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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 ...
300 series stainless steels are the larger subgroup. The most common austenitic stainless steel and most common of all stainless steel is Type 304, also known as 18/8 or A2. Type 304 is extensively used in such items as cookware, cutlery, and kitchen equipment. Type 316, also known as A4, is the next most common austenitic stainless steel.
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 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]
Sandwich panels have λ-values from 0.024 W/(m·K) for polyurethane to 0.05 W/(m·K) for mineral wool. Therefore, they can achieve different U-values depending on the core and the thickness of the panel. The installation of a system with sandwich panels minimizes thermal bridges through the joints.
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.
Type 304—the most common grade; the classic 18/8 (18% chromium, 8% nickel) stainless steel. Outside of the US it is commonly known as "A2 stainless steel", in accordance with ISO 3506 (not to be confused with A2 tool steel). [6] The Japanese equivalent grade of this material is SUS304.
While these curtain wall systems are more energy-efficient than older, single-glazed versions, they are still significantly less efficient than opaque (solid) wall construction. [13] For example, nearly all curtain wall systems, thermally-broken or otherwise, have a U-value of 0.2 or higher, which is equivalent to an R-value of 5 or lower. [14]