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Glossary of Terms
OCTAVE BAND: A frequency band with an upper frequency limit equal to twice the lower limit.
OFFSET: A change in location or direction of a main, branch or runout. It may be located in a riser or horizontal run of piping or duct.
ONE COAT CEMENT: A mixture of various insulation fibers, fillers and binders with hydraulic cement. The material can be applied directly to fittings to match adjacent insulation thickness in one application and smoothed to provide a hard finish.FLAME RETARDANT: An added substance that inhibits the initiation and/or spread of flame.
or finishes for insulation materials using eyelets, hooks, wire, cord, etc.
PANEL: A prefabricated unit of insulation and lagging.
PATCHING: Repair or restoration of damaged existing insulation. See Reinsulate.
PERLITE: A material composed of volcanic rock and produced in expanded cellular form or loose fill.
PERM: The measure of vapor transmission in grains of water through one sq. ft. of a membrane in an hour at one inch mercury pressure difference.
PERMEABILITY: The property of a substance which permits passage of water vapor and is equal to the permeance of an inch (1) of thickness of the substance. Permeability is measured in Perm inches. Top of Page
PERMEANCE (Perms): 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.
PERSONNEL PROTECTION: Insulation installed for the purpose of protecting personnel from hot surfaces.
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. (pH = Potential of Hydrogen)
PHENOLIC FOAM: A foamed insulation made from resins of phenols condensed with aldehydes.
PIN WELD: Attachment of insulation anchor pins to ductwork or equipment usually by capacitor discharge welding.
PINHOLE: Very small hole through a mastic or coating.
PIPE: A circular conduit for the conveyance of liquids or semisolids.
PLENUMS: Enclosures 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.
POINTING: Applying or shaping cements or mastic with a small pointed trowel.
POLYETHYLENE: A closed cell material used for insulation. Top of Page
POLYISOCYANURATE: Polyisocyanurate (polyiso or PIR) is a closed cell, thermoset plastic rigid foam formed spontaneously when isocyanate and polyether are mixed in the presence of a catalyst that helps the molecules to rearrange and join, and a blowing agent to create the closed cells. Polyisocyanurate foam is similar in physical form to polyurethane foam but has improved dimensional stability over a wider operating temperature range, as improved insulating characterisitics and fire/smoke resistance. Polyisocyanurate's usage is increasing since it is the only plastic insulation to pass UL 1256, "Fire Test of Roof Deck Constructions," and FM 4450, "Class 1 Insulated Steel Deck Roofs," fire tests without a thermal barrier.
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, we get the synthetic resin polyethylene.
POLYMER: A high molecular weight substance, natural or synthetic, which can be represented as a repeated small unit (monomer). A copolymer contains more than one type of monomeric unit.
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: A closed cell material used for insulation.
POLYSTYRENE: A resin made by polymerization of styrene as the sole monomer.
POLYURETHANE: A resin made by the condensation of organic isocynates with compounds or resins that contain hydroxyl groups. Top of Page
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): A polymerized vinyl compound using chloride.
POLYVINYL FLUORIDE (PVF): A polymerized vinyl compound using fluoride.
PRESSURE SENSITIVE TAPE: A tape with adhesive preapplied.
PUMPED CONDENSATE (Discharge): Condensate in liquid state from condensate receivers to feed water heaters, deaerators or boilers.
PUNCTURE RESISTANCE: That property of a material which enables it to resist punctures or perforations under blows or pressure from sharp objects.
PUNKING: Burning out of binder due to excessive heat.
"R" VALUE (Resistance): A measure of the ability to retard heat flow rather than the ability to transmit heat. "R" is the numerical reciprocal of "U" or "C", thus R = 1/U or 1/C. Thermal resistance "R" 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.
RADIANT HEAT: Heat radiating from a heated body, as distinguished from that transmitted by an intervening body.
RADIATION: The passage of heat from one object to another without warming the space between.
REFLECTIVE INSULATION: Insulation composed of closely spaced sheets of either aluminum or stainless steel which obtains its insulating value from the ability of the sheets to reflect a large part of the radiant energy incident on them.
REFRACTORY INSULATION: Insulation of extremely high temperatures above 815.5C (1500F). Top of Page
REFRACTORY MATERIALS: Materials, usually fibers, which do not significantly deform or change chemically at high temperatures. Manufactured in blanket, block, brick or cement form.
REINFORCING CLOTH OR FABRIC: A woven cloth or fabric of glass or resilient fibers used as reinforcement to a mastic.
REINSULATE: To repair insulation to its former condition. (If insulation is to be removed and replaced, it should be so stated.)
REMOVABLE AND REUSABLE COVERS: Insulation materials pads, enclosed in a fabric or metal (mesh, or sheet), designed to be readily removed and reinstalled.
