spaced a minimum of 12 inches OC. A nominal 1- by 3-inch or 1- by 4-inch wood member can be used for roof or ceiling members spaced not more than 24 inches OC. A nominal 2- by 2-inch or 2- by 3-inch member should be satisfactory for truss or ceiling joist spacing of up to 48 inches. In locating the strips, first measure the width of the room (the distance parallel to the direction of the ceiling joists). If, for example, this is 11 feet 6 inches, use ten 12-inch-square  tiles  and  9-inch-wide  tile  at  each  side edge. The second wood strips from each side are located so that they center the first row of tiles, that can now be ripped to a width of 9 inches. The last row will also be 9 inches, but do not rip these tiles until the last row is reached so that they fit tightly. The tile can be fitted and arranged the same way for the ends of the room. Ceiling tiles normally have a tongue on two adjacent sides  and  a  groove  on  the  opposite  adjacent  sides.  Start with the leading edge ahead and to the open side so that it can be stapled to the nailing strips. A small finish nail or adhesive should be used at the edge of the tiles in the first row against the wall. Stapling is done at the leading edge and the side edge of each tile (fig. 5-26, view B). Use one staple at each wood strip at the leading edge and two at the open side edge. At the opposite wall, a small finish nail or adhesive must again be used to hold the tile in place. Most ceiling tile of this type has a factory finish; painting or finishing is not required after it is placed. Take care not to mar or soil the surface. INSULATION LEARNING OBJECTIVE: Upon completing this section, you should be able to identify the types of insulation and describe the methods of installation. The inflow of heat through outside walls and roofs in  hot  weather  or  its  outflow  during  cold  weather  is  a major source of occupant discomfort. Providing heating or cooling to maintain temperatures at acceptable limits for occupancy is expensive. During hot or cold weather, insulation with high resistance to heat flow helps save energy. Also, you can use smaller capacity units to achieve the same heating or cooling result, an additional savings. Most materials used in construction have some insulating value. Even air spaces between studs resist the passage of heat. However, when these stud spaces are filled or partially filled with material having a high insulating value, the stud space has many times the insulating ability of the air alone. TYPES Commercial insulation is manufactured in a variety of  forms  and  types,  each  with  advantages  for  specific uses. Materials commonly used for insulation can be grouped in the following general classes: (1) flexible insulation  (blanket  and  batt);  (2)  loose-fill  insulation; (3) reflective insulation; (4) rigid insulation (structural and  nonstructural);  and  (5)  miscellaneous  types. The insulating value of a wall varies with different types  of  construction,  kinds  of  materials  used  in construction, and types and thicknesses of insulation. As we just mentioned, air spaces add to the total resistance of a wall section to heat transmission, but an air space is not as effective as the same space filled with an insulating material. Flexible Flexible  insulation  is  manufactured  in  two  types: blanket and batt. Blanket insulation (fig. 5-27, view A) is furnished in rolls or packages in widths to fit between studs and joists spaced 16 and 24 inches OC. It comes in thicknesses of 3/4 inch to 12 inches. The body of the blanket is made of felted mats of mineral or vegetable fibers,  such  as  rock  or  glass  wool,  wood  fiber,  and cotton.  Organic  insulations  are  treated  to  make  them resistant to fire, decay, insects, and vermin. Most blanket insulation is covered with paper or other sheet material with tabs on the sides for fastening to studs or joists. One covering  sheet  serves  as  a  vapor  barrier  to  resist movement  of  water  vapor  and  should  always  face  the warm side of the wall. Aluminum foil, asphalt, or plastic laminated paper is commonly used as barrier materials. Batt insulation (fig. 5-27, view B) is also made of fibrous material preformed to thicknesses of 3 1/2 to 12 inches for 16-and 24-inch joist spacing. It is supplied with or without a vapor barrier. One friction type of fibrous glass batt is supplied without a covering and is designed to remain in place without the normal fastening methods. Loose Fill Loose-fill insulation (fig. 5-27, view C) is usually composed  of  materials  used  in  bulk  form,  supplied  in bags  or  bales,  and  placed  by  pouring,  blowing,  or packing by hand. These materials include rock or glass 5-20