R-Value (insulation)

Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online.The R value or R-value is a measure of thermal resistance used in the building and construction industry. Under uniform conditions it is the ratio of the temperature difference across an insulator and the heat flux (heat flow per unit area, dot QA) through it or R = Delta T/dot QA. The bigger the number, the better the building insulation''s effectiveness. R-value is the reciprocal of U-value. Around most of the world, R-values are given in SI units, typically square-metre Kelvin per watt or m²·K/W (or equivalently to m²·°C/W). In the United States customary units, R-values are given in units of ft²·°F·h/Btu. It is particularly easy to confuse SI and US R-values, because R-values both in the US and elsewhere are often cited without their units, eg R-3.5. Usually, however, the correct units can be inferred from the context and from the magnitudes of the values.

Klappentext

The R value or R-value is a measure of thermal resistance used in the building and construction industry. Under uniform conditions it is the ratio of the temperature difference across an insulator and the heat flux (heat flow per unit area, dot QA) through it or R = Delta T/dot QA. The bigger the number, the better the building insulation's effectiveness. R-value is the reciprocal of U-value. Around most of the world, R-values are given in SI units, typically square-metre Kelvin per watt or m²·K/W (or equivalently to m²·°C/W). In the United States customary units, R-values are given in units of ft²·°F·h/Btu. It is particularly easy to confuse SI and US R-values, because R-values both in the US and elsewhere are often cited without their units, eg R-3.5. Usually, however, the correct units can be inferred from the context and from the magnitudes of the values.