1. Lighting Design
1. Function of the lighting system
a. Task Illumination:
The requirement maintained level of illumination depends on character of the visual tasks performed in the area.
b. Lighting as an Element of Architectural Design:
The Character of the space determines to a large extent the type of lighting, its quality and quantity.
2. Elements of the lighting system
a. Ambient Lighting
Ambient lighting is defined as an arrangement of permanently installed lighting equipment which will yield a relatively uniform level of illumination on work plane at some defined height above the floor of the space.
b. Task lighting
Task lighting can be achieved by either permanently installed luminaries located in the proximity of a fixed work station, or by portable lighting equipment which may be moved as the location of the task changes.
B. Illumination Levels- Relation to HVAC
1. Light and Heat
Radiant energy of every lamp consists of different proportions of visible light, infrared radiation and conducted heat.
The useful light percentage of the total energy in watts used by the fixture depends on the Luminous efficiency (lumens/watts) of the lamp and efficiency of the fixture
2. Approximate Watts per Square foot for Various level of illumination
It is necessary to estimate the electrical load on the basis of the watts per square foot in order to provide adequate wiring and air conditioning.
1. Zonal cavity method
This is the most common used method for calculating general illumination levels.
Cavity Ratio = 5h (room length + room width)/ room length x room width
Number of fixtures= maintained foot-candle level x Area / (lumen per lamp) x (lamps per fixture) x Coefficient of Utilization (C.U) x Light Loss Factor (LLF)