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The process of drawing fluid or gas into a porous material, such as a sponge soaking up water.

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. 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.

Device to maintain a ventilation space between the insulation and roof deck, assuring air flow from the eave/soffit vents to ridge vent or other roof vents provided in attics and cathedral ceilings

Band Joist
Vertical member that forms the perimeter of a floor system in which the floor joists tie in. Also known as the rim joist.

Pre-cut pieces of fiber glass or mineral fibre insulation.

Bottom Plate (Sole Plate)
The lowest horizontal member of a wall which rests on the sub-floor, to which the studding is nailed.

Blower Door
Diagnostic equipment consisting of a fan, removable panel and gauges, used to measure and locate air leaks.

British Thermal Unit - The amount of energy that is required to raise 1 lb. of water up 1°F

A rate of energy transfer - can be expressed as BTUs/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.

Celsius (formerly Centigrade)
A thermometric scale in which the freezing point of water is 0°C and its boiling point 100°C at normal sea level atmospheric pressure (14.7 psi). °C = (°F-32)/1.8.

Collar Beam
A horizontal board connecting two opposite rafters at a level considerably above the wall plate. Also known as collar tie.

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% converts 60% of the fuel’s energy content into useful heat. The rest is lost as exhaust gases.

Changing a substance from a vapor to a liquid state by removing the heat. The condensate shows up on surfaces as a film or drops of water.

Conductance, Thermal (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.
C = Btu/hr•ft2•°F (W/m2•°C)

Conductivity, Thermal
The time rate of steady state heat flow through a unit area of homogeneous material induced by a unit temperature gradient perpendicular to that unit area.
k = Btu•in/hr•ft2•°F (l = W/mS°C)

Transmission of energy (heat/sound) from one place to another by movement of a fluid such as air or water.

Cooling Degree Day (hour)
A unit, based on temperature difference and time, used in estimating fuel consumption and specifying nominal cooling load of a building in summer.

Crawlspace Vents
An opening to allow the passage of air through the unfinished area under a first floor. Ideally there should be at least two vents per crawlspace.

Cross Bridging
Small wood pieces placed at angles so that they extend from the bottom of one floor joist to the top of the adjacent joist to add stability to the structural members.

The mass of a substance per unit of volume of that substance.

Dew Point
The temperature at which a vapor begins to condense.

The movement of water vapor from regions of high relative humidity (RH) toward regions of lower RH driven by a higher to lower temperature differential.

Eave Vents
Vent openings located in the soffit under the eaves of a house to allow the passage of air through the attic and out the roof vents.

Energy Audit
A thorough assessment of a home’s thermal efficiency.

Uncontrolled leakage of conditioned air from inside the home to the outside.

A thermometric scale in which 32°F denotes freezing and 212°F the boiling point of water under normal sea level atmospheric pressure of 14.7 psi. °F = 1.8°C + 32

Fiber Glass or Glass Fibers
Glass in a strand form.

Fiber Glass Insulation
An effective resistor of heat flow that is spun from molten sand and recycled glass into fibers.

Flame Spread
Standard test for determining relative combustibility. The flame spread of a tested material is rated relative to red oak (flame spread = 100).

Flat Ceiling
A ceiling with no change in elevation.

Frequency (Hz)
The number of cycles per second measured in units of Hertz.

Furring Strips
Flat pieces of lumber used to build out framing to an even surface, either the leveling of a part of a wall or ceiling. In block or concrete construction, they may be used as a means of attaching the interior or exterior finish.

Gable End Walls
The triangular end of an exterior wall above the eaves.

Gable Vents
A louver vent mounted in the top of the gable to allow the passage of air through the attic.

Glass Fibers
Glass in a strand form. The ingredients are essentially the same that go into any glass product such as a window pane or drinking glass.

Heat Flow
The rate at which heat moves from an area of higher temperature to an area of lower temperature. Btu/hr (W/hr). Heat flow is generally used to quantify the rate of total heat gain or heat loss of a system.

Heat Loss
Heat that is lost from a building through 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.

