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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).
Abatement To reduce or make void any substance such as the removal of noise, asbestos or lead. See asbestos abatement definition as one form of removal.
Abrasion Resistance The ability of a material to withstand abrasion without appreciative erosion.
Absorptance The ratio of the radiant flux absorbed by a body to that incident upon it.
Absorption 1. Transformation of radiant energy to a different form of energy by interaction with matter. 2. The process of drawing fluid or gas into a porous material, such as a sponge soaking up water.
Abuse Coverings and Finishes Jackets, mastics or films used to protect insulation from mechanical and personnel abuse.
Accoustical Treatment Application of materials for sound control. A common practice is the use of insulation to absorb sound.
Adhesive A substance used to bond materials by surface attachment.
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.
Aerogel Insulation A homogeneous, low-density solid state material derived from a gel, in which the liquid component of the gel has been replaced with a gas. The resulting material has a porous structure with an average pore size below the mean free path of air molecules at standard atmospheric pressure and temperature.Some aerogel materials contain nano particles.
Air Infiltration Air that unintentionally leaks into a building.
Air Sealing Air sealing is one of the least expensive and most cost-effective measures you can take to improve your home’s comfort and energy efficiency. By sealing uncontrolled air leaks, you can expect to see savings of 10% to 20% on your heating and cooling bills.
Alkalinity The quality of a material to be basic or alkaline when exposed to moisture or water producing a blue reaction to litmus paper. ApH measure greater than 7.0.
Ambient Surrounding-encompassing (Generally applied to temperature, humidity and atmospheric conditions).
Ambient Temperature The average temperature of the medium, usually air, surrounding the object under consideration.
Annular Space (Annulus) The distance between a penetrating item and the surrounding opening.
Anti-abrasive Coating Cushioning material applied where insulation contacts the pipe, duct, vessel or adjacent insulation to prevent eroding of either or both.
Anti-sweat Applications which prevent or reduce condensation.
Appearnace Covering Materials used to improve the aesthetics of the finished insulation.
Application Temperature Limits Minimum and maximum temperatures between which it is usually safe to service finishes, adhesives and sealants without endangering the integrity of the material.
Approved Contractor A contractor approved by the organization.
Area Weight Weight per unit area for a specified sample, typically given in units of lbs/ft2 (kg/m2).
Asbestos Abatement A procedure for the removal, enclosure or encapsulation of asbestos containing materials from buildings or areas.
ASJ All-Service Jacket: A vapor retarder/laminate facing or covering constructed with a white kraft paper, fiberglass scrim, and aluminum foil.
Asphalt Cut-Back Petroleum asphalt coating with mineral solvents. (This is a vapor-retarder mastic).
Asphalt Emulsion A colloidal dispersion of petroleum asphalt coating with water. (This is a breather mastic).
ASTM ASTM, formerly known as the American Society for Testing and Materials. An independent non-profit organization that has accepted responsibility for the development and administration of voluntary standards for the testing and evaluation of a wide range of products.
Attenuation The limiting of sound propagation from one area to another.
Attic Cards Attic cards are supplied by manufacturers of blown-in insulation and show the type and R-value of the insulation, the thickness, as well as the installer’s name and company address. An attic card is not required by the FTC’s Home Insulation Rule.
Attic Rulers When blown insulation is used, NAIMA recommends that attic rulers should be installed, one for every 300 square feet of attic area. The installed thickness of blown insulation should not be less than the minimum settled thickness on the attic card. The Federal trade Commission does not require attic cards, but it is typical practice and helpful to the current and future homeowner. Consult CABO/MEC Guidelines on attic cards & rulers.
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 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.
Bands Strapping used to fasten insulation and/or jacketing in place.
Batts Pre-cut pieces of insulation in standard sizes; batts may have a facing of kraft paper, aluminum foil or poly (plastic) or no facing at all.
Beading Process of curling the edge of metal jacketing to accommodate sealing.
Beading Compound A plastic material (mastic) used to imbed insulation. Acts as a cushion, anti-abrasive and adhesive.
Bends Pipe, factory or field formed, to pre-determined radii.
Binder Substance contained in insulation material that stabilizes or bonds the fibers (sometimes called a thermal setting resin) and helps provide form for products such as batts, blankets, and pipe insulation sections.
Blackbody The ideal, perfect emitter and absorber of thermal radiation. It emits radiant energy at each wavelength at the maximum rate possible as a consequence of its temperature, and absorbs all incident radiance.
Blanket Insulation A relatively flat and flexible insulation in coherent sheet form furnished in units of substantial area.
Blanket Insulation (metal mesh) Blanket insulation covered by flexible metal-mesh facings attached on one or both sides.
Blankets Insulation which is typically wider than batts and is supplied in rolls. It may have facing of kraft paper or aluminum foil backed paper.
Bleeding The diffusion of coloring through a coating from its base or substrate (such as bleeding of asphalt mastic through a paint top coat).
Blister Rounded elevation of the surface of a mastic resembling a blister on the human skin, usually the entrapment of air or vapor.
Block Insulation Rigid insulation preformed into rectangular units.
Blown-in Blanket Systems (BIBS) BIBS® is a proprietary insulation system which blows dry white fiberglass insulation into wall, floor, attic and cathedral ceiling cavities.
Board Insulation Semi-rigid insulation preformed into rectangular units having a degree of suppleness, particularly related to their geometrical dimensions.
BOCA `Building Officials and Code Administrators.The BOCA code organization was combined with ICBO and SBCCI to form the International Code Council (ICC).
Body The viscosity or consistency of a mastic or coating.
Bond Strength The force in tension, compression, cleavage or shear required to break an adhesive assembly.
Bonding Time The time required for an adhesive to reach its optimum bonding strength.
Bottom Plate (Sole Plate or Toe Plate) The lowest horizontal member of a wall which rests on the sub-floor, to which the studding is nailed.
Box Trench Built-up enclosure either in a shallow trench or buried underground.
Branch Distribution piping or ductwork, same as a main duct or pipe except, smaller and from or returning to the main, serving two or more runouts.
Breather Coating A weather barrier coating designed to prevent water (rain, snow, sleet, spillage, wash water, etc.) from entering the insulation system, while still allowing the escape of water vapor when heat applied to the moisture entrapped in the insulation.
Breeching A duct through which the products of combustion are transported from the furnace to the stack; usually applied in steam boilers.
British Therma Unit (BTU) The heat required to raise the temperature of one pound of water 1°F.
Building Envelope The exterior assembly that encloses the interior space of a building. It serves as the outer shell to protect the indoor environment as well as to facilitate its climate control. Building envelope design is an application area that draws from all areas of building engineering, especially building science and indoor climate control. Building envelope design includes four major performance objectives: Structural integrity; Moisture control; Temperature control; and control of air pressure boundaries (this includes air movement into and out of the interior space and through the components of the building envelope-interstitial). The physical components of the envelope include the foundation, roof, and walls, along with the insulation encompassed in these components, as well as the doors and windows.
