Definitions for

**"U-Factor"****Related Terms:**U-value, U value, Thermal conductivity, K-factor, Thermal conductance, Heat transfer coefficient, R-value, Thermal coefficient of expansion, Thermal resistance, Heat capacity, Cte, Thermal insulation, Coefficient of expansion, Thermal, Coefficient of thermal expansion, Specific heat, Heat loss, Heat flow, Specific heat capacity, Thermal capacity, Conductance, Btu, Thermal inertia, Pyrometer, British thermal unit, Relative heat gain, Thermometer, Negative temperature coefficient, Positive temperature coefficient, Hspf, Solar heat gain coefficient, Temperature coefficient, Solar heat gain, R value, Ptc, Heat load, Temperature, Heat content, Differential scanning calorimetry, Heat rise, Temperature rise, B.t.u, Thermal expansion, Btuh, Shgc, Cold junction compensation, Enthalpy, Thermal efficiency, Heating value, Degree-day

a measure of the rate of heat flow through a material or assembly. It is expressed in units of Btu/hr-ft2-[ring]F. 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. The lower a window's U-factor, the greater are its resistance to heat flow and its insulating value.

A measure of total heat flow through a window or door barrier from room air to outside air. Lower numbers indicate greater insulating capabilities.

The factor representing resistance to heat flow of various building materials.

A measure of the rate of non-solar heat loss or gain through a material or assembly. The lower the U-Factor, the greater a window's resistance to heat flow and the better its insulating values.

A measure (Btu/h ft2 °F) of how well a material or series of materials conducts heat. U-factors for window and door assemblies are the reciprocal of the assembly R-value. The smaller the number, the less the heat flow.

Numeric measurement of a material's transmission of heat. Reciprocal of R-value. The smaller the number, the less heat is transfered through the material.

A measure of the rate of heat flow through a material or assembly. It is expressed in units of Btu/hr-ft 2 -°F or W/m 2 -°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.

The overall heat transfer coefficient of the glazing system. U-Factor is a measure of the heat transfer that occurs through the glazing system, and its outer and inner surfaces. This value is a function of temperature, and is expressed in BTU per square foot per hour per degree Fahrenheit (BTU/sq. ft./hr Fahrenheit degree). The lower the U-Factor, the better the insulation qualities of the glazing system.

Quantitative measure of heat flow or conductivity, the reciprocal of R-value. While building scientists will use R-values for measures of the resistance to heat flow for individual building materials, U-factor is always used as a summary measure for the conductive energy measure of building enclosures.

Also called U-value or coefficient of heat transmission, it is a measure of the insulating value of building materials, expressed in B.T.U.'s per hour per square foot per degree Fahrenheit temperature difference between each side. The lower the u-factor, the better the insulation.

U-factor measures the rate of non-solar heat transfer from one side of the window to the other. Heat transfer implies both heat loss out of a living space during cold weather and non-solar heat gain during hot summer months. The lower the U-factor, the better the performance of the window.

A measure of heat transmission through a wall or window. The lower the U-factor, the better the insulating value. R-value is calculated as R = 1/u-value.

A U-factor measures the rate of non-solar heat transfer from one side of the window to the other. Heat transfers to both heat loss out of a living space during cold winter weather and non-solar heat gain into a living space during hot summer weather. This energy transfer, measured in BTUs, is know as conduction.

The rate of heat loss through windows or insulation. The lower the U-factor, the better the insulating qualities.

Rate of heat flow-value through a building component, from room air to outside air. Also referred to as U-value. The lower the U-factor, the better the insulating value. U-fact, a rating more generally used in the window industry, is the recipricol of R-value, a rating commonly used in the insulation industry.

The quantity of heat transmitted per hour through one square foot of a building section (wall, roof, window, etc.) for each degree Fahrenheit of temperature difference between the air on the warm side and the air on the cold side of the building section.

A measure of heat transmission through a wall or window. The rate of heat flow-value through the complete heat barrier, from room air to outside air. The lower the U-factor, the better the insulating value.