Final Steps. Receive prices for materials and subcontracts. Review the estimate and carefully note exclusions and exceptions in each subcontract bid and in material quotations. Fill in with allowances or budgets those items or trades for which no prices are available. Decide on the markup. This is an evaluation that should be made by the contractor, weighing factors such as the amount of extras that may be expected, the reputation of the owner, the need for work on the part of the general contractor, and the contractors overhead. Finally, and most importantly, the estimate must be submitted in the form requested by the owner. The form must be filled in completely, without any qualifying language or exceptions, and must be submitted at the time and place specified in the invitation to bid. Figure 17.3 shows part of an estimate and bid summary produced for a multistory apartment building by a computer. Contractors usually submit bids for a lump-sum contract or a unit-price-type contract, when based on complete plans and specifications. When plans and specifications have not yet advanced to a stage where a detailed estimate can be made, the type of contract usually resorted to is a cost-plus-fee type. The bid may be based on either a percentage markup the contractor will receive over and above costs, or may include a lump-sum fee that the contractor charges over and above costs. Sometimes an incentive fee is also incorporated, FIGURE 17.3 Output from a computer spreadsheet program of an estimate and bid summary

Small facilities may only need emergency power for emergency and egress lighting, in which case, fixtures with self-contained battery backup may be adequate. Larger facilities generally require an engine generator to provide emergency power. Emergency loads are connected to a dedicated panelboard or switchboard fed through an automatic transfer switch (ATS) that will detect loss of utility power, signal the generator to start, and transfer the emergency loads onto the generator, all in 10 s or less. After utility power returns, the ATS will retransfer the emergency loads back to utility power and then stop the generator. To prevent equipment damage and voltage surges, an ATS should be provided with an in-phase monitor that waits until the generator drifts into synchronism with the utility source before allowing retransfer. Generator fuel source may be gasoline, LP gas, diesel fuel, or (if acceptable to the authority having jurisdiction) public utility gas. Local and federal environmental regulations should be consulted if it will be necessary to store liquid fuels. If an aboveground storage tank will be needed, it must be a double-walled tank equipped with electronic leak detection. A subbase, fuel-storage tank, that is an integral part of the generator frame, may also be used for liquid fuel. Though normally used only for emergency power, the generator, if large enough, may be used to reduce electric bills through demand peak shaving or as a cogen- erator. Opportunities for these possibilities should be reviewed with the utility company. Where acceptable to the authority having jurisdiction, a second utility service may be used to provide emergency power. This approach should be evaluated carefully to ensure that the separate service is designed to minimize the possibility of simultaneous interruption of both services. All metals conduct electricity but have different resistances. Some metals, like gold or silver, have very low resistance, but they do not have the tensile strength required for electrical wire and are too costly. Consequently, only two metals are used extensively in buildings as conductors, copper and aluminum. The choice of copper or aluminum will be based on installed cost, and since aluminum conductors are less costly than copper conductors, one would expect that aluminum conductors would always be chosen. However, several factors should be considered: To carry a given amount of current, a larger aluminum wire is needed, and its raceway may also need to be larger. Because aluminum conductors expand more than copper as they warm up under load, they tend to move back and forth at terminals and, unless the proper termination methods and wiring devices (marked CO/ALR) are used, the conductors may work loose and create a fire hazard. Also, some local building codes and agency standards either do not permit aluminum conductors to be used, or restrict their use to larger wire sizes. Conductors may be solid round wire, stranded wire, or bus bars of rectangular cross section. Usually, conductors are wrapped in insulation of a type that prevents electric shock to persons in contact with it. The type of insulation also depends on the immediate environment surrounding the wire in its proposed use; dry or moist air, wetness, buried in earth, temperature, and exposure to mechanical or rodent

Manufacturers have contributed substantially toward standardization of window sizes and greater precision in fabrication. The American National Standards Institute has established an increment of sizing generally accepted by the building industry (Basis for the Coordination of Building Materials and Equipment, A62.1). The basis for this standardization is a nominal increment of 4 in in dimension. However, it will be noted in Fig. 11.30, that for double-hung wood windows the 4-in module applies to the grid dimensions, whereas the standard window openings is 4 in less in width and 6 in less in height than the grid opening. Also, to accommodate 2- and 6-in mullions for multiple openings in brick walls, it is necessary to provide a 2-in masonry offset at one jamb (Fig. 11.31). Use of modular planning effects maximum economies from the producer and simplification for the building industry. At the same time, a given layout does not confine acceptable products to such a limited range. Window frames are generally made of wood or metal. Plastics have been employed for special services. Use of metal in window construction has been highly developed, with aluminum and steel most commonly used. Bronze, stainless steel, and galvanized steel are also extensively used for specific types of buildings and particular service. Use of metal windows is very often dictated by fire-resistance requirements of building