Built Up Roof A composition roof composed of layers of roofing felt mopped with hot asphalt and usually topped with gravel.
Butt Joists The end joints of pipe insulation where individual pieces are in contact.
Butt Strip Strips of similar jacket material applied around pipe insulation butt joints.
C-Value A measure of the rate of heat flow for the actual thickness of a material (either more or less than 1 inch), 1 square foot in area, at a temperature difference of 1°F. If the K-value of a material is known, the C-value can be determined by dividing the K-value by the thickness. The lower the C-value, the higher the insulating value. (Btu/h·ft2·°F)
Calcium Cilatate Insulation composed principally of hydrous calcium silicate, and which usually contains reinforcing fibers.
Canvas A plain-weave cotton fabric used for jacketing or covering.
Capillarity The ability of a cellular, fibrous or granular material to diffuse water into its structure.
Caulk To seal and make water and/or airtight using liquid caulking materials.
Cavity The empty space between studs or joists typically filled with insulation.
Cellular Elastometric Insulation composed principally of natural or synthetic elastomers, or both, processed to form a flexible, semi-rigid or rigid foam that has a closed-cell structure.
Cellular Glass Insulation composed of glass processed to form a rigid foam having a predominately closed-cell structure.
Cellular Insulation Insulation composed of small, individual cells separated from each other. The cellular material may be glass or plastic such as polystyrene, polyurethane, polyisocyanurate or elastomeric.
Cellular Plastic Expander Beads of plastic expanded by chemical or thermal means and bonded together chemically or thermally.
Cellular Pollymide Insulation composed of the reaction product in which the bonds formed between monomers during polymerization are essentially imide units forming a cellular structure.
Cellular Polystyrene Insulation composed principally of polymerized styrene resin processed to form a rigid foam having a predominately closed-cell structure.
Cellular Polyurethane Insulation composed principally of the catalyzed reaction product of polyisocyanate and polyol compounds, processed usually with fluorocarbon or hydrocarbon gas to form a rigid foam having a predominately closed-cell structure.
Cellulosic Fibers Insulation composed principally of cellulose fibers usually derived from paper, paperboard stock or wood, with or without binders.
Celsius (formerly Centigrade) A thermometric scale in which the freezing point of water is 0°C and its boiling point 100°C at normal sea level atmospheric pressure (14.7 psi). °C = (°F-32)/1.8
Cement, Finishing A mixture of dry fibrous or powdery materials, or both, that when mixed with water develops a plastic consistency, and when dried in place forms a relatively hard, smooth protective surface.
Cement, Insulating A mixture of dry granular, fibrous or powdery (or both) materials that when mixed with water develops a plastic consistency, and when dried in place forms a coherent covering that affords substantial resistance to heat transmission.
Ceramic Fibers Pure silica heated and expanded to produce fibers from which high-temperature insulation can be made. Sometimes called Refractory Ceramic Fibers.
Chalking A soft white or gray appearance on the surface of a weathered finish.
Checking Openings of a coated surface characterized by the appearance of fine cracks in all directions.
Chemical Resistance Capability of a material to withstand exposure to acids, alkalis, salts and their solutions.
Chicken Wire Hexagonal wire netting (poultry mesh or netting) used as reinforcement or as a metal-mesh facing.
Cladding-Jacketing Jacketing installed over insulation.
Closed Cell Foam A material comprised predominantly of individual non-interconnecting cellular voids.
Coating 1.  A liquid or semi-liquid protective finish capable of application to thermal insulation or other surfaces usually by brush or spray in moderate thickness, less than 30 mils. (0.030″). 2.  A liquid or semi-liquid that dries or cures to form a protective finish, suitable for application to thermal insulation or other surfaces in thickness of 30 mils.
Code (Building) A set of construction and materials standards, usually statutory. Model building codes are adopted by each municipality from the major code organizations. The major code authority is the International Code Council (ICC). The local municipality or state can choose which major building code is adopted.
Coefficient of Expansion/Contraction The change in a unit length of a material corresponding to a unit change in the temperature of the material.
Collar Beam A horizontal board connecting two opposite rafters at a level considerably above the wall plate. Also known as collar tie.
Combustible Capable of catching fire or bursting into flames.
Commercial A building classification – related to business as in commercial building.
Compaction Resistance The property of a fibrous or loose-fill material that resists compaction under load or vibratory conditions.
Compatible Materials Two or more substances that can be mixed or used together without separating, reacting, or adversely affecting the materials.
Copmpressive Strength The property of material to resist any change in dimensions when acted upon by a compaction force.
Concealed Spaces Spaces not generally visible or accessible after the project is completed such as furred spaces, pipe spaces, pipe and ductshafts, spaces above ceilings, unfinished spaces, crawl spaces, attics and tunnels.
Condensate Drain Piping carrying condensed water from air conditioning or refrigeration drip pans to a point of discharge.
Condensate Return Piping carrying water form condensed steam back to the equipment used to generate the steam.
Condensation The liquid water that results when water vapor changes to liquid form. This commonly occurs when warm moist air comes in contact with cold surfaces.
Conditioned Air Air treated to control simultaneously its temperature, humidity and cleanliness to meet the requirements of a conditioned space. (May be cool and/or heated and should be clearly defined).
Conductance, Thermal ( C ) Thermal conductance, C,  is the quantity of heat that passes in unit time through a plate of particular area and thickness when its opposite faces differ in temperature by one degree Kelvin.
Conduction The transfer of heat energy within a body or between two bodies in physical contact.
Conductivity, Thermal (K) Thermal conductivity, k, is the property of a material that quantifies its ability to conduct heat. Commonly expressed in BTU·in/hr·ft2·°F.
Contact Adhesive An adhesive that when tacky to the touch will adhere to itself on contact.
Convection The transfer of heat energy by air or fluid movement. This motion is a spontaneous circulation due to the combined actions of gravity and changes in air or fluid density. In space heating, the operation of a baseboard heater is a good example of convection.
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.
Corrosion Deterioration by chemical action such as rust/oxidation on steel.
Couplings Screwed, soldered, welded or mechanical/grooved connections between links of pipe.
Cover To place insulation and/or finish materials on, over or around a surface so as to insulate, protect or seal.
Coverage 1.  The rate in square feet per gallon (coatings), or gallons per hundred square feet (mastics), at which products must be applied to obtain satisfactory performance. 2.  The area to be covered per unit volume of coating to obtain specified dry thickness and desired performance. 3.  The quantity of loose-fill insulation required to provide a given thermal performance for a given square footage.
