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Abrasion Resistance: What is Abrasion Resistance? The ability of a material to withstand abrasion without appreciative erosion.

Absolute Humidity: What is 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.

Absolute temperature: What is Absolute temperature? Absolute temperature is the temperature expressed in degrees above absolute zero. Absolute Zero is the lowest temperature theoretically attainable. The temperature at which there is no more heat and no longer molecular movement. The zero point of the scale is 459.6 degrees below the zero of the Fahrenheit scale and 273.2 degrees below the zero of the centigrade scale.

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

Absorption (water): What is Water Absorption?  Absorption is the action of a material in extracting water from the atmosphere often leading to a physical change in the absorbent.

Absorption (thermal): What is Thermal Absorption? Transformation of radiant energy to a different form of energy by interaction with matter.

Acidity: What is 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: What is Acoustical Treatment? Application of absorbing insulation for sound control.

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

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

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

Adhesive Failure: What is 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.

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

Aerogel: What is an 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.

Aliphatic: What is Aliphatic? An organic substance containing straight or branched chain arrangements of carbon atoms.

Alkalinity: What is 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 Air: What is Ambient Air? Ambient Air is generally the air surrounding an object or a surface, consisting of ambient temperature, ambient humidity, etc.

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

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

Annular Space (Annulus): What is an Annular Space (Annulus)? The distance between a penetrating item and the surrounding opening.

Anti-Abrasive Coating: What is an 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: What is 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: What is 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: What is Appearance Covering? Materials used to improve the aesthetics of the finished product.

Application Temperature Limits: What are 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. For instance, a thermoset material such as polyisocyanurate is acceptable in manufacturing processes up to 300F (350 intermittent), while a substantial percentage of composite substrates are thermo-plastics that soften above 165F.

Aramid: What is an Aramid? Aromatic polyamide fibers.

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

Aromatic: What is an Aromatic? A class of organic compounds containing a resonant, unsaturated ring of carbon atoms. Included are benzene, naphthalene, anthracene and their derivatives.

ASTM International: What is 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: What is Attenuation? The limiting of sound propagation from one area to another.


Basic: What is Basic? See Alkalinity.

Batch: What is a Batch? A quantity of material formed during the same process or in one continuous process and having identical characteristics throughout. Also known as "lot." A Batch process can be characterized as the opposite of a continuous process.

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

Bedding Compound: What is a Bedding Compound? Typically a plastic material used to imbed insulation. Acts as a cushion, anti-abrasive and adhesive.

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

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

Bleeding: What is 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: What is a 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: What is a Blowing Agent? A substance incorporated in a mixture for the purpose of producing foam. For polyurethanes and polyisocyanurates this is usually a low boiling hydrocarbon liquid (such as pentane) or possibly carbon dioxide generated from the diisocyanate/water reaction or introduced as liquid CO2.

BOCA: What is BOCA? Building Officials and Code Administrators.

Body: What is Body? The viscosity or consistency of a mastic or coating.

Bond Strength: What is Bond Strength? Bond Strength is the force in tension, compression, cleavage or shear required to break an adhesive assembly. For insulation boards with a cladding, it is the bond between the cladding and the insulant. For pipe insulation it may be the bond between insulant segments.

Bonding Time: What is Bonding Time? Bonding Time - The time required for an adhesive to reach its optimum bonding strength.

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

Branch: What is a 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: What is Breaking Load?  In some installations the composite or 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: What is a Breather Coating? A weather barrier coating designed to prevent water (rain, snow, sleet, spillage, wash water, etc.) from entering a composite or 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): What is a British Thermal Unit? The British thermal unit (Btu or BTU) is a traditional unit of heat, defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. Its counterpart in the metric system is the calorie.


C" VALUE (Thermal Conductance): What is “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: What is Calcium Silicate? A hard granular molded insulation manufactured from a hydraulic cured mixture of calcium, silicate, water and inorganic binders.

“C": What is "C"? “C” represents the thermal conductance of a material and is used to show the amount of heat (Btu's) that will pass per hour through 1 square foot of a homogeneous or non-homogeneous material or a combination of materials for the thickness or type under consideration for a difference in temperature of 1°F between the two surfaces. The average "C" value of an 8 inch hollow concrete block is 0.90.

Calorie: What is Calorie? A Calorie (Gram Calorie) is a unit of heat or energy. It is the amount of heat necessary to raise the temperature of 1 gram of water 1°C.

Canvas: What is Canvas? A plain-weave cotton fabric used for jacketing or covering.

Capillarity: What is Capillarity? The ability of a cellular, fibrous or granular material to diffuse water into its structure.

Carbon Fibers: What are 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: What is a 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: What is Caulk? To seal and make water and/or airtight.

Cavity: What is a 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: What is a 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 vs. polyiso: What is ISO-C1 polyiso versus cellular glass performance? ISO-C1 polyisocyanurate has >95% closed cells in its 2 lb/ft3 density. Cellular glass is roughly 3x heavier, higher cost, has higher compressive strength yet is very brittle, and has thermal insulation performance roughly 65% worse than polyiso.

Cellular Glass: What is Cellular Glass? Cell glass is typically used as a thermal insulation made by foaming softened glass to produce many sealed bubbles, thus producing a closed-cell structure. Cellular glass can molded into board and small blocks, usually with a rather heavy density of about 7 to 10 lb per cu ft (14.4 to 16 kg per cu m).

Cellular Insulation: What is Cellular Insulation? Cellular Insulation is 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 insulation may have “open” or “closed” cells.

Cellular Plastic Expanded: What is Expanded Cellular Plastic? Beads of plastic expanded by chemical or thermal means and bonded together chemically or thermally. Expanded Polystyrene (EPS) is an example.

Cellular Plastic Extruded: What is Extruded Cellular Plastic? Extruded plastic with cells formed by thermal or chemical means. Extruded Polystyrene (XPS) is an example.

Cellular Plastic: What is a Cellular Plastic? Plastic expanded by thermal or chemical means, typically containing open cells throughout. A cellular plastic could be either a thermoset or a thermoplastic.

Cellular Polyimide: What is a 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: What is a Cellular Polystyrene? Thermoplastic rigid board composed principally of polymerized styrene resin processed to form a rigid foam having an open-cell structure. Expanded Polystyrene (EPS) is an example. Often used as composite substrate, insulation, or a combination thereof.

Cellular Polyurethane: What is a Cellular Polyurethane? Thermoset rigid foam 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. Often used as composite substrate, insulation, or a combination thereof. Polyisocyanurate is a modified polyurethane.

Cellulosic Fiber:  What is Cellulosic Fiber? Insulation composed principally of cellulose fibers, across a wide range of densities and strengths, usually derived from paper, paperboard stock or wood, with or without binders.

Cement, Finishing: What is finishing cement? 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: What is an Insulating Cement? 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.

Centigrade: What is Centigrade? The Centigrade (C) temperature scale is a thermometric system in which 0 degrees denotes the freezing and 100 degrees the boiling point of pure water at standard atmospheric pressure.

Ceramic Fibers: What are Ceramic Fibers? Pure silica heated and expanded to produce fibers from which high-temperature insulation can be made. Sometimes called Refractory Ceramic Fibers.

Chalking: What is Chalking? A soft white or gray appearance on the surface of a weathered finish.

Chemical Resistance: What is Chemical Resistance? The capability of a material to withstand exposure to acids, alkalis, salts and their solutions.

Chicken Wire: What is Chicken Wire? Hexagonal wire netting (poultry mesh) used as reinforcement or as a metal-mesh facing.

Cladding: What is Cladding? Cladding is jacketing installed over insulation. Jacketing is a covering over the insulation system primarily to protect from mechanical abuse yet also to provide some protection from environmental/atmospheric elements such as rain and solar radiation.  Jacketing can be metal (e.g. aluminum or stainless steel), or PVC.

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

Clearance: What is Clearance? Clearance is the adequate space allowed for installation of insulation, or composite materials that may require thermal performance. Composites/insulants with higher R-values (lower K-factors) need less thickness to fit constrained spaces.

Closed Cell Foam: What is Closed Cell Foam? Closed Cell Foam is a material comprised predominantly of individual non-interconnecting cells, that in the context of composite materials and insulation (or a combination) yields a rigid foam board, block, or bunstock. The percent of closed cell structure, the size of the cells, the circularity of the cells, cell wall thickness and chemical makeup, and the specific gas within the cells will have a major impact on various strengths, stiffness, flexibility, and thermal conductivity.

Coating: What is a Coating? A “coating” is a liquid or semi-liquid that dries or cures to form a protective finish, suitable for application to composites or thermal insulation, or other surfaces. A coating may protect from water, moisture, solar irradiation, or certain chemicals. A mastic is a coating often applied in locations where a vapor barrier sheet wrap is not practical.

Code (Building): What is 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 Thermal Expansion: What is the Coefficient of Thermal Expansion? The fractional change in length of a material for each unit change in temperature.

Cohesion: What is 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: What is Combustible? Provides enough fuel to make material capable of burning.

Compaction Resistance: What is Compaction Resistance? The property of a fibrous or loose-fill material that resists compaction under load or vibratory: conditions.

Compatible Materials: What are Compatible Materials? Two or more substances that can be mixed or used together without separating, reacting, or: adversely affecting the materials.