RESILIENCY: That property of a material which enables it to recover its original shape and thickness after compression.
RESISTANCE (THERMAL) "R": The overall resistance of a "system" to the flow of heat.
RESISTANCE TO ACIDS, CAUSTICS, AND SOLVENTS: The property of a material to resist decomposition by various acids, caustics and solvents to which it may be subjected.
RESISTANCE TO AIR EROSION: The property which indicates the ability of an insulation material to resist erosion by air currents over its surface.
RESISTANCE to ultraviolet light: Significant if application is outdoors.
RESISTANCE to fungal or bacterial growth: Is necessary in food or cosmetic process areas.
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: A duct carrying air from a conditioned space to the mixing air duct or plenum unit. Top of Page
RETURN AIR: Air returned from conditioned spaces to an air handling unit.
RIGID WRAP-AROUND INSULATION: Segments of insulation material which have been adhered to a facing giving rigid insulation materials flexibility of application.
RIGIDITY: That property of a material which opposes any tendency for it to bend (flex) under load.
RISER: The vertical portion of a main, branch or runout.
ROCK WOOL: A type of inorganic fibrous insulation manufactured from basalt or other types of rock mined out of the earth.
RUBBERIZED ASPHALITIC VAPOR RETARDER: Polymer modified bituminous jacketing.
RUN-OUT: Piping or duct work from or to a branch or main serving one: (a. plumbing unit or fixture connection, (b. heating and/or cooling unit, coil, convector, unit heater, fin tube, equipment connection, etc. (c. HVAC diffuser or register or (d. process equipment connection.
"S" CLIP: A device (in the shape of an "s") for supporting insulation, bands or jacketing.
SADDLE: Rigid support for piping or equipment with allowance for insulation.
SBCCI: Southern Building Code Congress, International
SCORE: (v.) To cut grooves in rigid insulation so that it may be cracked and fitted to round or irregular surfaces.
SEAL: (v.) To make water or air tight. Top of Page
SEALANT: Sealants in insulation work 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: A liquid coating used to prevent excessive absorption of finish coats into porous surfaces.
SECUREMENTS (Insulation): Any device, wire, strap or adhesive used to fasten insulation into its service position and hold it there.
SELF-EXTINGUISHING: That property of a material which enables it to stop its own ignition after external ignition sources are removed.
SERVICE TEMPERATURE LIMITS: This refers to the temperature to which the jacket or coating may be subjected when applied over insulation. It does not refer to the operating temperature of the equipment, vessel or pipe.
SHEAR 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: The ability of a material to resist cleavage, or the maximum shear stress that can be sustained by a material before rupture.
SHELF LIFE: The period of time during which a packaged adhesive, coating, or sealant can be stored under specified temperature conditions and remain suitable for use.
SHIELD: Metal protector to prevent crushing of insulation at hangars.
SHRINKAGE: That property of a material which indicates its proportionate loss in dimensions or volume due to temperature changes or aging. Significant on applications involving cements and mastics.
SLAG WOOL: A type of inorganic, fibrous insulation manufactured from blast furnace slag.
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.
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. Top of Page
SOLAR RESISTANCE: The property of a material to resist decomposition by the ultraviolet rays from the sun or the passage of radiant heat from the sun.
SOLIDS CONTENT: The percentage of the nonvolatile matter in adhesives, coatings or sealants. It may be based on weight or volume.
SOLVENT: Any substance, usually a liquid, which dissolves another substance.
SOUND ABSORPTION COEFFICIENT (SAC): The percentage of sound energy incident on the surface of a material that is absorbed by the material. Must be considered when sound attenuation is required, as it is in radio stations, some hospital areas, etc.
SOUND TRANSMISSION CLASS (STC): A single number rating based on sound transmission loss measurements of a partition between adjacent closed rooms.
SOUND TRANSMISSION LOSS (STL): The reduction in level measured in decibels as sound energy passes through a material or composite construction. Sound transmission loss value is significant when constructing a sound barrier.
SPECIFIC HEAT: The ratio of the amount of heat required to raise a unit mass of a material 1 degree, to that required to raise a unit mass of water 1 degree at some specified temperature.
SPRAYED-ON INSULATION: Insulation of the fibrous or foam type which is applied to a surface by means of power spray devices.
SSL: Self sealing lap.
STANDING SEAM: Folded configuration of jacketing to achieve watershed for the top flat surfaces of ductwork, vessels, or tanks. Also used to provide rigidity. Top of Page
STIFFENER (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 to prevent vibration.
STRAINER: A filter or sieve used in fluid piping to trap scale and other intrained particles.
STUD WELD: Attachment of insulation anchors to tanks or vessels by means of drawn arc welding.