Covering Capacity, Dry The area covered to a dry thickness of 1 inch (25 mm) by 100 lb. (45.4 kg) of dry cement when mixed with the recommended amount of water, molded and dried to constant weight.
Covering Capacity, Wet The area covered to a wet thickness of 1 inch (25 mm) by 100 lb. (45.4 kg) of dry cement when mixed with the recommended amount of water and molded.
Crawlspace Vents An opening to allow the passage of air through the unfinished area under a first floor. Ideally there should be at least two vents per crawlspace. Refer to your local building code for requirements in your area.
Crimping Corrugating of the metal edge to reduce diameter or facilitate bending. Used on fitting gores to mate with beaded edge of adjacent segment or on end caps for tanks and vessels.
Cross Bridging Small wood or steel pieces placed at angles so that they extend from the bottom of one floor joist to the top of the adjacent joist to add stability to the structural members.
Cryogenic Insulation Insulation for extremely low-temperature processes surfaces from-100 F to -459 F (absolute zero).
Cupped Head Pin A welded insulation fastener pin with a fixed washer for attaching duct liner within metal ducts, typically attached to the duct walls using an automatic arc welder.
Cure To change the properties of a plastic or resin by chemical reaction, usually accomplished by the action of either heat or a catalyst.
Damming The use of a substance to support firestopping materials until cured.
Decibel (Db) A logarithmic measure used in describing levels of sound pressure or sound power.
Decomposition The separating or breaking down of a substance into its component compounds or basic elements.
Delamination The separation of the layers of material in a laminate.
Dew Point Saturation temperature where water vapor and liquid occur simultaneously.
Dew Point Temperature The temperature at which condensation of water vapor in a space begins for a given state of humidity and pressure as the vapor temperature is reduced; the temperature corresponding to saturation (100% relative humidity) for a given absolute humidity at constant pressure.
Diatomaceous Silica Insulation composed principally of diatomaceous earth with or without binders, and which usually contains reinforcing fibers.
Diffusivity, Thermal The ratio of thermal conductivity of a substance to the product of its density and specific heat. In heat transfer analysis, thermal diffusivity is the thermal conductivity divided by the volumetric heat capacity. Substances with high thermal diffusivity rapidly adjust their temperature to that of their surroundings, because they conduct heat quickly in comparison to their volumetric heat capacity or ‘thermal bulk’.
Dimensional Stability That property of a material that enables it to maintain its original size, shape and dimensions.
DN Diameter, Nominal (millimeters) Metric equivalent of NPS (Nominal Pipe Size, inches).
Dry To change the physical state of a substance by the loss of solvent constituents by evaporation, absorption, oxidation or a combination of these factors.
Duct Flange (Stiffener) A structural or fabricated shape,such as an angle iron, attached to the exterior surfaces of a duct at specified intervals for the purpose of reinforcing the metal and assembly of the ducts.
Eave Vents Vent openings located in the soffit under the eaves of a house to allow the passage of air through the attic and out the roof vents.
Economic Thickness That thickness of insulation which provides the lowest possible annual cost of energy, insulation, and energy producing equipment combined.
Efflorescence A white powdery substance occurring on the surface caused by the migration of soluble salts from the insulation, followed by precipitation and carbonation.This phenomena can occur on the surface of some insulation materials.
Elastomeric A closed-cell foam insulation containing elastomers that provide the property of high elasticity.
Emissivity A measure of the ability of a material to radiate energy. It is expressed as a ratio (decimal) of the radiating ability of a given material to that of a black body. A black body emits radiation at the maximum possible rate at any given temperature, and has an emissivity of 1.0.
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.
Emittance, Directional The ratio of the radiance from a surface in a particular direction to the radiance from a blackbody at the same temperature under the same conditions.
Emittance, Hemispherical The average directional emittance over a hemispherical envelope covering a surface.
Emittance, Spectral An emittance based on the radiant energy emitted per unit wavelength interval (monochromatic radiant energy).
Emitaance, Total An emittance that is an integrated average over all wavelengths of radiant energy emitted.
Emulsion Insoluble fine solids or liquids dispersed in another liquid, usually water.
Energy Code Local requirement that outlines the minimum level of insulation and other energy-efficiency measures for new construction. Energy Codes are updated on an ongoing basis, and minimum levels of insulation are set by considering the cost of energy and what level provides a reasonable payback.
Epoxy Resins A two-part compound of an epoxy and catalyst that cures at ambient temperatures to form finishes which are highly resistant tosolvents and chemicals. A high bond adhesive.
Equivalent Thickness (Of insulation) – When r1 = the inner radius of a single layer of cylindrical insulation and r2 = the outer radius, equivalent thickness = r2·ln(r2/r1).
Exhaust Duct A duct carrying air from a conditioned space to an outlet outside the building.
Existing Buildings Homes or commercial structures currently standing.
Expanded Metal Lath See lath-expanded metal.
Exposed Spaces Those spaces not referred to as concealed or as defined by the specifier.
F-rating A rating usually expressed in hours indicating the length of time that the temperature on the non-fire side of a fire-rated assembly exceeds 325°F above its ambient temperature as determined by ASTM E-814 (UL-1479).
Face Staple Stapling facing flange to the front side of a stud or rafter, along the 1-1/2″ dimension.
Faced Insulation Insulation with a facing already attached. Kraft paper or foil-backed paper are common facings.
Facing Definition One: A thin layer of laminate, usually factory applied, on the surface of an insulating material. Definition Two: A protective or decorative (or both) surface applied as the outermost layers of insulation.
Fan A mechanical air-moving device.
Fiberglass A material consisting of glass fibers used in making various products, including yarns, fabrics, insulation, and structural objects or parts. Fiberglass is resistant to heat and fire.
Fibrous Glass A synthetic vitreous fiber insulation made by melting predominantly silica sand and other inorganic materials, and then physically forming the melt into fibers. To form an insulation product, there are often other materials applied to the loose fibers such asbinders, oils, etc. Commonly referred to as either fiberglass or fiberglass.
Fibrous Insulation Insulation composed of small diameter fibers that finely divide the air space. Fibers used are silica, rock wool, slag wool or alumina silica.
Film (Wet) The applied layer of mastic or coating before curing or drying.
Finishing Cement A mixture of various insulating fibers, fillers and binders with water, with or without hydraulic cement, to form a smooth trowelable paste insulation for smooth application over insulating cement or unfinished block insulation.
Fire Resistance The property of a material or assembly to withstand fire or give protection. It is characterized by the ability to confine a fire and to continue to perform a given structural function.
Fire Retardance (FR) The property of a material that retards the spread of fire.
Fire Blocking Building materials installed to resist the free passage of flame of flame and gasses to other areas of the building throughconcealed spaces.
Fire Stopping A firestop is a passive fire protection system of various components used to seal openings and joints in fire-resistance rated wall and/or floor assemblies, based on fire testing and certification listings.
