Definitions for

**"U-value"****Related Terms:**U value, U-factor, R-value, Heat transfer coefficient, Thermal conductivity, K-factor, Thermal conductance, Thermal coefficient of expansion, Coefficient of expansion, Thermal resistance, Relative heat gain, Cte, Heat capacity, Thermal, Coefficient of thermal expansion, Thermal insulation, Heat loss, Specific heat, Specific heat capacity, R value, Temperature coefficient, Heat flow, Btu, Heating value, Thermal capacity, Heat content, Hhv, Higher heating value, British thermal unit, Thermal inertia, Thermometer, Positive temperature coefficient, Heat rise, Heat load, Pyrometer, Conductance, Negative temperature coefficient, Thermal expansion, Lower heating value, Temperature rise, Total heat, Differential scanning calorimetry, Ptc, Hspf, Temperature, Solar heat gain coefficient, Bowen ratio, Enthalpy, B.t.u

Rate of heat flow-value through the complete heat barrier, from room air to outside air. The lower the U-value, the better the insulating value.

A measure of air-to-heat transmission (loss or gain) due to the thermal conductance and the difference in indoor and outdoor temperatures. As the U-value decreases, so does the amount of heat that is transferred through the glazing material. The lower the U-value, the more restrictive the fenestration product is to heat transfer. Reciprocal of R-value.

The reciprocal of R-value. The rate of heat transmittance through a material, or assemblage, of one square foot in area, measured in BTUs per hour, and based on an indoor-outdoor temperature difference of 1 degree F (BTU/hr-square foot-degrees F). See R-value.

insulation rating. It is the inverse of R-value. The lower the u-value the better insulating capacity. Windows are often rated in U-value.

The rate at which heat flows through a glazing system is called the U-value. The lower the U-value the better the insulating quality. U-value can be compared to the R-value by dividing 1 by the R-value. (U=1/R) A U-value of 0.5 equals an R-value of 2.

Measurement of the thermal conductivity of a material, or inverse of R-Value. The lower the U-Value, the greater resistance to heat flow (lower U-Value = Higher R-Value.)

A measure of energy efficiency based on the conductivity of complete heat barrier, from room air to outside air. The lower the U-value, the better the insulating performance of the barrier.

The reciprocal of R-Value. The lower the number, the greater the heat transfer resistance (insulating) characteristics of the material.

is a measure of the rate of non-solar heat loss or gain through a material or assembly. In windows, the U-value may be expressed for the glass alone or the entire window, which includes the effect of the frame and the spacer materials. For a wall assembly, the U-value typically reflects all the components such as studs, concrete blocks, insulation, and wall board. The lower the U-factor, the greater the material's resistance to heat flow and the better its insulating value. U-value is the inverse of R-value.

A measure of a material’s ability to conduct heat. The thermal performance of windows and doors is commonly stated in U-values. U-value is equal to 1/R (R-Value). The lower the U-Value, the better the material's insulating capacity. The heat loss rate of a building is the product of U-value, surface area, and temperature difference between indoors and outdoors.

VERY SIMPLY, IT IS THE RATE OF HEAT TRANSFER THROUGH A COMPLETE WINDOW OR IT'S INSULATED GLASS UNIT. IT IS EXPRESSED IN TERMS OF BTU PER HOUR PER SQUARE FOOT IN FAHRENHEIT DEGREES. THE NUMBER RANGES BETWEEN 0 AND 1.13; THE LOWER THE NUMBER, THE BETTER. A U-VALUE OF 0.30 IS BETTER THAN A U-VALUE OF 0.50.

The U-value (u-factor) is a measure of the rate of heat flow through a window system or assembly. It is expressed in units of Btu/hr-ft²-°F or W/m².°C. Window manufacturers and engineers commonly use the U-factor to describe the rate of non-solar heat loss or gain through a window or skylight. Lower window U-factors have greater resistance to heat flow and better insulating value.

A measure of the thermal conductivity of a window: The lower the U-value, the better a window is at limiting heat losses. A single-glazed window has a U-value of about 6 W/m 2-K, while triple-glazed windows have U-values between 1 and 2.

heat flow through unit area of a planar component of the thermal envelope under steady conditions per unit temperature gradient maintained in the direction perpendicular to the area [W/m2K] Wärmedurchgangs- gangskoeffizient (k-Wert bzw. flächenbezogener Leitwert)

U-value is the overall coefficient of heat transmission. It is a measure of the rate of heat flow through any given combination of materials, air layers, and air spaces. It is equal to the reciprocal of the sum of all resistances (R). In other words, the U-value can be calculated for a particular wall, roof, or floor system by finding the resistances (R-value) of each of its materials, its air layers, and its internal air spaces, then adding all of these resistances and finding the reciprocal. The lower the U-value, the lower the heat loss or the higher the insulating value. The units are Btu/hour/square foot/degree Fahrenheit.

a measure of heat-loss from

A measure of a material's ability to transfer heat. Describes how well an item conducts heat. The formula for U-Value is U = 1/. This value is expressed as BTU/h/square ft.

Measurement of heat transfer through a given material. The lower the U-Value, the better the insulation value.

A measure of heat transmission through a wall or window. The lower the U-value, the better the insulating value.

the measurement of how readily heat can flow through glass, brick, drywall and other building materials. U-values, which are expressed in decimals, are the opposite of R-values. The higher the U-value, the less efficient the building material will be.

