Boundary Conditions
Reference for the Boundary Conditions panel: simplified mode with type assignment and default boundary conditions as well as detailed mode with interior and exterior view
Overview
Boundary conditions define how the sides of a construction are thermally coupled — to a zone (interior), to the outdoor climate, to the ground or a fixed temperature, or adiabatic (no heat flow across the exterior side). They define the convective and radiative heat transfer parameters of the component sides. The Boundary Conditions panel offers two ways of working for this: the simplified mode with four type buttons and automatic assignment, and the detailed mode, in which individual boundary condition records from the database are assigned side by side.
Opening the panel
Activate the Building mode in the mode toolbar, then select the Boundary Conditions page in the property area. Use the radio buttons Simplified and Detailed to switch between the two modes; the scene colouring follows the selected mode.
Simplified mode
Colour table of boundary condition types
The scene colours each surface according to the boundary condition type determined from the component link; the table Boundary conditions/construction types used lists the types occurring in the visible model:
| Type | Colour |
|---|---|
| Interior constructions | Violet (#6A2EBF) |
| Exterior construction | Yellow (#FDBD01) |
| Ground/constant temperature | Brown (#945D28) |
| Adiabatic constructions | Green (#45FE45) |
| Invalid/missing boundary conditions | Dark grey (#404040) |
With 
Select you select all surfaces of the type highlighted in the table — useful, for example, for finding all grey surfaces with missing boundary conditions.
Type assignment (“Assign boundary conditions to the selected constructions”)
Four coloured buttons assign the project’s default boundary conditions to the selected surfaces (active only when a selection exists):
- Interior constructions — sets the default interior boundary condition on both sides. Only permitted for interior components with two connected surfaces; single-sided components are skipped with an error message.
- Exterior construction — the interior side receives the default interior boundary condition, the surfaceless exterior side the default exterior boundary condition. Only permitted for single-sided components; for interior components, the connection must first be split.
- Ground/constant temperature — like exterior, but with the default boundary condition for ground/fixed temperature on the exterior side.
- Adiabatic constructions — the interior side receives the default interior boundary condition, the exterior side remains without a boundary condition. In VICUS Buildings, adiabatic simply means: no boundary condition on the side facing away.
Successfully processed surfaces are automatically deselected; surfaces that cannot be assigned (e.g. without a construction) remain selected and are listed with a reason in a warning message.
Automatic assignment
Assign matching conditions to the selected constructions replaces the boundary conditions of all selected components based on their topology: components with two surfaces receive the interior boundary condition on both sides; for single-sided components, the surface side receives the interior boundary condition and the opposite side — depending on the boundary condition present there — the exterior or ground boundary condition. To standardise the entire building, simply select the complete geometry.
Default boundary conditions
The Show default boundary condition types checkbox reveals the selection of the three project defaults: Interior:, Exterior: and To ground:. Use the … buttons to select the respective record from the boundary condition database; defaults not yet set are shown as “<not yet defined>”. During selection, VICUS Buildings checks the suitability: for interior/exterior, the boundary condition must couple to an active zone or the outdoor climate, for the ground to a constant or schedule-controlled temperature — unsuitable records are rejected with a note. The change is saved as the undo step “Default boundary condition changed”. The same defaults are also used by the automatic boundary condition assignment of the auto-connect and by the creation of new component links when assigning constructions.
Good to know:
For most projects the simplified mode is sufficient: set the default boundary conditions once, select the entire geometry, Assign matching conditions to the selected constructions — done. You only need the detailed mode for special cases, such as different transfer coefficients on individual façades or components facing unheated neighbouring zones with a fixed temperature.
Detailed mode
In detailed mode you work with specific boundary condition records from the database instead of with types. The radio buttons View from inside and View from outside determine the perspective:
- View from inside — each surface is coloured with the colour of the boundary condition of its own component side; interior components therefore appear on both sides with the respective side boundary condition.
- View from outside — only single-sided (exterior) components are considered; the surface shows the colour of the boundary condition of the side facing away. If a boundary condition is missing there, the surface is shown as adiabatic (green). Interior components are not coloured in this view.
The table lists the boundary conditions used (column Boundary condition), including a collective row for adiabatic constructions. In addition:
Edit… — opens the highlighted record in the boundary condition database dialog (also via double-click). Not possible for the adiabatic row (“An adiabatic boundary condition cannot be edited.”).- Select… — selects all surfaces with the highlighted boundary condition.
Assignment in detailed mode
In the Selected surface(s) group, Selected boundary condition: shows the state of the selection. Behind Assign boundary condition: the following are available:
DB… — choose a boundary condition in the database dialog and assign it to the selected surface sides.
Table — assign the boundary condition highlighted in the table directly.- Create adiabatic construction — removes the boundary condition of the side facing away (only meaningful in the exterior view).
The assignment acts perspective-dependently: in the interior view, the boundary condition of the selected surface side is set; in the exterior view, for single-sided components, that of the side facing away. Boundary conditions coupled to ground/fixed temperature can only be assigned in the exterior view and not to interior components; impermissible combinations are skipped and explained in a warning message. Surfaces without a construction cannot receive a boundary condition — first assign a construction.