Fish Mouth A gap between layers of sheet materials caused by warping or bunching of one or both layers. Typically seen when stapling kraft face insulation or the jacketing on pipe insulation.
Fitting Cover The insulation for a pipe fitting composed of the specified thickness of insulation material, which may be preformed. Also, a preformed jacketing.
Fittings Items used to change size, direction of flow, level or assembly of piping, except for unions, grooved couplings, flanges, valvesor strainers.
Fixture Connection Final piping connections to plumbing fixtures (usually exposed and chrome-plated).
Flame Retardant The chemicals or materials used to limit the flame spread across a building product’s surface, including insulation surface.
Flame Spread Index NFPA 255 Standard Method of Test of Surface Burning Characteristics of Building Materials, utilizes ASTM E 84 Standard Test Method for Surface Burning Characteristics of Building Materials. This test method measures flame growth on the underside of a horizontal test specimen. The result is derivation of a Flame Spread Index (FSI), which is a non-dimensional number which is placed on a relative scale in which asbestos-cement board has a value of 0, and red oak wood has 100. Evaluation of a FSI by this test method does not provide a good understanding of how fire would propagate in full scale, such as in a room, for some materials. In particular, the results for materials that drip, such as thermoplastics, are not indicative of the fire hazard as installed on walls and ceilings because they tend to melt and drip away from the underside of the horizontal ceiling in the test chamber.
Flange Cover A projecting collar attached to a pipe for the purpose of connecting to another pipe, valve or fitting.
Flash Point The temperature at which combustion is initiated.
Flashing The arrangement of metal or other weather barrier.
Flat Ceiling A ceiling with no change in elevation.
Flexibility That property of a material that allows it to be bent (flexed) without loss of strength or integrity.
Foamed Plastic Plastic expanded by thermal or chemical means, containing closed cells throughout.
Foil-Faced Vapor Retarder Created by coating a foil-backed paper with a thin layer of adhesive, then attaching it to the fiberglass.
Freeze/Thaw Stability The property of a product that allows it to be subjected to temperatures below freezing and still be useable when returned to room temperature.
Frequency (Hz) The number of cycles per second measured in units of Hertz.
Fresh Air Air taken from outdoors.
Fresh Air Duct (Make-Up Air) A duct used to convey outdoor air to a point within the building, terminating at the mixing plenum, air handling unit or discharge grill.
FRK A vapor retarder laminate of foil/ scrim (reinforcement) kraft construction. Also known as FSK.
FSK Foil Scrim Kraft (FSK) is a facing with aluminum foil on the exterior side that is laminated to fiberglass insulation. When exposed (where codes permit), the reflective foil surface helps maximize lighting efficiency and may reduce lighting requirements. It also serves as a excellent vapor retarder.
Fuel Contribution Combustible by-products from a substance generated or emitted in a burning environment.
Furring Strips Flat pieces of wood (typically 3/4″ thick) 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.
Gable End Walls The triangular end of an exterior wall above the eaves. (The wall with the pointy part.)
Gable Vents A louver vent mounted in the top of the gable to allow the passage of air through the attic. (The hole near the pointy part of the wall.)
Galvanic Corrosion (Electrolysis) Effect of two dissimilar metals in the presence of an electrolyte to produce a weak voltaic cell causing depleting or pitting of the more soluble metal.
Girt A girt is a horizontal structural member usually located on the wall in a framed wall – used as a term in metal building construction
Glass Cloth Closed-weave glass fiber used as a finish jacket.
Glass Fabric Open-weave glass fiber used as a reinforcing membrane.
Glass Fiber A material consisting of glass fibers used in making various products, including yarns, fabrics, insulation, and structural objects or parts. Fiberglass is resistant to heat and fire.
Gore Curved segment of a finish jacket used for elbows, tank heads or other curved surfaces.
Grant A sum of money given for a specific purpose.
Granular Insualtion Insulation composed of small nodules that contain voids or hollow spaces. The material may be calcium silicate, diatomaceous earth, expanded vermiculite, perlite, cellulose or microporous insulations.
Graybody A body having the same spectral emittance at all wavelengths.
Handicapped Fixtures Exposed fixture connections located in facilities for the handicapped. Waste and hot piping exposed connections in these areas are usually insulated for personnel protection.
Hanger Pipe Devices used to support piping.
Heat Flow Rate 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.
Heat Flux The heat flow rate through a surface of unit area perpendicular to the direction of heat flow.
Heat Flux Transducer (HFT) A device containing a thermopile (or equivalent) that produces an output that is a function of the heat flux.
Heel The outside radius of an elbow.
HERS Home Energy Rating System (established by RESNET)
Hertz A measurement of sound frequency measured in cycles per second.
High Pressure Condensate That condensate directly received from high-pressure steam lines.
High Pressure Steam Steam at or above 75 pounds per square inch gauge pressure.
High Rib Lath A metal lath with a built-in rib used to provide air space under insulation applications.
High Velocity Duct A duct designed with air flow at more than 2,000 feet per minute velocity with a static pressure exceeding 6 inches.
High Performance Insulation Fiberglass insulation with densely packed fibers, resulting in higher R-values for a given thickness. Most commonly used in confined spaces such as walls or cathedral ceilings.
Home Audit or Energy Audit An assessment performed by an energy specialist in order to identify how a structure’s energy efficiency can be improved. Many incentives or rebates require an audit be conducted before and after the improvements in order to verify savings. (See HomeEnergy Audit)
Home Energy Audit A thorough assessment of a home’s thermal efficiency, often conducted free of charge by most utility companies. (See Home Audit or Energy Audit)
Homogeneous Material A material in which relevant properties are not a function of the position within the material.
Horizontal Piping Any piping that is less than 45° from the vertical plane.
Housings (Built Up) Assembled or fabricated at the construction site.
Housings Casings Enclosures of sheet metal or other material to house fans, coils, filters or other components of air handling equipment.
HSPP Health and Safety Partnership Program, NAIMA’s voluntary worker protection program developed in concert with OSHA.
Hubs Caulking or cement connections between pipe joints.
Humidity A measure of the amount of water vapor in the atmosphere.
Humidity, Absolute Humidity is the amount of water vapor in the air. (See Relative Humidity)
Humidity, Relative Relative humidity is defined as the ratio of the partial pressure of water vapor in a parcel of air to the saturated vapor pressure of water vapor at a prescribed temperature.
I.C. Insulation Contact Marking on recessed lighting fixtures indicating that they are designed for direct insulation contact.
ICBO International Council of Building Code Officials.
ICC International Council of Building Code Officials (ICBO). The ICBO code organization was combined with BOCA and SBCCI to form the International Code Council (ICC).
