Division 22 23 Ebook Page 26 Glossary of Insulation Terms

Glossary Glossary of Insulation Terms Absorption : Refers to the taking up of water in bulk by matter (such as insulation); penetration of water into the insulation. Also see Sorption . Adsorption : Refers to the surface retention or adhesion of a very thin layer of water molecules to the surfaces of a material (such as insulation fibers) with which they are in contact. Also see Sorption . A-Scale : An acoustical filter system with characteristics that roughly match the response characteristics of the human ear at low sound levels (generally below <55 dB but often used to gauge levels to 85 dB). Attenuation : The sound reduction process in which sound energy is absorbed or diminished in intensity as the result of energy conversion from sound to motion or heat. British Thermal Unit (Btu) : The heat required to raise the temperature of a pound of water 1F. Celsius (formerly Centigrade) : A thermometric scale in which the freezing point of water is 0C and its boiling point 100C at normal sea level atmospheric pressure (14.7 psi). C = (F-32)/1.8. Condensation : The changing of vapor to liquid by extracting heat. Conductance, Thermal (C) : The time rate of steady state heat flow through a unit area of a material or construction induced by a unit temperature difference between the body surfaces. C = Btu/hrft 2 F (W/m2C) Conductivity, Thermal : The time rate of steady state heat flow through a unit area and unit thickness of homogeneous material induced by a unit temperature gradient perpendicular to that unit area. k = Btuin/hrft 2 F (l = W/mC) Apparent Thermal Conductivity : A value assigned to a material that exhibits thermal transmission by several modes of heat transfer resulting in property variation with specimen thickness or surface emittance. Cooling Degree Day (hour) : A unit, based on temperature difference and time, used in estimating fuel consumption and specifying nominal cooling load of a building in summer. Density : The mass per unit volume of in-place thermal insulation. Emittance : The ratio of the radiant flux emitted by an ideal, perfect emitter and absorber of thermal radiation at the same temperature and under the same conditions. Fahrenheit : A thermometric scale in which 32F denotes freezing and 212F the boiling point of water under normal sea level atmospheric pressure of 14.7 psi. F = 1.8C + 32. Frequency (Hz) : The number of cycles per second measured in units of Hertz. FRK : A vapor retarder laminate of foil/scrim (reinforcement) kraft construction. Also known as FSK. Heat Flow : The rate at which heat moves from an area of higher temperature to an area of lower temperature. Btu/hr (W/hr). Heat flow is generally used to quantify the rate of total heat gain or heat loss of a system. Humidity : See Relative Humidity. Inch of Water (in. w.g.) : A unit of pressure equal to the pressure exerted by a column of water 1" (25 mm) high at a temperature of 39.2F (4C). Mean Temperature : The arithmetic mean between hot and cold surface temperatures of an insulated pipe, duct or vessel. tm = (t 1 + t 2 )/2. Noise Reduction Coefficient (NRC) : A single number rating, the arithmetic average of the individual sound absorption coefficients of a material at 250, 500, 1000 and 2000 Hz to the nearest .05. Octave Band : A range of frequency where the highest frequency of the band is double the lowest frequency of the band. The band is usually specified by the center frequency. Perm : The mass rate of water vapor flow through one square foot of a material or construction of one grain per hour induced by a vapor pressure gradient between two surfaces of one inch of mercury or in units that equal that flow rate. Pressure, Static : See Static Pressure.

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