Thermal Bridge Heat Transfer & Vapour Diffusion Simulation Program AnTherm Version 6.115 - 8.133 

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Basics and Some Theory of AnTherm

Thermal Transmission and Thermal Bridges

Energy in the form of heat in building constructions is generally transmitted by a combination of conduction, convection, and radiation. When considering heat transfer within and through solid (homogeneous or non-homogeneous) building materials, heat conduction is the primary transmission factor; the effects of convection and radiation are typically negligible.

heat conduction Conduction through homogeneous planar building components (i.e. composed of one or more layers of material with parallel surface planes) occurs in a single direction: normal to the component surface. This is referred to as one-dimensional heat flow, and is characterised by a constant surface temperature over the entire surface plane.

Such idealised conditions can, of course, only be assumed in limited regions of an actual building structure. Geometries of non-planar components (construction joints, floor-wall connections, balconies, etc.) give rise to heat flow patterns of more than one direction, that is, to two- or three-dimensional heat flow.
 

thermal bridge
cold bridge
heat bridge
Regions or elements of a building construction characterised by multi-dimensional heat flow patterns are called thermal bridges. In contrast to regions of one-dimensional heat flow, thermal bridges are typically associated with local peaks of heat loss, which correspond to characteristic drops in the interior surface temperature.

Thermal bridges, which in general occur at any junction between building components or where the building structure changes composition, have two consequences:
  1. a change in heat flow rate
    and
  2. a change in internal surface temperature
compared with those of the unbridged structure.
Although similar calculation procedures are used, the procedures are not identical for the calculation of heat flows and of surface temperatures.

thermal bridge
(defined in ISO 10211)
Part of the building envelope where the otherwise uniform thermal resistance is significantly changed by:
  • full or partial penetration of the building envelope by materials with a different thermal conductivity
    and/or
  • a change in thickness of the fabric
    and/or
  • a difference between internal and external areas, such as occur at wall/floor/ceiling junctions

linear thermal bridge
Thermal bridge with a uniform cross-section along one of the three orthogonal axes (as defined by ISO 10211)
point thermal bridge
Localized thermal bridge whose influence can be represented by a point thermal transmittance (as defined by ISO 10211)

See also: Thermal Heat Conductance, Methods of thermal heat bridge survey in international perspective


 Model, Calculate, Simulate and Analyse Thermal Heat Bridges in 2D and 3D with AnTherm®  

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2017-03-22 10:19 +0100