Personal Environmental Controls: Saving Energy and Boosting Occupant Satisfaction

Objectives

To evaluate the benefits of personal controls over lighting and ventilation/temperature in offices in terms of occupant satisfaction, mood and visual comfort, as well as energy efficiency.

Background

Previous research on individual lighting control demonstrates energy savings of 15-40%, while improving occupant satisfaction, mood and visual comfort.  Studies of individual control of ventilation/temperature also suggest energy savings, improvements in satisfaction, and a decrease in discomfort complaints.  More research is needed to better evaluate the benefits of integrated Personal Environmental Controls (PEC), to optimize their functionality in practice, and to provide guidance to the controls industry and facility managers.

Statement of Work and Results

The research was carried out in three phases:

Field study
An already installed lighting system with personal controls, combined with daylight-linked dimming and occupancy sensors, was evaluated in terms of energy use, electrical demand and occupant satisfaction.  This lighting system used 69% less energy than the conventional recessed parabolic system installed elsewhere in the building.  Two-thirds of these savings were due to the lower installed lighting power density of the system (5.8 W/m² vs. 10 W/m²), and one-third was associated with the controls.  Furthermore, there were concomitant reductions in the daily peak power demand for lighting.  The daily average effective lighting power density, accounting for the fact that not all luminaires were on at full power at any given time, peaked at only 3 W/m².  System data allowed us to derive the energy savings that would have occurred had only one type of control been installed, so we can compare the relative energy savings potential of each control option.  If used on their own, and averaged across all 86 studied workstations, the occupancy sensors would have saved about 35% compared to the direct-indirect luminaires at full power.  In comparison, daylight harvesting would have saved about 20%, and the individual controls about 10%; as expected, savings for both these control types were higher near to windows.  The studied lighting system was also associated with higher occupant satisfaction.  This was likely due to the individual dimming control, although use of this control beyond an initial preferred setting was rare.

Laboratory studies
Using six open-plan workstations installed in NRC-IRC's Indoor Environmental Research Facility, this phase evaluated how occupants use personal environmental controls over lighting and ventilation and how that use affects their mood, satisfaction and performance, as well as energy consumption, under a variety of conditions.

Participants (N=126) spent a day in a full-scale office laboratory with little daylight, completing questionnaires and standard office tasks.  Some participants experienced typical constant lighting and ventilation conditions, whereas others were given personal control over the dimming of lighting in their workstation and over the flow rate of air from a ceiling-based nozzle in their workstations.  Results showed that personal environmental control improved environmental satisfaction.  Personal control over lighting led to an average energy reduction of around 10% compared to a typical fixed system; participants with personal control also reduced flow rate compared to the constant condition.  Use of each control type averaged 2 – 3 control actions per person per day, which dropped to less than one control action per person per day in a longer-term pilot study (N=5) conducted in the same space.  Another related study in a laboratory with a large daylight contribution found that, on average, manual-dimming control reduced energy use for lighting by 25% compared to a fixed system delivering 500 lx of electric lighting on the desktop.

Field study in a building with a personal ventilation system.
The study took place in a six-story building in Toronto, Ontario, which had had some personal environmental control units in open-plan areas since a renovation in the late 1990s.  The units allowed individuals to adjust the airflow through a nozzle on the ceiling, by adjusting the position of a sliding switch located on the panel of the cubicle.  Overall, the potential benefits in the form of increased satisfaction and energy savings were not being realised.  Based on our observations during the site visits, this is not an indictment of the technology, but of its maintenance over the decade since its installation.  It remains possible that with regular system maintenance to ensure that the controls are functioning and that the jets are aimed appropriately, and with ongoing occupant training, the provision of individual control over ventilation could improve occupant satisfaction and building energy use.

Partners

Natural Resources Canada, Public Works and Government Services Canada, BC Hydro Power Smart

Start/Completion Dates

The project began in April 2004 and was completed in March 2008.

Publications

Energy savings due to occupancy sensors and personal controls: a pilot field study
Galasiu, A.D. Newsham, G.R.
Lux Europa 2009, 11th European Lighting Conference (Istanbul, Turkey, 2009-09-09)
pp. 745-752.
[Full citation / Référence complète]

Control strategies for lighting and ventilation in offices: effects on energy and occupants
Newsham, G.R. Mancini, S. Veitch, J.A. Marchand, R.G. Lei, W. Charles, K.E. Arsenault, C.D.
Intelligent Buildings International, 1 (2)
pp. 101-121. 2009-01-01
[Full citation / Référence complète]

Individual control of electric lighting in a daylit space
Newsham, G.R. Aries, M. Mancini, S. Faye, G.
Lighting Research & Technology, 40 (1)
pp. 25-41. 2008-03-01
[Full citation / Référence complète]

Research matters : (comparing individual dimming control to other control options in offices)
Newsham, G.R.
Lighting Design + Application : LD + A., 37 (10)
pp. 24, 26, 28. 2007-10-01
[Full citation / Référence complète]

Energy saving lighting control systems for open-plan offices: a field study
Galasiu, A.D. Newsham, G.R. Suvagau, C. Sander, D.M.
Leukos, 4 (1)
pp. 7-29. 2007-07-01
[Full citation / Référence complète]

Effect of dimming control on office worker satisfaction and performance
Newsham, G.R. Veitch, J.A. Arsenault, C.D. Duval, C.L.
IESNA Annual Conference (Tampa, Florida, 2004-07-26)
pp. 19-41. 2004-07-01
[Full citation / Référence complète]

Related Information

Institutes:

• NRC Institute for Research in Construction