Can R values be calculated from the conductivity of a material instead of tests?
Answer – Not very accurately. The idea of R values began because science could not separate the radiative component outside from the other components that exist on the outside of a material and its environment. All materials have capacities to absorb heat. This results from mass. Mass can also reflect heat which results from it’s density, surface finish and temperature change and wetness or wind currents relative to the other surfaces. In ways similar to reflection it can radiate heat at various wavelengths and velocities. The only simple way to combine everything into one single non-dimensional unit was to make some simple assumptions. Because of heat reflection, the expected temperature a given distance from a hot body is not always the inverse square root of the unit distances. (1/d^2). When near a reflecting body, the measured temperature shows a near field effect where a zone of constant temperature heat surrounds the radiating material. That is the only difference between reflect
