A-Scale : A 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).
Absorption : The process of drawing fluid or gas into a porous material, such as a sponge soaking up water.
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.
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.
Baffles: Device to maintain a ventilation space between the insulation and roof deck, assuring air flow from the eave/soffit vents to ridge vent or other roof vents provided in attics and cathedral ceilings.
Band Joist : Vertical member that forms the perimeter of a floor system in which the floor joists tie in. Also known as the rim joist.
Bottom Plate (Sole Plate) : The lowest horizontal member of a wall which rests on the sub-floor, to which the studding is nailed.
Foil-Faced Vapor Retarder : Created by coating a foil-backed paper with a thin layer of adhesive, then attaching it to the fiber glass.
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.
Furring Strips : Flat pieces of lumber used to build out framing to an even surface, either the leveling of a part of a wall or ceiling. In block or concrete construction, they may be used as a means of attaching the interior or exterior finish.
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.
Knee Walls : Walls of varying length. Used to provide additional support to roof rafters with a wide span or to finish off an attic.
Kraft-Faced Vapor Retarder : Created by coating kraft paper with a thin layer of asphalt adhesive. The coated side of the kraft paper is then applied to the unfaced insulation material. The asphalt adhesive bonds the kraft paper and the insulation together.
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.
Polyethylene Vapor Barrier : Plastic film used to prevent moisture from passing through unfaced insulation. Both 4- and 6-mil polyethylene are preferred because they are less likely to be damaged during construction.
Rafters : A slope framing member that supports a pitched roof.
Relative Humidity : A measure of the amount of moisture in the air with respect to the temperature. It is the ratio of the moisture present to the maximum amount of moisture the air can hold at that temperature.
Resilient Channels : Metal channels used to further inhibit sound transmission through wall and ceiling framing. Create a break in the vibration path from drywall to the framing.
Ridge Vents : A vent mounted along the entire ridge line of the roof to allow the passage of air through the attic or cathedral ceiling.
Roof Vents : A louver or small dome mounted near the ridge of the roof to allow the passage of air through the attic.
R-Value : Measure of resistance to heat flow. Insulation materials have tiny pockets of trapped air. These pockets resist the transfer of heat through material. The ability of insulation to slow the transfer of heat is measured in R-values. The higher the R-value, the better the insulation material's ability to resist the flow of heat through it.
SSL : Self-sealing lap, a feature of pipe insulation covering in which an adhesive strip provides mechanical and vapor retarder closure of the longitudinal seam. See also SSL II.
SSL II : Pipe insulation jacket closure with a double adhesive, self-sealing lap to close the longitudinal seam.
Sorption : Refers to the taking up and holding of water by various processes such as absorption and adsorption.
Sound Absorption : The process of dissipating or removing sound energy; the property possessed by materials, objects and structures (such as rooms) of absorbing sound energy; the measure of the magnitude of the absorptive property of a material, object or structure.
Wall Plates : In wood-frame construction, the wall is composed of both vertical and horizontal wood members. The vertical members are usually called studs, while the horizontal members are usually called plates. A bottom plate is at the bottom of the wall frame assembly, while two plates are usually used at the top (double top plate).
Warm-In-Winter Side : In heating climates, it is the interior side of an exterior wall assembly.
Water Vapor Permeance : Time rate of water vapor transmission through unit area of flat material or construction, induced by vapor pressure difference between two specific surfaces, under specified temperature and humidity conditions.
Water Vapor Retarder : A material or system that adequately impedes the transmission of water vapor under specified conditions.
References: NEBB, National Environmental Balancing Bureau: Environmental Systems Technology, Chapter 19, Glossary. ASTM, American Society for Testing and Materials: ASTM C 168-90, Standard Terminology Relating to Thermal Insulating Materials.