Evaluating design strategies, performance and occupant satisfaction: a low carbon office refurbishment

Abstract

Existing buildings present the best opportunity for reducing greenhouse gas emissions in developed economies, given that only 2–3% of the building stock is newly built each year. Insights from a post-occupancy evaluation of a large-scale refurbishment project of a head office building in Sydney, Australia, are presented to inform future refurbishment strategies. The study evaluates occupant satisfaction and energy performance, and elicits influencing factors arising from the design process and interventions, ongoing building management, and operational performance. Occupants returned a high level of satisfaction across the range of environmental variables for overall comfort, temperature, lighting, and air quality as well as perceived productivity and health. These outcomes highlight the importance of improving indoor environmental quality for occupants particularly through increased fresh air, daylight, glare control, access to views, and noise management. The positive results reinforce the value of an integrated and user-responsive approach that was adopted for building design, development, and management. The reduction in operational energy (in this project, coupled with carbon reduction) as a consequence of refurbishment and positive user feedback demonstrates the potential to future-proof existing buildings in the context of climate change.

Les bâtiments existants offrent la meilleure possibilité de réduction des émissions de gaz à effet de serre dans les économies développées, étant donné que les constructions neuves ne représentent chaque année que 2 à 3% du parc bâti. Les enseignements retirés d'une évaluation après occupation d'une opération de rénovation à grande échelle réalisée dans l'immeuble d'un siège social de Sydney, en Australie, sont présentés afin d'infléchir les futures stratégies en matière de rénovation. L'étude évalue la satisfaction des occupants et les performances énergétiques, et met au jour les facteurs d'influence qui découlent du processus de conception et des interventions réalisées, de la gestion en cours du bâtiment et des performances de fonctionnement. Les occupants ont exprimé un degré de satisfaction élevé sur l'ensemble des variables environnementales concernant le confort global, la température, l'éclairage et la qualité de l'air, aussi bien que la productivité et la santé telles qu'ils les ont perçues. Ces résultats mettent en évidence le fait qu'il est important d'améliorer la qualité environnementale intérieure pour les occupants, tout particulièrement en apportant davantage d'air frais et de lumière du jour, un plus grand contrôle de l'éblouissement, un accès accru à des panoramas et une gestion renforcée du bruit. Ces résultats positifs renforcent l'utilité d'une approche intégrée et sensible aux besoins des utilisateurs, telle qu'elle a été adoptée pour concevoir, aménager et gérer ce bâtiment. La réduction de l'énergie de fonctionnement (dans cette opération, conjointement avec la réduction du carbone) en conséquence de la rénovation et du feedback positif des utilisateurs démontre le potentiel de cette approche pour permettre aux bâtiments existants de bien affronter l'avenir dans le contexte du changement climatique.

Mots clés: adaptation, changement climatique, confort, énergie, qualité environnementale intérieure, conception intégrée, occupants, évaluation après occupation, rénovation

Keywords:

• adaptation
• climate change
• comfort
• energy
• indoor environmental quality
• integrated design
• occupants
• post-occupancy evaluation
• refurbishment

Acknowledgements

This paper draws on findings from an independent post-occupancy evaluation undertaken by the author for Stockland Pty Ltd, which included use of the BUS questionnaire under licence. The author wishes to acknowledge the range of stakeholders for the Stockland Head Office project whose support and participation made this study possible. The author thanks staff at Stockland, in particular G. Johnson, D. Rooney, C. Hughes, J. Metske, and J. Zannino, for their generous assistance with the study over its two-year course. Thanks are also due to A. Galvin of BVN Architecture, and H. Schepers of Arup for providing insights into the building's design and functionality, and to A. Leaman of Building Use Studies for his feedback and support during the project.

Notes

In Australia, a building that achieves the top level of a 5 Star NABERS energy rating (see endnote 3) delivers 58% CO₂ reductions in comparison with the industry average of 2.5 Stars. Further CO₂ reductions are achievable for buildings that target incremental improvements over this target and towards zero-carbon emission targets.

EPLabel (available at: http://www.eplabel.org/) (accessed on 1 February 2010).

National Australian Building Environmental Rating Scheme (NABERS), NABERS Office (available at: http://www.nabers.com.au/office.aspx) (accessed on 1 February 2010).

Green Star, Green Star Rating Tools (available at: http://www.gbca.org.au/green-star/rating-tools/green-star-rating-tools/953.htm) (accessed on 1 February 2010).

LEED: The Leadership in Energy and Environmental Design Green Building Rating System (available at: http://www.usgbc.org/DisplayPage.aspx?CategoryID=19) (accessed on 21 February 2010).

Building Research Establishment Environmental Assessment Method (BREEAM) (available at: http://www.breeam.org/) (accessed on 5 February 2010).

Building Use Studies (available at: http://www.usablebuildings.co.uk) (accessed on 12 February 2010).

Twenty-three Probe study papers were published in Building Services Journal between September 1995 and October 2002.

The response rate for the post-occupancy survey is based on the total number of respondents (n = 238) as a percentage of staff present during the survey period (n = 595). Of the 622 employees, 27 were away on extended or annual leave and not included in the count.

Developed in 1998 as Australian Building Greenhouse Rating (ABGR), the NABERS energy rating system is arguably one of the first formal protocols for rating actual energy performance and CO₂-equivalent in the world. It is currently administered by the New South Wales Department of Environment and Climate Change (DECC) on behalf of commonwealth, state, and territory governments. Although a voluntary system, it is now quasi-mandatory. For example, the commonwealth and many state governments mandate a minimum NABERS energy rating for buildings that are leased or owned by these agencies (Department of Environment and Water Resources (DEWR), 2007).

Percentage dissatisfied as reported in this paper refers to the percentage of respondents choosing the lower end of the scale. In A-type scales, where 1 is worst and 7 is best, percentage dissatisfied refers to the percentage of respondents choosing 1, 2 or 3. For B-type scales, where 4 is best, percentage dissatisfied refers to the percentage of respondents choosing 1, 2, 6 or 7. For C-type scales, where 1 is best and 7 is worst, percentage dissatisfied refers to percentage of respondents choosing 5, 6 or 7.

T _vis = visible transmittance, SHGC = Solar Heat Gain Coefficient and U or U value = overall thermal transmittance.