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Although the concept of U-value (or U-factor) is universal, U-values can be expressed in different units. In most countries, U-value is expressed in SI units, as watts per square metre-kelvin: W/(m 2 ⋅K) In the United States, U-value is expressed as British thermal units (Btu) per hour-square feet-degrees Fahrenheit: Btu/(h⋅ft 2 ⋅°F)
The respective tables of data were generally developed by using the more complex transfer function method to determine the various cooling loads for different types of heating. [2] [3] The results gained by doing so are then normalized for each type of heat gain used for the tables, CLTD, CLF, and SCL. [4]
In the 1995 Building Regulations, insulation standards were cut to the following U-values: 0.45 for exposed walls, floors and ground floors; 0.6 for semi-exposed walls and floors; 0.25 for roofs; the limit on window area was raised to 22.5%; The 2002 regulations reduced the U-values, and made additional elements of the building fabric subject ...
Architects and engineers call the resulting values either the U-Value or the R-Value of a construction assembly like a wall. Each type of value (R or U) are related as the inverse of each other such that R-Value = 1/U-Value and both are more fully understood through the concept of an overall heat transfer coefficient described in lower section ...
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]
Although the concept of U-value (or U-factor) is universal, U-values can be expressed in different units. In most countries, U-value is expressed in SI units, as watts per square metre-kelvin: W/(m 2 ⋅K) In the United States, U-value is expressed as British thermal units (Btu) per hour-square feet-degrees Fahrenheit: Btu/(h⋅ft 2 ⋅°F)
For this building, the researchers conclude that meeting the requirements of Step 1 would involve a construction cost premium of $560 per unit above the cost of building to the BC Building Code. Meeting the requirements of Step 2 would incur a 0.4% construction cost premium, about CAD$1,250 per unit.
The units of an R-value (see below) are usually not explicitly stated, and so it is important to determine from context which units are being used: an R-value expressed in I-P (inch-pound) units [13] is about 5.68 times larger than when expressed in SI units, [14] so that, for example, a window that is R-2 in I-P units has an RSI of 0.35 (since ...