Absorptance

The fraction of incident radiation that is absorbed.

Adhesion

The ability of a coating or sealant to stick or bond to the surface to which it is applied.

Adhesive Failure

Failure of a compound by pulling away from the surface with which it is in contact. (See cohesive failure.)

Annealed Glass

Standard sheet or plate glass.

BTU (British Thermal Unit)

The energy used for heating and cooling is measured by the number of BTUs needed
to keep a building at a comfortable temperature. Scientifically, it is the amount
of heat energy necessary to raise the temperature of one pound of water one degree Fahrenheit (1 Btu = 252 calories).

Cohesive Failure

Splitting and opening of a compound resulting from over-extension of the compound. (See adhesive failure)

Condensation

When water vapor, which is present in all but the driest air, comes on contact with a
surface that is below what is called the “dew point temperature,’’ the vapor becomes
liquid and is called condensation.An example is as follows: Condensation forms on a glass of ice water since the surface of the glass is down to the dew point temperature of the inside air.

Conduction

Process to heat transfer through a material from a warm surface to a cool surface.

Conduction Factor

The difference in the “U-values” before and after film application to glass multiplied by 24 hours/day. This factor is used in calculating heating energy savings.

Convection

Heat transfer by the movement of fluid or air.

Cooling Days

The number of days in a year that the air conditioning equipment is used.

Cooling Degree Day

Cooling and heating engineers have found a way to relate the typical climate conditions of different areas to the amount of energy needed to cool and heat a building. The term they use is “Degree-Day” using a base temperature of 65°F (18°C).A cooling degree-day is counted for each degree above 65°F (18°C) reached by the average (between the highest and lowest) daily outside temperatures in the summer. For example, if on a given summer day the high is 90°F (32°C) and the low is 70°F (21 °C), the daily average temperature is 80°F (26°C). This is 15°F (8°C) above the base temperature of 65°F (18°C difference). So, on that day, you would have gone through 15 (8) cooling degree-days.

Corrosion

The deterioration of metal by chemical or electro-chemical reaction resulting from exposure to weathering, moisture, chemicals, or other agents or media.

CRF (Condensation Resistance Factor)

Gives an indication of a window’s ability to resist condensation. The higher the CRF, the less likely condensation is to occur.

Curtain Wall

An exterior building wall which carries no roof or floor loads and consists entirely or principally of metal, or a combination of metal, glass, and other surfacing materials supported by a metal framework.There are two basic types: CUSTOM:Walls designed specifically for one project, and using parts and details specially made for this purpose.
STANDARDS:Walls made up principally of parts and details standardized by their
manufacturer and assembled in accord with either the architect’s design or the manufacturer’s stock patterns.

Degree Day

A unit that represents a 1°F (1°C) deviation from some fixed reference point (usually 65°F [18°C]) in the mean, daily outdoor temperature. (See heating degree-day and cooling degree day)

Desiccant

An extremely porous crystalline substance used to absorb moisture from within the sealed air space of an insulating glass unit.

Dew Point

The temperature at which the condensation of water vapor in a space. Used in testing sealed insulated glass. The lower the number, the higher the resistance to forming condensation.

Emissivity

This is a measure of the ability of a surface to emit room temperature radiant heat
energy. It is also a measure of the ability of the surface to reflect room radiant energy
since, for window systems. the emissivity and the reflectivity of room radiant energy
add up to unity. A low emissivity means a high reflectivity of room radiant energy.

Float Glass

Glass which has its bottom surfaces formed by floating on molten metal, the top surface
being gravity formed, producing a high optical quality of glass with parallel surfaces and, without polishing and grinding, the fire-finished brilliance of the finest sheet glass. Float glass is replacing plate glass.

Fogging

A deposit of contamination left on the inside surface of the sealed insulating glass unit
due to extremes of temperatures. Usually happens with failed sealed insulated glass.

Glare Reduction

This is the ratio of the difference in visible transmission of the glass before and after installing him to the visible transmission of the glass with no film. It is expressed as a
percentage and is determined by the respective visible transmission values of the glass with and without film.

Glass

A transparent, brittle substance formed by fusing sand with soda or potash or both; it
often has lime, alumina or lead oxide.