Compressive Strength: What is Compressive Strength? Compressive Strength is the property of an insulation material that resists any change in dimensions when acted upon by a compaction force.

Concealed Spaces: What is a Concealed Space? 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: What is a Condensate Drain?  A Condensate Drain is the Piping carrying condensed water from air conditioning or refrigeration drip pans to a point of discharge.

Condensate Drain: What is a Condensate Drain? Piping carrying condensed water from air conditioning or refrigeration drip pans to a point of: discharge.

Condensate Return: What is Condensate Return? Condensate Return is the liquid formed by condensation of vapor. In steam heating it is water condensed from steam. In air conditioning it is the water extracted from the air by cooling.

Condensation: What is Condensation? Condensation is the act of water vapor turning into liquid upon contact with a cold surface.

Conditioned Air: What is 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: What is a 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: What is 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": What is Thermal Conductance "C"? The time rate of steady state heat flow through a unit area of a material or construction induced by a unit temperature difference between the body surfaces. [The rate of heat flow for the actual thickness of a material].

Conductance, Air Film: What is Air Film Conductance? 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.

Conduction: What is Conduction (Thermal)? Thermal Conduction is the transfer of energy by virtue of a temperature difference. It is the process of heat transfer through a substance in which energy is transmitted from particle to particle without gross displacement of the particles.

Conductivity, Thermal (k-value): What is Thermal Conductivity (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: What is a Contact Adhesive? A Contact Adhesive is an adhesive that when tacky to the touch will adhere to itself instantaneously on contact.

Contact Molding: What is a 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: What is Convection? Convection is the motion resulting in a fluid from the differences in density and the action of gravity. A warm-air furnace transfers heat to the rooms of the house by moving air. This transfer of heat by moving air is called Convection.

Cooler: What is a Cooler? In cold-storage practice, an insulated room maintained at 30°F or above.

Corrosion: What is Corrosion? Deterioration by chemical action such as rust on steel.

Couplings: What is a Coupling? Screwed, soldered, welded or mechanical/grooved connections between links of pipe.

Cover: What is a Cover? To place insulation and/or finish materials on, over or around a surface so as to insulate, protect: or seal.

Coverage: What is Coverage? The area to be covered per unit volume of coating to obtain specified dry thickness and desired: performance.

Cryogenic insulation: What is best Cryogenic insulation? Cryogenic pipe insulation systems consist generally of either polyisocyanurate or cellular glass. In the vast majority of applications polyiso has the lowest cost and highest insulating performance.

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

Cure Stress: What is 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: What is to 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.

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


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

Decibel (Db): What is a Decibel? A logarithmic measure of the ratio of like power quantities as used in describing levels of sound: pressure or sound power.

Decomposition: What is Decomposition? The separating or breaking down of a substance into its component compounds or basic: elements.

De-humidification: What is De-humidification? De-humidification is the removal of water vapor from a gas and can be accomplished by physical, chemical, or thermal means.

Density: What is Density? Density of a material is the mass or weight per unit volume. The density of insulants is typically in the range of 1 to 10 lb/ft3.

Dew Point: What is Dew Point? The Dew Point is the temperature at which the condensation of water vapor begins for a given condition of humidity and pressure as the temperature of the water vapor is reduced. The dew point temperature corresponds to 100 percent relative humidity for a given absolute humidity at constant pressure.

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

Dewpoint Temperature: What is 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: What is Thermal Diffusivity? The ratio of thermal conductivity of a substance to the product of its density and specific heat.

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

Dry: What is to 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: What is Dual Temperature? Systems of equipment that operate as cold condition and hot application.

Duct Flange (Stiffener): What is a Duct Flange? 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: What is a Duct? A Duct is a passageway made of sheet metal or other suitable material used for conveying air or other gas.


Efflorescence: What is 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: What is 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: What is an 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: What is an Elastomeric? An elastomeric insulant is a closed-cell foam insulation containing elastomers that provide the property of high elasticity.

Elongation: What is 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.)

Emissivity: What is Emissivity? Emissivity is a characteristic of a surface which determines its ability to emit or give off heat by radiation. Its value is the ratio of heat radiated by a body to the heat radiated by a black body under the same conditions. Values range from 0 to 1.

Emittance, Directional: What is Directional Emittance? 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: What is Hemispherical Emittance? The average directional emittance over a hemispherical envelope covering a surface.

Emittance, Spectral: What is Spectral Emittance? An emittance based on the radiant energy emitted per unit wavelength interval (monochromatic: radiant energy).

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

Emittance: What is 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: What is an Emulsion? Insoluble fine solids or liquids dispersed in another liquid, usually water.

Epoxy Resins: What are 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.

EPS versus XPS: What is the difference between EPS and XPS? EPS (expanded polystyrene) and XPS (extruded polystyrene) are white, rigid, thermoplastic foams, typically manufactured in densities ranging from 0.8 -  2 pcf. As the name indicates, EPS is expanded into very large blocks. XPS is extruded, thus the billets are much smaller. XPS is generally considerably more expensive than EPS, yet the physical properties of each (at comparable densities) are actually quite similar, yet often advertised as quite different. Often the differences are due to the ASTM testing protocols and the fact that XPS may have “skins” on the surface prior to fabrication that affect, for example, water absorption. Also, whereas EPS will generally wick away any absorbed moisture, XPS does not.

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

Exotherm: What is an Exotherm? The liberation or evolution of heat during the curing of a plastic product.

Expanded Metal Lath: What is Expanded Metal Lath? See lath—expanded metal.

Expanded Polystyrene (EPS): What is Expanded Polystyrene (EPS)? Expanded Polystyrene (EPS) is the generic industry name for the white rigid material made by expanding polystyrene beads with steam and pressure to bond the beads together to form blocks or to shape molds. Expanded polystyrene, manufactured from styrene is a open-cell, thermoplastic rigid foam material often fabricated into lightweight foam products such as composite sheets, special shapes, insulation, or other products combining the physical properties or each.

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

Extruded Polystyrene (XPS): What is Extruded Polystyrene (XPS)? XPS is an extruded thermoplastic that soften at 165F. Since it is extruded rather than expanded the billets are somewhat small. XPS is generally considerably more expensive than Expanded Polystyrene, yet the physical properties of each (at comparable densities) are actually quite similar, yet often advertised as quite different. Often the differences are due to the ASTM testing protocols and the fact that XPS may have “skins” on the surface prior to fabrication that affect, for example, water absorption.


Facing: What is a Facing? A thin covering adhered to the surface of insulation prior to field installation.

Fahrenheit: What is Fahrenheit? Fahrenheit (F) is a temperature scale in which 32 degrees denotes freezing and 212 degrees the boiling point of pure water at standard atmospheric pressure.

Fatigue Strength: What is Fatigue Strength? The maximum cyclical stress a material can withstand for a given number of cycles before failure occurs. The residual strength after being subjected to fatigue.

Fatigue: What is Fatigue? The failure or decay of mechanical properties after repeated applications of stress. Fatigue tests give information on the ability of a material to resist the development of cracks, which eventually bring about failure as a result of a large number of cycles.

FDA Approval: What is FDA Approval? Compliance with the Food and Drug Administration's regulations for food handling operations.

Fiber Content: What is Fiber Content? The amount of fiber present in a composite. This is usually expressed as a percentage volume fraction or weight fraction of the composite.

Fiber GlassWhat is Fiber Glass? A synthetic vitreous fiber made by melting predominantly silica sand and other inorganic materials, and then physically forming the melt into fibers. Often used as an insulation product, there are often other materials applied to the mineral wool such as binders, oils, etc. Commonly referred to as either fiber glass or fiberglass.

Fiber-Reinforced Plastic (FRP): What is Fiber-Reinforced Plastic (FRP)? A general term for a composite that is reinforced with cloth, mat, strands, or any other fiber form.

Fibrous Glass: What is Fibrous Glass? Fibrous glass is a synthetic vitreous fiber made by melting predominantly silica sand and other inorganic materials, and then physically forming the melt into fibers. Often used as an insulation product, there are often other materials applied to the mineral wool such as binders, oils, etc. Commonly referred to as either fiber glass or fiberglass.

Fibrous Insulation: What is 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.

Filament: What is a Filament? The smallest unit of a fibrous material. The basic units formed during drawing and spinning, which are gathered into strands of fiber for use in composites. Filaments usually are of extreme length and very small diameter, usually less than 25 mm (1 mil). Normally filaments are not used individually. Some textile filaments can function as yarn when they are of sufficient strength and flexibility.

Film (Wet): What is Film (Wet)? The applied layer of mastic or coating before curing or drying.

Finish: What is a Finish? A “Finish” in an insulation system may be a jacket, mastic and/or a strong film/coating/paint used for either for aesthetics or to protect insulation from at least one or more of the following: weather, mechanical, and/or personnel abuse.

Finishing Cement: What is 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: What is Fire Resistance? Fire Resistance is 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): What is Fire Retardance (FR)? The property of a material that retards the spread of fire.

Firestopping: What is Firestopping? Fire stopping is the furnishing and installing a material or a combination of materials to form an effective barrier against the spread of flame, smoke, gases and moisture. It is to maintain the integrity of the fire-rated construction.

