Lighting Appearance

The lighting of hospital tasks is as important as the illuminated appearance of the interior. There can be a conflict of requirements.  On the one hand, there are high technology and critical tasks, some of which can have life or death implications.  This suggests a crisp high-tech appearance, which will stimulate staff to a high level of performance.  But on the other hand, the patients, particularly as they recover, may require a softer approach closer to that of a domestic environment. 

This same sort of conflict is shown in entrance and reception areas.  The patient or visitor arrives wanting reassurance about the quality and care level of the hospital.

This can be demonstrated by the quality of the interior design, which includes the way the space is lit.  However, patients or visitors also need to have clear direction to the reception desk.  If the lighting scheme is well designed, some of the apprehensions will be alleviated.  Also if they have to wait in an unappealing space where the lighting has a functional appearance, they may become agitated and restless – a state unhelpful for a medical consultation or examination.

Some research has been done in this area, which shows that occupants like a room to have a measure of “visual lightness.”  But they also like measures of light and shade to provide “visual interest.”  The degree of these elements is determined by the use of the space.  For example, you would not expect the same lightness and degree of light and shade for a sophisticated restaurant as a staff canteen.  Research has also shown that lighting appearance is mainly determined by the brightness pattern of surfaces and objects in the most common area of view.  This is the zone occupied by people’s sight as they look horizontally.  This includes walls and furniture but in large spaces, or wards where patients are lying down, this will also include the ceiling.  Spaces with little light on the walls and ceiling will look gloomy.

To achieve a sense of lightness, it will be necessary to ensure that some walls receive some direct light – but not all walls, otherwise there will be no impression of light and shade and the space will appear bland and unappealing.  As a guide, the average vertical illuminance within the normal horizontal sight-band needs to be about half of the task illuminance.  An important issue in designing for lighting appearance is to provide a pattern of light that relates to the architecture and application of the room in a meaningful way.  The light pattern does not need to be obvious, but a natural element of the overall impression. One aspect of lightness is that it is not just the role of the lighting but also of the reflectance of the surface or object – it will be impossible to make a room that is decorated in a low reflectance colour appear light.  This does not mean that you cannot use low reflectance colours, but they will need to be used sparingly if a light appearance is required.

A further element of lighting appearance is concerned with the colour appearance of the light.  Electric lamps come in a range of different colours, ranging from those that give a cool to those that give a warm glow – this is described by a lamp’s “correlated colour temperature” (CCT) and is measured in degrees Kelvin (K).

On balance, since most areas of hospitals have daylight at some time, it is preferable to use a lamp colour that blends reasonably well with daylight but does not appear too cool at night.  For this, a lamp with a CCT of 4000 K is recommended.  It is impossible to categorise in detail this element of lighting design because of the number of variables, which makes it important to commission an experienced lighting designer.

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