Glass Thermal Stress

An applied force, caused by absorbed solar heat, that tends to strain or deform glass.

Heat Gain

The transfer of heat from outside to inside. Both heat loss and heat gain are measured
in terms of the fuel consumption required to maintain a comfortable indoor temperature.

Heat Loss

The transfer of heat from inside to outside by means of conduction, convection, and radiation through all surfaces of the building.

Heat Loss Reduction

This is the ratio of the difference in heat loss through the glass after installing film to the
heat loss Through the glass with no film It is expressed as a percentage and is determined by the respective “U” values of the glass with and without film.

Heating Days

The number of days in a year that the heating equipment is used.

Heating Degree-Day

Heating and cooling engineers have found a way to relate the typical climate conditions of different areas to the amount of energy needed to heat and cool a building.The term
they use is “Degree-Days” using a base temperature of 65°F ( 18°C).A heating degree-day is counted for each degree below 65°F (18°C) reached by the average (between the highest and lowest) daily outside temperatures in the winter. For example, if on a given winter day the high is 40°F (4°C) and the low is 20°F (-6°C), the daily average temperature is 30°F (-1°C). This is 35°F (19°C difference) below the base temperature of 65°F (18°C). So, on that day, you would have gone through 35 (19) heating degree-days.

Hermetically Sealed Unit

An insulated glass unit made up of two lites of glass, separated by a roll formed aluminum spacer tube (at the full perimeter) which is filled with a moisture absorbing material. The unit is then completely sealed, creating a moisture free, clean, dead air space.

HVAC

An abbreviation for Heating, Ventilating, and Air Conditioning equipment.

Insulating Glass

Insulating glass refers to two pieces of glass spaced apart and hermetically sealed to form a single-glazed unit with an air space between. Heat transmission through this type of glass may be as low as half that without such an air space. It is also called Double Glazing.

Interior Stop

The removable glazing bead that holds the glass in place, when it is on the interior side of the lite, as contrasted to an exterior stop which is located on the exterior side of a glass or panel.

KWH

An abbreviation for kilowatt-hour.A unit of electric power consumption. Equivalent to 3413 Btu’s of energy or heat. (1 kWh = 3.60 MJ)

Laminated Glass

Two or more sheets with an inner layer of transparent plastic to which the glass adheres if broken. Used for overhead, safety glazing, and sound reduction.

Lite

Another term for a pane of glass used in a window. Frequently spelled “light" in the industry literature, but spelled “lite. in this text to avoid confusion with light as in “visible light”.

Low-e Glass

Glass which restricts the passage to radiant heat, in and out; a metal or metal oxide coating applied to the glass to provide low emissivity.

Maximum Heat Gain

The maximum per hour amount of solar heat coming through one square foot of glass. Measured in units of Btu/hr/sq.ft. (W/m2).

MCF

An abbreviation of one thousand cubic feet. A unit of natural gas consumption. Equivalent to 1,000,000 Btu’s (37,300 Kj/m3) of energy or heat.

MLB

An abbreviation for one thousand pounds.A unit of steam consumption. Equivalent to 1,000,000 Btu’s (2330 Kj/kg) of energy or heat.

Mullion

An intermediate connecting member used to “marry” two or more windows or patio doors together in a single rough opening without sacrificing air or watertight performance.A mullion also can give added strength to the connection for structural stability.

Muntin

A decorative design in cut-ups of glass lites.
Examples:

• Painted muntin grids (enamelite) applied to an interior lite of glass in a sealed insulated glass unit to simulate cut-ups of glass lites either in colonial or diamond patterns.
• Use of aluminum muntin bar betweenlites of glass in a sealed insulated glass unit to simulate glass cut-ups.
• Use of actual vertical and horizontal bars to divide windows into smaller lites of glass. The bars are termed muntin bars.
  

Obscure Glass

Mainly used for decoration, diffusion, or privacy. The design is pressed into the glass during the rolling process.There are many patterns available. Obscure glass can be created through the addition of 3M Fasara Window Films .

Passive Solar Heat Gain

Solar heat that passes through a material and is captured naturally, not by mechanical means. (ex Large windows facing south will take advantage of passive solar heat gain in Northern Hemisphere.)

