Glossary of Terms


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.

Absolute Humidity: The ratio of the mass of water vapor to total volume of an air sample. The I-P units are pounds of: moisture per pound of cubic foot of air and the SI units are grams or kilograms of moisture per: cubic meter of air.

Absorptance: The ratio of the radiant flux absorbed by a body to that incident upon it.

Absorption: Transformation of radiant energy to a different form of energy by interaction with matter.

Acidity: The quality of a material to be acidic (pH under 7) when exposed to moisture or water producing a red/pink reaction to litmus paper. In the insulation industry, materials with pH between 6 and 8 are generally considered non-acidic and non-alkaline.

Acoustical Treatment: Application of absorbing insulation for sound control.

Acrylonitrile-Butadiene-Styrene (ABS): A high-impact plastic.

Additive: Any substance added to another substance, usually to improve properties, such as plasticizers, initiators, light stabilizers, and flame retardants. See also filler.

Adhesion: The state in which two surfaces are held together at an interface by mechanical or chemical forces, interlocking action, or both.

Adhesive: A substance used to bond materials by surface attachment.

Adhesive Failure: Failure of a bonded joint between the adhesive and the substrate. Can be indicative of poor surface preparation or contamination, or incorrect adhesive selection for the substrate materials.

Aerogel: 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.

Air-Bubble Void: Air entrapment within and between the plies of reinforcement or within a bondline or encapsulated area; localized, non-interconnected, spherical in shape.

ALIPHATIC: An organic substance containing straight or branched chain arrangements of carbon atoms.

Alkalinity: The quality of a material to be basic or alkaline when exposed to moisture or water producing a: blue reaction to litmus paper. A pH measure greater than 7.0.

Ambient Temperature: The average temperature of the medium, usually air, surrounding the object under consideration.

Ambient: Surrounding-encompassing (Generally applied to temperature, humidity and atmospheric: conditions).

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.

Apparent Thermal Conductivity: A thermal conductivity assigned to a material that exhibits thermal transmission by several: modes of heat transfer resulting in property variation with specimen thickness, or surface: emittance. (See conductivity, thermal).

Apparent Thermal Resistivity: A thermal resistivity assigned to a material that exhibits thermal transmission by several modes: of heat transfer resulting in property variation with specimen thickness, or surface emittance. (See resistivity, thermal, R-value).

Appearance Covering: Materials used to improve the aesthetics of the finished product.

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.

Aramid: Aromatic polyamide fibers.

Area Weight: Weight per unit area for a specified sample, in units of lbs/ft² (kg/m²).

AROMATIC: A class of organic compounds containing a resonant, unsaturated ring of carbon atoms. Included are benzene, naphthalene, anthracene and their derivatives.

ASTM International: ASTM International provides a global forum for the development and publication of: international voluntary consensus standards for materials, products, systems, and services.

Attenuation: The limiting of sound propagation from one area to another.

Balanced Laminate: A composite laminate in which all laminate at angles other than 0° and 90° occur only in + pairs (not necessarily adjacent) and are symmetrical around the centerline.

Barcol Hardness: A hardness value obtained by measuring the resistance to penetration of a sharp steel point under a spring load. The instrument, called the Barcol impressor, gives a direct reading on a 0 to 100 scale. The hardness value is often used as a measure of the degree of cure of a plastic.

BASIC: See Alkalinity.

Batch: A quantity of material formed during the same process or in one continuous process and having identical characteristics throughout. Also known as "lot."

Beading: Process of curling the edge of metal jacketing to accommodate sealing.

Bedding Compound: A plastic material (mastic) used to imbed insulation. Acts as a cushion, anti-abrasive and: adhesive.

Bias Fabric: A fabric in which warp and fill fibers are at an angle to the length.

Binder: The resin or cementing constituent (of a plastic compound) that holds the other components together. The agent applied to fiber mat or preforms to bond the fibers before laminating or molding.

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.

Bladder: An elastomeric lining for the containment of hydroproof or hydroburst pressurization medium in filament-wound structures.

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.

Blowing Agent: A substance incorporated in a mixture for the purpose of producing foam. For polyurethanes, this is usually either carbon dioxide generated from the diisocyanate/water reaction or introduced as liquid CO2 or a low boiling hydrocarbon liquid (such as pentane) volatilized by the heat of the polyurethane-forming reactions.

BOCA: Building Officials and Code Administrators.

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.

Box Trench: Built-up enclosure either in a shallow trench or buried underground.

Branch: Distribution piping or ductwork, same as a main duct except, smaller and from or returning to the: main, serving two or more runouts.

BREAKING LOAD: In some installations the insulation material must "bridge" over a discontinuity in its support. The Breaking Load is the force necessary to create structural failure in a "bridging" condition. See Flexural Strength.

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 small quantities of water: vapor resulting from heat applied to the moisture entrapped in the insulation.

