Adjust Surface Emissivity

Surface emissivity refers to a property of a material or surface that describes its ability to emit thermal radiation. It represents the ratio of the actual emitted radiation from a surface to the radiation emitted by a perfect blackbody at the same temperature. Read more.

Surface emissivity is set at a material level, whether from a supplier or as generic material. Therefore, the emissivity value for the material cannot be changed. However, as materials often have varying surface emissivity values for both sides of a product, the direction the material faces can be adjusted when applicable.

To adjust the surface emissivity, hover over any material with a defined surface emissivity lower than 0.9. These are typically insulation or building membranes. In the example above, a Class 1 - Single-sided Reflective Vapour Barrier - 0.0022 µg/N.s (max) has been used to demonstrate variable emissivities. Left-click the material icon in the top left corner. A detailed dropdown will then collapse, showing the assumed direction the material is facing. Click 'To External' or 'To Internal' to change direction. Where significantly different surface emissivities are present on both sides of a material and when facing into a slightly ventilated and unventilated cavity, the Total R-value will change when updating a simulation.