ABSTRACT
The change to metric involves the use of new units. These are as follows. For the ‘K’ value (thermal conductivity) the new unit is watts per square metre of surface area, with a temperature difference of 1 degree C, and is written W/m deg C. The reciprocal of this (1/k) is the thermal resistivity: if the thickness of a material is known (in metres and decimal fractions) 1/k times the thickness equals the thermal resistance, which is written m 2 deg C/W. The ‘U’ value, or thermal transmittance is derived as follows.