IECC International Energy Conservation Code is the predominant model energy code in the US and the  basis used for most state and local energy codes.
Impact Resistance Capability of an insulation material and/or finish to withstand mechanical or physical abuse.
Impale To pierce or fix by piercing on a sharp point or pin.
Incentive Type The form of financial assistance offered by utilities, states, and/or local organizations to encourage homeowners and/or businesses to increase energy efficiency. Examples include loans, rebates, grants, tax incentives, and free services.
Inch of Water (in w.g) A unit of pressure equal to the pressure exerted by a column of water 1 inch (25mm) high at a temperature of 39.2°F (4°C).
Inset Staple Stapling to the inside portion of the stud or rafter.
Insulate To cover with a material of low conductivity in order to reduce the passage or leakage of heat, reduce the surface temperature, or reduce the noise emanating from the object.
Insulating Cement A mixture of various insulating fibers and binders with water to form a moldable paste insulation for application to fittings, irregular surfaces or voids.
Insulation (Thermal) Those materials or combination of materials that slow the flow of heat.
Insulation Density Denser insulation products generally have more fibers in the same given area and generally have greater insulating power.
Insulation Hanger A device such as a welded pin, stud or adhesive secured fastener that carries the weight of insulation.
Insulation Supports 16” or 24” wire rods, nylon banding, or crisscrossed wire to hold floor insulation in place. Sometimes called “lightning rods.”
Insulation Supports A characteristic of certain firestop products that when exposed to heat, expand to seal and fill any void in the penetration or covercombustible materials. When exposed to fire, intumescent products will form a hard char.
IPS Iron Pipe Size (IPS) refers to a pipe sizing system in use by some industries, including major metals, alloys, and plastic pipe manufacturers.
Jacket 1.  A covering placed over insulation for various functions. 2.  A form of facing applied over insulation.
Joint The place where two adjacent pieces of material or jacketing meet. They may be overlapped, sealed, filled (pointed) or finished by the application of tape, cement, mastic, coatings, additional layer of insulation materials or other compounds.
Joist Horizontal framing member set from wall to wall to support the floor or ceiling.
K-Value (Conductivity) The measure of heat in Btus that pass through one square foot of a homogeneous substance, 1 inch thick, in an hour, for each degree F temperature difference. The lower the K value, the higher the insulating value. Textbook definition: The time rate of steady heat flow through a unit area of a homogeneous material induced by a unit temperature gradient in a direction perpendicular to that unit area.  (Btu•in/h•ft2°F).  K value is typically used to characterize the efficiency of pipe insulation products.
Knee Walls Walls of varying length. Used to provide additional support to roof rafters with a wide span or to finish off an attic. An example of these are the short walls usually found in the top floor/attic of a cape cod style home.
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, which acts as a vapor retarder. Because they are flammable, kraft-faced vapor retarders are combustible and should never be left exposed in a building. See Vapor Retarder.
Lacing A method of joining or securing insulation materials, reinforcements, or finishes for insulation materials using eyelets, hooks, wire, cord, etc.
Lag (v.) To apply lagging. (n.) A single piece of covering material.
Lagging Adhesive Water based resin emulsion products that are used to adhere lagging cloth to the insulation and to itself at the lap joints. They also seal and size the fabric and shrink it tightly to the surface. They can be brushed or sprayed.
Lagging Insulation A block material for insulating tanks and boilers, usually curved or tapered and can be made from any of several insulation materials.
Laminate A product made by bonding together two or more layers of material or materials.
Lap Adhesive The adhesive used to seal the butt joints and laps of insulation jackets.
Lath Expanded Material A lattice type of material of various gauges and sizes, used to provide reinforcement for insulation materials. Also used as afacing for metal-mesh insulation.
Lath High Rib A metal lath with a built-in rib used to provide air space under insulation applications.
LEED  Leadership in Energy and Environmental Design– is a rating system developed by the US Green Building Council.
Log Mean (Radius) The equivalent value of insulation thickness for pipe (curved surfaces) to produce the same resistance to heat flow as per flat areas.
Loose-Fill Insulation Insulation in granular, nodular, fibrous, powdery or similar form designed to be installed by pouring, blowing or hand placement.
Low-Income A household with a combined income that qualifies them for certain incentive programs. The definition of low-income can vary from organization to organization and is expressed in relation to the Federal poverty level. Contact the organization offering the incentive for more information.
Low-Pressure Condensate Condensate directly received from low-pressure steam.
Low Pressure Steam Steam at or below 15 pounds per square inch gauge.
Low-Velocity Duct A duct designed with air flow at not more than 2,000 feet per minute velocity with static pressure not above 2 inches.
Main Piping or ductwork from a source to the last branch connection or from the last branch connection returning to the source or to a termination point.
Man-Made Vitreous Fibers ( MMVF ) (See also SVF) A generic term for a group of man-made materials reflecting the glassy, non-crystalline nature of these materials. This group was historically referred to as man-made vitreous fibers. Most definitions include fiberglass and rock and slag woolproducts used to make insulation in this category.
Mastic 1.  A protective coating, usually a petroleum or other base product, applied by spray or trowel to weatherproof or otherwise prevent deterioration of the insulation to which it is applied. 2.  A material of relatively viscous consistency that dries or cures to form a protective finish, suitable for application to thermal insulation in thickness greater than 30 mils (0.76 mm) per coat.
Mat A piece of insulation of the semi-flexible type, composed of fibers of one or more kinds in which the fibers are in random arrangement, used to support another material.
Mean Specific Heat The quantity of heat required to change the temperature of a unit mass of a substance one degree, measured as the average quantity over the temperature range specified. (It is distinguished from true specific heat by being an average rather than a point value).
Mean Temperature Sum of the cold surface temperature and the hot surface temperature divided by two. (Thermal conductivity charts are calculated to use mean temperatures).
Mechanical Couplings Bolting devices used in assembly of piping.
Medium Pressure Condensate Condensate directly received from medium-pressure steam.
Medium Pressure Steam Steam under 75 pounds per square inch gauge, but above 15 pounds psig.
Medium Velocity Duct A duct designed with airflow over 2000 feet per minute velocity with a static pressure below 6 inches.
Membrane Reinforcement Woven or non-woven fabrics used for saturation and embedment in mastic and coating applications to provide strength, continuity and impact resistance. See glass fabric.
Metal Flue A metal channel through which hot air, gas, steam or smoke may pass.
Microporous Insulation Material in the form of compacted powder or fibers with an average interconnecting pore size comparable to or below the mean free path of air molecules at standard atmospheric pressure. Microporous insulation may contain opacifiers to reduce the amount of radiant heat transmitted.
Mineral Fiber Insulation composed principally of fibers manufactured from glass, roc or slag, or glass, with or without binders.