Fish-Mouth: What is a Fish-Mouth? A gap between layers of sheet materials caused by warping or bunching of one or both layers.

Fitting Cover: What is a Fitting Cover? A Fitting Cover may be the insulation for a pipe fitting composed of the specified thickness of insulation material, which may be pre-formed. Also, may be a preformed jacketing.

Fittings: What are Fittings? Items used to change size, direction of flow, level or assembly of piping, except for unions, grooved couplings, flanges, valves or strainers.

Fixture Connection: What is a Fixture Connection? Final piping connections to plumbing fixtures (usually exposed and chrome-plated).

Flame Retardant: What is a Flame Retardant? The quality of a material to limit the flame spread across its surface.

Flame Spread: What is Flame Spread? Flame spread or surface burning characteristics rating is a ranking derived by laboratory standard test methodology (e.g. ASTM E84) of a material's propensity to spread flames. The ratings are generally compared to the flame spread of red oak as a baseline.

Flame Spread: What is Flame Spread? The index rate expressed in distance and time at which a material will propagate flame on its surface.

Flange Cover: What is a Flange Cover? The insulation for a pipe flange composed of the specified thickness of insulation material, may be preformed. Also, a preformed jacketing.

Flange: What is a Flange? A projecting collar attached to a pipe for the purpose of connecting to another pipe, valve or fitting.

Flash Point: What is Flash Point? The temperature at which combustion is initiated.

Flashing: What is Flashing? The arrangement of metal or other weather barrier or integrity.

Flexibility: How do you define Flexibility? That property of a material which allows it to be bent (flexed) without loss of strength.

Flexural Modulus: How do you define Flexural Modulus? Ratio of maximum fiber stress to maximum strain, within elastic limit of the stress-strain diagram obtained in the flexure test. The flexural modulus is a measure of elasticity, or the ability for the material to be deformed and return to its original shape. An alternate term is the Flexural Modulus of Elasticity.

Flexural Strength: How do you define Flexural Strength? The flexural strength of a material is its ability to resist deformation under load, or how much you can bend the material before it starts to break. For materials that do not break, the load at yield, typically measured at 5% deformation/strain of the outer surface, is reported as the flexural strength or flexural yield strength. The general term for bending stiffness is flexural rigidity, which is the product of the material's elastic modulus and the cross section moment of inertia.

Foamed Plastic: What is Foamed Plastic? Plastic expanded to a cellular form by thermal or chemical means. Extruded plastics are often considered foamed, as well.

Fracture: What is a Fracture? A rupture of the surface of a laminate because of external or internal forces, with or without complete separation.

F-Rating: What is F-Rating? A rating usually expressed in hours indicating a specific length of time that a fire resistive barrier can withstand fire before being consumed or permits the passage of flame through an opening in the assembly, as determined by ASTM E 814 (UL 1479).

Freeze/Thaw Stability: What is 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.

Freezer: What is a Freezer? A Freezer in cold-storage practice is an insulated room where the temperature is kept below 30°F.

Fresh Air Duct (Make-Up Air): What is a Freeze/Thaw Stability? A duct used to convey outdoor air to a point within the building, terminating at the mixing plenum, air handling unit or discharge grill.

Friability: What is Friability? The characteristic of a material to lose mass as a result of a combination of abrasion and impact produced by a laboratory tumbling mechanism. Insulation friability is of concern during handling and insulation, since insulation with higher friability can abrade unprotected hands and raise dust that can irritate lungs. Friability of preformed block-type thermal insulation is measured per ASTM C421.

FSK (Foil scrim Kraft): What is FSK (Foil scrim Kraft)? This is a laminate composed of a thin layer of aluminum foil, glass fiber reinforcing scrim, and Kraft paper.


Galvanic Corrosion (Electrolysis): What is 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.

Gel Coat: What is a Gel Coat? A quick setting resin applied to the surface of a mold and gelled before lay-up. The gel coat becomes an integral part of the finished laminate, and is usually used to improve surface appearance and bonding.

Gel Time: What is Gel Time? The time required for a liquid material to form a gel under specified conditions of temperature as measured by a specific test.

Gel: What is a Gel? The initial jellylike solid phase that develops during the formation of a resin from a liquid. A semisolid system consisting of a network of solid aggregates in which liquid is held.

Glass Cloth: What is Gel? Conventionally woven glass fiber material; certain lightweight glass fabrics are also called scrims.

Glass Fabric: What is Glass Fabric? Open-weave glass fiber used as a reinforcing membrane.

Glass Fiber: What is Glass Fiber? An inorganic fiber manufactured as continuous filament from molten glass or silica, normally: used for reinforcement, tissue or textiles.

Glass Scrim: What is Glass Scrim? See glass fabric.

Glass Transition Temperature (Tg): What is the Glass Transition Temperature? The approximate midpoint of the temperature range over which the glass transition takes place. The temperature at which increased molecular mobility results in significant changes in the properties of a cured resin system or other material. Also, the inflection point on a plot of modulus versus temperature. 

Gore: What is Gore? The curved segment of a finish jacket used for elbows, tank heads or other curved surfaces.

Granular Insulation: What is Granular Insulation? 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: What is a Graybody? A body having the same spectral emittance at all wavelengths.


Hanger: What is a Pipe Hanger? A Pip Hangar is a device (typically a metal bracket lined with an insulant) used to support piping.

Hardener: What is aa Hardener? A substance used to promote or control curing action by taking part in it; as opposed to catalyst.

Hardness: What is Hardness? The resistance to surface indentation usually measured by the depth of penetration (or arbitrary units related to the depth of penetration) of a blunt point under a given load using a particular instrument according to a prescribed procedure.

Heat Distortion Point: What is the Heat Distortion Point? The temperature at which a standard test bar deflects a specified amount under a stated load. Now called deflection temperature.

Heat Flow, Heat Flow Rate: What is the Heat Flow or Heat Flow Rate? The quantity of heat transferred to or from a system in unit time.

Heat Flux Transducer (HFT): What is a Heat Flux Transducer? A device containing a thermopile (or equivalent) that produces an output that is a function of the: heat flux.

Heat Flux: What is Heat Flux? The heat flow rate through a surface of unit area perpendicular to the direction of heat flow.

Heat Resistance: What is Heat Resistance? The property or ability of plastics and elastomers to resist the deteriorating effects of elevated temperatures.

Heat Sink: What is a Heat Sink? A contrivance for the absorption or transfer of heat away from a critical element or part. Bulk graphite is often used as a heat sink.

Heat Transmission: What is Heat Transmission? Heat Transmission is any flow of heat and usually refers to conduction, convection and radiation combined. https://insulationinstitute.org/tools-resources/

Hertz (Hz): What is Hertz? A measurement of sound frequency measured in cycles per second.

High Velocity Duct: What is a 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.

Homogeneous Material: What is a Homogeneous Material? A material in which relevant properties are not a function of the position within the material.

Hubs: What are Hubs? Caulking or cement connections between pipe joints.

Humidity, Absolute: What is Absolute Humidity? The ratio of the mass off 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.

Humidity, Ratio: What is the Ratio Humidity? The ratio of the mass of water vapor to the mass of dry air in an air sample. The I-P units are: either pounds of moisture per pound of dry air or grains of moisture per pound of dry air; the SI: units are grams of moisture per gram of dry air.

Humidity, Relative: What is Relative Humidity? One of the following ratios (a) the mole fraction of water vapor in a given moist air sample to the: mole fraction in the air sample saturated at the same temperature and pressure; (b) the vapor: pressure in a given moist air sample to the vapor pressure in the air sample saturated at the same: temperature and pressure and (c) the humidity ratio in a given moist air sample to the humidity: ratio in the air sample saturated at the same temperature and pressure. There are no units.

Humidity: What is Humidity? A measure of the amount of water vapor in the ambient air.

Humidity-Absolute: What is Humidity-Absolute? Absolute Humidity is the weight of water vapor per unit volume (lb/cu.ft.).

Humidity-Relative: What is Humidity-Relative? Relative Humidity is the ratio of the weight of water vapor in a mixture of water vapor and air to the weight of water vapor in dry saturated air at the same temperature. The ratio is usually expressed as a percent of relative humidity.

Humidity-Specific: What is Specific Humidity? Specific Humidity is the weight of water vapor per pound of dry air in a mixture of water vapor and air.

Hygroscopy: What is Hygroscopy? Tendency of a material to absorb water vapor from the air. Especially pertinent for materials whose physical characteristics are altered by effects of water vapor.


IARC: What is the IARC? International Agency for Research on Cancer

ICBO: What is the ICBO? International Council of Building Code Officials.

ICC: What is the ICC? International Code Council.

Impact Resistance: What is Impact Resistance? Capability of a material and/or finish to withstand mechanical or physical abuse.

Impact Strength: What is Impact Strength? A material's ability to withstand shock loading as measured by the work done in fracturing a specimen

Impale: What is to Impale? To pierce or fix by piercing on a sharp point or pin.

Impregnate: What is to Impregnate? To saturate the voids and interstices of a reinforcement with a resin.

IMPs Installation: How are IMPs installed? Insulated Metal Panels (IMPs) generally consist of a metal sheet laminated/adhered to an insulant such as polyisocyanurate or polystyrene. The installation may vary from a large refrigerated warehouse to a much small sharp-freezer application where the quality of the IMP and the precision/methodology of the installation is more challenging. Consult your engineer for installation guides for the specific application.

