177 buildings half of which had been designed with ‘green’ aims. The findings indicated a wide spread of scores for green buildings, with improvements particularly in areas such as image and speed of response when comfort thresholds are breached. Green buildings revealed some concerns in terms of operational management, although users showed a tendency to be more tolerant to such deficiencies compared to occupants of conventional buildings. Finally, of particular relevance is the work of Newsham et al. [27], which analyzed 2545 occupant responses collected simultaneously with physical building measurements (e.g., thermal, air quality, acoustics, and lighting conditions), appraisal of workstations characteristics (e.g., workstation size, ceiling height, window access, shading, electric lighting system, and surface finishes) and energy use data from 24 buildings (12 LEED/green buildings ‘twinned’ with 12 similar conventional buildings) in Canada and the US. The results indicated that LEED/green buildings exhibited superior environmental performance, with improvements particularly in overall environmental satisfaction, satisfaction with thermal conditions, view to the outside, aesthetic appearance, disturbance from HVAC noise, workplace image, night-time sleep quality, mood, physical symptoms, and number of airborne particulates.

In summary, the researches described here show evidence that occupant satisfaction, health and productivity is generally higher in green buildings compared to conventional ones. In light of these studies, the aim of this paper was set to analyze the responses of the CBE Occupant Indoor Environmental Quality Survey, selecting a larger sample of LEED buildings than those included in the literature available to date. This was to effectively measure up the perception of occupants of commercial office buildings in terms of satisfaction with the building, the workspace, and a wide range of IEQ parameters, and measure it against a comparable set of responses in non-LEED certified buildings. In order to do so, a re-analysis of part the CBE survey database had to be performed so as to select an appropriate dataset of buildings and occupants' responses for the purpose of the proposed analysis.

Section snippets

Selection of buildings

A subset of the CBE Occupant IEQ Survey database has been used for the study presented in this paper. The chosen subset – for consistency, comparability of results, and ease of examination – has been based on the dataset utilized by the mentioned study by Frontczak et al. [1]. We focused on the survey's main core questions.

To identify the buildings and occupants' responses to be included in their evaluation, Frontczak et al. [1] made a selection from the CBE database based on whether: the

Statistical results of occupant satisfaction

In Fig. 1 (left) are plotted the mean, median, first and third quartile of occupant satisfaction with the building, the workspace, and each of the 15 IEQ parameters of the CBE survey, for both the LEED and the non-LEED groups of buildings. In addition, Fig. 1 (center) illustrates the difference between the mean values of satisfaction achieved for each parameter in LEED and non-LEED buildings (LEED minus non-LEED), and also provides (right) the effect size index (Spearman Rho). The plotting

Occupant satisfaction with IEQ in office buildings

This study has analyzed a subset of the CBE Occupant Indoor Environmental Quality Survey database to investigate occupant satisfaction with indoor environmental quality in LEED and non-LEED rated commercial offices, and ultimately ascertain if LEED certified buildings lead to a higher, equal or lower satisfaction with the building, with the workspace, and with each of the 15 IEQ parameters assessed by the CBE survey.

The subset for the study presented in this paper has been based on the dataset

Conclusions

The main conclusions that can be drawn from the analysis presented in this paper include the following:

  • Occupants of LEED certified buildings have equal satisfaction with the building overall (LEED: M = 1.08; non-LEED: M = 1.07; ΔM = +0.01, p < 0.001; effect size = 0.02 (negligible)) and with the workspace (LEED: M = 0.95; non-LEED: M = 0.87, ΔM = +0.08, p < 0.001; effect size = 0.03 (negligible)) than occupants of non- LEED buildings. Therefore, LEED rating does not significantly affect

Acknowledgments

This paper is part of the research activities developed by the first author at the Center for the Built Environment (CBE), University of California Berkeley (USA), funded by the HEA-Higher Education Academy (United Kingdom), International Scholarship Scheme. The authors would like to thank Gail Brager, Ed Arens and John Goins for their valuables advices, and Monika Frontczak for the development of the dataset in R.

References (46)

  • J.H. Heerwagen

    Green buildings, organizational success and occupant productivity

    Building Research & Information

    (2000)
  • V. Loftness et al.

    Education and environmental performance-based design: a Carnegie Mellon perspective

    Building Research & Information

    (2005)
  • U.S. Green Building Council. Foundations of LEED. 2009;...
  • U.S. Green Building Council. LEED – leadership in energy and environmental design;...
  • U.S. Green Building Council. LEED – new construction and major renovations;...
  • U.S. Green Building Council. LEED – existing buildings;...
  • U.S. Green Building Council. LEED for commercial interiors;...
  • U.S. Green Building Council. LEED v4 – the next version of LEED;...
  • L. Zagreus et al.

    Listening to the occupants: a Web-based indoor environmental quality survey

    Indoor Air

    (2004)
  • Huizenga C, Zagreus L, Arens EA, Lehrer D. Measuring indoor environmental quality: a web-based indoor occupant...
  • Huizenga C, Laeser K, Arens EA. A web-based occupant satisfaction survey for benchmarking building quality. Proceedings...
  • Huizenga C, Zagreus L, Abbaszadeh S, Lehrer D, Goins J, Hoe L et al. LEED post-occupancy evaluation: taking...
  • S. Abbaszadeh et al.

    Occupant satisfaction with indoor environmental quality in green buildings

    Proceedings of Healthy Buildings

    (2006)
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