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Building Design and Construction Handbook - Merritt - Ventech!

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ELECTRICAL SYSTEMS 15.73<br />

Similar consideration should also be given to luminaire selection. Efficient luminaires<br />

can produce more light on a task with less power consumption. Additional<br />

consideration, however, should be given to ease of cleaning <strong>and</strong> relamping, to prevention<br />

of direct glare <strong>and</strong> veiling reflections, <strong>and</strong> to removal of heat from the<br />

luminaires.<br />

Control of lighting should be flexible. Conveniently located, separate switches<br />

or dimmers should be installed for areas with different types of activities. It should<br />

be easy to extinguish lights for areas that are not occupied <strong>and</strong> to maintain minimal<br />

emergency lighting, for safety.<br />

Where feasible, daylighting should be used, supplemented, as needed, with artificial<br />

lighting. Light from windows can be reflected deeply into rooms, with venetian<br />

blinds, glass block, or other architectural elements. Glare <strong>and</strong> solar heat can<br />

be limited with blinds, shades, screens, or low-transmission glass. Provision should<br />

be made for decreasing or extinguishing supplementary artificial lighting when there<br />

is adequate daylight. Consideration should be given to use of photoelectric-cell<br />

sensors with dimmers for control of the artificial lighting.<br />

Maximum use of daylighting <strong>and</strong> other energy conservation measures are often<br />

essential, not only to meet the owner’s construction budget but also to satisfy the<br />

energy budget, or limitations on power consumption, set by building codes or state<br />

or federal agencies.<br />

15.19 SPECIAL ELECTRICAL SYSTEMS<br />

Enhancing the functions performed by the power <strong>and</strong> lighting systems, the special<br />

systems in a building serve the life safety, communication, <strong>and</strong> security needs of a<br />

facility <strong>and</strong> its occupants.<br />

15.19.1 Lightning Protection<br />

The design of lightning protection systems should conform with the st<strong>and</strong>ards of<br />

the American National St<strong>and</strong>ards Institute, the National Fire Protection Association<br />

(Bulletin No. 780, ‘‘Lightning Protection Code’’) <strong>and</strong> Underwriters Laboratories<br />

(St<strong>and</strong>ard UL96A ‘‘Master-Labeled Lightning Protection Systems’’).<br />

In deciding whether to provide a building lightning protection system, designers<br />

should first perform a risk assessment in accordance with NFPA 780, ‘‘Lightning<br />

Protection Code.’’ This evaluates such factors as building height, terrain, building<br />

construction, proximity to other buildings, type of occupancy, <strong>and</strong> isoceraunic level<br />

(frequency of thunderstorms). If the risk assessment warrants, a lightning protection<br />

system is designed.<br />

Protection for a building may be accomplished by several methods. An installation<br />

recognized by NFPA <strong>and</strong> UL consists of lightning rods or air terminals placed<br />

around the perimeter of the roof <strong>and</strong> on vertical projections, such as chimneys <strong>and</strong><br />

the ridge of a peaked roof. These air terminals are bonded together <strong>and</strong> to a copper<br />

or aluminum conductor that extends down to a good electrical ground. There are<br />

also two less conventional types of installation that can be used. One involves the<br />

use of an air terminal containing a low-level radioactive source that produces a<br />

stream of ionized particles. This creates a low-resistance path that draws a lightning<br />

stroke to the air terminal, where it can be safely discharged to ground. The other

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