U-value is a measure of a construction's ability to allow heat to pass through itself. It is the reciprocal of a construction's R-value [U = 1/R] Because U-values are for constructions, they always include air film resistances.

The overall heat transfer rate through a combination of materials, it is measured by BTUâ€(tm)s (energy units) transferred per hour, per square foot, per degree of temperature difference. The lower the U-Value, the lower the heat transfer.

The measurement used in determining the ability of different structural components (such as windows) to conduct heat. The U-value of a window is measured by the number of BTU's that will pass through each square foot of area per degree of temperature difference from one side of the window to the other. U-values can tell you how well your windows will hold in your heated or cooled air. The lower the number, the better.

The rate of heat loss, in British thermal units per hour, through a square foot of a surface (wall, roof, door, windows, or other building surface) when the difference between the air temperature on either side is 1° Fahrenheit. The U-value is the reciprocal of the R-Value.

The amount of heat a door or window conducts between the inside air and the environment.

A measurement that indicates the rate at which the window loses heat through conduction and radiation. The lower the U-value, the more efficient the window. It is the reciprocal of R-value: U-1/R.

Overall thermal conductance. U value is equal to the inverse of the sum of the R-values in a system (U = 1 /R total).

This is a measure of the rate of heat loss of a building component. It is expressed as Watts per square metre, per degree Kelvin, W/m2 K.

A measurement of how much energy a material conducts. The lower the U-Value, the greater the insulating effect.

A window's U-value refers to how much heat passes through the glass. The lower the U-value, the better the insulation.

The ability for heat to transfer through 1 square foot of window film for each 1° fahrenheit difference in temperature. It is dependent upon the local climate or environment that the window is located in effects the level of heat transfer and the rate; in summer, heat transfers from the outdoor air to indoor air. In winter, heat transfers from indoor air to outdoor air. The lower the U-Value, the better insulating qualities of the window film/glass system.

see Coefficient of Heat Transmission.

The overall rate of heat flow. It is the coefficient of heat transfer from outside air to inside air. It is expressed in BTU/h*ft2*F. The lower the U-value, the less heat flow that occurs through a roof assembly from the warm side to the cooler side.

Describes the rate of non solar heat gain or loss through glass.

The overall coefficient of heat transfer of an assembly measured in BTUs per square foot, per degrees Fahrenheit difference in temperature per hour.

A measure of air-to-air heat transmission (loss or gain) due to thermal conductance and the difference in indoor and outdoor temperatures. As the U-Value decreases, so does the amount of heat transferred through the glazing material. The lower the U-Value, the better. The U Value can be illustrated as follows: 1 / the R-Value

A measure used to indicate the insulating value of a window. The U-value measures the heat flow. The smaller the U-value, the better a material can stop heat flow.

Amount of heat transferred through a material. The lower the U-value, the slower the rate of heat flow and the better the insulating quality.

A measure of the rate of non-solar heat loss or gain through a material or assembly. It is expressed in units of Btu/hr-sq ft-ÂºF (W/sq m-ÂºC). Values are normally given for NFRC/ASHRAE winter conditions of 0ÂºF (18Âº C) outdoor temperature, 70Âº F (21Âº C) indoor temperature, 15 mph wind and no solar load. The U-factor may be expressed for the glass alone or the entire window, which includes the effect of the frame and the spacer materials. The lower the U-factor, the greater a windowâ€(tm)s resistance to heat flow and the better its insulating value.

Measures the heat loss or gain due to differences between indoor and outdoor air temperature and is expressed in terms of BTU'S/hr/ft2. The U-value equals one divided by the R-value. The lower the U-value the better the insulating performance.

The heat flow rate through a given glass construction due to the difference between indoor and outdoor temperatures, expressed in Btu/hr/sq.ft. The lower the U-value, the less heat transmitted through the glazing material and the more efficient the window is at reducing winter heating costs and summer cooling costs. There are different U-values for a product used during the winter and summer.

The reciprocal of R-value (that is, 1/R-value). This measures the energy flowing through a wall, roof, window, door, or floor per hour per each degree of temperature difference between the inside and outside air temperatures.

A number that measures the rate of heat flow through the complete heat barrier from room air to exterior air.

A measure of heat gain or heat loss through glass due to the differences between indoor and outdoor temperatures. These are center pane values based on NFRC standard winter nighttime and summer daytime conditions. U-values are given in BTU/hr/ft^2/°F for the English system. Metric U-values are given in W/m^2/°C. NFRC winter nighttime U-values are based on an outdoor temperature of 0°F (-17.8°C), an indoor temperature of 70°F (21°C) and a 12.3 mph (19.8 km/h) outdoor air velocity. NFRC summer daytime U-values are based on an outdoor temperature of 89°F (32°C), an indoor temperature of 75°F (24°C), a 6.2 mph (10.1 km/h) outdoor air velocity and a solar intensity of 248 BTU/hr/ft^2/°F (782 W/m^2).

A number which describes in specific terms, the ability of a material or assembly to transmit heat from outside to inside surfaces. Assemblies with lower U-values transmit less heat than those with higher values. SeeR-value. A U-value is the inverse of an R-value.

Amount of heat conducted by a window or door between the air in the environment and the inside air.