School lighting
1. Requirements for lighting and trends in school design
Good lighting is an important part of school buildings. The relevant lighting act in the UK stipulates that the illumination of all teaching rooms and kitchens on the corresponding horizontal plane in the normal use area should not be less than 10 lumens/square foot (108 lux), and the natural lighting factor should not be less than 2%. In this area, any luminous body with a maximum brightness greater than 1500 foot-lamberts (5140 candlelight/square meter) or an average brightness greater than 1000 foot-lamberts (3430 candlelight/square meter) cannot be seen within the specified viewing angle. The specified viewing angle refers to: the vertical line from the eye to the floor is 135° with the eye as the center of the arc. Sufficient light emitted from the lamp should illuminate the ceiling and the upper part of the wall to prevent the brightness difference between the lamp and its background.
Although these regulations refer to tungsten lamps, they are still valid when fluorescent lamps have replaced tungsten lamps to a large extent due to their high light efficiency and low management costs.
In the past few years, the important factor in school construction and design has been economic accounting. At present, the biggest problem in the scope of teaching buildings may be: to adapt to the growing needs of modern education and to meet the requirements of a 2% natural light factor. In multi-story school buildings, the requirements for high windows and increased flat roof height will cause problems such as increased construction costs and heat loss.
2. Lighting problems and typical solutions
The lighting problems in school teaching areas mainly require that the desktop illumination is not less than 300 lux, the blackboard illumination is not less than 400 lux, and the glare index limit is 16. Due to the need for storage cabinets and homework display areas in the classroom, coupled with the economic height of the ceiling, sometimes the requirement of a 2% natural light factor cannot be achieved. In this case, permanent artificial auxiliary lighting is required. In some places, large and deep windows are not encouraged because they will distract young students from listening to classes, and it is also for economic reasons. There have also been experiments with using sight slits to maintain visual contact with the outside world, while cooperating with permanent artificial auxiliary lighting. This method is more suitable for large and deep classrooms, especially in primary schools with group classes. For the natural light factor, skylights can sometimes be used to increase it.
Some schools experimentally use 1.8-meter modulus caisson-style skylight ceilings to easily achieve a 2% natural light factor. The advantage of this method is that it can obtain the maximum wall utilization area required for modern education. The required lighting level and glare index limit can be achieved by simply installing a 125-watt mercury lamp in a simple light-shielding lampshade under the skylight (see Figure 25-3).
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