LIGHTING AND ITS IMPACT
Figure 3: Condition 3 – Office space lit by a new dynamic LED system, with variable LED lighting at a higher level.
completed and one ongoing – the impacts of circadian lighting on the occupants of working offices are being investigated.
Lighting for circadian rhythms A study of people working in an open- plan office has been carried out by researchers from building science centre, BRE (with financial support from the BRE Trust and CIBSE), to translate experimental knowledge about the effects of lighting in the workplace into real-world good practice.
Many people work in poorly daylit spaces with relatively low levels of electric light, where it may be hard for their bodies to maintain their circadian rhythms. Dynamic circadian lighting is being marketed using dimmable, colour- tuning LEDs to give brighter, bluer light in the middle of the day, and dimmer light – with less blue – later in the day, when it is time to relax. However, there has been little scientific investigation into the best way of controlling this tuneable lighting under real-world conditions. Research is needed to investigate the effects of dynamic lighting and its timing on how people feel (i.e. their subjective assessments), and their activities and reported sleep.
Lighting conditions investigated This research project took the form of a field study of 23 participants working in an open plan office at the University of East Anglia. Four conditions were administered over several weeks during winter months: n Condition 1 – Old constant fluorescent lighting – i.e. the office’s existing lighting (see Fig 1).
n Condition 2 – New dynamic LED system – with variable LED lighting at a lower level (see Fig 2).
n Condition 3 – New dynamic LED system – with variable LED lighting at a higher level (see Fig 3).
n Condition 4 – New dynamic LED system – set up to provide constant lighting. (see Fig 4).
Figure 6: The Fromm Area – Accessible biophilic design. Visualisation of the space. 46 Health Estate Journal May 2020
Figure 4: Condition 4 – Office space lit by a new dynamic LED system – set up to provide constant lighting.
compared to assess the potential impacts of variable lighting. In addition, these results were correlated with the activity level data and the measurements of the site’s environmental conditions – temperature and relative humidity.
Research findings Greater alertness and reaction time scores
Figure 5: The exterior of the test building for the BRE Biophilic Office Project.
Factors measured
Site measurements, lighting monitoring, and computer modelling, were combined with subjective and objective measures of performance – including questionnaires, regular pop-up questions, and computer- based performance tests – along with the monitoring of light exposure and levels of participant activity using activity tracking watches.
The responses of the participants to questions and computer-based tests were assessed to identify links between key participant performance indicators – subjective alertness, reaction time ,and concentration – and the measurement and calculation results of circadian light metrics for each of the four lighting conditions. Participant answers to general questionnaires following each lighting condition were also analysed and
The average scores for subjective alertness and reaction time were significantly better with the new dynamic LED system (Condition 2), than with the old constant fluorescent lighting (Condition 1). However, comparisons of average subjective alertness and reaction time scores with the LED systems set up to provide variable lighting (Condition 3), and constant lighting (Condition 4), revealed no statistically significant differences.
Extra light not a factor
Most participants felt more alert under the dynamic LED lighting in Condition 2 compared with the constant fluorescent lighting in Condition 1, but this also happened for the small number of people who received less light in Condition 2. The increase in alertness did not depend significantly on how much extra light people had with the LEDs. Similarly, there were no statistically significant correlations between the higher scores for reaction time and the increases in
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