IMPs Manufacture: Where are IMPs manufactured?  Insulated Metal Panels are manufactured at dozens of facilities across North America, yet the insulants, laminates, the quality, and the size can vary considerably. Internet searches of local suppliers and evaluation of each is warranted. For instance. www.alibaba.com displays over 16, 000 results when searching for Insulated Metal Panels

Injection Molding: What is Injection Molding? Method of forming a plastic to the desired shape by forcing heat-softened plastic into a relatively cool cavity under pressure.

Insulate: What is to Insulate? To cover with a material of low thermal conductivity in order to reduce the passage or leakage: of heat.

Insulated Metal Panel: What is an Insulated Metal Panel (IMP)? In either case, an Insulated Metal Panel consists either of a rigid insulant (such as polyiso or polystyrene) laminated to a structural metal sheet(s) or a liquid insulant (such as pour-in-place polyurethane) is poured between two metal sheets, the result of which is structural.

Insulated Metal Panel Manufacturers: Who manufactures Insulated Metal Panels (IMPs)? IMPs manufactured?  Insulated Metal Panels are manufactured at dozens of facilities across North America, yet the insulants, laminates, the quality, and the size can vary considerably.

Insulated Panel: What is an Insulated Panel? The term most generically applies to a panel of rigid sheet insulation that is sufficiently structural to “stand on its own” (such as polyisocyanurate or polystyrene), rather than for instance a batt of insulation fibers that must be adhered to a wall. More general the term applies to either a Structural Insulated Panel (SIP), or an Insulated Metal Panel (IMP). In either case, the rigid insulant is either laminated to a structural sheet (wood or metal) or a liquid insulant is poured between two structural sheets.

Insulating Cement: What is 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 Hanger: What is an Insulation Hanger? A device such as a welded pin, stud or adhesive secured fastener that carries the weight of: insulation.

Insulation: What is Insulation (Thermal)? Thermal Insulation consists of any material having a relatively high resistance to heat flow, and is used principally to retard the flow of heat.

Insulation: What is Insulation? Those materials or combination of materials that retard the flow of heat.

Intumescent: What is Intumescent? A characteristic of certain firestop products that when exposed to heat, expand to seal and fill: any void in the penetration. When exposed to fire, intumescent products will form a hard char.

Isocyanate: What is Isocyanate? A compound containing the isocyanate group, -N=C=O, attached to an organic radical or hydrogen.

Isotropic: What is Isotropic? Having uniform properties in all directions. The measured properties of an isotropic material are independent of the axis of testing.


Jacketing: What is Jacketing: Jacketing is a covering over the insulation system primarily to protect from mechanical abuse yet also provides some protection from environmental/atmospheric elements such as rain and solar radiation.  Jacketing can be metal (e.g. aluminum or stainless steel), or PVC.

Joint: What is a 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.


Kelvin: What is Kelvin? Kelvin (K) is a temperature scale sometimes called centigrade absolute. Its zero is at the lowest attainable temperature or 273.15° below the zero on the centigrade scale.

k-factor: What is “k-factor”? Thermal conductivity (k) is the amount of heat (Btu's) transferred in 1 hour through 1 square foot of a homogeneous material 1 inch thick for a difference in temperature of 1°F. For example, the average "k" for Armaflex is 0.25. This means that for a 1 inch thickness, there is a heat transfer of 0.25 Btu per hour per square foot for each degree difference in temperature between its two surfaces. Usually expressed in Btu/hr, sq.ft.(F/in.) in the insulation field.


Laminate (n.): What is a Laminate? A product made by bonding together two or more layers of material or materials.

Laminate (v.): How do you Laminate? By bonding together two or more layers of material(s).

Laminate Orientation: What is Laminate Orientation? The configuration of a cross-plied composite laminate with regard to the angles of cross-plying, the number of laminae at each angle, and the exact sequence of the lamina lay-up.

Laminating: What is Laminating? Laying up with resin and reinforcing fabric on virtually any surface.

Liquid Natural Gas (LNG): What are the most widely used insulations for Liquid Natural Gas (LNG)? There is considerable disagreement among insulation manufacturers, yet the majority of qualified insulation engineers would attest to polyisocyanurate and cellular glass as representing the best insulation alternatives. This is validated by the fact that the majority of installed (and yet-to-be-installed) worldwide LNG insulation systems are either polyiso or cell glass. (see polyiso versus cellglass).

LISTING (UL): What is a LISTING with Underwriters Laboratories? The UL permits the use of its listing mark (the UL mark) as its stamp of approval on goods and materials after standardized and stringent testing. Thereafter its inspectors regularly visit the producer to audit compliance with its certification requirements.

LNG insulation specification: Is there an LNG insulation specification? There are many LNG insulation specifications available online, yet they are in general agreement about the process of installation. An Installation Guide is available at https://tinyurl.com/yc69o8gg.

LNG insulation plants: Who has installed Polyiso on LNG insulation plants, and has it performed well? There are over 1200 million tons/year of LNG gasification and liquefaction plants in dozens of countries, as well as over 400 LNG shipping vessels, spanning almost 50 years of construction and operation experience. While there are no single reporting protocols relating to insulation failures, the vast majority of LNG piping has been either polyisocyanurate or cellular glass. In Dyplast’s 50 years of insulation experience, no client has reported a failure of the polyiso system. Additionally, the most experience LNG design engineers continue to specify either polyiso or cellular in the majority of LNG installations.

LNG Insulation (polyiso or cell glass): Are LNG insulation options only polyisocyanurate or cellular glass? LNG (liquid natural gas) systems consist of both pipe, equipment, and tanks. LNG pipe insulation is generally either polyisocyanurate or cellular glass. In the vast majority of applications polyiso has the lowest cost and highest insulating performance.

LNG pipe half-shells: Can I get Polyiso for a 24 inch LNG pipe half-shell insulation segments that don’t require glued segments as cellular glass requires? Yes, polyisocyanurate is manufactured as large continuous bunstock approaching 4 ft x 4 ft by virtually any length (typically 17 feet). Cellular glass billets, on the other hand, are considerably smaller and may need to be glued together to achieve larger pipe half-shell insulant segments.

LNG storage tank insulation: How are LNG storage tanks Insulated? The sidewalls of largest LNG containment tanks are usually insulated with a combination of loose-fill perlite and fiber glass blankets since there are generally no space constraints for these low R-value insulants. The tank roof typically has a floating component insulated with closed cell foams with better R-values and low-density. The tank base is usually insulated with multiple layers of high-density/higher-cost cellular glass simply because the compressive factors may be high. In smaller LNG tanks and/or in tanks that have space limitations (such as on ships), polyisocyanurate sheet insulation may be preferable since it has much higher insulating value and certain polyiso manufacturers advertise that large sheets can be bent/flexed around tanks making installation easy and joints/seams minimized.

Lot: What is a Lot? A specific amount of material produced at one time using the same process and the same conditions of manufacture, and offered for sale as a unit quantity.

Low-Velocity Duct: What is a 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.


Manufacturing: How long is the Manufacturing and delivery process? Of course the answer depends on the type of material as well as the supplier, yet Dyplast has a very large inventory, considerable production capacity, and a fleet of trucks as well as alternative delivery arrangements with trains, ships, and aircraft.

Mastic: What is a Mastic? A protective coating applied by spray or trowel to weatherproof or otherwise prevent: deterioration of the insulation to which it is applied.

Mat: What is a Mat? A fibrous reinforcing material comprised of chopped filaments (for chopped-strand mat) or swirled filaments (for continuous-strand mat) with a binder to maintain form; available in blankets of various widths, weights, and lengths.

Matrix: What is a Matrix? A material in which the fiber of a composite is imbedded; it can be plastic, metal, ceramic, or glass.

MDI: What is MDI? An abbreviation for 4,4’ diphenylmethane diisocyanate.

Mean Specific Heat: What is 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: What is Mean Temperature? Mean Temperature is the arithmetic mean of inner and outer surface temperatures of insulation. Mean temperature is used to select a value for conductivity in heat-loss calculations.

Mechanical Insulation: What is Mechanical Insulation? Mechanical Insulation is insulation over pipes or equipment.

Medium Velocity Duct: What is a Medium Velocity Duct? A duct designed with airflow over 2000 feet per minute velocity with a static pressure below 6: inches.

Metric Perm: What is a Metric Perm? Perm measured at 23C Kilogram per Pascal Second square meter [kg/Pa-s-m2]

Microporous Insulation: What is Microporous Insulation? Material in the form of compacted powder with an average interconnecting pore size comparable: to or below the mean free path of air molecules at standard atmospheric temperature and: pressure. Microporous insulation may contain fibers to add integral strength and opacifiers to: reduce the amount of radiant heat transmitted.

Mil: What is a Mil? The unit used in measuring the diameter of glass fiber strands, wire, and so forth (1 mil = 0.001 in.).

Mineral Fiber: What is Mineral Fiber? Insulation composed principally of fibers manufactured from rock, slag, or glass, with or without binders.

Mineral Wool: What is Mineral Wool? 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): What is a 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 air handling unit.

