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Creating a better open-plan work environment
N R C C - 4 8 6 5 3
B u r r o w s , J .
A version of this paper is published in / Une version de ce document se trouve dans: I Homes & Buildings, v. 3, no. 2, Summer 2006, pp. 8-9
Creating a Better Open-Plan Work Environment By John Burrows
Submitted to i-Homes and Buildings
This article presents the key results of a comprehensive research project on Cost-effective Open-Plan Environments (COPE) carried out by the NRC Institute for Research in Construction from 1998 to 2003. It updates the article published in the Fall 2004 issue of i-Homes & Buildings.
Cet article rassemble les résultats majeurs d'un projet de recherche sur la planification rentable des bureaux à aires ouvertes (PRAO) mené par l'Institut de recherche en construction du CNRC entre 1998 et 2003. Il met à jour l'article publié dans le numéro sorti à l'automne 2004 de i-Homes & Buildings.
It is estimated that about 70% of office workers are housed in open-plan offices. The COPE project, supported by public and private sector partners, arose from the realization that the open-plan office, or cubicle, often falls short of expectations in terms of worker comfort and satisfaction. The study looked at the three key elements that make up the workplace environment: lighting, privacy and acoustics, and ventilation and air quality. The project included experiments in open-plan office mock-ups, a field study, computer simulations, and reviews of research conducted by others. The field study involved measurements of the indoor environment conditions in 779 cubicles in nine office
buildings, and a survey of their occupants. The survey showed that occupant satisfaction with the workplace environment is positively related to overall job satisfaction; improved job satisfaction is known to be an important contributor to organizational productivity. The project culminated in a number of recommendations and design tools to help designers improve occupant satisfaction.
Effect of the Office Environment on Worker Satisfaction with Lighting
The researchers found that proximity to a window had the biggest effect on an occupant’s satisfaction with lighting. The higher light levels achieved and the view to the outside were positive elements. People tended to prefer a brighter environment as long there was no glare. Simulations showed that reducing partition heights and increasing surface reflectances increased both daylight penetration and light levels. Preferred light levels do vary substantially from person to person, and satisfaction is improved if an individual can obtain their preferred lighting level through the use of controls.
Recommendations for Lighting
Provide as many people as possible with a window, or at least a view of one.
Reduce partition heights to increase daylight penetration and to increase illuminance and lighting uniformity from electric lights.
Use lighter-coloured surfaces to increase illuminance and improve lighting uniformity. Use luminaires that have low brightness when viewed directly and do not create reflections on a computer screen.
Use electronic ballasts to eliminate flicker from fluorescent lights and to conserve energy.
Provide individual light dimming control so that personal preferences can be selected. In the open-plan office, this requires aligning and assigning luminaires to workstations.
Effect of the Office Environment on Worker Satisfaction with Privacy and Acoustics
The COPE survey affirmed that conversation noise is a major irritant in open offices. Studies in a mock-up office showed that if partitions were already high enough to block the direct sound path from the source, the next most significant path for speech
propagation between workstations is reflection off the ceiling. Therefore, reducing the level of speech sounds requires a high-absorption ceiling. Sound absorption by partitions was of lesser importance, while floor type was found to have little effect.
Speech privacy can also be improved by means of a loudspeaker noise-masking system, which mimics the sound of a ventilation system. Care should be taken not to make the masking noise too loud, so that it becomes annoying in itself.
Recommendations for Privacy and Acoustics
Specify partitions that are high enough so that most people standing cannot see someone seated in a workstation.
Choose highly absorbent ceiling tile to reduce the level of reflected speech sounds.
Increase the size of workstations to increase the distance between neighbours. Use a well-designed masking-noise system.
Locate workstations away from high-traffic areas to improve both acoustic and visual privacy.
Effect of the Office Environment on Worker Satisfaction with Ventilation
The COPE studies were confined to mechanically ventilated office buildings in which the ventilation system operator can control the amount of outdoor air delivered. This outdoor air is usually mixed with re-circulated building air and is heated or cooled, depending on the thermal load in the building.
An extensive review of the literature affirmed that satisfaction decreases if the widely recommended outdoor air provision rate of 10 L/s/person is not met. Increasing the proportion of outdoor air, which would require additional heating/cooling energy, did not result in a consistent improvement in occupant satisfaction. Thus, the research focused on examining whether office design could affect air quality and thermal comfort at the recommended level of 10 L/s/person.
An office mock-up study found that workstation size, partition height and distance from a supply diffuser had little effect on the efficiency of supply air delivery. However, the field study suggested that higher partitions reduce satisfaction with ventilation. The laboratory study demonstrated that certain supply-diffuser and occupant geometries can increase the risk of draught. The effect of these geometries can be accentuated in smaller workstations, where there is higher occupant density, where occupants have less
flexibility in their positioning and where total air-flow rates are likely to be raised due to increased demand for cooling.
The field study also suggested that satisfaction can be improved by providing occupants with some control over the ventilation in their workstations, supporting conclusions derived from a literature review. The field study data also showed that being seated next to a window can reduce thermal comfort because temperatures there tend to vary more than elsewhere in the building.
Recommendations for Ventilation
Ensure that the HVAC system is well maintained and delivers 10 L/s/person of outdoor air.
Adjust supply-air diffusers to avoid discomfort from localized draughts. Avoid very high partitions, which can create an impression of poor air flow.
Give individuals control over one or more of the following: air-flow rate, direction and temperature.
Holistic Design of Open-plan Offices
It is clear that achieving satisfaction for one design criterion may compromise another. For example, while lower partitions improve daylight penetration, the view to windows, electric light distribution and satisfaction with ventilation, they also increase noise and reduce visual privacy. If the needs and preferences of occupants are known, it is easier to choose partitions to meet the conflicting demands of acoustics and daylighting.
Occupants who prefer daylight to privacy can be located near the windows, with low partitions. Those for whom acoustic privacy is more important can be located further from the window, with higher partitions. Consulting with workers to determine needs and preferences can go a long way toward achieving a good design for the space. COPE researchers developed software tools to help assess trade-offs. COPE-ODE evaluates cost relative to projected worker satisfaction, and COPECalc evaluates the effects of design an acoustics. These tools are available at:
http://irc.nrc-cnrc.gc.ca/ie/cope/07_e.html.
Anotheroutcome of the project is the guide Workstation Design for Organizational
Productivity reviewed elsewhere in this issue of i-Homes & Buildings. The guide,
developed in collaboration with Public Works and Government Services Canada, is available for downloading at http://irc.nrc-cnrc.gc.ca/ie/productivity/index_e.html. The findings of the COPE research have been detailed in Construction Technology Updates (Numbers 60, 61, 62, 63 and 64) available on the NRC-IRC Web site: http://irc.nrc-cnrc.gc.ca/pubs/ctus/index_e.html.
COPE results highlighted the benefits of personal control over indoor environment conditions in improving occupant satisfaction. IRC continues to conduct research in this area. For more information see: http://irc.nrc-cnrc.gc.ca/ie/lighting/office/control_e.html.
This article was adapted from other published information at NRC-IRC. For more information, contact Dr. Guy Newsham, manager of the COPE project. He can be reached at 613.993.9607; fax 613.954.3733; [email protected]. John Burrows is an Ottawa-based consultant and technical writer.
