Thermal Bridge Heat Transfer & Vapour Diffusion Simulation Program AnTherm Version 6.115 - 10.137 [ ← ] [ ↑ ] [ → ] [ToC]

Psi-Value Calculator (Tool)

The Psi-Value Calculator is used for rapid calculation of the linear thermal transmittance of the thermal heat bridge (correction factors Psi (Ψ, LΨ, ) resulting from the input of U-values and lengths specific to the building component concerned and its thermal coupling coefficient L2D as calculated within a steady state, two dimensional thermal heat bridge simulation.
Calculating U-values needed is supported by the U-value Calculator integrated within this application. U-Value The U-Value specific the the components part concerned (as calculated with a U-Value Calculator, for example).Remark: If specific U-Value is provided by a layered construct entered within a U-Value calculator, the checkmark left to the button "Layered Construct" is marked checked and this field is marked read-only. To override the value manually uncheck the checkmark left to the button "Layered Construct". Length The length to be used for the respective U-Value above Coupling Coefficient L2D The thermal coupling coefficient specific to the component under consideration (as calculated and reported within the Coupling Coefficients report, for example). U * l The result of the multiplication of respective values of U and l. Total U * l The sum of respective U * l multiplications. Psi-Value (Ψ) The resulting Psi-Value (Ψ, LΨ, ); the linear thermal transmittance

Up to two U-Value and Length pairs can be entered. The formulas used for this calculation are defined in the EN ISO 10211.

Remark: Obtaining the thermal coupling coefficient L2D can be accomplished with an appropriate two dimensional, steady state, thermal bridge heat transfer simulation software. AnTherm provides class A precision method for such calculation.

Calculating U-Values with U-Value Calculator To calculate respective U-Value with an integrated U-Value Calculator, press the button "Layered Construct", build or load the layered construct within the U-Value Calculator which is shown thereafter and confirm the calculated result by pressing the Ok-button therein.
The calculated U-Value of a layered construct is shown in the U-Value field which is then marked read-only. The checkmark left to the button "Layered Construct" confirms, that the value shown is based on respective layered construct.

The actual data of a layered construct can be changed at any time by pressing the button "Layered Construct" again and editing the data within the U-Value Calculator shown thereafter.

Remark: The actual data of a layered construct is retained until the form is closed. To save the data of each respective layered construct use the "Save" function within the U-Value Calculator.
Remark
: You can drag & drop any layered construct (as it is available from a U-Value Calculator if it is run separately) onto the one of U-Value / Length blocks in this window also.
Remark
: To override the value manually uncheck the checkmark left to the button "Layered Construct".
Remark
: If no data of a layered construct has been applied yet, the checkmark left to the button "Layered Construct" is shown greyed.

Entering the Thermal Coupling Coefficient L2D obtained from AnTherm

AnTherm's "Coupling Coefficients Report" provides the matrix of thermal coupling coefficients resulting from steady state simulation of respective modelled construction. As AnTherm displays both, the interior and exterior calculated values for precision validation purposes, you can either use any one of the two or apply the mean value of both for example, provided that precision criteria is satisfied.

Important: U-Values and lengths used for the Psi-Value calculation must correspond to the thermal coupling coefficient of the modelled component in the manner defined within EN ISO 10211 and EN ISO 13789.

As soon as simulation results of a two dimensional calculation are available or created in AnTherm you can pick the value of thermal coupling coefficient from the coupling coefficients report manually.
Remark: The model is interpreted as two dimensional if it is homogenous in the Z direction (the grid contains only one layer in Z). You shall transfer a median value of the two corresponding matrix elements divided by the thickness in Z (within a 2D project it is 1 meter) and rounded according to the close-up error.

Remark: The project specific Psi Value Determination Form will pick values automatically as soon as calculation results are available.

Entering U-Values obtained from AnTherm

AnTherm's "Modelling Report" shows U-Values for all layered constructs at adiabatic cut-off planes of the modelled component.

Important: U-Values and lengths used for the Psi-Value calculation must correspond to the thermal coupling coefficient of the modelled component in the manner defined within EN ISO 10211 and EN ISO 13789.

Remark: The project specific Psi Value Determination Form will pick values automatically as soon as calculation results are available.