Modulus: What is Modulus? A measure of the ratio of load (stress) applied to the resultant deformation of a material, such as elasticity or shear.

Moisture Barrier (as related to Insulation Jacketing): What is a Moisture Barrier? A polymeric film or coating applied to the inner surface of metal jacketing for the primary: purpose of reducing electrolytic, pitting, or crevice corrosion of the jacketing: Discussion – moisture barriers are not water vapor barriers or water vapor retarders.

Moisture Content: What is Moisture Content? The amount of moisture in a material determined under prescribed conditions and expressed as a percentage of the mass of the moist specimen, that is, the mass of the dry substance plus the moisture present.

Moisture Retarder (as related to Insulation Jacketing): What is a Moisture Retarder: See Moisture Barrier (as related to insulation jacketing): Mold and Mildew Resistance: The property of a material that enables it to resist the formation of fungus growth.

Mold and Mildew Resistance: What is Mold and Mildew Resistance? Mold and Mildew Resistance is the property of a material that enables it to resist the formation of fungus growth.


NFPA: What is NFPA? National Fire Protection Association.

Noise Reduction Coefficient (NRC): What is a Noise Reduction Coefficient? A single number rating that is the arithmetic average of the individual sound absorption: coefficients at 250, 500, 1000 and 2000 Hz to the nearest 0.05.

Nominal Value: What is a Nominal Value? A value assigned for the purpose of a convenient designation. A nominal value exists in name only. It is often an average number with a tolerance so as to fit together with adjacent parts.

Noncombustible: What is Noncombustible? Noncombustible applies to a material that will not contribute fuel or heat to support a fire to which it is exposed.

Nondestructive Testing (NDT): What is Nondestructive Testing? Broadly considered synonymous with nondestructive inspection (NDI).

Nonflammable: What is Nonflammable? Nonflammable applies to a material that will release very little heat when exposed to fire or flame.

Nonflammable: What is Nonflammable? A material that will release very little heat when exposed to fire or flame.


Octave Band: What is an Octave Band? A frequency band with an upper frequency limit equal to twice the lower limit.

One-coat Cement: What is a One-coat Cement? A mixture of various insulation fibers, fillers and binders with hydraulic-setting cement. The: material can be applied directly to fittings to match adjacent insulation thickness in one: application and smoothed to provide a hard finish.

Open Cell Foam: What is aa Open Cell Foam? A material comprised predominantly of interconnecting cellular voids.


Perlite: What is Perlite? Insulation composed of natural perlite ore expanded to form a cellular structure.

Perm: What is a Perm? A Perm is a measure of vapor transmission rate. Defined as 1 grain of water vapor per hour for 1 square foot area for 1 inch of mercury-pressure difference. Other units are also used to express vapor transmission rates. Grains/hr., sq.ft., in.Hg.

Permeability: What is Permeability? Permeability is a rating of a material giving the amount of water vapor that passes through 1 inch thickness of the material. Grains/hr., sq.ft. (in.Hg/in.). Permeability is measured in Perm inches.

Permeance (Perms): What is Permeance? 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.

pH: What is 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: What is Phenolic Foam? Phenolic Foam is a closed cell, foamed insulation made from resins of phenols condensed with aldehydes.

Pinhole: What is a Pinhole? Very small hole through a mastic or coating.

Pipe Insulation Thickness: How do you calculate A872? There are a number of tools to calculate pipe insulation thickness. The dominant calculator generally available is 3E-Plus® software available at www.insulation.org.

Plenum: What is a Plenum? A Plenum is an enclosure for the collection of air at the termination or origin of duct systems. They may be a space below floors, above ceilings, a shaft or a furred area.

Ply: What is a Ply? In general, fabrics or felts consisting of one or more layers (laminates, for example). The layers that make up a stack. Yarn resulting from twisting operations (three-ply yarn, for example). A single layer of prepreg. A single pass in filament winding (two plies forming one layer).

Pointing: What is Pointing? Applying or shaping cements or mastic with a small pointed trowel.

Polyethylene: What is Polyethylene? Polyethylene is a closed-cell, thermoplastic material used for insulation or composites.

Polyimide: What is a Polyimide? See cellular polyimide.

Polyiso Industrial Insulation: Where is Polyiso Insulation for industrial or commercial use sold? Polyisocyanurate insulation can be for pipe, equipment, cold storage walls, or sheets for composite applications. There are generally only 4-5 reputable manufacturers of polyiso insulation for these applications. Dyplast Products is one; an internet search for “polyisocyanurate mechanical insulation” may bring up others. Dyplast shows up at the top in internet searches for “polyiso composites”. There is also a laminated polyiso sheet product used specifically for commercial roofing; www.pima.org list suppliers of that material, and an internet search for “polyiso roof insulation”

Polyiso Insulation and Vapor Barriers: Can Polyiso Insulation be installed without vapor barriers? Yes, but in applications where the humidity may be high or rainfall is possible virtually all insulants should be protected against moisture with a zero-perm vapor barrier.

Polyiso Insulation brands: Are all Polyiso Insulation brands the same? No! There are only a handful of reputable manufacturers of polyisocyanurate bunstock for mechanical insulation or composite applications. Each manufacturer uses different formulations, and both Product Datasheets and an experience list should be perused closely.

Polyiso Insulation in buildings: Can Polyiso Insulation be used in interior cold piping? Yes in most cases, yet some building codes for inhabited areas require stricter flame spread and smoke development criteria than is generally available from thermoset or thermoplastic insulants.

Polyiso Insulation manufacture: How is Polyiso Insulation manufactured? When manufacturing Polyisocyanurate Insulation (non-roof insulation) the primary chemical ingredients include methylene diphenyl diisocyanate (MDI) and polyols, plus blowing agents, catalysts, and fire retardants. The liquid combination flows onto a continuously moving belt, and over a period of 1-3 minutes rises (expands) and solidifies into the final bunstock, which can then be cut into virtually any length.

Polyiso Insulation vs. cell glass: Is Polyiso Insulation as good as cellular glass? Polyiso insulant has better thermal performance (higher R-value/lower k-factor), is much lighter and easier to install, has better delivery times, comes in larger chunks so does not need to be glued together, and is lower cost. So this is a simple question unless there are extenuating circumstance (e.g. high foot-traffic on pipe that requires high compressive strengths). See https://tinyurl.com/y9cugn5s .

Polyiso LNG pipe insulation: Will Polyisocyanurate on an LNG pipe insulation lose its thermal insulating properties over time? The answer is NO. The ASTM protocols for polyiso insulants utilizing non-air/non-CO2 blowing agents require manufacturers to report and advertise “aged k-factors” representing thermal insulating characteristics representative of the life of the insulation system. In other words “the aging” of the insulant [as low conductivity gases in each cell of the closed-cell insulant may diffuse (at low temperatures it literally may not) out of the cells over the years] has already been incorporated into the advertised aged k-factors. A different perspective to demonstrate the same point is that insulants using low R-value air/CO2 as their blowing agent NEVER have greater insulating properties than insulants such as polyisocyanurate.

Polyiso Mechanical Insulation: Which Polyiso Mechanical Insulation brand is best? Polyiso insulation manufacturers of course debate this question. Dyplast Products likely as first on an internet search for this question.

Polyiso vs. Cellular Glass LNG: When is Polyiso better than cellular glass on LNG pipe? This is a simple question unless there are extenuating circumstance (e.g. high foot-traffic on pipe that requires high compressive strengths). The simply answer to the vast majority of LNG installations is that polyisocyanurate has considerably better thermal insulations properties (higher R-value/lower k-factor), a lower cost, better delivery times, at one-third the weight. See https://tinyurl.com/y9cugn5s.

Polyisocyanurate versus Foamglas: What is performance of polyisocyanurate versus Foamglas? See above.

Polyisocyanurate: How does Polyisocyanurate Insulation (also called PIR) work? Polyisocyanurate is a rigid closed cell thermoset plastic foam whose cells contain a gas with very high thermal resistance (“R-value”), making it one of the best thermal insulators for pipe, equipment, or panel insulation.

Polyisocyanurate Look/Feel: What does Polyisocyanurate (polyiso) insulation look and feel like? Polyisocyanurate (polyiso or PIR) is a rigid foam thermoset “plastic” that is generally tan in color and its texture is somewhat like fine sandpaper surface on a rigid foam.

Polyisocyanurate: What is Polyisocyanurate (polyiso)? Polyisocyanurate (a modified polyurethane) is a rigid closed cell thermoset foam with insulating properties better than most competitive insulants such as polystyrene, fiberglass, cellular glass, or elastomeric.

Polymer: What is a 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.

Polymerization: What is Polymerization? A chemical reaction in which the molecules of monomers are linked together to form polymers.

Polyol: What is a Polyol? An organic compound having more than one hydroxyl (-OH) group per molecule. In the cellular plastics industry, the term includes monomeric and polymeric compounds containing alcoholic hydroxyl groups such as polyethers, glycols, glycerol, and polyesters, used as reactants in polyurethane foam.

Polyolefin: What is Polyolefin? A polyolefin is a closed-cell thermoplastic material used for insulation.

