Spray Foam Glossary


See Air Barrier Association of America

A material that is applied in conjunction with a building component (such as a wall, ceiling or sill plate) to prevent the movement of air through that component.  

  ABAA is an organization that promotes the use of air barriers; offers technical specifications to designers; and offers on-site inspections. It develops standards of proficiency in the industry through the ABAA On-Site Quality Assurance Program. ABAA offers training to installers, estimators, managers and administrators on the contractor side, as well as AIA accredited courses for design professionals.  Some types of SPF are recognized as an air-barrier materials via product testing and certified contractors.

The assembly of components used in building construction to create a plane of air tightness throughout the building envelope and to control air leakage.  

AIR IMPERMEABLE: An insulation having an air permanence at a specific thickness that is equal to or less than 0.02 L/s•m2 at 75 Pa pressure differential (0.004 ft3/ft2•min at 1.57 lb/ft2) tested in accordance with ASTM E 2178 or E 283.

AIR LEAKAGE: The uncontrolled flow of conditioned air through gaps, cracks or holes in the building envelope or its components.  

AMBIENT TEMPERATURE: The surrounding air temperature.  

ATTIC – VENTED: The unfinished space between the ceiling assembly of the top story and the roof assembly that has openings to the outside adequate to promote natural or mechanical air exchange.

ATTIC – UNVENTED: The unfinished space between the ceiling assembly of the top story and the roof assembly that has no openings to the outside adequate to promote natural or mechanical air exchange.  


BIO-CONTENT: Materials which are natural, non-petroleum based, that have harvest cycles of 10 years or less (per LEED [see also] standards).  Bio-Content is determined by ASTM D 6866 where by the percentage of new carbon atoms are measured in relationship to old carbon atoms.  All Bio-content claims shall be based on the finished foam product and not the individual raw materials.

BLOWING AGENT: A chemical additive formulated into either the A-side or B-side which creates bubbles that are trapped in the polyurethane as it solidifies to form foam cells. The gas produced from the blowing agent contributes to over 97% of the volume of polyurethane foam.  The blowing agent can be physical or reactive in nature. The physical blowing agents (for example, liquid fluorocarbon) vaporize with the heat of the polyurethane reaction, where a reactive blowing agent (for example, water) reacts with one of the other chemicals in the formulation to produce a gas during the reaction (for example, water and isocyanate yields carbon dioxide).

BOARD-FOOT: A volume measurement of materials such as SPF insulation, board-stock insulation and lumber. One board-foot equals a volume of 12 inches by 12 inches by 1 inch. Abbreviated bd•ft. (1 bd•ft = 1/12 cubic ft = 0.00236 m3).

BUILDING ENVELOPE: The exterior shell of the building that provides structural integrity and control of heat, air and moisture.



CONDENSATION: The action of a vapor converting into a liquid.  

CPI: Center for the Polyurethanes Industry, a division of the American Chemistry Council, whose members include producers or distributors of chemicals and equipment used to make polyurethane products.

cPVC: Chlorinated polyvinylchloride. A thermoplastic resin used to form sprinkler and high temperature water piping and fittings.

CRAWLSPACE, VENTED: A low space beneath the floor of a building, giving workers access for the service of utilities, which is ventilated to the exterior of the building envelope. Insulation is typically installed in the crawlspace overhead (beneath the floor of the building).

CRAWLSPACE, UNVENTED: A low space beneath the floor of a building, giving workers access for the service of utilities, which is not ventilated to the exterior of the building envelope. Insulation is typically installed in the crawlspace walls. Also known as “conditioned crawlspace.”

CURE TIME: The time required for a foam to achieve substantial completion of reaction


DEGRADATION: The deterioration of a substance caused by contact with its environment.  

DEW POINT: The temperature at which a vapor begins to condense.  

DIISOCYANATE: An organic chemical compound having two reactive isocyanate (N=C=O) groups; used in the production of polyurethane foams and polyurethane coatings.  



EVALUATION SERVICE REPORT: An evaluation report presenting the findings of ICC-ES (International Code Council Evaluation Service) as to the compliance with building code requirements of the subject of the report—a particular building product, component, method or material.


FIREBLOCKING: Building materials or constructions designed, approved and installed to resist the free passage of flame to other areas of the building through concealed spaces.

FIRESTOP: A material, device or construction, installed to resist for a prescribed time period, the passage of flame and heat through openings in a protective membrane in order to accommodate cables, cable trays, conduit, tubing, pipes or similar items.

FLAME RETARDANT: A substance that is added to a coating or polyurethane foam formulation to reduce or retard its tendency to burn.  

