Lighting plays an important role in the comfort and safety of occupants of the building. Lighting contributes to the décor of a room and should be both decorative as well as functional without causing glare or appearing flat and dull lighting needs.

 

1. Function: Certain specialised activities will require specific amounts and possible certain kinds of light, function must be evaluated in terms of both quality and quantity of light. E.g. reading, writing etc. all demand proper illumination. Functional lighting will prevent eye strain and make it possible to carry out the activities in a comfortable and efficient manner.

2. Safety: Improper lighting is a particular hazard in several areas that may escape notice. E.g. staircases or doorways where there is a step up and step down. Another aspect of safety involves adequate wiring and sufficient outlets for all needs. It is dangerous as well as unattractive to use long extension cords. Electric wires should never be placed under rugs where traffic is more.

3. Beauty: We begin to appreciate light on a decorative medium when we see a room bathed in a pleasing glow of illumination. There is also a close relationship between the type of light and appearance of colours.

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Measurements of Light

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Lumen is the unit of luminous flow that is the amount of light emitted per second in a cone of a certain size by a point source of known intensity. The lux is the unit of illumination equal to 1 Lumen per mt. sq.

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Lumen: It is a unit for measuring the quantity of light emitted at the source.

Lux: It is the measure of illumination level at or on the surface being illuminated.

Illumination: The distribution of light on a horizontal surface is called its illumination. It is measured in footcandles.

Footcandles: A foot-candle is a lumen of light distributed over the one-square-foot area.

Glare: It is defined as dazzling brilliance which can obstruct vision. It can also produce eye damage and should be avoided. It is caused by:

• Natural sunlight streaming in through a window.

• Reflected light from mirrors, shiny surface.

• Direct light rays from a light bulb or a spotlight.

 

It can be reduced or eliminated by:

• Using frosted bulb.

• Using diffused light.

• Using fluorescent tubes, lamp shade or venation blends.

• Correct positioning of light.

 

Types of Lighting

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Direct Lighting: In case of direct lighting the fittings throw the light onto the surface below producing over bright areas and hand shadows resulting in glare. E.g. down lighting-a direct light is hung pointing down to become a downlight used to highlight.

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Direct lighting does not require elaborate electric wiring and may be used to throw light on an empty textured wall. This process is called wall washing. It can also be used to spotlight a collection of pictures.

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Indirect Lighting: Is produced by a light source that is hidden. The light is directed to the ceiling or another surface from which it is reflected back into the room. Indirect lighting creates no shadows when used next to the ceiling. Indirect lighting reflected down from the ceiling tends to raise the ceiling height. E.g. up lighting-canister shapes are used in a variety of locations on the floors, in corners of rooms, at either side of sofa or behind plants.

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Diffused Lighting: When fittings are completely closed or concealed, the light is diffused as it passes through cover.

 

Direct/Indirect Lighting: It is distributed evenly in all the directions. Here some light is diffused through bowl and some light is reflecting from the ceiling.

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Semi-Direct: In semi-direct fixtures, 60% of light is directed down to work surface and remaining amount is directed upwards.

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Semi-Indirect: It is converse of semi-direct. Here 60%-90% of light is directed to the ceiling and other 10%- 40% is directed towards work surface.

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Kinds of Lighting

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General Lighting or Overall Illumination: Should be provided at various intensities so that by pressing different buttons or dimmers, we can produce bright, dim or medium light. General lighting may be direct, indirect or a combination of both.

 

Task Lighting or Local Lighting: Is particularly needed while reading, working, grooming, playing indoor games etc. it can be brought up by using lamps.

 

Accent Lighting-For beauty

Without general lighting, the task lighting will produce a glare accent lighting emphasising a centre of interest in the room.

 

Methods of Lighting

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• Day Light

• Architectural Lighting

• Non-Architectural Lighting

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1. Day Light

Only about 10% of normal daylight enters a room, in spite of this, it is brighter than artificial light. Colours look different in daylight. It varies in intensity and colour throughout the day. Another aspect is that it gives a colder and less variable light and is better for areas where colour matching is important. Most large buildings require artificial lighting even during the day.

 

Advantages of Daylight

• It costs nothing except the cost of making a few windows.

• It is natural.

• It varies according to the time of the day so it is soothing and possibly causes less fatigue. But it can cause hindrance to the human eye.

• The windows and the changing light add another dimension to the room and the view from there can be refreshing.

 

Disadvantages of Daylight

• The variation in the strength of daylight can change the atmosphere of the room.

• Brilliant sunshine fades some colours and rots some materials.

• The heat from the sun rays can cause discomfort.

• Daylight does not uniformly illuminate a room.

• A window should be kept clean to get the maximum advantages from daylight.

• Supplementary light is required since daylight is not constant.

• Large windows with a southern or western aspect can make a room unbearable in summer and too cold in winter.

