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--- basics:building_physics_-_basics:thermal_bridges:tbcalculation:ground_contact:procedure [2016/08/09 14:18] – created mschueren
+++ basics:building_physics_-_basics:thermal_bridges:tbcalculation:ground_contact:procedure [2019/02/21 10:20] (current) – cblagojevic
@@ Line 1: / Line 1: @@
 ====== Recommended procedure for calculating thermal bridges of components in contact with the ground ======
-to be translated and corrected
 In practice, very different methods are often used for calculating thermal bridges of components in contact with the ground (thermal bridges towards the ground).
 The ground especially is taken into account in the calculation in different ways:
-  * taking into account of the ground as a material
+  * taking into account the ground as a material
-  * partial taking into account of the ground with small layers of earth or with small blocks of earth in the calculation models
+  * partial taking into account the ground with small layers of earth or with small blocks of earth in the calculation models
   * no depiction of the ground, in a similar way to calculations of regular thermal bridges towards the air
   * or the ground is depicted  as an additional boundary condition for the temperature (see DIN 4108 Supplementray Sheet 2)
@@ Line 23: / Line 24: @@
   * The ground must be depicted with the same length for the x and y directions in both calculation models with at least five or six times the floor slab length (see illustration).
   * The external dimensional reference applies for the floor slab length (in contrast to the DIN EN ISO 10211). This is recommended for a length of 4 metres.
   * For calculation of the additional conductances, it is recommended that the components in contact with the ground should be represented with a boundary condition corresponding with their heat transfer resistance R = 1/U, rather than with their build-up.
   * The block of earth must exhibit adiabatic boundary conditions at the interfaces.
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 [{{:picopen:charaktbpm.png?nolink&400 | Characteristic floor slab size }}]
 With the aid of the characteristic floor slab size it is possible to reduce the actual three-dimensional heat flow issue (three-dimensional distribution of the soil around the building) to a two-dimensional heat flow issue as an approximation.
 The calculation of the corresponding conductances by means of heat flow simulations takes place additionally using an "infinitely" long analogous model (only two-dimensional heat flows). The previously mentioned approximation functions in the Ground worksheet are also based on $B'$. The use of $B'$ is not absolutely necessary for determining Ψ-values, but this is necessary for a two-dimensional dynamic calculation, otherwise three-dimensional transient calculation would be necessary.