British Thermal Unit (Btu): The amount of heat required to raise one pound of water one degree Fahrenheit at 59 F.,: specifically 778.26 ft. lbs.

“C" VALUE (Thermal Conductance): A measure of the rate of heat flow for the actual thickness of a material. If the "K" of a material is known, the "C" can be determined by dividing the "K" by the thickness. The lower the "C", the higher the insulating value. Calcium Silicate: A hard granular molded insulation manufactured from a hydraulic cured mixture of calcium, silicate, water and inorganic binders.

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.

Carbon Fibers: Fibers produced from pyrolytic degradation of synthetic organic fibers, polyacrylonitrile (PAN) or rayon, which contain about 92-99% carbon content and typically have modulus values up to 75 x 106 psi.

CATALYST: A substance that causes or accelerates a chemical reaction when added to the reactants in a minor amount, and that is not consumed in the reaction.

Caulk: To seal and make water and/or airtight.

Cavity: The space inside a mold in which a resin or molding compound is poured or injected. The female portion of a mold. That portion of the mold that encloses the molded article (often referred to as the die). Depending on the number of such depressions, molds are designated as single cavity or multiple cavity.

Cellular Elastomeric: 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 Expanded: Beads of plastic expanded by chemical or thermal means and bonded together chemically or: thermally.

Cellular Plastic Extruded: Extruded plastic with cells formed by thermal or chemical means.

Cellular Plastic: Plastic expanded by thermal or chemical means, containing closed cells throughout.

Cellular Polyimide: 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 Fiber: Insulation composed principally of cellulose fibers usually derived from paper, paperboard stock: or wood, with or without binders.

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) used as reinforcement or as a metal-mesh facing.

Cladding-Jacketing: Jacketing installed over insulation. Also, see “Jacketing.”

Clearance: Adequate space allowed for installation of insulation materials.

Closed Cell Foam: A material comprised predominantly of individual non-interconnecting cellular voids.

Coating: A liquid or semi-liquid that dries or cures to form a protective finish, suitable for application to: thermal insulation or other surfaces in a dry thickness of 30 mils or less per coat.

Co-bonding: The curing together of two or more elements, : The curing together of two or more elements, of which at least one is fully cured and at least one is of which at least one is fully cured and at least one is uncured uncured. Requires careful surface preparation of the previously Requires careful surface preparation of the previously - cured substrate substrate. Additional adhesive may be required at interface Additional adhesive may be required at interface

Co-Cured: Cured and simultaneously bonded to another prepared surface.

Co-Curing: The act of curing a composite laminate and the act of curing a composite laminate and simultaneously bonding it to some other uncured material, simultaneously bonding it to some other uncured material, or to a core material such as balsa, honeycomb, or foam or to a core material such as balsa, honeycomb, or foam core.  All resins & adhesives are cured during the same essentially the same process. 

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 authorities are: BOCA, (Building Officials and Code Administrators, primarily Midwest), ICBO (International: Council of Building Code Officials, West and Indiana) and SBCCI (Southern Building Code: Congress, International, South). 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.

Coefficient of Thermal Expansion: The fractional change in length of a material for each unit change in temperature.

Cohesion: The propensity of a single substance to adhere to itself. The internal attraction of molecular particles toward each other. The ability to resist partition of itself. The force holding a single substance together.

Combustible: Provides enough fuel to make insulation capable of burning.

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.

Composite: A material made up of 2 or more individual components whose combined physical strength exceeds their individual properties.

Compression Molding: A technique for molding thermoset plastics in which a part is shaped by placing the fiber and resin into an open mold cavity, closing the mold, and applying heat and pressure until the material has cured or achieved its final form.

Compressive Strength: Ration of compressive stress to compressive strain below the proportional limit. Theoretically equal to Young's modulus determined from tensile experiments.

Concealed Spaces: Spaces not generally visible after the project is completed such as furred spaces, pipe spaces,: pipe and duct shafts, 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.

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.)

Conditioned Space: Building area supplied with conditioned air that is heated or cooled to a certain temperature and: may be mechanical controlled to provide a certain humidity level.

Conditioning: A material's ability to resist a force that tends to crush or buckle; maximum compressive load a specimen sustains divided by the specimen's original cross-sectional area. ALSO: Subjecting a material to a prescribed environmental and/or stress history before testing.

Conductance (Thermal) "C": The rate of heat flow for the actual thickness of a material.

Conductance, Air Film: The time rate of heat flow from a unit area of a surface to its surroundings, induced by a unit: temperature difference between the surface and the environment.

Conductance, Thermal, C-value: 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.

Conduction: The transfer of heat energy within a body or between two bodies in physical contact.

Conductivity, Thermal (k-value): The measure of heat that pass through a unit area of a homogeneous substance, through a unit: thickness, in a unit of time, for each unit temperature difference. The lower the k-value, the: higher the insulating value. Note: I-P units are Btu – in / hr – ft2 - °F and typical SI units are Watts / m - °C. 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.