 

2. Architectural Lighting

Includes portable lamps, ceiling and wall fixtures. Lamps provide a certain amount of flexibility in that they can be moved from one place to another. There are no rules about where to use lamps and mounted fixtures. The ultimate goals are to provide the type of light needed and to choose designs that are in keeping with the decorative schemes. In choosing lamps the following points must be considered:

• A sturdy and heavy base prevents limping.

• A lamp that has a diffused bowl will give a less glare.

• A harp makes it possible to adjust the height of the shade or to tilt the shade if necessary.

• A table lamp intended for reading should have the lower edge of the shade about 40-42 inches from the floor. The lower edge of the shade of a floor lamp should be around 49 inches from the floor.

• Lampshade should be used according to the colour or texture of the food.

 

Ceiling and Wall Fixtures:

In choosing fixtures these points may be implied:

• Adjustability of position often increases functionalism. E.g. chandeliers that may be raised or lower will provide a variety of lighting effect.

• Diffused light is more pleasant in many fixtures. The bulb may be exposed giving an irritating glare.

• The design of the fixture should be in harmony with the character of the room.

 

Types of Fixtures

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i) Filament Bulb: This has a glass container with a vacuum or is filled with an inert gas. In these containers is a highly resistant filament element to which an electric current passes heating it sufficiently to make it incandescent. This filament maybe single coil or a coiled coil. The latter maintains a higher temperature and emits more light but it is susceptible to damage from knocks and vibrations.

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Advantages

• Easy to install.

• Give an acceptable with little colour distortions.

• The amount of light required can be altered by simply changing the bulb for one of greater or less strength.

 

Disadvantages

• They are not of uniform quality so its makers and the supplier should be reputable.

• The light does not mix comfortably with daylight.

• Except for a few decorative types they are rather ugly and unpleasant.

• The bulbs are connected to the light source with an additional crew fitting.

 

They can have various glasses for various effects:

• Clear Glass: Through which the filament can be easily seen. It is suitable where sparkle is required and is used with shade.

• Pearl Glass: Is frosted on the inside to mask and diffuse the glare from the filament.

• Color Bulbs: Used for decorative purposes.

• Opal: Is heavier white internal silica coating which diffuses the light more than the pearl. The filament is invisible and shadow is minimized.

• Redactor: Are used for floodlights and spotlighting. The internal silver surface reflects the light with greater intensity towards the definite area.

 

ii) Fluorescent Tubes: They are also referred as strip lights. These are long tubes vapour filled with florescent powders. The light is produced by ultra-violet radiations from an electrical discharge falling on the powder. Different powders produce different colour light. These can be placed behind pelmets at the window on the wall or in front of mirrors. Tubes are much cheaper than a filament bulb and have a much longer life.

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These are of 2 types:

• Hot Cathode Tube: Are the most commonly used. Light efficiency is better but they are slow to light up and flicker before lighting fully.

• Cold Cathode Tube: these can be produced in a variety of shapes. They light up immediately without flickering. They are more expensive than the hot cathode tube and they require a higher and normal voltage. They require special fitting so installation cost is higher.

 

Non-Architectural Lighting

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a. Glamorous Effects

For general lighting. May be achieved by the mounting of simple fixtures in valances, cornices, coves etc. One may light a window area wall, ceiling, floor or any special area for emphasis. Fluorescent tubes are useful for such lighting because they provide an even line of light.

• Valance Lighting: the light source is mounted so that some of the light is directed towards the ceiling and come down over the draperies. Fluorescent tubes are installed behind the valance frames which are painted white to reflect the light. At least the 10 inches space between the top of the valance and ceiling is necessary. The frame will conceal both the fixtures the top of the draperies.

• Cornice Lighting: Can be used to give general illumination. In this fluorescent tubes are placed behind the cornice which is at least 6 inches in depth. It is built at the junction between the ceiling and the wall. It is good for low ceiling room because it gives the impression of the greater ceiling height.

• Cove Lighting: It implies a rough light arrangement. Usually near the ceiling with the light directed upwards. Cove lighting creates an effect of openness and the quality of the light is soft.

• Brackets: Are located at a lower height than valances and are not necessarily related to window treatments.

• Soffit Lighting: Is the underside of an architectural member. Often space provides housing for a light source and is mostly used in bathrooms, kitchens, bookshelves and mirrors.

• Recessed Lighting: this includes built-in panel fixtures that provide concentrated light. The fixtures can be round, square or rectangular metal boxes set in a ceiling or wall.

• Sky Light: Is the glared opening in the roof of a house constructed to allow a natural light into space.

• Translucent Panel: Are set on a surface that reflects light. The light source is concealed under the panel which may be on the floor or the ceiling or a free-standing decorative unit. These are used in discotheques, kitchens, bathrooms or other work areas and provide comfortable glare-free illumination.

• Track Lighting: These are lighting fixtures fitted on the track. This may be used to throw light to highlight the wall or the contents of the wall.

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b. Suitable Room Lighting:

• Living Room and Family Room: Lighting a wall surface improves visual purpose as well as makes the wall and the ceiling appear lighter and more attractive. This is achieved by either valance, cornice, cove or recessed lighting. Table lamps or floor lamps provide general illumination.

