R-VALUES in Software

Generate Code-39 in Software R-VALUES

Insulation quality is often expressed in R-values An R-value is merely a quantitative expression of the ability of any material to resist the passage of heat For example, a fiberglass batt 6 inches thick has an R-value of approximately 19 The same material in batts 12 inches thick will possess an R-value of about 38 The greater R-value, the greater the material s resistance to the passage of heat (or coolness), and the better its insulation value Table 211 gives an insulation materials comparison Table 212 lists some of the same kinds of insulations, and shows what their most common thicknesses equal in insulating values Because heat rises, the potential heat loss in a house is greatest through the roof, and least through the floors Therefore, different recommendations exist for insulating those areas as well as the walls each with a different, appropriate R-factor Here are some conservative recommended R-values for your house: walls R-20; floors R-27 (above grade), which includes overhangs, cantilevers, and below projecting windows; and ceilings R-40

Fiberglass Rock Wool Fiberglass Polystyrene Rock Wool (blown) Fiberglass (blown)

1 1 5 5 1 1

R-Values: Fiberglass blankets/batts Rock wool blankets/batts Fiberglass loose/blown Rock wool loose/blown R-11 31 2" 4" 3" 31 2" 5" 4" R-19 6" 61 2" 5" 6" 81 2" 61 2" R-22 7" 71 2" 6" 7" 10" 71 2" R-30 91 2" 10" 8" 91 2" 131 2" 10" R-38 12" 13" 101 2" 12" 17" 13"

On occasion you might find the thermal qualities of an insulation material expressed in terms of U The U-value is the reciprocal of the R-value and can be determined by dividing the R-value into the numeral value For example, a fiberglass batt having an R-value of 19 has a Uvalue of 1 19, or 053 Basically, the lower the U-value, the greater the thermal resistance of the material, and the better its insulation quality

While it s true that each material used to make up your house possesses some insulating value, the effectiveness of individual types of materials varies greatly For example, a 1-inch-thick blanket of fiberglass insulation has the same insulation value as approximately a 31 2inch thick layer of pine wood planking, a 22-inch-thick wall of common brick, a 40-inch-thick layer of solid concrete, or a 54-inchthick (41 2 feet!) layer of stone The most popular types of insulation used in modern homes are blankets and batts of fiberglass and rock wool, rigid boards of polystyrene, fiberglass board, rigid foam boards, and various loose forms of fiberglass and rock wool

These two products make up about 90 percent of all homeowner insulation (Figs 211 and 212) They re made of compressed fibers that come

in a continuous roll form (blanket) or in rolls having perforations along every few feet or yards so you can pull off regular rectangular pieces (batts) Both blankets and batts are available in various thicknesses and widths, and with or without facing material or vapor barrier material on one side Fiberglass and rock wool also come in shredded forms for hand-pouring or F I G U R E 2 1 1 machine-blowing applications Be aware that both of these materials can be irritatBlanket insulation ing if they come into direct contact with your skin Rock wool is the less bothersome of the two Although loose insulation is more economical to purchase and install, it will eventually settle and lose some of its insulating value, and it s difficult to move out of the way, if need be Fiberglass and rock wool insulation can be used throughout the entire house, for ceilings, walls, floors, basements, around windows and doors, or anywhere else F I G U R E 21 2 energy might otherwise be lost to conductivBatt insulation ity and air infiltration They both have good insulation values and are among the most economical types to purchase Rock wool insulation batts are available in semirigid models with unique flexible edges designed to compress as the batt is placed into walls, attics, ceiling, and floor frames The flexible edge springs back, expanding against whatever it is filling, to give a tight fit