Polystyrene: What is Polystyrene? Polystyrene is a versatile plastic used to make a wide variety of consumer products. In the context of composite applications and insulation (or composites benefiting from thermal performance) polystyrene is a foam material, called expanded polystyrene (EPS) or extruded polystyrene (XPS), which is valued for its insulating, cushioning, and strength properties at low cost.

Polyurethane: What is a Polyurethane? Polymeric substance containing many urethane linkages. Abbreviated as PUR or PIR, depending on whether there is a greater proportion of polyol or isocyanate. [Rigid foam polyurethanes with higher isocyanate indexes are referred to as PIR, or polyisocyanurate foam]. Polyurethanes actually include a very large family of polymers with widely ranging properties and uses, all based on the reaction product of an organic diisocyanate with compounds containing a hydroxyl group, and having the 'RNHCOOR’- group in their chains. The types and properties of polyurethanes are so varied that they have been dubbed the "erector set" of the plastics industry. They may be thermosetting or thermoplastic, rigid and hard or flexible and soft, solid or cellular; and the properties of any of these types may be varied within wide limits to suit the desired application. See Polyisocyanurate.

Polyvinyl Chloride (PVC): What is a Polyvinyl Chloride? A polymerized vinyl compound using chloride.

Polyvinyl Fluoride (PVF): What is a Polyvinyl Fluoride? A polymerized vinyl compound using fluoride.

Post Cure: What is Post Cure? The exposure of certain resins to higher than normal curing temperatures after the initial cure cycle. This second stage is necessary to attain the complete cure and desired mechanical properties of the resins involved. The higher temperatures are used separately because they would result in an excessive reaction if applied throughout the entire cure.

Potential Heat: What is Potential Heat? Potential Heat is the approximate amount of Btu's required to fully burn or incinerate 1 lb. Armaflex -- 9,000 Btu's for 4.5 lb. of Armaflex.

Pressure Sensitive Tape: What is Pressure Sensitive Tape? A tape with adhesive pre-applied.

Price of polyiso: What is the Price of polyisocyanurate? The price of polyisocyanurate is generally quoted in cents per board foot, and varies with density. For 2 lb/ft3 polyiso rigid foam, the price can be well under a $1.00/board foot.

Primer: What is a Primer? A coating applied to a surface, before the application of an adhesive, lacquer, enamel, and so forth, to improve the adhesion performance or load-carrying ability of the bond.

Processing Window: What is the Processing Window? The range of processing conditions, such as stock (melt) temperature, pressure, shear rate, and so on, within which a particular grade of plastic can be fabricated with optimum or acceptable properties by a particular fabricating process.

Project Management: Who manages my Project at Dyplast?  We will assign a project engineer to your project who will be responsible for managing every aspect of the project, from identifying performance requirements to producing prototypes to delivering the first articles for production. Generally, your globe composite project engineer will interface directly with your program manager, engineer, or user representative to make sure we understand the requirements of the project and ultimately deliver the best parts for the application.

Project Tracking: How do you keep track of my Project?  Dyplast composite manages anywhere between 75 to 100 projects at any given time. We understand how important it is that your project gets the attention it deserves. That's why every project is maintained on our customized workflow management system, giving us up-to-the-minute information on project status, deliverables, and costs.

Puncture Resistance: What is Puncture Resistance? That property of a material that enables it to resist punctures or perforations under blows or: pressure from sharp objects.

Punking: What is Punking? An exothermic reaction that occurs inside insulation material, on a hot surface, and usually is the result of the combustion of gasses resulting from chemically decomposed binder or resin.



Radiance: What is 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: What is Radiant Flux Density? The rate of radiant energy emitted from unit area of a surface in all radial directions of the: overspreading hemisphere.

Radiant Heat: What is Radiant Heat? Heat radiating from a heated body, as distinguished from that transmitted by an intervening body.

Radiation: What is Radiation? Thermal Radiation is the transmission of energy by means of electromagnetic waves. Radiated heat moves at high speed through the air without heating the air and flows in direct lines from a warm surface to a cooler one. Sun heat is radiated heat.

Rankine: What is Rankine? The Rankine (R) temperature scale is sometimes called Fahrenheit absolute. Its zero is at the lowest attainable temperature or 459.67 (460) degrees below the zero on the Fahrenheit scale.

Reflectance: What is Reflectance? The fraction of the incident radiation upon a surface that is reflected from the surface.

Reflective Insulation: What is 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.

Reflectivity: What is Reflectivity? Reflectivity is the fraction of the incident radiation reflected by a surface. (No radiant heat is reflected by a perfect black body.) With an opaque non-black body: Emissivity = Absorptivity = 1 – Reflectivity

Refractory Insulation: What is Refractory Insulation? Insulation for extremely high temperatures, applications usually above 1500°F.

Refractory Materials: What are 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.

Refrigeration insulation specification: Is there a Refrigeration insulation specification? Yes, and example is available at https://tinyurl.com/yc2u4jae.

Refrigeration insulation: Are Refrigeration insulation options only polyisocyanurate or cellular glass? Refrigeration insulation can refer to insulation fabricated to tightly fit over pipe and equipment or sheet insulation within the walls of a freezer or cooler. An internet search for refrigeration insulation will bring up many competitors of refrigerant pipe insulation. Polyisocyanurate is often considered the optimal insulant considering its thermal performance versus cost.

Refrigeration insulation: What is Refrigeration insulation? Refrigeration insulation can refer to insulation fabricated to tightly fit over pipe and equipment carrying a cold refrigerant, or sheet insulation within the walls of a freezer or cooler.

Refrigeration storage tanks: What insulation is used on Refrigeration storage tanks? The insulation on refrigeration system (e.g. large HVAC or chilled water) storage tanks is generally either polyisocyanurate, fiberglass, or cellular glass. Increasingly polyisocyanurate is acknowledged as the optimal based on price and thermal performance.

Refrigeration Ton: What is Refrigeration Ton? The removal of heat at a rate of 12,000 Btu per hr. This figure is obtained from the commercial unit of refrigerating capacity, which is the heat required to melt 2,000 lbs. of pure ice to water at 32°F in 24 hours. The latent heat of ice is 144 Btu per lb. Therefore, a ton of refrigeration is 144 x 2,000 = 288,000 Btu per 24 hrs. or 12,000 Btu per hr.

Reinforcement: What is Reinforcement? A material added to the matrix to provide the required properties; ranges from short fibers through complex textile forms.

Reinforcing Cloth or Fabric: What is Reinforcing Cloth or Fabric? A woven cloth or fabric of glass or resilient fibers used as reinforcement to a mastic.

Relative Humidity: What is Relative Humidity? One of the following ratios (a) the mole fraction of water vapor in a given moist air sample to the: mole fraction in the air sample saturated at the same temperature and pressure; (b) the vapor: pressure in a given moist air sample to the vapor pressure in the air sample saturated at the same: temperature and pressure and (c) the humidity ratio in a given moist air sample to the humidity: ratio in the air sample saturated at the same temperature and pressure. There are no units.

Removable and Reusable Covers: What are Removable and Reusable Covers? Insulation materials or pads, enclosed in a fabric or metal (mesh, or sheet), designed to be readily: removed and reinstalled.

Resiliency: What is Resiliency (Thermal)? Thermal Resiliency is the property of a material that enables it to recover its original shape and thickness after compression.

Resistance to Acids, Caustics, and Solvents: Define Resistance to Acids, Caustics, and Solvents? The ability of a material to resist decomposition by various acids, caustics and solvents to which: it may be subjected.

Resistance to Air Erosion: Define Resistance to Air Erosion? The ability of a material to resist erosion by air currents over its surface.

Resistance to fungal or bacterial growth: What is Resistance to fungal or bacterial growth? Is necessary in food or cosmetic process areas.

Resistance to ultraviolet light: Why consider Resistance to ultraviolet light? Significant if application is outdoors.

Resistance, Abrasion: What is Abrasion Resistance? The ability to withstand scuffing, scratching, rubbing or wind-scouring.

Resistance, Freeze-Thaw: What is Freeze-Thaw Resistance? Resistance to cycles of freezing and thawing that could affect application, appearance or: performance.

Resistance, Impact (Toughness): What is Impact Resistance? Ability to withstand mechanical blows or shock without damage seriously affecting the: effectiveness of the material or system.

Resistance, Thermal (R-value): What is Thermal Resistance? A measure of the ability to retard heat flow rather than the ability to transmit heat. R-value is the: numerical reciprocal of “U” or “C,” thus R = 1/U or 1/C. Thermal resistance R-value is used in: combination with numerals to designate thermal resistance values: R-11 equals 11 resistance: units. The higher the “R,” the higher the insulating value. The I-P units are °F – ft2 – hr / Btu; the: SI units are °C – m2 / W.

Resistivity, Thermal (r): What is Thermal Resistivity? The quantity determined by the temperature difference, at steady state, between two defined: parallel surfaces of a homogeneous material of unit thickness, that induces a unit heat flow rate: through a unit area. (r in SI units: m K/W.) (r in inch-pound units: h ft F/Btu or, h ft ² F/Btu in.).

Retrofit: What is an insulation Retrofit? The application of additional insulation over existing insulation, new insulation after old insulation has been removed, or new insulation over existing, previously uninsulated surfaces.

Return Air Duct: What is a Return Air Duct? A duct carrying air from a conditioned space to the mixing air duct or plenum unit.

