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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 ...
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)
Sol-air temperature (T sol-air) is a variable used to calculate cooling load of a building and determine the total heat gain through exterior surfaces.It is an improvement over:
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]
Heat flux sensors can be used like this to determine the R-value or U-value of building envelope materials while they are still installed in buildings. A heat flux sensor is a transducer that generates an electrical signal proportional to the total heat rate applied to the surface of the sensor.
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If the value is less than or equal to zero, that day has zero HDD. But if the value is positive, that number represents the number of HDD on that day. (For cooling degree days, the process works in reverse: the base temperature is subtracted from the average, and if this value is positive, that number represents the CDD.) This method works ...