• Kitchen: Good lighting is required. The ceiling fixtures provide general lighting and should furnish at least 150-200 watts of incandescence or 60-80 watts of fluorescent for each 50 sq. ft. of space. Long fluorescent tubes may be attached under the cabinets to light the work surface.

• Bedroom: Bedroom lights should usually be local light in the place where needed. Lights for reading may be on floor lamps or attached to the wall or ceiling. For applying makeup and grooming, lamps with translucent shades should be on either side of the mirror approximately 36 inches apart. The centre of the shades should be at the height of the face. Strip lighting can be used on the sides and the top of the mirror.

• Bathroom: Requires both general and task lighting. The bathroom mirror must be lighted either by soffit or strip lighting. A vapour proof lighting fixture is useful near the tub and the shower so that when the shower curtain is closed there is still general lighting.

• Stairways, Hallways and Closets: Hallways and stairways must be well lighted for safety reasons. Recessed lighting may be secured to the risers on the stairs and give a feeling of elegance to the room while adding to the safety of the stairs. Lighting near the baseboards in the hallways create a warm glow and gives a good effect to the area. Closets with automatic switches that activate when the door is opened and deactivate when the door is closed are convenient as well as energy saving.

• Lobby and Reception: Must be adequately and without any obstructions be lit with good general lighting and brighter but concealed lighting at the reception desk, where guests, as well as the staff, have to read and write. Small table lamps can also be used giving pools of soft light and making these areas attractive and welcoming by creating a small focal point in the large lobby area.

• Restaurant: These are often dimly lit to create an atmosphere but there should be attractive pools of light. Fast food cafeteria and restaurant require a brisk atmosphere for a fast turn over. So the lighting should be bright but not harsh or glaring and adequate enough to see that the table cutlery is clean. A hotel restaurant or a luxury restaurant requires soft lighting for a relaxed atmosphere. Individual lamps on table or candles give adequate task lighting to read the menu and see the food or the skin color of the customer. Individual table lamps must have shades which protect the eye of the customer from the glare of the bulb.

• Cloak Room and Toilet Area: The lighting should be overall of such a level that one can see that it is clean mirror light and shade should be neutral in order not to distort makeup colour.

• Function Room (Banquet): Since these rooms are used for a variety of purposes like conferences, meetings, dinner, dance etc. they need to have a flexible, decorative and functional lighting. Source of lighting may be concealed like cornice, valance etc. Standard lamps might complement with the décor together with a track or spotlight. Dimmer switches are used which will reduce the light when a subdued light is required.

• Out Door Lighting: A picture window that frames an attractive view all day long can be merely a dark area on the living room wall after sundown. When the garden is lighted, it is possible to have a good view day and light outdoor lighting on the house or in a tree 12-20 feet above the ground. Aim to light flower and bushes at an angle that is 45°-90° from the principal viewing angle. A beautiful tree should be lighted from 2-3 dimensions to avoid a flat appearance. Lighted steps and walkways invite one to tour the garden after dark as well as preventing dangerous slips and falls. Outdoor lighting also discouraging trespassing. Small fixtures need to be near the entrance to welcome guest and aloe them to see the house or apartment members.

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Factors to Consider when Planning a Lighting System

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1. Amount of light required for an area will depend on various factors like:

• Location and direction of the light sources.

• Reflected qualities of colour.

• Textures used in the room.

• The number of lamps and fixtures.

• The wattage of bulbs and tubes.

2. If artificially lighting a room check on heat gains.

3. Design and durability.

4. Ease of replacement especially if lampshades are used.

5. Cleaning-they should be easily cleaned.

6. Cost.

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Recommended Value of Illumination

• General Labs- 400 Lux

• Reading Tables- 600 Lux

•  Bars- 50-70 Lux

• Kitchens- 200 Lux

• Restaurant Tables- 100 Lux

• Bedroom- 100 Lux

• Hospital Wards-   50 Lux

• Stairs and Corridors- 100 Lux

 

Principles of Lighting Designs

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The use of lighting is visually pleasing when it follows the following principles:

1. Balance: Is achieved by placing light sources throughout the room avoiding a concentration of light on any side or area of the space. Balance can be symmetrical or asymmetrical.

2. Unity: Can be achieved by duplicating the fixtures as well as repeating the materials, finishes, colours, textures and maybe lampshades.

3. Variety: Can be created by using similar but not identical fixtures. Variety can also be created by having general and local lighting also by changing the level of illumination with dimmers.

4. Emphasis: Is given by highlighting. Lack of emphasis in an interior causes boredom, confusion and uncertainty as to the design content and intention.

5. Rhythm: The sequence of lighting will create a luminous rhythm giving the space a dynamic quality.

6. Scale and Proportion: The fixtures must be in proportion and scale to the room, themselves and to the relative objects in the room.

7. Harmony: If the contrast between general and accent lighting is too strong there will not be enough luminous transaction and the lighting composition will lack harmony.