Return Air: What is Return Air? Air returned from conditioned spaces to an air-handling unit.

Rigid Wrap-around Insulation: What is Rigid Wrap-around Insulation? Segments of insulation material that have been adhered to a facing giving rigid insulation: materials flexibility of application.

Rigidity: What is Rigidity? The property of a material that opposes any tendency for it to bend (flex) under load.

Riser: What is a Riser? The vertical portion of a main, branch or runout.

Rock Wool (Mineral Wool): What is Rock Wool? A synthetic vitreous fiber insulation made by melting predominantly igneous rock and other: inorganic materials, and then physically forming the melt into fibers. See Mineral Wool.

R-Value (Thermal Resistance): What is R-Value? See Resistance, thermal.


Saddle: What is a Pipe Saddle? An insulated pipe saddle is a rigid support for piping or equipment with allowance for insulation.

Sample: What is a Sample? A group of items, observations, test results, or portions of material, taken from a large collection: of items, observations, test results, or quantities of material, which serves to provide information: that may be used as a basis for making a decision concerning the larger collection.

Sandwich Construction: What is Sandwich Construction? A composite composed of lightweight core material (usually honeycomb or foamed plastic) to which two relatively thin, dense, high-strength, functional, or decorative skins (also called faces) are adhered.

Saturation: What is Saturation? Saturation is the condition of co-existence in stable equilibrium of a vapor and a liquid or a vapor and a solid of the same substance.

SBCCI: What is SBCCI? Southern Building Code Congress, International.

Score: What is to Score? To cut grooves in rigid insulation so that it may be cracked and fitted to round or irregular: surfaces.

Scrim: What is Scrim? A low-cost reinforcing fabric made from continuous filament yarn in an open-mesh construction. Used in the processing of tape or other B-stage material to facilitate handling. Also used as a carrier of adhesive, to be used in secondary bonding.

Seal: What is to Seal? To make water-tight or airtight.

Sealant: What is a Sealant? Sealants in insulation function primarily as water and vapor seals. They may also be used as: adhesives, and for expansion joints for metal, masonry, cellular glass, etc. They must exhibit low: shrinkage, excellent adhesion and permanent flexibility.

Sealer: What is a Sealer? A liquid coating used to prevent excessive absorption of finish coats into porous surfaces.

Secondary Bonding: What is Secondary Bonding? The joining together, by the process of adhesive bonding, two or more pre-cured composite parts, during which the only chemical or thermal reaction occurring is the curing chemical or thermal reaction occurring is the curing of the adhesive itself of the adhesive itself. Requires careful preparation of each previously cured substrate at the bonding surfaces substrate at the bonding surfaces. Usually requires well designed fixturing to align & clamp parts during processing parts during processing. Re-heating previously cured substrates can be risky.

Securements: What are Securements? Any device, wire, strap or adhesive used to fasten insulation into its service position and hold it there.

Self-Extinguishing: What is Self-Extinguishing? Self-extinguishing is the property of a material that enables it to stop its own ignition after external ignition sources are removed.

Service Temperature Limits: What is the Service Temperature Limit? The temperature to which the material may be subjected during continuous operation or intermittent exposure.

Sharp freezer: What is a Sharp freezer? In cold-storage practice, a freezer room generally operating at -10°F or lower.

Shear Modulus: What is Shear Modulus? Shear modulus, sometimes referred to as the modulus of rigidity, is defined as the ratio of shear stress to the shear strain. Shear modulus is usually measured in ksi (kips per square inch) or GPa (gigapascals). 

Shear Strength: What is Shear Strength? The maximum shear stress that a material is capable of sustaining. Shear strength is calculated from the maximum load during a shear or torsion test and is based on the original cross-sectional area of the specimen.

Shelf Life: What is Shelf Life? The length of time a material, substance, product, or reagent can be stored under specified environmental conditions and continue to meet all applicable specification requirements and/or remain suitable for its intended function.

Shield: What is a Shield? Metal protector to prevent crushing of insulation at pipe hangars.

Shrinkage: What is Shrinkage? The relative change in dimension from the length measured on the mold when it is cold to the length of the molded object 24 hours after it has been taken out of the mold.

Slag Wool: What is Slag Wool? A type of inorganic, fibrous insulation manufactured from blast furnace slag.

Smoke Density: What is Smoke Density? The amount of smoke given off by the burning material compared to the amount of smoke given: off by the burning of a standard material.

Smoke Development: What is Smoke Development? Smoke Development is the characteristic of a material to emit smoke when exposed to flame or fire. Building codes generally require a smoke development rating of 50 or less, as measured per ASTM E84. Other codes require a rating of 450 or less, which meets Class 1 requirements. Smoke development can also be measured per UL723.

Soaking Heat: What is Soaking Heat?  A test condition in which the specimen is completely immersed in an atmosphere maintained at a: controlled temperature.

Solar Resistance What is Solar Resistance? Solar Resistance is 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: What is Solids Content? The percentage of the non-volatile matter in adhesives, coatings or sealants. It may be based on: weight or volume.

Solvent: What is a Solvent? Any substance, usually a liquid, that dissolves another substance.

Sound Absorption Coefficient (SAC): What is Sound Absorption Coefficient? The percentage of sound energy incident on the surface of a material that is absorbed by the: material.

Sound Transmission Class (STC): What is Sound Transmission Class? A single number rating based on sound transmission loss measurements of a partition between: adjacent closed rooms.

Sound Transmission Loss (STL): What is Sound Transmission Loss? The reduction in level measured in decibels as sound energy passes through a material or: composite construction.

Specific Gravity: What is Specific Gravity? The density (mass per unit volume) of a material divided by that of water at a standard temperature.

Specific Heat What is Specific Heat? Specific Heat is the heat absorbed (or given up) by a unit mass of a substance when its temperature is increased (or decreased) by 1 degree. Or the ratio of the amount of heat required to raise unit mass of a material 1 degree to that required to raise unit mass of water 1 degree at some specified temperature.

Sprayed-on Insulation: What is Sprayed-on Insulation? Insulation of the fibrous or foam type that is applied to a surface by means of power spray: devices.

SSL: What is a Self-sealing lap (SSL)? A self-sealing-lap is typically an adhesive overlap of the vapor barrier wrap (over pipe insulation) to seal vapor barrier (or potentially jacket) without using strips of tape.

Standard Deviation: What is a Standard Deviation? A measure of dispersion of data from the average. The root means square of the individual deviation from the average.

Standing Seam: What is a Standing Seam? Folded configuration of jacketing to achieve watershed for the top flat surfaces of ductwork, vessels, or tanks. Also used to provide rigidity.

Steady State (Thermal): What is Thermal Steady State? 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): What is a Duct Flange Stiffener? 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.

Stiffness: What is Stiffness? A measure of modulus. The relationship of load and deformation. The ratio between the applied stress and resulting strain. A term often used when the relationship of stress to strain does not conform to the definition of Young's modulus.

Strainer: What is a Strainer? A filter or sieve used in fluid piping to trap scale and other entrained particles.

Structural Adhesive: What is Structural Adhesive? Adhesive used for transferring required loads between adherends exposed to service environments typical for the structure involved.

Structural Bond: What is a Structural Bond? A bond that joins basic load-bearing parts of an assembly. The load may be either static or dynamic.

Structural Insulated Panel Manufacturers: Who manufactures Structural Insulated Panels (SIPs)? An internet search of the keyphrase results in dozens of returns.

Structural Insulated Panel Load: How much load could a Structural Insulated Panel take? The strengths of a SIP generally depend on the external material (wood or metal), the type of insulant, and the thickness.

Structural Insulated Panel Definition: What is a Structural Insulated Panel (SIP)? A structural insulated panel, or structural insulating panel, (SIP), is a form of sandwich panel used in the construction industry. It is structural to the extent the SIP can form the wall of a 1-2 story building without or with minimal additional wood or metal studs. The exterior of the SIP is generally either wood (e.g. OSB or plywood) or metal. The insulation is typically expanded polystyrene or polyisocyanurate.

Supply Air Duct: What is a Supply Air Duct? A duct that carries conditioned air from air supply units to room diffusers or grilles.

Support (Insulation): What is an Insulation Support. A mechanical device that carries the weight of insulation.

Surface Coefficient: What is the Surface Coefficient? The ratio of the steady-state heat exchange rate (time rate of heat flow per unit area of a: particular surface by the combined effects of radiation, conduction, and convection) between a: surface and its external surrounding (air or other fluid and other visible surfaces) to the: temperature difference between the surface and its surroundings. (See conductance, film).

Surface Conductance: What is Surface Conductance? Surface Conductance (h) is the amount of heat transmitted by radiation, conduction, and convection from a surface to the fluid surrounding it, or vice versa, in one hour for each square foot for a temperature difference of 1 degree between the surface and the fluid. Usually expressed as Btu/hr., sq.ft., F.


Tack: What is Tack? 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: What is Tear Strength? The property of a material that enables it to resist being pulled apart by opposing forces.

Temperature Dry-bulb: What is Temperature Dry-bulb? Dry-bulb Temperature is sometimes called ambient or sensible temperature and it is the temperature of a gas or mixture of gases as measured by a transducer that remains dry. The transducer may be a thermometer, thermocouple, resistance bulb or any other temperature measuring device. To be truly accurate, it should be shielded from radiation or corrected for it.

