Air Changes per Hour (ACH) An expression of ventilation rates - the number of times in an hour that a home's entire air volume is exchanged with outside air.
Air barrier A layer of material resistant to air flow usually in the form of polyolefin (i.e. Typar, Tyvek, and other housewraps). A material which 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.
Air barrier system The assembly of components used in building construction to create a plane of air tightness throughout the building envelope and to control air leakage.
Blower Door Diagnostic equipment consisting of a fan, removable panel and gauges, used to measure and locate air leaks.
Blowing agent A gas or a substance capable of producing a gas used in making foamed materials.
Btu British Thermal Unit - The amount of energy that is required to raise 1 lb. of water up 1° F.
Btuh A rate of energy transfer - can be expressed as Btu/hour.
Building Envelope The external elements walls, floor, ceiling, roof, windows and doors of a building that encloses conditioned space; the building shell.
Capillary Action, Capillarity The movement of liquid within a material against gravity as a result of surface tension.
CFC (Chloroflourocarbon) Any of various halocarbon compounds consisting of carbon, hydrogen, chlorine, and fluorine, once used widely as aerosol propellants and refrigerants. Chlorofluorocarbons are believed to cause depletion of the atmospheric ozone layer.
Combustion efficiency A measure of useful heat extracted from a fuel source by an operating heating appliance. For example a furnace with a combustion efficiency of 60 percent converts 60 percent of the fuels energy content into useful heat. The rest is lost as exhaust gases.
Conduction Transmission of energy (heat /sound) through a material or from one material to another by direct contact. Materials with low rates of conductive heat transfer make good insulation.
Convection Transmission of energy (heat /sound) from one place to another by movement of a fluid such as air or water.
Density Determined by the weight expressed in pounds of a cubic foot of any material.
Dew Point The temperature at which a vapor begins to condense.
Diffusion The movement of water vapor from regions of high relative humidity (RH) or pressure toward regions of lower RH driven by a higher to lower temperature differential.
Exfiltration Uncontrolled leakage of conditioned air from inside the home to the outside.
Flame Retardant A substance, which is added to a polymer formulation to reduce or retard the tendency to burn.
Flame Spread Unit of measure generated by a standard test for determining relative combustibility. The flame spread of a tested material is rated relative to red oak (flame spread = 100). ASTM = E84 is the test method used to determine the above.
Flammability Relative ability of a material to support combustion as expressed by its flash point.
Heat loss Heat that is lost from a building by air leakage, conduction, and radiation. To maintain a steady interior temperature, heat losses must be offset by a combination of heat gains and heat contributed by a heating system.
Heat recovery ventilation system A mechanical ventilation system that recovers energy from exhausted indoor air and transfers it to incoming air. This system usually incorporates an air-to-air heat exchanger which transfers the heat from exhaust air to the incoming air or vice versa.
HCFC (Hydrochlorofluorocarbons) are halogeneted compounds containing carbon, hydrogen, chlorine and fluorine. They have shorter atmospheric lifetimes than CFCs and deliver less reactive chlorine to the stratosphere where the "ozone layer" is found.
Humidistat A humidity sensitive control device that signals the ventilation system to operate if the humidity goes above a preset limit.
Hydrophobic Having no affinity for water; not compatible with water. "Water fearing" Also preventing growth of mold and mildew.
Infiltration Uncontrolled leakage of air into a building through cracks around doors, windows, electrical outlets and at structural joints. Uncontrolled leakage of conditioned air from outside of the home to the inside.
Insulation Materials with low thermal conductivity characteristics that are used to slow the rate of heat transfer
Humidistat A humidity sensitive control device that signals the ventilation system to operate if the humidity goes above a preset limit.
Isocyanate (typically MDI) One of a group of neutral derivatives of primary amines (R-N=C=O) groups. An essential component (A) of urethane foam chemistry.
Kilowatt-hour (kWh) Standard unit for measuring electrical energy consumption-kilowatts X hours.
Material Safety Data Sheet (MSDS) A standard formatted information sheet, prepared by a material manufacturer, describing the potential hazards, some physical properties, and procedures for safe use of a material.
Mold Fungal growths often resulting in deterioration of organic materials, especially under damp conditions.
Organic Compounds containing carbon.
Overspray (1) Airborne particle loss of polyurethane foam in spray application. (2) Undesirable depositions of airborne spray loss.
Perm A unit of water vapor transmission defined as 1 grain of water vapor per square foot per hour per inch of mercury pressure difference (1 inch mercury = 0.49 psi). Metric unit of measure is ng/m2 s Pa. 1 perm = 55 ng/m2 s Pa.
