A human-centric lighting project is intended to improve learning performance and sleep patterns for students, explains MAURY WRIGHT, and the lighting design also optimizes cylindrical illuminance.
The new Holla comprehensive school near Telemark, Norway opened for the 2016 school year with LED-based lighting inside and out, including tunable-white lighting in class and group rooms. The tunable lighting is considered human-centric lighting (HCL) or what is sometimes referred to as lighting for health and wellbeing. The spectrum can be set to boost alertness at times, for instance, during an exam, or for a relaxed environment at other times. The school hopes the system will improve learning and also help students sleep better at night. The solid-state lighting (SSL) project further included other standard LED fixtures with fixed spectrum indoors and out.
Glamox Luxo Lighting supplied the lighting products for the school. The company specializes in lighting products for schools, healthcare facilities, retail, hospitality, and commercial and industrial buildings. HCL capabilities are offered in a number of Glamox luminaires. The company relies on the DALI (digital addressable lighting interface) platform for control and supports control components and systems from a number of third parties such as Tridonic and Helvar.
The C90-R family of luminaires used in the Holla teaching rooms have the HCL capability (Fig. 1). The recessed 2×2-ft, troffer-style fixtures have a planar optic that delivers uniform light across the surface. The HCL version of the fixture can produce light across the spectrum of 2500K CCT to 7000K CCT - from warmer than incandescent lamps to a very cool color temperature. The luminaire design closely tracks the black-body locus across that range. The luminaires also deliver excellent color rendering with CRI above 90. And the school feels that such high CRI will further enhance the learning experience.
Given the control system involved, a teacher or school administrator could potentially set the CCT and dim level of the installed lighting to any desired configuration. Lumen output ranges to 4616 lm. But the installation has been customized to enable simple adjustments of the lighting for the typical modes that might come into play on a daily basis.
FIG. 1. Classrooms are primarily lit by Glamox
C90-R troffers with tunable-white capabilities.
The Standard setting for most activities configures the lighting to 3500K. Teachers have a DALI panel in each room to turn lights on or off and to adjust the dim level. The Standard setting is designed to deliver horizontal illuminance of 300 lx on a plane 0.75m above the floor - desk level.
Energy and focus
The system also includes Energy and Focus settings. First, let's discuss the photometric characteristics, which are the same for both settings, and then we will consider the different ways in which the two settings are applied.
The lighting design took into account the concept called cylindrical illuminance and often abbreviated Ez. The Ez metric is a value in lux that represents the mean value of vertical illuminance on a cylinder. Requirements for cylindrical illuminance have been defined in the European standard EN 12464-1:2011 for indoor workplace lighting, and for sitting workers that calculation is based on a height of 1.2m from the floor - typical head height. The school system delivers Ez of 350 lx at 1.2m and a CCT of 6500K in the Energy or Focus modes.
The Energy setting is managed by the building management systems (BMS) to which all of the SSL products are linked. The BMS enables the Energy setting automatically for the first lesson of the day in each classroom. The intent is to adjust the circadian rhythm of the students first thing in the morning.
The installation of the system was in part based on work done at the Norwegian Competence Center for Sleep Disorders at Haukeland University Hospital. University researcher Ingvild West Saxvig said, "During puberty, the sleep pattern often shifts towards later bedtime and awakening. This may reduce the performance among adolescents and adults."
The HCL implementation is intended to help prevent delayed sleep-wake cycles among the students. The cool to cold lighting presumably pushes the circadian rhythm forward to improve alertness and also makes the students sleepy at the appropriate time at night.
At the first break of the learning day, the BMS automatically transitions the lighting to the Standard setting. The change is not accomplished immediately. Instead, the system is programmed to gradually change over a 10-minute period so that students and teachers don't even notice the transition.
Still, the teacher can take advantage of the cooler light by selecting the Focus setting from the control panel on an ad hoc basis. That setting would typically be applied during tests or for other lessons where acute focus is required. When the Focus setting is deselected, the lighting gradually transitions back to Standard.
Meanwhile, the Calm setting is warmer than Standard. The CCT is a warm 2700K with horizontal illuminance maintained at 300 lx on desks. Teachers select the Calm setting for periods of relaxation or calm activities. The BMS is also programmed to deactivate both Focus and Calm settings after 30 minutes in case teachers forget to do so. After such a period, the lighting returns to a standard setting.
The concept behind the HCL implementation is simplicity for teachers that may not understand the deep science behind tunable lighting. In fact, we have seen similar implementations from other lighting manufacturers. Acuity Brands, for instance, has preconfigured modes in its Mainstream Dynamic product lines intended specifically for educational environments.
Other SSL for the school
The Holla project, as mentioned at the start, was a comprehensive LED project. The specifiers also used the CR15-R square troffer in some areas where tunable capabilities were not required (Fig. 2). Other indoor areas are lit with Reed LED linear pendant-style fixtures such as to light the presentation boards in classrooms, as you can see in Fig. 1.
Outdoors, O50 LED floodlights in a cobra-head style illuminate parking and pedestrian areas. In addition, decorative O46 post-top luminaires are used in some outdoor recreational areas (Fig. 3).
and parking-area fixtures in the cobra-head format.
HCL remains a hot and somewhat controversial topic around the globe. Some scientists believe that we don't understand enough about the non-visual impact of light to deploy HCL concepts, while others think we should move forward with what is known. We published an editorial on that topic last year that also links to a number of other HCL articles that we have published.