Acronym for Heating, Ventilation and Air-Conditioning systems

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.

(Hydrochlorofluorocarbons) are 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.

A humidity sensitive control device that signals the ventilation system to operate if the humidity goes above a preset limit.

Having no affinity for water; not compatible with water. "Water fearing" infiltration

Uncontrolled leakage of air into a building through cracks around doors, windows, electrical outlets and at structural joints.

Materials with low thermal conductivity characteristics that are used to slow the transfer of heat.

Horizontal framing member set from wall to wall to support the floor or ceiling.

Knee Walls
Walls of varying length. Used to provide additional support to roof rafters with a wide span or to finish off an attic.

Kilowatt-hour (kWh)
Standard unit for measuring electrical energy consumption-kilowatts X hours.

Loose-Fill Insulation
Particulate insulation, made from either fiber glass or cellulose, that is blown into a home using a motor and hose

Man-Made Vitreous Fibers (MMVF) (See also SVF)
A generic term for a group of man-made materials reflecting the glassy, non-crystalline nature of these materials. This group was historically referred to as man-made vitreous fibres. Most definitions include fiber glass and rock and slag wool products used to make insulation in this category.

Material Safety Data Sheet (MSDS)
A standard formatted information sheet, prepared by a material manufacturer, describing the potential hazards, physical properties, and procedures for safe use of a material.

Mineral Wool
A broad term used to refer rock wool and slag wool.

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

Compounds containing carbon.

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 = 57 ng/m2 s Pa

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".

A slope framing member that supports a pitched roof.

Relative Humidity
A measure of the amount of moisture in the air with respect to the temperature. It is the ratio of the moisture present to the maximum amount of moisture the air can hold at that temperature.

The modification of an existing building or facility to include new systems or components.

Ridge Vents
A vent mounted along the entire ridge line of the roof to allow the passage of air through the attic or cathedral ceiling.

Roof Vents
A louver or small dome mounted near the ridge of the roof to allow the passage of air through the attic.

Measure of resistance to heat flow. The ability of insulation to slow the transfer of heat is measured in R-values. The higher the R-value, the better the insulation material’s ability to resist the flow of heat through it.

A unit of measurement of resistance to heat flow in m2 ° C/W per 25 mm. R = 0.176 RSI

Sound Transmission Class (STC)
A numerical rating of the sound control performance of a wall or ceiling; the higher the number, the better the sound control.

Sound Absorption
The process of dissipating or removing sound energy; the property possessed by materials, objects and structures (such as rooms) of absorbing sound energy; the measure of the magnitude of the absorptive property of a material, object or structure.

A vertical framing member used in both exterior and interior walls.

The structural material that spans across floor joists. It serves as a working platform during construction and provides a base for the finish floor.

Temperature sensitive control device that signals a heating or cooling system to operate if the temperature in the building reaches a preset limit.

Thermal Barrier
A material applied over combustible plastic insulation, to slow the temperature rise of the plastic insulation during a fire so as to 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 Shock
A building materials reaction to rapid changes in temperature.

A building energy diagnostic technique using an infrared camera for locating areas of temperature differential in a building.

Top Plate
The horizontal member nailed to the top of the studding of a wall.

Vapor Retarder/Barrier
A layer of moisture resistant material usually which controls moisture diffusion (defined as less than 1 perm) to prevent moisture build up in walls ceilings and floors.

Creates a positive flow of air that allows the house to "breathe" and helps prevent moisture build-up year-round.

Volatile Organic Compounds (VOC)
Any compound containing carbon and hydrogen or containing carbon and hydrogen in combination with other elements.

Wall Plates
In wood-frame construction, the wall is composed of both vertical and horizontal wood members. The vertical members are usually called studs, while the horizontal members are usually called plates. A bottom plate is at the bottom of the wall frame assembly, while two plates are usually used at the top (double top plate).

Water Vapor Permeance
Time rate of water vapor transmission through unit area of flat material or construction, induced by vapor pressure difference between two specific surfaces, under specified temperature and humidity conditions.

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