Lighting Design in Building
Light is the band of electromagnetic radiation of wave length-380-780 nm (1nm=10-9 m). Lighting is the desirable effect in the building envelope. It is the most important communication channel of man with environment and it is the prerequisite of seeing. Good lighting is necessary to enable work with efficiency.
Natural light:
The ultimate source of natural light is sun. Radiation (heat) with light is received from sun . Bright sun gives about 100 Klux (100000 lux). Intensity of radiation is likely to be 1 kw/m2.
Quality of sun light: It may be harsh, sparkling, hazy, sub-dared. Quality depends on length of day, weather, seasons. These are external conditions.
Day light
Source of day light is sun. The factors affecting penetration of light through openings depends upon the types, size, placement and orientation of the opening. Skylight may be direct or overcast. Overheating and glare have to be avoided. The quality of day light in rooms is proportional to the area of glass in windows relative to floor area and this is conformed by the measure of day light factor.
Day light factor
It is the ratio of internal illumination in a certain point of building with the simultaneous outdoor illumination. It is expressed in percent. Day light varies considerably in intensity both hourly and daily due to the rotation of the earth and the consequent relative position of sun. It is commonly used for artificial lighting.
DF=Ei/Eo*100
Here, Ei is indoor illumination at a point
Eo is outdoor illumination from unobstructed sky
This formula is valid under overcast sky condition (no direct sun). DF=SC+ERC+IRC
SC is sky component
ERC is externally reflected component
IRC is internally reflected component
Example: Given DF = 8%
Eo=6000 lux Then,
DF=Ei / Eo *100
8 =(Ei / 6000) *100 Ei=480 lux
Good visibility depends on:
– Characteristics of work
– The sight of workers
– Speed and accuracy necessary in the performance of work
– The ease and comfort of working
Glare: It is the condition of vision in which there is discomfort or a reduction in the ability to see significant objects or both, due to an unsuitable distribution or range of illumination or to extreme contrast in space in a room
Guidance for good lighting
• Broader opening gives better distribution of light.
• Openings on two oppose sides will give greater uniformity.
• Cross lighting with openings on adjacent walls tends to increase the diffused light with in a room.
• Deep openings tend to minimize the glare.
• Openings provided with sunshades, louvers etc. excludes as far as possible the direct sun light from the room.
Artificial lighting
The primary purpose of artificial lighting system is to provide sufficient illumination for the performance of visual tasks.
• Artificial lighting requirements
– The source of light should be steady.
– Glare should be eliminated.
– Inconvenient shadows should be avoided.
– The degree of illumination must be suitable for the particular visual task.
– Lighting should not cause excessive heat.
Energy conscious design: renewable and non-renewable source of energy, active and passive methods of solar cooling and heating. Energy conscious design deals with:
– Effective design,
– Effective planning,
– Reusing available resources,
– Maximum use naturally available energy
Energy conscious design is the design of buildings such that it has maximum use of renewable energy and exploitation of non-renewable sources of energy is to be minimum level.
Renewable Energy:
• It is the term used to cover energy flows, that occurs naturally and repeatedly in the environment and can be harnessed for human benefits.
• The ultimate source of renewable energy: sun, gravity force, earth’s rotation etc.
• Example: Solar energy, wind energy, wave energy, Hydroelectric energy, Bio-mass energy, Energy from wastes, Tidal power, Geo-thermal energy etc.
Non-renewable energy:
• The flow of energy that can be extracted from the elements available.
• As the source element goes on consuming while generating energy, the term used for this energy is non-renewable.
• Sources:
– Minerals
– Nuclear elements • Examples:
– Fuel energy (from minerals-petroleum products)
– Nuclear energy,
– Electricity by fuel etc.
Active method of solar heating:
• The process of heating directly with the use of solar collectors using the heat for human comfort.
Passive method of solar heating:
A building in which the various components are arranged in a manner that maximizes the collection of solar heat, it is stored and finally distributed in to the building space with out any expenditure of conventional form of energy (Flavin 1980). Building is designed in such a way that maximum amount of solar energy is trapped inside the building.
Design considerations:
• Location • Layout
• Orientation • Shape
• External color • Openings etc.
No comments:
Post a Comment