Contact Adhesive: An adhesive which when dry to the touch will adhere to itself instantaneously on contact.

Contact Molding: A molding technique in which reinforcement and resin are placed in a mold, with cure taking place at room temperature with a catalyst/promoter system or in a heated oven. No additional pressure is used.

Convection: The transfer of heat by movement of fluids.

Core: The central component of a sandwich construction to which the sandwich faces or skins are attached; also, part of a complex mold that forms undercut parts.

Corrosion Retarder (as Related to Insulation Jacketing): See Moisture Barrier (as related to insulation jacketing): Couplings: Screwed, soldered, welded or mechanical/grooved connections between links of pipe.

Corrosion: Deterioration by chemical action such as rust 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: The area to be covered per unit volume of coating to obtain specified dry thickness and desired: performance.

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.

Creep: The dimensional change in a material under physical load over time beyond instantaneous elastic deformation.

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 Laminated: Material laminated so that some of the layers are oriented at various angles to the other with respect to the laminate grain. A cross-ply laminate usually has plies oriented only at 0 and 90 degrees.

Cross-Linking: Applied to polymer molecules, the setting-up of chemical links between the molecular chains. When extensive, as in most thermosetting resins, cross-linking makes one infusible supermolecule of all the chains.

Cryogenic Insulation: Insulation for extremely low-temperature processes surfaces from –100 F to –459 F (absolute: zero).

Cupped Head Pin: Capacitor discharge welded insulation fastener pin with a fixed washer.

Cure Cycle: The time/temperature/pressure cycle used to cure.

Cure Stress: A residual internal stress produced during the curing cycle of composite structures. Normally, these stresses originate when different components of a wet lay-up have different thermal coefficients of expansion.

Cure: To change the properties of a material irreversibly by chemical reaction, i.e., moisture loss, off-gassing, condensation, ring closure, or addition. Cure may be accomplished with or without catalyst, and with or without heat.

Cure: To change the properties of a plastic or resin by chemical reaction, usually accomplished by the: action of either heat or a catalyst.

C-Value (Thermal Conductance): See Conductance, thermal.

Damming: The use of a substance to support firestopping materials until cured.

Decibel (Db): A logarithmic measure of the ratio of like power quantities as 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 a laminated plastic material along the plane of its layers.

Delamination: The separation of the layers of material in a laminate.

Density, Apparent (of Applied Insulation): The mass per unit volume of in-place mass thermal insulation.

Dew Point: Saturation temperature where water vapor and liquid occur simultaneously.

Dewpoint 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.

Dimensional Stability: That property of a material that enables it to maintain its original size, shape and dimensions.

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.

Dual Temperature: Systems of equipment that operate as cold condition and hot application.

Duct Flange (Stiffener): A structural or fabricated angle iron shape, attached to the exterior surfaces of a duct at specified: intervals for the purpose of reinforcing the metal and assembly of the ducts.

Duct: A passageway made of sheet metal or other suitable material used for conveying air or other gas.

Efflorescence: A white powdery substance occurring on the surface of coated insulation products caused by the: migration of soluble salts from the insulation, followed by precipitation and carbonation.

Elasticity: That property of materials by virtue of which they tend to recover their original size and shape after removal of a force causing deformation.

Elastomer: A material that at room temperature can be stretched repeatedly to at least twice its original length and, immediately upon release of the stress, return with force to its approximate original length. This definition is one criterion by which materials called plastics in commerce are distinguished from elastomers and rubbers.

Elastomeric: A closed-cell foam insulation containing elastomers that provide the property of high elasticity.

Elongation: Deformation caused by stretching. The fractional increase in length of a material stressed in tension. (When expressed as percentage of the original gage length, it is called percentage elongation.)

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).

Emittance, Total: An emittance that is an integrated average over all wavelengths of radiant energy emitted.

Emittance: The ratio of the radiant flux emitted by a specimen to that emitted by a blackbody at the same: temperature and under the same conditions.

Emulsion: Insoluble fine solids or liquids dispersed in another liquid, usually water.

Epoxy Resins: A two-part compound of an epoxy and catalyst that cures at ambient temperatures to form: finishes which are highly resistant to solvents and chemicals. A high bond adhesive.

Exhaust Duct: A duct carrying air from a conditioned space to an outlet outside the building.

Exotherm: The liberation or evolution of heat during the curing of a plastic product.

Expanded Metal Lath: See lath—expanded metal.

Expanded Polstyrene (EPS): Expanded polystyrene, manufactured from styrene, is a closed-cell, thermoplastic material often molded into low-density foam articles, such as protective packaging, foam insulation and building and construction.

Exposed Spaces: Those spaces not referred to as concealed or as defined by the specifier.