FLAME SPREAD: Per ASTM E-84, a measure of relative combustibility. The flame spread of a tested material is rated relative to fiber cement board (flame spread = 0) and red oak flooring (flame spread = 100).  

FLAMMABILITY: Relative ability of a material to support combustion as expressed by its flash point.  

FLASH IGNITION TEMPERATURE: The lowest temperature of a material required to initiate combustion in the presence of a spark or flame.



HOME ENERGY RATING SYSTEM (HERS):  HERS is a rating system for residential energy efficiency developed by EnergyStar and RESNET.  Through a comprehensive design review and analysis, it incorporates HVAC, building enclosure and orientation, as well as appliance and lighting selection. A HERS score of 0 indicates a net zero-energy home, while a HERS score of 100 represents the energy consumption of  home built to the 2003 IECC model energy code.  A maximum HERS score of 70 is required for a home to be EnergyStar compliant.

HYBRID INSULATION: A combination of insulation types typically arranged so the SPF insulation acts as an air barrier and/or a vapor retarder, and the other insulation type contributes by adding R-Value.



IGNITION BARRIER: A building code permitted protective covering applied over foam plastic insulations, including SPF, in attics and crawlspaces to increase the time it takes for the foam plastic to become involved in a fire. Ignition barriers do not provide as much fire protection as THERMAL BARRIERS (see also). The building code restricts the use of ignition barriers to attics and crawlspaces of limited access (check the local building code for exact requirements).


INTERNATIONAL CODE COUNCIL (ICC): The ICC formed in 1994 by the merger of BOCA (see also), ICBO (see also) and SBCCI (see also) to promulgate a common set of model building codes. Codes developed by the ICC are commonly referred to at the I-Codes (see also).

INTUMESCENT COATING: Coatings which are formulated to swell and char when exposed to heat. When applied to a combustible (or non-combustible) substrate, this “swollen char” is designed to insulate the substrate from the heat source, thus reducing the potential and/or increasing the time that the substrate becomes involved in a fire.

ISOCYANATE: A highly reactive organic chemical containing one or more isocyanate   (-N=C=O) groups. A basic component in polyurethane foam chemical systems and some polyurethane coating systems.    




LEADERSHIP IN ENERGY AND ENVIRONMENTAL DESIGN (LEED):  Commonly referred to as LEED, it is a prominent green building rating system, developed by the U.S. Green Building Council (USGBC), that provides a suite of standards for environmentally sustainable construction. Energy efficiency, through proper application of insulation and air sealing technologies, plays an important role in the LEED evaluation process.


LOW-DENSITY SPF (Open-cell SPF, ocSPF): A type of spray polyurethane foam expanded with reactive blowing agents to yield a semi-rigid cellular structure and a density between 8 and 22 kg.m3 (0.5 and 1.4 lb/ft3).


MATERIAL SAFETY DATA SHEET (MSDS): A standard formatted information sheet prepared by a material manufacturer which describes the potential hazards, physical properties, and procedures for safe use of a material.

MEDIUM-DENSITY SPF (Closed-cell SPF, ccSPF): A type of spray polyurethane foam expanded with non-reactive blowing agents to yield a rigid cellular structure. It is characterized by a predominance of closed-cells and a density between 1.5 and 2.5 lb. per cubic foot.

MILDEW: A superficial coating or discoloring of an organic material due to fungal growth, especially under damp conditions.

MOLD: Fungal growths often resulting in deterioration of organic materials, especially under damp conditions.  


NFPA: National Fire Protection Association. The NFPA promotes safety from fire and other hazards through the promulgation of codes, standards, research, training and education.



OVERSPRAY: (1) Airborne spray loss of polyurethane foam or coatings. (2) Undesirable depositions of airborne spray loss.  


PERM RATING: The permeance of a material. Breather materials have relatively high perm ratings, vapor retarders have relatively low perm ratings, vapor barriers have essentially zero (negligible) perm ratings. See also: VAPOR RETARDERS.

PERMEABILITY, AIR: The rate at which air will diffuse through a unit area of material induced by a unit differential in air pressure. Air permeability is generally used as a descriptive term and specific values are not usually reported. See PERMEANCE, AIR.

PERMEABILITY, WATER VAPOR: The rate at which water vapor will diffuse through a unit thickness and area of material, induced by a unit differential in water vapor pressure. Permeability values are related to a common thickness and can be used to compare various materials. Units are usually Grains•in/ft2•hr•in Hg or Perm•in. SI unit for permeability is ng/s•m•Pa (1 perm•in = 1.46 ng/s•m•Pa).

