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The R-value is the building industry term [3] for thermal resistance "per unit area." [4] It is sometimes denoted RSI-value if the SI units are used. [5] An R-value can be given for a material (e.g. for polyethylene foam), or for an assembly of materials (e.g. a wall or a window). In the case of materials, it is often expressed in terms of R ...
Thermal insulance (R-value) is a measure of a material's resistance to the heat current. It quantifies how effectively a material can resist the transfer of heat through conduction, convection, and radiation.
To calculate thermal transmittance when there are "bridging" mortar joints it is necessary to calculate two quantities, known as R max and R min. R max can be thought of as the total thermal insulance obtained if it is assumed that there is no lateral flow of heat and R min can be thought of as the total thermal insulance obtained if it is ...
In the walls of buildings the above formula can be used to derive the formula commonly used to calculate the heat through building components. Architects and engineers call the resulting values either the U-Value or the R-Value of a construction assembly like a wall.
The construction industry makes use of measures such as the R-value (resistance) and the U-value (transmittance or conductance). Although related to the thermal conductivity of a material used in an insulation product or assembly, R- and U-values are measured per unit area, and depend on the specified thickness of the product or assembly. [note 2]
Producers report an average R-value of 2.0 - 5.5, significantly more than that of other siding products including fiber cement, brick and stucco. Homeowners also report insulated siding serves as a noise barrier to external sound. Insulated vinyl siding with added fan fold foam board insulation raises the R-value to 3.5 - 7.5.
Closed-cell foams are superior insulators. While open-cell foams typically have R-values of 3 to 4 per inch (RSI-0.53 to RSI-0.70 per inch), closed-cell foams can attain R-values of 5 to 8 per inch (RSI-0.88 to RSI-1.41 per inch). This is important if space is limited, because it allows a thinner layer of insulation to be used.
Mineral wool insulation, 1600 dpi scan. Thermal insulation is the reduction of heat transfer (i.e., the transfer of thermal energy between objects of differing temperature) between objects in thermal contact or in range of radiative influence.