Parameters for Opaque Materials

Parameter

Details

Name

Name of the material

Description

Details about the layer. In the case of material data supplied by the Building Services Research and Information Association (Names beginning with 'am1') the description includes a star rating which gives an indication of the reliability of the data.

Width

Width of the layer. This value can be edited when copied into a construction.

Conductivity

The thermal conductivity of the material.

Specific Heat

The specific heat capacity of the material.

Solar Absorptance

The fraction of incident solar radiation which is absorbed by the material.

Density

The density of the material.

Vapour Diffusion Factor

The specific moisture diffusion resistance of the material (the ratio of the permeability of air (1.92e-10 kg/Ns ) to the permeability of the material)

External Solar Reflectance

The fraction of external solar radiation at normal incidence which is reflected by the layer.

Internal Solar Reflectance

The fraction of internal solar radiation at normal incidence which is reflected by the layer. This will differ from the External Solar Reflectance if the layer is unsymmetrical.

External Light Reflectance

The fraction of external visible radiation at normal incidence which is reflected by the layer.

Internal Light Reflectance

The fraction of internal visible radiation at normal incidence which is reflected by the layer.

External Emissivity

The fraction of external incident long-wave radiation which is absorbed by the material (or, equivalently, its efficiency as a radiator of thermal radiation, expressed as a fraction of the efficiency of a black body radiator at the same temperature).

Internal Emissivity

The fraction of internal incident long-wave radiation which is absorbed by the material (or, equivalently, its efficiency as a radiator of thermal radiation, expressed as a fraction of the efficiency of a black body radiator at the same temperature). This will differ from the External Emissivity if the layer is unsymmetrical.