Mineral Wool 1.  A broad term used typically to refer to rock wool and slag wool. In some countries, this term is also used to refer to fiberglass. 2.  A synthetic vitreous fiber insulation made by melting predominantly igneous rock, and or furnace slag, and other inorganic materials, and then physically forming the melt into fibers. To form an insulation product, there are often other materials applied to the mineral wool such as binders, oils, etc.
Mixed Air Duct Plenum A duct or plenum located at a point where air returned from a space inside the building, and fresh air are mixed or metered by dampers for redistribution through the airhandling system.
MMVF Man-Made Vitreous Fibers – A generic term for a group of man-made materials reflecting the glassy, non-crystalline nature of these materials. This group was historically referred to as man-made vitreous fibers. Most definitions include fiberglass and rock and slag wool products used to make insulation in this category. (See also SVF)
Moisture Barrier (mechanical system) A coating or laminate on the inner surface of metal lagging or jacketing to reduce corrosion or electrolysis on the metal when water or moisture is present.
Moisture or Vapor Retarder (building) A coating or laminate facing that reduces the water vapor transfer from ambient air through a substrate to a colder substance or surface. The retarder usually has a low perm rating, typically less than 1.
Mold and Mildew Resistance The property of a material that enables it to resist the formation of fungus growth.
Multi-Family A structure with individual units intended for housing more than one family.
Net Zero Energy Home A home that produces as much or more energy than it uses.
NFPA National Fire Protection Association.
Noise Reduction Coefficient 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.
Non-Combustible This is a technical term used in the building industry to refer to products that are not capable of combustion.
Non-Flammable A material that will release very little heat when exposed to fire or flame. The glass fibers in fiberglass insulation and the rock and slag wool in mineral wool insulation have a natural fire resistance and are considered non-combustible when tested in accordance to ASTM E136.
NPS Nominal Pipe Size, inches. Metric equivalent of DN (Diameter, Nominal, millimeters).
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.
Offset A change in location or direction of a main, branch or runouts. It may be located in a riser or horizontal run of piping or duct.
One-Coat Cement A mixture of various insulation fibers, fillers and binders with hydraulic-setting cement. The material can be applied directly tofittings to match adjacent insulation thickness in one application and smoothed to provide a hard finish.
Open Cell Foam A material comprised predominantly of interconnecting cellular voids.
Panel Insulation A prefabricated unit of insulation and lagging.
Patching Repair or restoration of damaged existing insulation. See Reinsulate.
Perlite Insulation composed of natural perlite ore expanded to form a cellular structure.
Perm/Perm Rating The measure of vapor transmission in grains of water through one square foot of a membrane in an hour at 1-inch mercury pressure difference.
Personal Protection Insulation installed for the purpose of protecting personnel from hot or cold surfaces capable of injuring workers
Ph A measure of the acidity or alkalinity of a solution, numerically equal to 7 for neutral solutions, increasing with increasing alkalinity and decreasing with increasing acidity (potential of hydrogen).
Phenolic Foam A foamed insulation made from resins of phenols condensed with aldehydes.
Pin Weld Attachment of insulation anchor pins to ductwork or equipment usually by capacitor discharge welding.
Pinhole Very small hole. With regard to insulation systems this usually refers to a small hole through a mastic , vapor retarder orcoating.
Pipe A circular conduit for the conveyance of liquids or semisolids.
Pipe Insulation Insulation in a form suitable for application to cylindrical surfaces.
Plenums Enclosures for the collection of air at the termination or origin of duct systems. They Plenums may be a take the form of a space below floors, above ceilings, a shaft or a furred other enclosed area.
Pointing Applying or shaping cements or mastic with a small pointed trowel.
Polyethylene A closed-cell, thermoplastic material used for insulation.
Polyethylene Vapor Retarder 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.
Polyimide See cellular polyimide.
Polyisocyanurate A closed-cell, thermoset, plastic foam formed by combining isocyanurate, polyol, surfactants, catalysts and blowing agents.
Polymer A long chain molecule resulting from the chemical attachment of short molecules (monomers) of the same product. For example, when ethylene (a gas) is polymerized, the synthetic resin polyethylene is produced.
Polyolefin A closed-cell thermoplastic material used for insulation.
Polyvinyl Chloride (PVC) A polymerized vinyl compound using chloride.
Post Project Inspection/Rating An assessment performed after energy efficiency improvements are made.
Pressure Sensative Tap A tape with adhesive pre-applied.
Pumped Condensate (Discharge) Condensate in liquid state from condensate receivers to feed water heaters, deaerators or boilers.
Puncture Resistance That property of a material that enables it to resist punctures or perforations under blows or pressure from sharp objects.
Punking An exothermic reaction that usually is the burning out of binder/resin due to excessive fuel with oxygen.
Purlin A purlin (or purline) is a horizontal structural member in a roof. Purlins support the loads from the roof deck or sheathing and are supported by the principal rafters and/or the building walls, steel beams.  Term used frequently in the construction of metal buildings.
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. The Federal Trade Commission prohibits expressing R-value in terms of inches, because R-value is not a linear measurement. R-values can be added togehter for a total system R-value.
Radiance The rate of radiant emission per unit solid angle and per unit projected area of a source in a stated angular direction from the surface (usually the normal).
Radiant Flux Density The rate of radiant energy emitted from a unit area of a surface in all radial directions of the overspreading hemisphere.
Radiation The transfer of heat by direct rays traveling through space to a solid substance, but without heating the air (similar to light rays). An example is the sun warming the earth. Radiant heat can also be reflected (via a mirror) or absorbed (through dark clothing) by highly absorptive surfaces (e.g. a black car).
Rafters A slope framing member that supports a pitched roof.
Rebate A deduction from an amount charged or a return of a price paid.
Reflectance The fraction of the incident radiation upon a surface that is reflected from the surface.
Reflective Insulation Insulation depending for its performance upon reduction of radiant heat transfer across air spaces by use of one or more surfaces of high reflectance and low emittance.
Refractory Insulation Insulation for extremely high temperatures, applications usually above 1500°F.
Refractory Materials Materials, usually fibers, that do not significantly deform or change chemically at very high temperatures. Manufactured in blanket, block, brick or cement form.
Reinforcing Cloth or Fabric A woven cloth or fabric of glass or resilient fibers used as reinforcement to a mastic.
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.
Removable and Reusable Covers Insulation materials or pads, enclosed in a fabric or metal (mesh, or sheet), designed to be readily removed and reinstalled. These product are typically used to insulate areas and features (like valves) that require easy access.
Residential Pertaining to a home or homes where people reside on a permanent basis.
Resiliency The property of a material that enables it to recover its original shape and thickness after compression.
Resiliant Channels Metal channels used to further inhibit sound transmission through wall and ceiling framing and create a break in the vibration path from drywall to the framing.
