AIF- Acoustic Insulation Factor, a sound transmission measure used in Canada
Argon- An inert, colorless, and harmless gas used instead of air in sealed spaces between panes of glass in insulated glass units to increase insulation. Argon gas is less conductive to heat than air
American Society of Heating, Air-conditioning and Refrigeration Engineers
Ambient Temperature- outdoor temperature
Awning- Type of window with a top hinged sash that swings out at the bottom- lets in fresh air, while keeping out rain

Bay- A type of window consisting of a central picture window flanked by a pair of narrow casement windows set at an angle- provides a panaramic outlook
Bow- A type of window made up of equal-sized casement/picture units in a gentle outward curve- allows for a wider view and more living space
BTU- British Thermal Unit- a basic measurement of heat. One BTU equals the amount of heat needed to raise one pound of water 1 degree Farenheit

Casement- A type of window with a side-hinged sash that opens like a door- the best window for catching breezes and provide cross-ventilation
Caulking- Sealants used to seal fixed and movable construction joints and prevent infiltration
Center of Glass- All glass area of a window except that within 2.5"(10cm) from the edge of the glass- used in measuring and calculating glazing performances such as R-values and U-values
Clerestory- A window placed vertically in a wall above one's line of vision to provide natural light- often at the intersection of two offset roof planes
Collection- The act of trapping solar radiation and coverting it to heat
Comfort Engineering- Optimizing glazing selections on a window-by-window basis to fulfill a prioritized set of objectives- eg. comfort, energy efficiency(both summer and winter), UV protection, natural lighting, desired aesthetics, views, and budget.
- The change of a gas to a liquid state. Because warm air can hold more water vapor than cold air, as warm air cools its ability to hold water vapor is reduced. Excess moisture condenses on the warm side of the glass.
- A process of heat transfer whereby heat moves directly through a material by molecular agitation.
Conductivity- The transfer of heat through a given material- see U value whcih is the measure of conductivity, the inverse of its R value.
Conferous Trees- Evergreens, or trees that do not shed their leaves(needles) at the end of a growing season.
Convection- A process of heat transfer whereby heat energy is transferred from one location to another- created by the motion of air resulting from a differenece in temperature and the action of gravity.
Curb Appeal- The visual attractiveness of a home as seen from the street- often the first impression. Realtors see curb appeal as an influential factor in evaluating and selling homes.

Daylight Transmittance- The percentage of visible light that glazing transmits through a window- a standard clear dualplane has a daylight transmittance of 82%.
Deciduous Trees-
Trees which shed their leaves each winter at the end of the growing seasons; useful for summer shading
Crystalline substance used to absorb moisture from air within IGUs
Dew Point
- The temperature at which water vapor will condense as warm, moist air is cooled
Direct Gain-
A direct gain passive solar system utilizes south-facing windows to open a house to the sun. A large window area accepts direct sunlight while thermal mass serves as storage
Double-Hung A type of window that has an upper (outside) sash that slides down, and lower(inside) sash that slides up
Dualpane- Two panes of glass with a single airspace, held together by an edge spacer- the most economical IGU.

Edge of Glass- The glass area within 2 1/2"(10cm) of the edge of the window
Emission, or the ability to radiate heat in the form of long-wave radiation
ER Rating- Energy Rating Number developed by CSA(Canadian Standards Association) to compare the thermal performance of windows. Measured in watts per square meter.

Fenestration- The arrangement of windows in a buildling
Fixed Unit- A stationary window or door that does not open- also referred to as a fixed sash
Frame- Consists of a head, jambs and sill to form an opening into which the sash or door panels fit

- The installation of glass into a window or door sash. Also refers to the type of glass used in the process
Greenhouse Effect-
The property of glass that permits the transmission of short wave solar radiation, but is opaque to long wave thermal radiation
Grilles- Decorative inserts for windows or door glazing that add a traditional touch

Heat Mirror- A transparent coated film used in high performance windows. Heat Mirror film is manufactured with a variety of clear coatings to block the sun's heat or to provide solar gain where desired and to eliminate UV fading. It is permanently suspended between sealed panes of glass, creating additional air spaces for superior insulation, reduction of outside noise and interior condensation control

Infiltration- The uncontrolled movement of outdoor air into a house through cracks around windows, doors etc.
Insolation- Incident solrar radiation- the total radiation striking an exposed surface
Insulation- A material with high resistanct(high R value or low U value) that is used to retard heat flow. Air, argon or Krypton gas spaces between panes of glass provide insulation in IGUs
Insulating Glass Unit-IGU- A combination of two or more panes of glass with sealed air space(s) between panes- dualpanes, tripanes and quadpanes. Also referred to as thermopanes or sealed units
Internal Gain- The heat produced in the interior of a dwelling from the operation of lights, appliances etc.

Jamb- The sides of a window frame

Kitchen Bay- A small bay window used about counter-height in kitchens- allows for a wider view and an inside sill for herbs/flowers
Krypton- An inert, colorless gas used instead of air in sealed spaces between panes of glass in insulating glass units to increase insulation. Provides greater insulation than Argon

Laminated Glass- A type of safety glass comprised of two pieces of glass with a clear vinyl interlay
Low E Glass- low-emissivity glass with a transparent coating which acts as a thermal mirror- used to increase a window's insulating value, block or increase heat flow, and reduce fading

Operating Unit- A window or door that opens- also referred to as a vent unit or operator
Orientation- The compass direction that s structure faces. To optimize heatgain, the major facade of a building should face South(a variation as much as 30 degrees eat or west of south will not seriously affect performance)

Pane- a framed sheet of glass
Passive Solar- A solar heating system wihch operates on natural thermal processes, and that uses no external mechanical power to move the collected heat. Generally, the buildings structure itself form the solar system
Patio Doors- Sliding glass doors, often used for access to a deck or terrace
Picture Windows- A type of window using only fixed units- best for a clear view and energy efficiency
Pyrolytic Coating- A special cating"sprayed" directly onto glass whiee it is still in a molten state, resulting in a permanently embedded surface coating

R-Value- A measure of a product's energy efficiency, or how a material resists heat transfer or flow. R-value is used to describe the insulative properties of construction materials- the higher the R value, the better the insulatng effect.(R=1/U)