CPD PROGRAMME | LIGHTING it was when LG5 was published in 2011. The impact of the lit environment on productivity, health and wellbeing has become far more widely appreciated and understood, with commonplace, and popular, discussion of such things as circadian rhythms; light induced sleep deficiency; intrinsically photosensitive retinal ganglion cells (ipRGC); and seasonal affective disorder (SAD). Alongside the drivers of physiological and psychological factors, the volatile energy markets are raising end-user interest in lighting efficacy and control that has also increased focus on improving the integration and utilisation of daylight. There have been many research projects in the education sector that have linked daylighting with increased achievement rates, health and attendance. One of the most recent2 examples, by Baloch et al, provides some evidence that 20% of the variability in performance test results was the result of classroom characteristics associated with daylighting (this was based on observations of 2,670 schoolchildren, aged eight to 13 years from 155 classrooms in 53 schools across 12 European countries). Guidance for assessing the opportunities for daylighting are provided in the UK Education funding agencys publication EFA daylight design guide Departmental advice version 2: January 2014. This describes climate-based daylight modelling (CBDM) that aims to provide a numerical approach to support good design, taking account of the quality and quantity of sunlight and daylight. The guide notes that real weather data are used to calculate lux levels and targets can be set which are relative to user needs. Also, the CBDM criteria sets a peak acceptable illuminance which reinforces the need to provide suitable glare control which modulates the light transmission rather than eliminating the light. CBDM determines a useful daylight illuminance (UDI) that was devised to ease the interpretation of climateArea as defined by BS EN 12464-1:2021 based simulation without sacrificing the detail of the output data. UDI indicates what proportion of the year illuminances on the working plane are within a range considered useful by occupants (this methodology is briefly described in LG5). Unlike commonly employed methods, such as the daylight factor that assumes a simplification of an overcast sky for a specific time, CBDM necessarily requires a significant digital modelling capability. Unlike many general-purpose buildings, educational facilities often cater for a majority of occupants from a particular age band ranging from pre-school children all the way through to late learners and so lighting levels may need to be changed, controlled, or adapted depending on who is using a specific area. For centres that deliver further and higher education, where there is likely to be a mix of learners, there may need to be an increase in light levels for older students. Approximately3 8% of UK higher education students are in their 50s and 60s. A recent review paper4 by Kunduraci reports on various studies that have presented that the elderly suffer from reduced visual ability and contrast sensitivity, with loss of depth perception, and increased sensitivity to glare and diminished light-dark adaption. It is typically considered that three times the illuminance may be required for elderly learners to see fine details, such as when reading, using a keyboard, or discriminating between low contrast objects. An example that considers younger learners is provided by Wessolowski5 et al, who examined the effect of variable lighting on pupils restlessness and behaviour. A variable lighting system employed seven lighting programmes that delivered different varieties of illuminance and colour temperature. In a controlled field study, including 110 pupils of various age levels and school types, and 11 teachers, the findings showed a significant decline in restlessness and aggressive behaviour and a tendency toward increased positive, social behaviour indicating that variable lighting can play a part in optimising general conditions for school learning. As an example of the metrics that are employed to define a suitable lit environment, Table 1 provides (in black text) general lighting requirements for a sample of educational spaces taken from BS EN 12464-1:2021,6 which sets the standard for UK and European working spaces. Additionally, the table includes the requirements from the UK DfE School Output Specification Technical Annex 2E7 (shown in green) that sets the technical requirements for the design and construction of schools. Table 1 provides: Em (lx) is maintained illuminance, the minimum average illuminance of an installation on a reference surface related to the specified task (at the required viewing location/height). Em required is a normal minimum value for normal working conditions. Em modified provides an indicative higher level related to application factors as needed for specific tasks, surfaces or visual abilities. This may be varied through control. Uo is uniformity of illuminance = minimum (derived) illuminance value/average illuminance value (increased values may be more appropriate for those with poorer vision). Em (lx) SOS Technical Annex 2E for similar area Em (lx) Uo Required Modified Ra RUGL Em,z (lx) Em, wall (lx) Em, ceiling (lx) Uo 0.10 Classroom general activities 300 500 1,000 0.60 80 19 150 150 100 Auditorium, lecture halls 300 500 750 0.60 80 19 150 150 50 Attending lecture in seating areas in auditoriums and lecture halls 300 200 300 0.60 80 19 75 75 50 Art rooms in art schools 300 750 1,000 0.70 90 19 150 150 100 Circulation areas 100 100 150 0.40 80 25 50 50 30 Table 1: A sample of lighting requirements for a selection of common spaces found in educational buildings (Source: BS EN 12464-1:2021 and School Output Specification (SOS) Technical Annex 2E: Daylight and Electric Lighting) 44 April 2022 www.cibsejournal.com CIBSE Apr 22 pp43-46 CPD 194 Supp.indd 44 25/03/2022 15:01