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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 ...
This is a list of insulation materials used around the world. 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.
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.
Research has shown that the insulation value of reflective bubble foil insulations and radiant barriers can vary from RSI 0 (R-0) to RSI 0.62 (R-3.5) per thickness of material. A study conducted by CMHC (Canada Mortgage & Housing Corporation) on four homes in Paris, ON found that the performance of the bubble foil was similar to an uninsulated ...
The effectiveness of bulk insulation is commonly evaluated by its R-value, of which there are two – metric (SI) (with unit K⋅W −1 ⋅m 2) and US customary (with unit °F⋅ft 2 ⋅h/BTU), the former being 0.176 times the latter numerically, or the reciprocal quantity the thermal conductivity or U-value W⋅K −1 ⋅m −2.
This means that VIPs have about one-fifth the thermal conductivity of conventional insulation, and therefore about five times the thermal resistance per unit thickness. Based on a typical k-value of 0.007 W/(m·K), the R-value of a typical 25-millimetre-thick (1 in) VIP would be 3.5 m 2 ·K/W (20 h·ft 2 ·°F/BTU). To provide the same R-value ...