Resistance to Acids, Caustics, and Solvents The property of a material to resist decomposition by various acids, caustics and solvents to which it may be subjected.
Resistance to Air Erosion The property that indicates the ability of an insulation material to resist erosion by air currents over its surface.
Resistance, Abrasion The ability to withstand scuffing, scratching, rubbing or deterioration due to physical contact.
Resistnace, Freeze Thaw Resistance to cycles of freezing and thawing that could affect application, appearance or performance.
Resistance, Impact (toughness) Ability to withstand mechanical blows or shock without damage seriously affecting the effectiveness of the material or system.
RESNET Residential Energy Services Network – An organization with the purpose to develop and maintain a national market for home energy rating systems and energy efficient mortgages.
RESNET Grade I Installation The highest standard for an insulation installation
Retrofit The application of additional insulation over existing insulation, new insulation if old insulation has been removed, or new insulation over existing, previously uninsulated surfaces.
Return Air Air returned from conditioned spaces to an air-handling unit.
Return Air Duct A duct carrying air from a conditioned space to the mixing air duct or plenum unit.
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.
Rigid Wrap-Around Insulation Segments of insulation material that have been adhered to a facing giving rigid insulation materials flexibility of application.
Rigidity The property of a material that opposes any tendency for it to bend (flex) under load.
Riser The vertical portion of a main, branch or runout.
Rockwool A synthetic vitreous fiber insulation made by melting predominantly igneous rock and other inorganic materials, and then physically forming them melt into fibers. See Mineral Wool.
Roof Vents A louver or small dome mounted near the ridge of the roof to allow the passage of air beneath the roof sheathing or through the attic.
Run-out Piping or duct work from or to a branch or main serving one: a) plumbing unit or fixture connection. b) heating and/or cooling unit, coil, convector, unit heater, fin tube, equipment connection, etc. c) HVAC diffuser or register or d) process equipment connection.
S-Clip A device (in the shape of an “S” ) for supporting insulation, bands or jacketing.
Saddle Rigid support for piping or equipment with allowance for insulation.
Score To cut grooves in rigid insulation so that it may be cracked and fitted to round or irregular surfaces.
Seal To make water-tight or airtight.
Sealant Sealants in insulation function primarily as water and vapor seals. They may also be used as adhesives, and for expansionjoints for metal, masonry, cellular glass, etc. They must exhibit low shrinkage, excellent adhesion and permanent flexibility.
Sealer A liquid coating used to prevent excessive absorption of finish coats into porous surfaces.
Securements Any device, wire, strap or adhesive used to fasten insulation into its service position and hold it there.
Self-Extinguishing The property of a material that enables it to stop its own ignition after external ignition sources are removed.
Self-Sealing Lap 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.
Service Temperature Limits The temperature to which the jacket or coating may be subjected when applied over insulation to while in service. In reference to insulation, it is typically the temperature to which the jacket or coating may be subjected when applied over insulation. It does not refer to the operating temperature of the equipment, vessel or pipe.
Shear Strength The ability of a material to resist cleavage.
Shelf Life The period of time during which a material or product can be stored under specified temperature conditions and remain suitable for use.
Shield Metal protector to prevent crushing of insulation at pipe hangars.
Shrinkage That property of a material that indicates its proportionate loss in dimensions or volume due to temperature changes or aging.
Slag wool Man-made material made primarily from iron ore blast furnace slag.
Slag Wool Insulation Man-made material made primarily from iron ore blast furnace slag which is spun into a fibrous form.
SMACNA Sheet Metal and Air Conditioning Contractors’ National Association
Smoke Density A measure of the amount of smoke in a given volume.
Smoke Developed Index (abbreviated SDI) is a measure of the concentration of smoke a material emits as it burns. Like Flame Spread Index, it is based on an arbitrary scale in which asbestos-cement board has a value of 0, and red oak wood has 100.
Soaking Heat A test condition in which the specimen is completely immersed in an atmosphere maintained at a controlled temperature.
Solar Resistance The property of a material to resist decomposition by the ultraviolet rays from the sun or the passage of radiant heat from the sun.
Solids Content The percentage of the non-volatile matter in materials.  It may be based either on or weight or volume.  This property is applicable to adhesives, coatings or sealants.
Solvent Any substance, usually a liquid, that dissolves another substance.
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.
Sound Absorption Coefficient (SAC) The ratio of sound energy absorbed to that arriving at a surface or medium. Also known as acoustic absorption coefficient; acoustic absorptivity.
Sound Transmission Class (STC) A numerical rating of the sound control performance of a wall or ceiling; the higher the number, the better the sound control.
Sound Transmission Loss (STL) The reduction in level measured in decibels as sound energy passes through a material or composite construction.
Specific Heat The ratio of the amount of heat required to raise a unit mass of a material 1 degree, to that required to raise a unit mass of water 1 degree at some specified temperature.
Sprayed-On Insulation Insulation of the fibrous or foam type that is applied to a surface by means of power spray devices.
Standing Steam Folded configuration of jacketing to achieve watershed for the top flat surfaces of ductwork, vessels, or tanks. Also used to providerigidity.
Stapling Flange A protruding edge on faced insulation used to staple attach the insulation to the framing, usually with staples. Tape may be used with metal framing.
Static Pressure The normal force per unit area at a small hole in the wall of a duct through which a fluid is flowing.
Steady State Thermal A condition for which all relevant parameters in a region do not vary over two consecutive steady-state time periods by more than the steady-state tolerance, and no long-term monotonic drifts are present. Where, the steady-state time period is the time constant of the apparatus-specimen system with additional time necessary if physical phenomena are present, such as moisture transport, which could cause a long-term monotonic drift.
Stiffener (Duct Flange) A structural or fabricated angle iron shape, attached to the exterior surfaces of a duct or bulkhead at specified intervals for the purpose of reinforcing the metal and to prevent vibration.
Strainer A filter or sieve used in fluid piping to trap scale and other intrained particles.
Strength, Transverse (or Flexural) The breaking load applied normal to the neutral axis of a beam.
Stud A vertical framing member (metal or wood) used in both exterior and interior walls.
Stud Weld Attachment of insulation anchors to tanks or vessels by means of drawn arc welding.
Subfloor The structural material that spans across floor joists. It serves as a working platform during construction and provides a base for the finish floor.
Supply Air Duct A duct that carries conditioned air from air supply units to room diffusers or grilles.
Support (Insulation) A mechanical device that carries the weight of insulation.
Surface Temperature The surface temperature of finished insulation.