Temperature Wet-bulb: What is Temperature Wet-bulb? Wet-bulb Temperature is the temperature indicated by a wet-bulb transducer when used according to accepted standards. Technically, the thermodynamic wet-bulb temperature is the temperature at which liquid or solid water, by evaporating into air, can bring the air to saturation adiabatically at the same temperature.

Temperature: What is Temperature? Temperature is the thermal state of matter as regards its tendency to communicate heat to matter in contact with it. If there is no difference in temperature, no heat will flow on contact.

Template: What is a Template? A pattern used as a guide for cutting and laying plies, or vapor barrier sheets.

Tensile Strength: What is Tensile Strength? The maximum load or force per unit cross-sectional area, within the gage length, of the specimen. The pulling stress required to break a given specimen.

Test Specimen: What is a Test Specimen? The portion of a test unit needed to obtain a single test determination.

Thermal Capacity: What is Thermal Capacity? The quantity of heat required to change the temperature of the body one degree. For a: homogeneous body, it is the product of mass and specific heat. For a nonhomogeneous body, it is: the sum of the products of mass and specific heat of the individual constituents. (May also be: seen as heat capacity.)

Thermal Conductivity: What is Thermal Conductivity? The ability of a material to conduct heat.

Thermal Insulation System: What is a Thermal Insulation System? An Insulation System is an applied or installed thermal insulation complete with any accessories, vapor retarder, adhesives, coatings, mastics, joint sealers, and/or jacketing required.

Thermal Insulation System: What is a Thermal Insulation System? Applied or installed thermal insulation complete with any accessories, vapor retarder, and facing: required. 

Thermal Insulation: What is Thermal Insulation? Definition One: Insulation applicable within the general temperature range of –300 F to 1800 F. Definition Two: A material or assembly of materials used to provide resistance to heat flow.

Thermal Properties of Insulation: What are the Thermal Properties of Insulation? Usually expressed as C-value, K-value, R-value and U-value.

Thermoplastic: What is a Thermoplastic? Capable of being repeatedly softened by an increase of temperature and hardened by an increase in temperature. Applicable to those materials whose change upon heating is substantially physical rather than chemical and that in the softened stage can be shaped by flow into articles by molding or extrusion.

Thermoset: What is a Thermoset? A plastic that, when cured by application of heat or chemical means, changes into a substantially infusible and insoluble material.

Throat: What is a Throat? Inside radius of an elbow.

Toxicity: What is Toxicity? Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Must be particularly considered in food processing plants and potential fire hazard areas.

Traced: What is a Traced pipe? 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.

Transference, Thermal: What is Thermal Transference? The steady-state heat flow from (or to) a body through applied thermal insulation and to (or: from) the external surroundings by conduction, 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: What is Heat Transmission? The quantity of heat flowing through unit area due to all modes of heat transfer induced by the: prevailing conditions.

Transmittance, Thermal (U-value): What is Thermal Transmittance (U-value)? The combined thermal value of all the materials in an insulation system, air spaces, and surface air: films. The heat transmission in unit time through unit area of a material or construction and: boundary air films, induced by unit temperature difference between the environments on each: side. The I-P units are Btu / (hr – sq ft – deg F temperature difference) and the SI units are W /: (sq m – deg C temperature difference). Note: This heat transmission rate has been called the: overall coefficient of heat transfer.

T-Rating: What is the T-Rating? A rating usually expressed in hours indicating the length of time that the temperature on the nonfire side of a fire-rated assembly exceeds 325°F above its ambient temperature as determined by: ASTM E-814 (UL-1479).


“U": What is "U"? “U” designates the total or overall transmission of heat (Btu's) in 1 hour per square foot of area for a difference in temperature of 1°F between the air on one side to air on the other side of a structure.

UL: Underwriters Laboratories: What is the Underwriters Laboratories (UL)?  An independent materials testing company. UL provides testing, evaluation, and listing services for products having specific safety-related features. UL test standards generally are similar to ASTM International standards when both exist.

Ultrasonic Testing: What is Ultrasonic Testing? A nondestructive test applied to materials for the purpose of locating internal flaws or structural discontinuities by the use of high-frequency reflection or attenuation (ultrasonic beam).

Ultraviolet Light: What is Ultraviolet Light resistance? Resistance to ultraviolet light is significant if application is outdoors.

Urethane: What is a Urethane? Plastic foam of rigid polyurethane closed-cell rigid foam thermoset plastic. Urethanes are used in a wide array of applications, including as insulation in boards, pipe insulation, foamed-in-place, or composite substrates.


Vapor Barrier: What is a Vapor Barrier? In the context of pipe insulation, a Vapor Barrier is a non-permeable sheet wrapped over the insulation to prevent moisture/water infiltration across this boundary protecting the insulation. A vapor barrier is generally defined as having a permeance less than 0.01 Perms (grains/[ft2*hr*inHg]).

Vapor Drive: What is Vapor Drive? Moisture vapor drive occurs as warmer, more humid air is drawn to colder surfaces and seeks to penetrate (or "drive") into the insulation. Vapor drive is greatly influenced by temperatures; hotter water vapor is more effective at penetrating barriers than cooler water vapor.

Vapor pressure: What is Vapor pressure? Vapor Pressure is that part of the atmospheric pressure which is exerted by the water vapor present in the air.

Vapor Retarder: What is a Vapor Retarder? A Vapor Retarder has less resistance to water vapor intrusion that a Vapor Barrier, and should generally have less than 0.1 Perms (10x more than a Vapor Barrier)

Vent: What is a Vent? A small hole or shallow channel in a mold that allows air or gas to exit as the molding material enters.

Ventilating Air: What is Ventilating Air? Air supplied to or removed from any space by natural or mechanical means.

Ventilating Duct: What is a Ventilating Duct? Duct supplying or removing air by natural or mechanical means.

Vibration Resistance: What is Vibration Resistance? Vibration Resistance is the property of a material that indicates its ability to resist mechanical vibration without wearing away, setting or dusting.

Vinyl: What is Vinyl? The name of a class of resins or sheeting.

Viscosity: What is Viscosity? The tendency of a material to resist flow.

Voids: What are Voids? Air or gas that has been trapped and cured into a laminate. Porosity is an aggregation of microvoids. Voids are essentially incapable of transmitting structural stresses or nonradiative energy fields.

Volatiles: What are Volatiles? Materials, such as water and alcohol, in a sizing or a resin formulation, that are capable of being driven off as a vapor at room temperature or at a slightly elevated temperature.


Warp: What is a Warp? A change in dimension of a cured laminate from its original molded shape.

Warpage: What is Warpage? The change in the flatness of a material caused by differences in the temperature and/or humidity applied to opposite surfaces of the material.

Water Absorption: What is Water Absorption? The increase in weight of a material expressed as a percentage of its dry weight or volume after: immersion in water for a specified time.

Water Resistant: What is Water Resistant? Capable of withstanding limited exposure to water.

Water Vapor Diffusion: What is Water Vapor Diffusion? The process by which water vapor spreads or moves through permeable materials caused by a: difference in water vapor pressure.

Water Vapor Permeability: What is Water Vapor Permeability? 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 permeability is measured in perm inches.

Water Vapor Permeance: What is Water Vapor Permeance? 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 permeance is measured in units: of perm.

Water Vapor Pressure: What is 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 Resistance: What is Water Vapor Resistance? The steady state vapor pressure difference that induces unit time rate of vapor flow through unit: area of a flat material (or construction that acts like a homogeneous body) for specific conditions: of temperature and relative humidity at each surface.

Water Vapor Retarder (Barrier): What is a Water Vapor Retarder (Barrier)? A material or system that significantly impedes the transmission of water vapor under specified: conditions.

Water Vapor Transmission Rate (WVTR): What is the Water Vapor Transmission Rate? The steady state 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. The I-P: units are lbs / hr – ft2; the SI units are grams / hr – m2.

Water Vapor: What is Water Vapor? Water Vapor is the gaseous state of liquid water. This gas phase of water and is colorless, odorless, and tasteless.

Waterproof: What is Waterproof? Impervious to prolonged exposure to water or water entry.

Weather Barrier: What is a Weather Barrier? A breather jacket or coating which allows passage of water vapor yet protects from atmospheric conditions.

Wetting and Adhesion, Surface: What is Surface Wetting and Adhesion? The mutual affinity of and bonding between finish and the surface to which it is applied.

Wicking: What is Wicking? A wicking material transports condensed water to the outside of the system for evaporation to the atmosphere. Wicking is the action of capillary action.


XPS vs. EPS: Why XPS vs. EPS? Both EPS and XPS are white, rigid, thermoplastic foams, typically manufactured in densities ranging from 0.8 to 2 pcf. As the name indicates, EPS is expanded into very large blocks. XPS is extruded, thus the billets are much smaller. XPS is considerably more expensive than EPS, yet the physical properties of each (at comparable densities) are actually quite similar, yet often advertised as quite different. Often the differences are due to the ASTM testing protocols and the fact that XPS may have “skins” on the surface prior to fabrication that affect, for example, water absorption. Also, whereas EPS is often advertised as wicking away any absorbed moisture, XPS does not.