Part 5 – LIGHTING

 

 

 

 

5.1    Scope

 

This section describes recommendations and requirements for interior and exterior electric lighting and recommendations for day lighting within buildings. The requirements of this section are in addition to those given in Part 9 of the Pakistan Building Code.

 

5.2    General

 

Lighting not only uses a significant proportion of the electricity consumed in most buildings but also contributes a large portion of the cooling load in air-conditioned buildings. As such, lighting installation should be carefully designed so as to achieve the desired illumination level and visual effect with a minimum requirement of energy. This can be achieved by limiting the installed lighting power load through the use of efficient lighting equipment and the maximum utilization of daylight. Where appropriate, return air may be exhausted through the lighting fixture to increase its output.

 

5.2.1    Light source

 

The choice of light source depends on the nature of the installation and the specific task performed. The designer should be able to make the appropriate choice from the many types of lamps available. High lamp efficiencies are necessary to ensure a low installed lighting load. Recommended minimum lamp efficiencies are given in Table 5.0

 

 

Table 5.0

 

Recommended Minimum Lamp Efficiencies

 

 

5.2.2    Luminaires

 

While it is essential in the design of an energy efficient lighting system to use the correct type of light sources, it is equally important to select the right type of luminaires that are efficient, have light distribution characteristics appropriate for the tasks and the environment, and not produce discomfort, glare or serious reflection. The most efficient luminaires for fluorescent lamps that at the same time meet the requirements of glare limitation are the mirror reflector or prismatic type, whereas for high‑pressure discharge lamps, luminaires should have high quality anodized aluminum reflectors.

 

In general, only luminaires of high efficiency having a high downward light output ratio should be used. The design of fluorescent luminaires should be such that the tube wall temperature is kept cool through return air flow, in air‑conditioned building.

 

The use of instant‑start, low loss, and solid‑state ballasts; may be considered in fluorescent and other luminaires. All luminaires should be power factor corrected to a value greater than 0.90.

 

5.3    Exterior Lighting

 

5.3.1    Incandescent Lighting

 

Incandescent lighting shall not be used for exterior lighting except for special cases including temporary decorative lighting, places where low lighting levels are needed and other applications that could not be met by other lighting types. Single family residences are excluded from this requirement.

 

5.3.2    Facade Lighting

 

Facade lighting shall be no greater than 2 percent of the total electrical interior load of the building. Additional exterior security lighting may be added if required.

 

5.3.3    Automatic Timers and Sensors

 

All exterior lighting shall be controlled by automatic timers or sensors to assure turnoff during daylight hours. Single family residences are excluded from this requirement.

 

5.4    Interior Lighting

 

Incandescent lighting shall not be used for area lighting. However, localized incandescent lighting may be used in areas for special tasks or for commercial display. All residential units and rooms designed primarily as living area (e.g. hotel rooms, hospital rooms, etc.) are excluded from this requirement.

 

5.5    Day lighting

 

5.5.1    Advantages

 

Making adequate use of natural light is one of the most important ways to reduce the building’s energy load. Daylight is an efficient and economical light source ‑ its cost being limited to the construction and maintenance of windows. It has additional advantages in that its provision can be combined with windows for natural ventilation and view: and it is generally preferred to artificial lighting because of its better color rendition.

 

5.5.2    Considerations

 

In designing a building for daylight, careful consideration should be given to the following factors:

 

a)              Glazing reduces the thermal performance of the wall. If necessary, the thermal performance of the glazing may need to be upgraded by installing sun shading devices and/or double glazing.

 

b)              The availability of daylight varies considerably, from day to day and even from minute to minute. This may make it difficult to adjust internal light levels with artificial light. There may thus be a need for automatic switching.

 

c)              Glare problems may be more difficult to deal with, as glare from daylight may come from several sources ‑ direct sun, bright sky, external objects, sunlit translucent glazing panels, interior  decor, etc.

 

5.5.3    Daylight Factor

 

The quantity of daylight in an interior can be specified by the "Daylight Factor". It is the ratio of the illuminance at a point inside to the illuminance on an unobstructed horizontal plane outside under a specified distribution of sky luminance, direct sunlight being excluded from both measurements.

 

5.6    Switching and Control

 

Energy used for lighting purposes is a product of the lighting load and the hours of use., Thus, individual switching of small groups is desirable to allow unnecessary lights to be switched off while permitting the others to be used. This will result in lower operating cost. The following points shall be considered in the design of switching to control lighting:

 

i)    Lighting in task areas larger than 1Om2 shall be provided with controls so that the lighting can be reduced by at least half when the task is not performed or relocated.

 

ii)   Except for enclosed stairways and corridors used by the public, switches should be provided at accessible locations within sight of the light they control.

 

iii)  Where lighting switches are grouped, they should be suitably identified to indicate the area controlled by each switch.

 

iv)   Luminaires should be switched in row parallel to the windows, so that the rows of lights near to the windows can be turned off (manually or automatically) when day lighting is adequate.

 

v)    Where task lighting is installed, such lighting should be provided with switches located adjacent to the work station.

 

Residential buildings and areas within buildings designed as living space are excluded from this requirement.