SVF Synthetic Vitreous Fibers –  A generic term for a group of man-made materials reflecting the glassy, non-crystalline nature of these materials. This group was historically referred to as man-made vitreous fibers. Most definitions include fiberglass and rock andslag wool products used to make insulation in this category. (See also MMVF)
Synthetic Vitreous Fibers (See also MMVF) A generic term for a group of man-made materials reflecting the glassy, non-crystalline nature of these materials. This group was historically referred to as man-made vitreous fibers. Most definitions include fiberglass and rock andslag wool products used to make insulation in this category.
Tack, Adhesive The property of an adhesive that enables it to form a measurable bond immediately after adhesive and adherent are brought into contact under low pressure.
Tear Strength The property of a material that enables it to resist being pulled apart by opposing forces.
Temperature Limits The upper and lower temperatures at which a materials will not have significant changes in their relevant  experience no change in its physical properties.
Test Specimen A sample used for analysis or diagnosis.
The surface temperature of finished insulation A rating usually expressed in hours indicating the length of time that the temperature on the non-fire side of a fire-rated assembly exceeds 325°F above its ambient temperature as determined by ASTM E-814 (UL-1479).
Thermal (or Heat) Capacity A measurable physical quantity that characterizes the amount of heat that is required to change a body’s temperature by a given amount.
Thermal Insulation 1: Insulation applicable within the general temperature range of 300 F to 1800 F. 2: A material or assembly of materials used to provide resistance to heat flow.
Thermal Insulation System Applied or installed thermal insulation complete with including any accessories, vapor retarder, and facing required.
Throat Inside radius of an elbow.
Top Plate The horizontal member nailed to the top of the stud of a wall.
Traced (with heat) The supplying of auxiliary heat to a pipe or piece of equipment by means of a companion line containing a hot fluid or electric resistance. It can be thermally or mechanically bonded to the pipe or equipment. The purpose of heat tracing is to prevent freezing or keep the liquid viscous enough to continue flowing in the system.
Transference, Thermal The steady-state heat flow from (or to) a body through applied thermal insulation and to (or from) the external surroundings byconduction, convection, and radiation. It is expressed as the time rate of heat flow per unit area of the body surface per unit temperature difference between the body surface and the external surroundings.
Transmission, Heat The quantity of heat flowing through unit area due to all modes of heat transfer induced by the prevailing conditions.
Transmittance, Thermal The heat transmission in unit time through unit area of a material or construction and the boundary air films, induced by unit temperature difference between the environments on each side.
Tube Turn (Bend) Pipe, factory or field formed, to pre-determined radii.
U-Value (Transmittance) The combined thermal value of all the materials in a building section, air spaces and surface air films. It is the time rate of heat flow per unit (sq. ft.), per degree F temperature difference with units in  (Btu/h•ft2•°F).  The lower the overall U-value, the more energy efficient the assembly.
Underground or Buried Insulation Insulation applied on piping and equipment located below grade and usually in direct contact with the surrounding soil.
Unfaced Insulation Insulation with no attached vapor retarder or facing.
Union A coupling device for connecting pipes.
Urethane Plastic foam of rigid polyurethane closed-cell insulation in board, pipe insulation or foamed-in-place form.
Vapor Retarder Helps control the amount of moisture passing through the insulation and collecting inside exterior walls, ceilings and floors. It is rated in perms (“permeance”). The lower the perm rating, the better the water vapor permeance. A vapor retarder should have a perm rating no greater than 1.0.
Vapor Retarder Jacket Any material or composite meeting the requirements of a vapor retarder and used for the finish of insulation material. It may be factory furnished or field applied. Generally materials with a perm rating of 0.02 or less are considered vapor retarder materials for mechanical systems.  (NOTE: Vapor retarders for building insulation systems generally have a perm rating of 1 or less.)
Ventilating Air Air supplied to or removed from any space by natural or mechanical means.
Ventilating Duct Duct supplying or removing air by natural or mechanical means.
Ventilation The act of supplying fresh air and getting rid of foul air  or a mechanical system in a building that provides fresh air.  In buildings ventilation creates a positive flow of air that allows the house to “breathe” and helps prevent moisture build-up year round.
Vermiculite Insulation composed of natural vermiculite ore expanded to form an exfoliated structure.
Vertical Piping Any piping that is less than 45° from the vertical plane.
Vibration Resistance The property of a material to resist mechanical vibration without wearing away, settling or dusting.
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, sometimes called the bottom, toe or sole plate and the two plates at the top of the wall are usually used at the top (double top plate).
Warm In Winter Side Refers to the living area of a house in climates where it is colder outside in the winter than it is inside. This is useful information for determining the proper placement of a vapor retarder.
Warpage The bend or change in the flatness of a material caused by differences in the temperature and/or humidities moisture applied to opposite surfaces of the material.
Washer (Insulation Clip) Self-locking flat metal device applied to anchor pins to secure the insulation in place.
Water Absorption The increase in weight of a test specimen expressed as a percentage of its dry weight after immersion in water for a specified time.
Water Resistant Capable of withstanding limited exposure to water.
Water Vapor Difussion The process by which water vapor spreads or moves through permeable materials caused by a difference in water vapor pressure.
Water Vapor Permeability 1.   The property of a substance that permits passage of water vapor and is equal to the permeance of 1 inch thickness of the substance. Permeability is measured in perm inches.  2.   The time rate of water vapor transmission through unit area of flat material of unit thickness induced by unit vapor pressure difference between two specific surfaces, under specified temperature and humidity
Water Vapor Permeance 1.   The ratio of water vapor flow to the vapor pressure difference between the two surfaces of a sheet of material (or the assembly between parallel surfaces). Permeance is measured in perms. 2.  The time rate of water vapor transmission through unit area of flat material or construction induced by unit vapor pressure difference between two specific surfaces, under specified temperature and humidity conditions.
Water Vapor Pressure The pressure of water vapor at a given temperature; also the component of atmospheric pressure contributed by the presence of water vapor.
Water Vapor Retarder (Barrier) A material or system that adequately impedes the transmission of water vapor under specified conditions.
Water Vapor Transmission Rate The steady water vapor flow in unit time through unit area of a body, normal to specific parallel surfaces, under specific conditions of temperature and humidity at each surface.
Waterproof Impervious to prolonged exposure to water or water entry.
Weather Barrier A breather jacket or coating which allows passage of water vapor and protects from atmospheric conditions.
Weatherization Typically refers to free services or grants available to low-income households for improvements to the thermal efficiency of dwellings (typically insulation, caulking, and weatherstripping).
Welded Pin Made of carbon steel, stainless steel or aluminum in various lengths for attaching insulation to metal surfaces. Applied by welding, usually with a weld gun.
Wetting and Adhesion Surface The mutual affinity of and bonding between finish and the surface to which it is applied.
Wicking Action of absorbing by capillary action.
Wood Fiber Insulation composed of Wood/cellulosic fibers, with or without binders. Wood fibers are the primary constituent in cellulose insulation which contains 20% (by weight) fire retardant chemicals.