PERMEANCE, AIR: The rate at which air can diffuse or leak through a unit area of material induced by a specific pressure differential (for example 75 Pa or 1.57 lb/ft2). ASTM E 2178 and ASTM E 283 are test methods used to measure air permeance. Units are L/s•m2 (ft3/min•ft2) with pressure reported as Pa (lb/ft2). See also: AIR IMPERMEABLE and AIR PERMEABLE.

PERMEANCE, WATER VAPOR: The rate at which water vapor will diffuse through a unit area of material induced by a unit differential in water vapor pressure. Permeance values are reported for specific thicknesses (usually recommended application thickness). Units are usually Grains/ft2•hr•in Hg or Perm. SI unit for permeance is ng/s•m2•Pa (1 perm = 57.4 ng/s•m2•Pa).

PERSONAL PROTECTIVE EQUIPMENT (PPE): Includes all protective equipment and supplies designed to protect employees from serious workplace injuries or illnesses resulting from contact with chemical, radiological, physical, electrical, mechanical, or other workplace hazards. Besides face shields, safety glasses, hard hats, and safety shoes, PPE includes a variety of devices and garments such as goggles, coveralls, gloves, vests, earplugs, and respirators.

PICTURE FRAMING: Outlining the perimeter of a stud wall cavity with spray polyurethane foam prior to filling the center.  

POLYURETHANES: Polyol and MDI react to form polyurethane.  When this reaction occurs multiple times a polyurethane molecule is created.  Many end-use products are created using polyurethane chemistry, including: rigid and flexible foams, rigid or flexible coatings, elastomers, structural materials, etc.  (See also AROMATIC, ALIPHATIC, ISOCYANATE, POLYOL, and RESIN)



R-VALUE: The resistance of a material to heat transfer. Insulators have relatively high R values. Units are ?K•m2/W (?F•ft2•hr/Btu).

RACKING TEST: Colloquial name for ASTM Standard E 72, “Standard Methods of Conducting Strength Tests of Panels for Building Construction.” ASTM E 72 tests a stud wall’s resistance to wind, seismic, and weight loads.  

RADIANT BARRIERS:  Typically in the form of a single highly-reflective sheet or coating (e.g., aluminum foil or metallized mylar) radiant barriers are applied as a component of the building enclosure to inhibit heat transfer by thermal radiation.  They do not provide resistance to heat transfer by conduction or convection.

RECYCLE CONTENT: The proportion of material (typically percentage by weight) in an end-use product that contains previously used materials.  Recycle content can be further classified as "post-industrial" or "post-consumer."  The former refers to re-use of by-product materials that are created during the manufacturing process, while the latter refers to waste materials that come from the consumer sector

RELATIVE HUMIDITY: The ratio of absolute humidity to saturation humidity, expressed as a per cent.  

RESIDENTIAL ENERGY SERVICES NETWORK (RESNET): is a trade association of energy raters (HERS Raters) serving the residential market.  This organization provides training and certification to home energy raters.  Certified home energy raters must evaluate the entire energy use of a residential building to become EnergyStar certified.

RESPIRATORY PROTECTION PROGRAM: An OSHA requirement whereby any employer who requires or permits employees to wear a respirator must have a written respiratory protection program. The written respirator program establishes standard operating procedures concerning the use and maintenance of respiratory equipment. In addition to having such a written program, the employer must also be able to demonstrate that the program is enforced and updated as necessary. (See CPI Publication AX246 “Model Respiratory Protection Program for Compliance with the Occupational Safety and Health Administration’s Respiratory Protection Program Standard 29 CFR § 1910.134.”)


SET OF FOAM: A container of A-side (MDI) and a container of B-side (polyol or resin blend) which can be combined through mixing equipment to form SPF. A set of foam consists of two containers, typically 55-gallon drums.

SMOKE DEVELOPED: The amount of smoke measured for a sample tested in the ASTM E 84 tunnel test when compared to inorganic reinforced cement board and select-grade red-oak flooring which have been arbitrarily established as zero and 100, respectively.

SPF: Acronym for Spray Polyurethane Foam.

SPFA: Spray Polyurethane Foam Alliance.

SPRAY POLYURETHANE FOAM (SPF): A foamed plastic material formed by the reaction of an isocyanate and a polyol and employing a blowing agent to develop a cellular structure. SPF may be a two-component reactive system mixed at a spray gun or a single-component system that cures by exposure to moisture. SPF can be formulated to have physical properties (such as density, compressive strength, closed cell content, and R-value) appropriate for the application requirements. Common uses of SPF include insulation, air barrier and roofing membrane.  

