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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 ...
Insulated vinyl siding with added fan fold foam board insulation raises the R-value to 3.5 - 7.5. Fan fold insulation is installed under the final siding product. The expanded polystyrene foam (EPS) insulation allows for more impact resistance than traditional vinyl siding. The rigid foam-backed siding creates straighter sight lines, and ...
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 ...
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]
Many builders in northern Canada use a simple 1/3 to 2/3 approach, placing the vapor barrier no further out than 1/3 of the R-value of the insulated portion of the wall. This method is generally valid for interior walls with little or no vapor resistance (e.g., they use fibrous insulation) and controls air leakage condensation and vapor ...
Unscrupulous contractors may "fluff" insulation using fewer bags than optimal for a desired R-value. Dry-spray (but not wet-spray) cellulose can settle 20% of its original volume. [28] However, the expected settling is included in the stated R-Value. The dense-pack dry installation reduces settling and increases R-value.
Typical R-values are given for various materials and structures as approximations based on the average of available figures and are sorted by lowest value. R-value at 1 m gives R-values normalised to a 1 metre (3 ft 3 in) thickness and sorts by median value of the range.