STUD: Used to hold heavy insulation and/or panels in place. Applied with arc welder, studs differ from pins in that they are generally 6.25mm (1/4") or greater in diameter.
SUPPLY AIR DUCT: A duct which carries conditioned air from air supply units to room diffusers or grilles.
SUPPORT (Insulation): A mechanical device which carries the weight of insulation.
SURFACE TEMPERATURE (Ta): The surface temperature of finished insulation.
"T" RATING: A rating usually expressed in hours indicating the length of time that the temperature on the non-fire side of a fire-rated assembly exceeds 162.8C (325F) above its ambient temperature.
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: That property of a material which enables it to resist being pulled apart by opposing forces. Top of Page
TEMPERATURE LIMITS: The upper and lower temperatures at which a material will experience no change in its properties.
THERMAL CONDUCTANCE "C": The rate of heat flow for the actual thickness of a material.
THERMAL CONDUCTIVITY "K": The rate of heat flow based on 25 mm (one inch) thickness.
THERMAL INSULATION: Insulation applicable within the general temperature range of -156.7C to 815.6C (-250F to 1500F).
THERMAL PROPERTIES OF INSULATION: Usually expressed as "C" value, "K" value, "R" value and "U" value.
THERMAL RESISTANCE "R": The overall resistance of a "system" to the flow of heat.
THERMAL TRANSMITTANCE "U": The overall conductance of heat flow through a "system".
THROAT: Inside radius of an elbow.
TOXICITY: Must be considered in food processing plants and potential fire hazard areas.
TRACED: 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.
TRANSMITTANCE (THERMAL) "U": The overall conductance of heat flow through a "system".
TUBE TURN ( Bend): Pipe, factory or field formed, to a predetermined radii.
"U" VALUE (TRANSMITTANCE): The combined thermal value of all the materials in a building section, air spaces and surface air films. It is the time rate of heat flow and usually expressed as Btu/(h).
UL: Underwriters Laboratories. An independent materials testing company. UL provides testing, evaluation, and listing services for products having specific safety-related features. UL test standards generally conform to ASTM standards when both exist.
ULTRAVIOLET LIGHT: Resistance to ultraviolet light is significant if application is outdoors.
UNDERGROUND: Insulation applied on piping and equipment located below grade and in direct contact with the surrounding soil.
UNION: A coupling device for connecting pipes. Top of Page
URETHANE: Plastic foam of rigid polyurethane closed cell insulation in board, pipe insulation or foamed-in-place form.
VALVE: Any of various devices that regulate liquid or gas flow by opening, closing or obstructing its passage.
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-RETARDER JACKET: Any material or composite meeting the requirements of a vapor retarder and used for the finish of insulation material. It may be factory furnished or field applied.
VAPOR-RETARDER: Vapor retarders inhibit moisture from traveling to lower temperature surfaces where it may condense. A vapor retarder material is usually a jacket or coating.
VENTILATING AIR: Air supplied to or removed from any space by natural or mechanical means.
VENTILATING DUCT: Duct supplying or removing air by natural or mechanical means.
VERMICULITE: Hydrated magnesium-aluminum-iron silicate used as fill insulation.
VERTICAL PIPING: Any piping which is less than 45 degrees from the vertical plane.
VIBRATION RESISTANCE: The property of a material which indicates its ability to resist mechanical vibration without wearing away, settling or dusting.
VINYL: The name of a class of resins. Top of Page
WARPAGE: The change in the flatness of a material caused by differences in the temperatures and/or humidities applied to opposite surfaces of the material.
WASHER: (Insulation/Clip) Self-locking device applied to anchor pins to secure the insulation in place.
WATER ABSORPTION: The increase in weight of a test specimen expressed as a percentage of its dry weight after immersion in water for a specified time.
WATER RESISTANT: Capable of withstanding limited exposure to water.
WATER VAPOR PERMEABILITY: The property of a substance which permits passage of water vapor and is equal to the permeance of an inch (1) thickness of the substance. Permeability is measured in Perm inches.
WATER VAPOR 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. For more information, click here.
WATERPROOF: (adj.) Impervious to prolonged exposure to water.
WATT: Both the inch pound and metric unit for heat flow.
WEATHER/VAPOR-BARRIER: A jacket or coating which does not allow the passage of vapor and protects from atmospheric conditions.
WEATHER/VAPOR-RETARDER: A jacket or coating which retards the passage of vapor and protects from atmospheric conditions.
WEATHER-BARRIER: A breather jacket or coating which allows passage of vapor yet protects from atmospheric conditions.
WELD PIN: Made of carbon steel, stainless steel or aluminum in various lengths for attaching insulation to metal surfaces. Applied by welding.
WICKING: Action of absorbing by capillary action.