EN ISO 6946:2017 pdf free
EN ISO 6946:2017 pdf free.Building components and building elements一Thermal resistance and thermal transmittance
The principle of the calculation method is as follows:
a) obtain the thermal resistance of each thermally homogeneous or inhomogeneous part of the building element;
b) combine these individual resistances to obtain the total thermal resistance of the building element,including (where appropriate) the effect of surface resistances;
c) calculate the thermal transmittance as given in 6.5.2;
d) corrections shall be applied to the thermal transmittance in accordance with Annex F if the total correction exceeds 3 % of the calculated thermal transmittance.
Thermal resistances of individual homogeneous layers of building element are obtained according to 6.7.1.1 and the total thermal resistance of the building element is calculated according to 6.7.1.2.
Thermal resistances of individual materials in inhomogeneous layers of a building element are obtained according to 6.7.1.1 and then used as arithmetic mean of the upper and lower limits of thermal resistance according to 6.7.2.2. The total thermal resistance of the building element is calculated according to 6.7.2.
The values of surface resistance given in 6.8 are appropriate in most cases. Annex C gives detailed procedures for low emissivity surfaces, specific external wind speeds and non-planar surfaces.
Air layers up to 0,3 m thickness may be regarded as thermally homogeneous for the purposes of this document. Values of the thermal resistance of large unventilated air layers with high emissivity surfaces are given in 6.9.2. Annex D provides procedures for other cases.
The thermal transmittance calculated in this way applies between the environments on either side of the component concerned, e.g. internal and external environments, two internal environments in the case of an internal partition, an internal environment and an unheated space. Simplified procedures are given in 6.10 for treating an unheated space as a thermal resistance.
NOTE Calculation of heat flow rates is commonly undertaken using operative temperature (usually approximated to the arithmetic mean of air temperature and mean radiant temperature) to represent the environment inside buildings, and air temperature to represent the external environment. Other definitions of the temperature of an environment are also used when appropriate to the purpose of the calculation. See also Annex C.EN ISO 6946 pdf download.