STACK EFFECT:  Also referred to as “chimney effect,” stack effect results from air density differences between building interiors and exteriors. During heating seasons, the stack effect results in higher relative pressures at the tops of buildings and lower relative pressures at the bases of buildings. These pressure differences can drive air infiltration/exfiltration. Proper sealing measures, such as air barriers formed by SPF foam and sealants can mitigate stack effect.

SUBSTRATE: The surface to which polyurethane foam is applied.  


TENSILE STRENGTH: The tensile (pulling or stretching) force necessary to rupture a material sample divided by the sample’s original cross sectional area. Units are usually kPa or psi or lb/in2.

THERMAL BARRIER: A material applied over spray polyurethane foam (and other foam plastics) designed to slow the temperature rise of the foam during a fire situation and delay its involvement in the fire. With few exceptions, building codes require that SPF be separated from interior spaces with a thermal barrier. Building codes require that thermal barriers for use with polyurethane foam: (1) limit the average temperature rise of the unexposed foam surface to no more than 139°C (250°F) after 15 minutes of fire exposure complying with ASTM E 119 or UL 263 standard time-temperature curve; and (2) will remain in place for 15 minutes based on a small room corner test.

THERMAL BRIDGE: A thermally conductive material which penetrates or bypasses an insulation system, such as a metal fastener or stud.  

THERMAL CONDUCTANCE (C): A unit of heat flow that is used for a specific thickness of material or for materials of composite construction, such as laminated insulation. C=k/thickness. Units are W/m2•?K (Btu/hr•ft2•?F).

THERMAL CONDUCTIVITY (k): The heat energy that will be transmitted by conduction through 1 square foot of 1 inch thick homogeneous material in one hour when there is a difference of 1 degree Fahrenheit perpendicularly across the two surfaces of the material. Units are W/m•?K  (Btu•in/hr•ft2•?F).

THERMAL RESISTANCE (R): An index of a material’s resistance to heat flow; it is the reciprocal of thermal conductance (C) or the thickness divided by THERMAL CONDUCTIVITY (k) (see also).  See also: R-VALUE.

THERMOSET: A polymer that irreversibly cures to its finished state through a catalytic reaction.  Unlike thermoplastic foam, a thermoset foam cannot be melted.  Polyurethane spray foam and polyisocyanurate board foam are examples of thermoset materials.

TINT: A color produced by the introduction of small amounts of a colored pigment.  

TOXICITY: The quality, property, or degree of being poisonous or toxic.  

TWO-COMPONENT SYSTEM: A coating or polyurethane foam formed by the mixing and the reaction of two different materials.  



ULTRA-VIOLET RADIATION (UV): Electro-magnetic radiation beyond the visible spectrum at its violet end. Invisible high-energy sunlight which degrades many organic materials.


VAPOR BARRIER: (1) A membrane, coating or other material that has very low water vapor transmission rates. (2) A component within a building assembly used to limit the transmission of water vapor by diffusion. Comment: The term vapor barrier is imprecise and the term VAPOR RETARDER (see also) is generally preferred.

VAPOR RETARDER: A vapor retarder is a component of the building enclosure used to control moisture diffusion through the component or assembly.  It is generally placed at the warm side of the enclosure assembly to control condensation.  In terms of the International Model Building Codes, there are three classes of vapor retarders used in building enclosures, categorized as follows, based on the measured water vapor transmission per ASTM E 96 dry-cup or dessicant method A:  
* Class I:  less than 0.1 perms
* Class II:  greater than 0.1 perms but less than or equal to 1.0 perms
* Class III:  greater than 1.0 perms but less than or equal to 10 perms.
Class II vapor retarders are generally required in colder climates – check with the local building code.  Examples of Class II vapor retarders include asphalt-kraft facings, ~2 inches of medium-density SPF.  Examples of Class I vapor retarders would be a 6 mil PE sheet.


WATER ABSORPTION: The percent increase in weight of a specimen after immersion in water for a specified time. For SPFs, water absorption is reported as volume percent in accordance with ASTM D 2842.

WATER RESISTANT BARRIER (WRB):  Materials or combination of materials which are primarily designed to be used to keep liquid water from entering the building enclosure. Water resistive barriers are combined with flashing and other materials to ensure that there is a shingled assembly to direct liquid water which passes on the cladding system to be directed to the exterior. Also known as weather resistive barrier.



WATER VAPOR TRANSMISSION: The migration of water vapor.  

WATER VAPOR TRANSMISSION RATE: The rate at which water vapor will diffuse through a unit area of material. Units are usually grains/ft2•hr.