Permeability The time rate of water vapor transmission through unit area of a material of unit thickness induced by unit vapor pressure difference between two specific surfaces, under specified temperature and humidity conditions. (add units like above)
pH A measure of acidity/alkalinity of aqueous mixtures. A measure of pH 7 is neutral, lower is more acidic, higher is more alkaline.
Pressurized Fog Testing Done in conjunction with a blower door test, presurized fog test visually identifies air leaks in a building's envelope. The test is usually done when temperature and weather conditions make an infrared scan difficult.
Product Data Sheet A listing of all the general characteristics and components of a chemical or product. (Also see MSDS).
PSI Pounds per square inch.
Radiation Transfer of energy (heat/sound) from one object to another through an intermediate space. Only the object receiving the radiation, not the space is heated. The heat is in the form of low frequency, infrared, invisible, light energy, transferring from a "warm" object to a "cold" object. It is known as the "black body effect".
Relative Humidity The ratio expressed as a percentage of the amount of moisture air actually contains to the maximum amount it could contain at that temperature.
R-Value A unit of measurement of resistance to heat flow in hr. ft2° F/BTU.in.
RSI A unit of measurement of resistance to heat flow in m2° C/W per 25 mm. (link to R-value table).
Resin Component B in urethane foam chemistry. This component is mixed with the A component to form foam insulation.
Retrofit The modification of an existing building or facility to include new systems or components.
Standard Testing Laboratory test methodology for determining relative properties of materials at specific conditions.
SUPERGREEN foam is a rigid plastic urethane foam that uses zero ozone depletion Freon (HFC-134a) as the blowing agent.
Superinsulation The word was coined during the energy crisis of the 70's it is an approach to solving thermal envelope problems. Superinsulation is usually, but not always, one of the several urethane foam systems.
Thermostat "Temperature sensitive" control device that signals a heating or cooling system to operate if the temperature in a conditioned space reaches a preset limit.
Thermal Barrier A material applied over insulation designed to slow the temperature rise of the foam during a fire situation and delay its involvement in the fire.
Thermal Bridge A thermally conductive material which penetrates or bypasses an insulation system; such as a metal fastener or stud.
Thermal Resistance (R) An index of a material's resistance to heat flow. See R-Value and RSI.
Thermal Shock A building materials reaction to rapid changes in temperature, usually associated with the curing process.
Thermography (Infrared Scan) A building energy diagnostic technique using an infrared camera for locating areas of temperature differential or air leakage in a building. Often used in conjunction with pressurization or depressurization.
U-Value Overall thermal conductance. U-value is equal to the inverse of the sum of the R-values in a system (U = 1 /R total).
Vapor Retarder/Barrier A layer of moisture resistant material usually which controls moisture diffusion (defined as less than 1 perm in typical building environments) to prevent moisture migration into building cavities.
Viscosity The thickness or resistance to flow of a liquid. Viscosity generally decreases as temperature increases; application temperatures of urethane foam components are specified in part, to control viscosity at the dispensing gun.
Volatile Organic Compounds (VOC) Any compound containing carbon and hydrogen or containing carbon and hydrogen in combination with other elements.

ABAAAir Barrier Association of America
AIAAmerican Institute of Architects
AISIAmerican Iron & Steel Institute
ALAAmerican Lung Association
ANSIAmerican National Standards Institute
ASHRAEAmerican Society for Heating, Refrigeration and Air Conditioning Engineers
BETECBuilding Environment & Thermal Envelope Council
BOCABuilding Officials and Code Administrators
CABO (ICC)Conference of American Building Officials (International Code Council)
CCMCCanadian Construction Materials Centre
CSACanadian Standards Association
DOEU.S. Department of Energy
EPAEnvironmental Protection Association
EEBAEnergy Efficient Builders Association
ERECEnergy Efficiency and Renewable Energy Clearing House (DOE program)
FSECFlorida Solar Energy Center
IBCInternational Building Code
ICBOInternational Conference of Building Officials
NAHBNational Association of Home Builders
NAHBRCNAHB Research Center
NBCNational Building Code of Canada
NEATNovel Environmental Advanced Technology
NERNational Evaluation Report
NIBSNational Institute of Building Sciences
NISTNational Institute of Standards and Technology
NRCNational Research Council of Canada
ORNLOak Ridge National Laboratories
SBCCISouthern Building Codes Congress International
SPFASpray Polyurethance Foam Alliance
UBCUniform Building Code
ULUnderwriter's Laboratories