LIGHTING test not only the melanopic lux effect, but also the effect of concomitant changes in CCT, as the visual comfort and overall experience that the light fixtures evoke is important for wellbeing, too. Measuring effects Subjective and objective measurements were taken throughout the study. As part of the subjective assessment, participants were asked to complete web-based questionnaires at four time points each weekday (on waking, mid-morning, midafternoon and before going to sleep) and at two time points (waking and before sleep) on each day of the weekend and holidays. As an objective measure, they were asked to wear, 24/7, a smart watch that keeps track of body temperature, illuminance exposure and activity levels. They were also asked to complete a five-minute visual attention task at two timepoints each weekday. This was a continuous performance task that assessed sustained attention and response time, implemented via a web-based JavaScript application. During the trials final two weeks, a calibrated spectrometer was installed in the buildings roof to measure daylight spectra every few seconds. Connected to a Raspberry Pi, the spectrometer sent the spectral information to the lighting system control unit, which very rapidly found the channel weights that gave the best spectral fitting to the target SPD. Any change in SPD or illuminance in the outdoor environment was smoothly translated inside the office. The final results need further analysis and elaboration, but the following are the initial conclusions drawn from the study: Those taking part in the study preferred the variability and tunability of lights, especially in areas with minimal daylighting They also preferred the variability in electric lighting that reflected real-time CCT (K) 400 4,000 300 Illuminance (lx) 500 4,500 3,500 200 3,000 2,500 10 11 12 13 14 Time (h) 15 16 17 R OHIT MANUDHANE is an architect, daylighting and lighting designer at Arup. Other project members included: Anya Hurlbert, professor of visual neuroscience at Newcastle University; Florence Lam, director, global lighting design, at Arup; Aleix Llenas, researcher at the Catalonia Institute for Energy Research; plus manufacturers Castan Architectural Lighting and Ledmotive The original research paper can be read at bit.ly/CJDec19light1 9:00h 10:00h 5,000 9 daylight conditions effected by a link to outside (in this case, a roof-mounted spectrometer connected to the lighting control system) Participants also did not perceive a higher CCT of around 5,500K as being too cold or unpleasant. This is an aspect of LED source specification that can be explored on future projects. Cooler colour temperatures have the benefit of imparting marginally higher lumens/W, boosting the energy-savings aspect Higher CCTs also lead to a higher melanopic ratio, which might be beneficial for projects targeting the circadian lighting feature in the Well Building Standard criteria. CJ 0.012 18 Spectral power distribution (au) 5,500 100 11:00h 0.010 12:00h 0.008 13:00h 14:00h 0.006 15:00h 16:00h 0.004 17:00h 18:00h 0.002 0.000 400 450 500 550 Wavelength (nm) Figure 4: Sequence A (left) was designed to have changing CCT, photopic lux and melanopic lux during the day. In situ measured spectra from sequence A SPD (right), varying from 9am (blue) to 6pm (red) 400 4,500 4,000 300 3,500 200 3,000 2,500 11 12 13 14 Time (h) 15 16 17 18 100 Illuminance (lx) CCT (K) 5,000 Spectral power distribution (au) 500 10 650 700 9:00h 0.020 5,500 9 600 600 CCT (K) Photopic lux Melanopic lux 6,000 BEHAVIOURAL EFFECTS 600 CCT (K) Photopic lux Melanopic lux 6,000 | 10:00h 11:00h 12:00h 0.015 13:00h 14:00h 0.010 15:00h 16:00h 17:00h 0.005 18:00h 0.000 400 450 550 Wavelength (nm) 400 600 650 700 Figure 5: Sequence B (left) was designed to have the same static CCT and photopic lux as baseline throughout the day, but with changing melanopic lux. In situ measured spectra from Sequence B SPD (right), varying from 9am (blue) to 6pm (red) www.cibsejournal.com December 2019 17 CIBSE Dec19 pp14-17 ARUP Lighting Supp.indd 17 22/11/2019 14:56