Payback

Savings from reducing energy cost and seeing this reflected in your heating/cooling bills.

Permeability

The quality of permitting passage of water through openings without causing rupture or  displacement

R Value

A measure of resistance to heat gain or loss (insulative ability). “R”-Values rather than thicknesses can be compared for different materials, since 6" (152mm) of fiberglass (R-19 [R-34]) might compare with 12" (305mm) of wood or 18' (15.5m) to stone.
“R”-Value of some common substances of 1" (25mm) thickness:

• Concrete 0.1 (0.018)
• Stucco and brick 1.2 (0 21)
• Plywood 1 (0.18)
• Sawdust 2 (0.36)
• Fiberglass batts 3 (0.54)
• Polystyrene 6.25 (1.10)
• Polyurethane foam 7.7 (1.36)

Radiation

Transmission of heat through space by wave motion; passage of heat from one object to another without warming the space between, such as sun light.

Reflectance

The fraction of the incident light that is reflected.

Relative Heat Gain

The amount of conduction heat gain plus solar heat gain, measured in terms of energy units per hour per square foot (compare U-Value). (Btu/hr/sq.ft. or W/m2).

Relative Humidity

The percentage of moisture in the air in relationship to the amount of moisture the air could hold at that given temperature. 100% relative humidity would be rain.

RFI

An abbreviation for Radio Frequency Interference.

Shading Coefficient

This is a ratio of the solar energy entering through a window compared to that which enters through a window of clear 1/8" (3mm) double strength sheet glass.The solar energy which enters includes both that which is transmitted directly through the window and that portion of the energy absorbed in the window that is transferred to the interior.

Solar Energy Spectrum

Solar radiation is typically divided into three categories, namely, the ultraviolet, the visible and the near infrared portions of the spectrum.All three portions result in heat when the solar radiation is absorbed. At the earth’s surface, approximately 3% of the solar energy is in the ultraviolet portion, 44% is in the visible portion and 53% is in
the near infrared.

Solar Heat Gain

The amount per hour of solar heat coming through a square foot of glass Measured in units of Btu/hr/sq.ft. (W/m2).

Solar Heat Reduction

This is the ratio of the difference in total solar energy entering before and after installing film on the glass to that entering through the glass with no film. It is expressed as a percentage and is determined by the respective shading coefficients of the glass with and without film.

Sunlight

The portion of solar energy which is detectable by the human eye; it accounts for about 44% of the total solar energy.

Tempered Glass

As with heat strengthened glass, it is reheated to just below the melting point but suddenly cooled.When shattered, it breaks into small pieces. It is approximately five times stronger than standard annealed glass. It must be used as safety glazing in patio doors, entrance doors, side lites, and other hazardous locations. It can’t be re-cut after  tempering.

Tinted Glass

A mineral admixture is incorporated in the glass, resulting in a degree to tinting. Any tinting reduces both visual and radiant transmittance.

Ton-HR

A unit to air conditioning consumption equivalent to 12,000 Btu’s (3024kcal) to energy.

Total Solar Energy

When solar radiant energy strikes the exterior surface of a window, the energy is reflected, absorbed and/or transmitted as defined above. The total of these three parameters must add up to 100%. 

Total Solar Energy Absorbed

This is a ratio of the solar energy that is absorbed by the window and converted to heat in the window to the total solar energy impinging on the window. It is typically expressed  as a percentage.

Total Solar Energy Reflected

This is a ratio to the solar energy that is reflected directly away by the window to the total solar energy impinging on the window. It is typically expressed as a percentage.

Total Solar Energy Transmitted

This is a ratio to the solar energy that is transmitted directly through the window where it is absorbed by interior surfaces to the total solar energy impinging on the exterior window surface. It is typically expressed as a percentage.

Transmit, Reflect, Absorb

There are three possible outcomes of Solar Energy when it hits a window or other structure:

• It can be Transmitted, or pass through the glass.
• It can be Reflected, or re-directed away from the glass.
• It can be Absorbed, heating the glass.

Plain 1/4" clear glass will transmit 88%, reflect 8%. Energy that is absorbed will be re-radiated.