Daylighting: Natural Light in Architecture

The Office Wing

The minimum daylight factor was calculated to be 1.78 per cent. This falls
below the recommended levels, but only applies to 2 per cent of the floor
area.
The average daylight factor was found to be 5.53 per cent. The
recommended level of daylight in an office is between 2.5 per cent and 5
per cent. Bearing in mind that the daylight will be linked to the artificial
lighting, the average level is adequate.
The maximum level of 28 per cent will cause problems of discomfort
glare, but this occurs only in the immediate vicinity of the windows.

ARTIFICIAL LIGHTING

An analysis was carried out to consider the most energy efficient lighting
system for the open plan spaces for Wessex Water New Operations
Centre.
The design criteria is as follows:

Lighting level 300–400 Lux

Room height 3.2 m

Window to window dimensions 15 m.

The design should take account of the following regulations which
directly affect the lighting:

The display screen equipment shall be free from disturbing glare and

reflections

There shall be an appropriate contrast between the screen and its

background

Adjustable coverings shall be provided for windows.

Several combinations of lamps and luminaires were investigated; the
final recommendation was for the use of twin 35 w T5 luminaires, installed
at a grid of 3 m by 2.4 m, suspended 400mm from the ceiling soffit.
To provide a design output of 400 lux, the system proposed provides
11.43 W/m.2 (for comparison the ‘Good practice benchmark for offices
would be 12 W/m. 2).

Calculations 53

Natural lighting contours calculated by

computer for a typical office floor

Buro Happold