R-value

A measure of the capacity of a material, such as insulation, to impede heat flow, with increasing values indicating a greater capacity.

[r(esistance) value.]

A measure of the heat conductivity of material. The higher the R value, the better the material serves as insulation from heat transfer. R value generally applies to insulating materials, roofs, exterior walls, and windows and doors.
Example: The walls in a building have an estimated R value of 20. Fiberglass insulation with an R value of 34 was installed in the walls to make the building more energy efficient.

A measure of the thermal resistance of a material or component.

R-value can refer to:

• Properties of materials:
  • R-value (insulation), the efficiency of insulation
  • R-value (soils), stability of soils and aggregates for pavement construction

• r-value, usually uncapitalized, is also term used in computer science. See value (computer science).

• In crystallography, the R-factor (also known as R-value), is a measure of the agreement between the crystallographic model and the diffraction data.

• In statistics, r refers to the Pearson product-moment correlation coefficient, often called simply correlation coefficient.

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