Evaluation of results
Final output data is obtained in the evaluation branch, during which the model under consideration (or rather, its characterisation through base solutions obtained from the calculation) is evaluated under specific thermal boundary conditions.
While thermal coupling coefficients, heat source distribution and weighting factors are boundary condition independent, further output data is dependant on air temperatures of spaces calculated and, in the event that heat source elements have been included in the model, power density values, which all must be assigned as a boundary conditions to these respective base solution cases as well.
Thermal coupling coefficients matrix and heat source distribution factors
As the direct result of the computation the matrix of thermal coupling coefficients is provided. For a two dimensional model the matrix shows length related transmittance L2D [Wm−1K−1] ; for three dimensional construction the matrix displays thermal coupling coefficients L3D per se [WK−1]. Because thermal coupling coefficients - and as such elements of the conductance matrix - are independent from particular boundary conditions, the matrix itself can be output prior to any user input of temperatures.
Based on the output of thermal coupling coefficients one can calculate the thermal transmittance values (linear thermal transmittance Ψ (Psi) for two dimensional linear thermal bridges (see Psi-Value Determination), or point thermal transmittance χ (chi) for the three dimensional point thermal bridges).
In the event heat sources are available also, the distribution factor of each source is shown too - like the thermal coupling coefficients this values are independent from boundary conditions also. If N spaces are attached to the considered construction the distribution table will shown N numbers. The i-th (i = 1,N) value of the distribution table shows the percentage of the heat provided by the particular heat source passing to the i-th space. The values of the distribution table are therefore from the range 0 to 1; because the steady state calculation does not cover the heat capacity storage, the sum of all distribution values must result in 1 (apart from minor rounding errors).
Dynamic, transient problems, in which the heat storage capacity is taken into account, result in the output of harmonic, periodic coupling coefficients, also calculated directly and not dependant from any particular boundary conditions, are output as a matrix for each specific period length chosen. This results can be used for the analysis of dynamic behaviour of the component for example to read out amplitudes and phase shifts / time lags (like Lpe needed within Passivhaus Projektierungspaket PHPP) or to calculate effective mass capacities.
Boundary conditions
Any further evaluation requires the definition of boundary conditions - these are specified by air temperatures of spaces connected to the building component and all power densities of all heat sources. Only after that data has been provided further results can be requested.
Temperature extremes, dew points, fRsi-temperature factors, g-values
As soon as the boundary conditions have been applied, the application determines locations on the surfaces of all spaces of the model at which the minimum temperature is reached for given boundary conditions. The report "Results" lists coordinates of such points together with the value of the temperature at that point, the dew point value [1] resulting from that temperature and the corresponding temperature factor fRsi. The temperature weighting factors ("g–values") are also output for these coldest points. It is worth to mention, that the temperature weighting factors are independent from the boundary conditions. Contrary, the location of coldest surface points is dependant on the boundary conditions chosen, and therefore the output of weighting factors for coldest points can be provided after boundary conditions have been set.
According to the standard conformance requirement of EN ISO 10211 the "Results report" can b output to the printer.
For some special purpose it might be desirable to receive some output of the distribution of g-values within the building construction or at it surfaces. This is possible within the evaluation stage also. By using the nature of g-values, which in particular are base solution values, the user has to assign the boundary condition of the base solution of interest to 1 to receive the kind of "temperature distribution" showing the g-values themselves. The output can then show isolines, false coloured images or visualizations of "surface g-values" for example.
Finally, the output of f-values is also possible because those are special case of g-values.
Graphical visualizations
Along with the numerical output formally required by EN ISO 10211 further extensive graphical evaluation (visualization) of the calculated results can be obtained and eventually passed to printer or other applications.
Quick view onto the calculated temperature distribution of the component can be obtained in the form of "false coloured" visualizations. For a two dimensional case there is only one such image, three dimensional cases can be visualized with slices through the model or arbitrary view onto the construction.
Some more detailed representation of the temperature distribution is available as isotherm images. Isotherms, i.e. lines of constant temperature, will be shown on the slice through the construction for a two dimensional model. Detailed appearance and content of the information shown can be defined by the user by defining the number of isotherms drawn - value of the first and last isotherm, interval between consecutive isolines etc. can be used to define the meaning of each particular isotherm..
For a three dimensional case the slice plane at which isotherms shall be drawn can be arbitrarily chosen. Furthermore isotherms can be shown on the surface of the model to emphasize the temperature distribution also.
Furthermore, one can query the value of temperature at any arbitrary point of the construction. The definition of points of interest is either provided by the coordinate entry via the menu "Probe points" or by setting the position of slice planes - the temperature value at the intersection the three planes will be shown on the screen.
Further evaluation of temperatures can be available as a graph of temperature values along an edge (surface) of one particular space in two dimensional case. (Remark! This option is currently not available!)
For three dimensional cases one shall request the graph of temperature values along arbitrary line (eventually parallel to coordinate axes). Such line might intersect the interior of the component or follow the surface of the construction - thus providing the ability to emphasize temperature values at components edges.
As an alternative to the visualization of calculated temperature distributions one shall request results showing dew point values (condensing humidity values) resulting from the current temperatures on the surfaces of the model. To achieve that simple activation of the switch "secondary functions" is required followed by the selection of "Relative Humidity %" within the box "Active function". This visualization provides by far much more information compared to the norm required printout "Results" because not only the "yes-no-decision" of norm conformant construction can be received, but additional, much more detailed conclusions about the distribution of dew point values at component's surfaces are possible. In particular, for construction non conformant to standards, the ability to draw an isoline at the humidity value which is critical by the standard (the value above which the condensation or mould growth shall occur) might be very instructive. Such an isoline will mark and emphasize the critical area of the components surface.
Very helpful hints regarding improvement of the thermal quality of building construction result from the visualization of heat streams through (and within) the construction. To receive output related to heat flux one simply needs to activate the switch "Secondary functions" and then, within the box "active function" choose the "Heat stream density W/m2". Variants of visualization options available to the calculated heat stream densities are the same as to temperature distribution. Locations of high heat stream densities shall emphasize thermally weak areas of the construction and can be immediately visualized as false colour diagrams or isoline views for better identification.
For both, the two as well as for three dimensional cases, the heat flow through the construction can be visualized with a streamline. The streamline is shown as soon as the control panel "Streamlines" is activated and coordinates of the starting point are chosen by placing the intersection of the slice planes X, Y and Z within the construction.
For two dimensional cases there is possibility to visualize multiple multiple heat flow streamlines. Since the area between the two neighbouring streamlines marks exactly the same amount of heat flow, the areas at which the density of streamlines is high emphasize potentially weak locations within the construction.
Visualisation of heat flow is also offered as hedge hog field of vector arrows. This display is controlled within HedgeHog (Arrows) control panel by defining the mesh of points at which the direction of heat flow and eventually its magnitude shall be shown.
See also: Evaluations and Results