Control of lighting should be flexible. Conveniently located, separate switches or dimmers should be installed for areas with different types of activities. It should be easy to extinguish lights for areas that are not occupied and to maintain minimal emergency lighting, for safety. Where feasible, daylighting should be used, supplemented, as needed, with artificial lighting. Light from windows can be reflected deeply into rooms, with venetian blinds, glass block, or other architectural elements. Glare and solar heat can be limited with blinds, shades, screens, or low-transmission glass. Provision should be made for decreasing or extinguishing supplementary artificial lighting when there is adequate daylight. Consideration should be given to use of photoelectric-cell sensors with dimmers for control of the artificial lighting. Maximum use of daylighting and other energy conservation measures are often essential, not only to meet the owners construction budget but also to satisfy the energy budget, or limitations on power consumption, set by building codes or state or federal agencies. Enhancing the functions performed by the power and lighting systems, the special systems in a building serve the life safety, communication, and security needs of a facility and its occupants. 15.19.1 Lightning Protection The design of lightning protection systems should conform with the standards of the American National Standards Institute, the National Fire Protection Association (Bulletin No. 780, Lightning Protection Code) and Underwriters Laboratories (Standard UL96A Master-Labeled Lightning Protection Systems). In deciding whether to provide a building lightning protection system, designers should first perform a risk assessment in accordance with NFPA 780, Lightning Protection Code. This evaluates such factors as building height, terrain, building construction, proximity to other buildings, type of occupancy, and isoceraunic level (frequency of thunderstorms). If the risk assessment warrants, a lightning protection system is designed. Protection for a building may be accomplished by several methods. An installation recognized by NFPA and UL consists of lightning rods or air terminals placed around the perimeter of the roof and on vertical projections, such as chimneys and the ridge of a peaked roof. These air terminals are bonded together and to a copper or aluminum conductor that extends down to a good electrical ground. There are also two less conventional types of installation that can be used. One involves the use of an air terminal containing a low-level radioactive source that produces a stream of ionized particles. This creates a low-resistance path that draws a lightning stroke to the air terminal, where it can be safely discharged to ground. The other type uses thousands of small air terminals spread along the high points of a structure to constantly dissipate any electrical charge in the air before it can build up high enough to induce a lightning stroke. The electrical wiring in a building is especially susceptible to the effects of a lightning stroke. To minimize these effects, a multilevel protective approach is used. Lightning arresters, which are connected from the phase wires to ground, are provided on the utility company lines and at the various voltage levels down to utilization voltage. Usually of the metallic oxide varistor (MOV) type, the arresters present a very high resistance to ground at normal system voltage, but quickly collapse to zero resistance during a lightning discharge, dissipating the discharge

Robustness of isolated piers is controlled by an equation, which gives a limit on height for one-way spanning members as follows: Where H = Cv t r H = Clear height of the member (in metres) t r = minimum thickness of the member Cv = Robustness coefficient for vertical span. For piers unreinforced vertically 13.5. For piers reinforced vertically or pre-stressed - 30. The stiffening action of engaged piers is only taken into account for walls in pure vertically spanning walls. Even then, the piers must be quite substantial before they are effective. Note that an engaged pier has insufficient strength and stiffness to provide lateral support to the wall. Both leaves of a cavity wall are considered to act together for the purposes of robustness, unlike for compressive strength design. The charts for walls with side support (leading to two way bending) show a smooth curve, unlike the cases with only top and bottom support, and this recognises the importance and effect of having at least one vertical support to stabilise the wall.

With member size of particular importance of fire endurance of wood, building codes classify buildings with wood framing as heavy-timber construction, ordinary construction, or wood-frame construction. Heavy-timber construction is the type in which fire resistance is attained by placing requirements on the minimum size, thickness, or composition of all loadcarrying wood members; by avoidance of concealed spaces under floors and roofs; by use of approved connections, construction details, and adhesives; and by providing the required degree of fire resistance in exterior and interior walls. (For design procedures and typical connector details, see Design for Code Acceptance #2, Design of Fire-Resistive Exposed Wood Members, American Forest & Paper Association, Washington, D.C.) Ordinary construction has exterior masonry walls and wood-framing members of sizes smaller than heavy-timber sizes. Wood-frame construction has wood-framed walls and structural framing of sizes smaller than heavy-timber sizes. Depending on the occupancy of a building or hazard of operations within it, a building of frame or ordinary construction may have its members covered with fireresistive coverings. The fire endurance rating of protected wood-frame assemblies is measured in a standard fire endurance test, ASTM E119. Fire endurance ratings for various assembly designs can be found in listings that are published by recognized fire testing laboratories. These listings are updated on a regular basis. Alternatively, for many assemblies, a conservative estimate of the fire endurance rating can be obtained through a simplified calculation method (Design for Code Acceptance #4, Component Additive Method (CAM) for Calculating and Demonstrating Assembly Fire Endurance, American Forest & Paper Association.) This method estimates the overall fire endurance rating as the sum of fire endurance times assigned to individual components of an assembly. The interior finish on exposed surfaces of rooms, corridors, and stairways is important from the standpoint of its tendency to ignite and spread flame from one location to another. The fact that wood is combustible does not mean that it will spread flame at a hazardous rate. Code requirements to limit the flame-spread propensity of interior finishes are based on the flame-spread index (FSI) measured in the ASTM E84 tunnel test. Most wood products of sufficient thickness (1/4 in or greater) have an FSI between 76 and 200 (Class III or C). Some wood products have an FSI between 26 and 75 (Class II or B). Fire-retardant treatment can improve performance to an FSI of 25 or less (Class I or A). For an extensive list of flame spread indices of wood products, see Design for Code Acceptance #1, Flame Spread Performance of Wood Products, American Forest & Paper Association. In general, codes require Class I or A materials for enclosed vertical exits. Class II or B materials in exit access corridors, and Class III or C materials in other areas and rooms. Thus, wood products are accepted by the codes for a wide range of interior finish uses. Most codes exclude the exposed wood surfaces of heavy-timber structural members from flame-spread requirements, if the exposed area is sufficiently