PsiValue Determination (ΨValue Calculation)
The
PsiValue Determination Form is used for automatic
calculation of the linear thermal transmittance Psi of the (linear) thermal heat bridge
(correction factors Psi (Ψ,
L_{Ψ}, ) for the currently analysed
two dimensional (2D)
building component according to the EN ISO 10211 (or EN ISO 10077).
Most typical 2D cases will be calculated without any additional user
intervention. The automation is supported by:
Some limitations of that automation depend on the particular geometry and can be
controlled by the user.
Remark: PsiValue Determination Form will show disabled if neither
automatic nor partly automatic determination is feasible for the particular
model. The message related to such situation will be displayed also. Manual arbitrary calculation of PsiValue is then supported by the
PsiValue Calculator tool only.
Remark: The model is interpreted as two dimensional if it is homogenous
in the Z direction (the grid contains only one layer in Z).
Space to assume
Exterior
Interior 
Select the space name which is to be assumed exterior at
first. The choice of the value of the thermal coupling coefficient L^{2D}, the
automatic determination of the Reference Point and
the selection of
characteristic UValue Profiles at adiabatic
boundaries all depend on that input. By default AnTherm will pick the name of
the first space (as sorted in alphabetic order) which in particular is
assigned the lowest temperature during later evaluations. 
Coupling Coefficient L^{2D} 
The thermal coupling coefficient specific to the component
under consideration (as calculated and reported within the
Coupling Coefficients
report,
for example). As soon as simulation results of a two dimension calculation are available or
created within AnTherm the PsiValue Determination Form will pick the value of the coupling
coefficient between the two spaces (exterior and interior) automatically.
The value transferred is the median of the two corresponding matrix elements
divided by the thickness in Z (in 2D it is 1 meter) and rounded according to the
closeup error. 
UValue Profiles at
adiabatic cutoff planes 
Turn that switch on to request AnTherm to pick the profiles
automatically at adiabatic boundaries. Available UValue Profiles are then
shown in the two choice boxes displayed just below the switch for further
selection. If turned off you will have to provide UValues manually (either
by the value input or as calculated with a UValue
Calculator) By default AnTherm attempts to automatically find
appropriate profiles.
Remark: If profiles cannot be found this control element will be
shown inactive (greyed).
Remark: If the layer is irregular we recommend that you use the manual PsiValue calculator! 
UValue Profile selection 
Characteristic profiles at adiabatic cutoff planes found
automatically are available for selection.
Remark: AnTherm will offer only profiles connected to the exterior or
interior spaces.
The layered construct at the profile chosen is automatically created and
passed to the respective UValue
Calculator in the fields shown below, thus replacing the earlier entries
therein.
By default AnTherm will automatically pick the first two orthogonal
profiles from the list available. 
Layered construct 
The button provides the means of viewing (or entering) a
layered construct for the calculation of its characteristic UValue. Remark: The layered construct editor (the
UValue Calculator) will block changes (editing buttons and menues will be grayed) if the construct is provided from the
profiles identified by AnTherm. If you wish to override the construct by changing it you must uncheck the "UValue Profiles at adiabatic cutoff planes" switch above. Remark: If specific UValue is
calculated from a layered
construct entered within a UValue calculator (or from the
characteristic profile selected), the checkmark left to the
button "Layered Construct" is marked checked. To override the UValue manually uncheck the checkmark left to the
button "Layered Construct". 
UValue 
The UValue specific the the components part concerned (as
calculated with a UValue
Calculator, for example). Remark: If specific UValue is
provided by a layered
construct entered within a UValue calculator, the checkmark left to the
button "Layered Construct" is marked checked and this field is marked
readonly. To override the value manually uncheck the checkmark left to the
button "Layered Construct". 
Length 
The length to be used for the respective UValue above.
Remark: If respective lengths are determined automatically from the
Reference Point, the respective fields are shown readonly. 
Determine Lengths by Reference Point 
Lengths shall be determined from the specific
Reference
Point found automatically for exterior or interior dimensions or given by
manual entry.
Remark: If respective lengths cannot be determined from any
Reference Point that choice box and controls
below it are shown disabled.. 
Reference Point at
exterior
interior
manual 
The Reference Point shall be found automatically at
exterior or interior dimensions or specified by manual entry.
Remark: If the respective reference point cannot be determined at
some specific automation, that choices are shown disabled.
See the explanation graphics below. 
U * l 
The result of the multiplication of respective values of U
and l. 
Total U * l 
The sum of respective U * l multiplications. 
PsiValue (Ψ) 
The resulting PsiValue (Ψ, L_{Ψ}, ); the
linear thermal transmittance 
Following picture describes the relations within the various objects used in
that automated calculation:
You can call the graphic for the Psi evaluation from the program or from the Result 3D window.
Note: The graphic can only be displayed if you use the automatically obtained U values and lengths. Otherwise this possibility is deactivated as it could lead to misinterpretations.
To call the graphic from the Result 3D window, do the following steps:
 Go to the Result 3D window.
 Click the tab "3D".
 Click the icon "Reset" (top left).
 Activate checkbox "Psi".
Calculating UValues with UValue Calculator
To
calculate respective UValue with an integrated
UValue Calculator, press
the button "Layered Construct", build or load the layered construct within the
UValue Calculator which
is shown thereafter and confirm the calculated result by pressing the Okbutton
therein.
The calculated UValue of a layered construct is shown in the UValue field
which is then marked readonly. 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 UValue
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
UValue Calculator.
Remark: You can drag & drop any layered construct (as it is available
from a UValue Calculator
if it is run separately) onto the one of UValue / 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.
Thermal Coupling Coefficient L^{2D} 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, the mean
value of both is used.
Important: UValues and lengths used for the PsiValue 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 dimension calculation are available or
created in AnTherm the PsiValue Calculator will pick the value of the thermal coupling
coefficient between the two selected spaces automatically.
Remark: The model is interpreted as two dimensional if it is homogenous
in the Z direction (the grid contains only one layer in Z).
Remark: The value transferred is calculated as the mean value of the two
matrix elements which apply and divided y the thickness in the Z direction (in
2D it is 1 Meter) and then rounded according to the current closeup error.
UValues obtained automatically by AnTherm
AnTherm's "Modelling
Report" shows UValues for all layered constructs at adiabatic cutoff
planes of the modelled component.
Important: UValues and lengths used for the PsiValue calculation
must correspond to the therml coupling coefficient of the modelled component in the
manner defined within EN ISO 10211 and EN ISO 13789.
Psi Value Calculation in 3 Space Case and for Unheated Buffer Spaces
The following documents are in the German language.
Zur Berechnung von
ΨWerten für Baukonstruktionen im Bereich bodenberührter Bauteile
Zur Berechnung von
ΨWerten im 3RaumFall; Spezialfall: unbeheizte Pufferräume
See also:
Coupling Coefficients and Precision report,
Modelling report,
PsiValue
Calculator (Tool),
UValue Calculator
(Tool), Project types,
Linear and Point
Transmittance, On calculation of Ψvalues for building
constructions in connection with ground, EN ISO 14683, EN ISO 13789
