In ordertoensurethatthe Royal Academy keeps pace with the daylighting requirements of fine art galleries, the lecture room, together with a number of related spaces, were studied in terms of their daylighting control, on the assumption their existing glazed roof forms might be retained, but modified as needed.
The general brief for the daylighting was to provide a flexible and easily controlled system suitable for all of the top lit galleries, irrespective of their orientation which allows for the average daylight level to vary from nil to 500 lux or more. One of the important factors is the need to cater for'indemnified exhibitions' or 'loan collections' where specific daylight levels are specified, from nil daylight to 300 lux, and where the gallery has a responsibility for its provision. This is different to the 'Summer collection', there for only a short period, and where it is not too important if the general level of daylight specified varies upwards on occasions.
After model studies were made the lighting consultants suggested a four-part solution, which was applied tothe large lecture room, but formed the basis for a unified system which might be applied to a series of related areas.
The system is shown in the diagram below and consists of four layers:
1. The outer layer is a black tarpaulin supported on stainless steel suspension wires. This is installed manually on those occasions when a complete blackout is desired. The system is not used on a day to day basis.
2. External motorized louvre blinds. Placed above the glazing to the roof, these are open to the atmosphere, and needed to be made to a high specification to withstand rain, snow and high winds. The blinds are linked to an automatic control system which is 'daylight linked' to react to the external level of light, allowing predetermined maximum daylight levels to be set, for the display areas below.
When the room is closed to the public the blinds can be closed to reduce the daylight level, in order to minimize degradation of the exhibits.
3. The internal face of the glass to the rooflight is protected by a diffuse privacy film. The film is designed to match that used in the other galleries. The film provides both safety and anti UV control as well as diffusing direct sunlight.
4. The lowest level of control is formed by motorized and tensioned blinds formed of white close-weave fabric, each half of the sloping roof being separately controlled. The blinds can be seen by the public, and can either allow maximum daylight through, when open, or reduce the amount by adding a further degree of diffusion of the light to the space below.
The design intent has been met within a realistic budget, to provide the flexibility necessary to satisfy the needs of daylighting in different types of exhibition, whilst allowing a quick turnround time between one to another, by means of the simplicity of control.
Interior during the day, using controlled daylight for an exhibition View up to rooflight
Picture of the model used to establish the daylight factors
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