BISTRA - Previous versions

Previous versions

Version 5

(Scroll down for presentation on new functionalities)

BISTRA v5.0.03

  • Column and row header of active cell highlighted with changed background color instead of bold font.
  • Bugfixes:
    • Tooltip uses correct font in table headers.
    • Allow double clicking to edit when the cell is too small to show all contents.
    • 'Escape' returns to Zoom > Select when in mode Bitmap > Bisect.

BISTRA v5.0.02

  • Bugfixes:
    • Default settings read correctly after first installation.
    • Colour database crash when editing thermal properties.

BISTRA v5.0.01

  • Always use default measures (pixel size and global triangulation size) when opening BMP files (Settings > Default Measures...).
  • Weather data files checked on windows format (Unix not accepted).
  • Bugfixes:
    • Area correction for solar transmission on small opaque barriers in radiosity system to avoid overestimating the radiative power.


  • Specular reflection of direct solar radiation implemented.
  • Calculation of the absorbed solar radiation of opaque surfaces behind transparent materials integrated (rendering the work-around of manually introducing a virtual layer in between superfluous).
  • External weather data files in EPW or TMY3 format can be read (for dry bulb temperature and solar radiation data).
  • Improved dialog box ‘Solar Data’ (visualization of bitmap placing in 3D, possibility to impose a constant value and any angle of incidence for the solar radiation in case of ‘Fixed sun position’).
  • Improved solar processor calculation (speeding up calculation time).
  • Increased calculation speed due to improved neighbouring nodes algorithm for viewfactor zones (RADCON).
  • Option to save Text Output in CSV format for post processing (e.g. MS Excel).
  • Calculation parameters:
    • Simulations can start on any time of the day.
    • Triangle faces are clustered into larger view factors in RADCON zones (according to calculation parameter).
  • Bitmap:
    • Snap to pixel when in ‘selecting’ or ‘drawing’ mode.
    • New drawing functions: rectangles and lines.
    • Possibility to bisect a colour zone (speeds up assigning glazing properties).
    • Pan by holding the mouse wheel.
    • Improved zooming by mouse wheel scroll.
    • Zoom out with right mouse click when zoom in is activated.
    • Cursor colour adjusted for background colour.
    • Colour > Copy Row menu function available when editing Bitmap.
    • Bitmap size editing dialog box improved.
    • Addition of Border U values window showing 1D U-values at the bitmap’s borders for information.
    • Default measures for new bitmaps as a program setting.
  • Improved navigation of tables in windows:
    • Mousewheel scroll.
    • Tab and arrow keys to move to adjacent table cells.
  • Colours window:
    • Revised Colour window to allow conformity with different EN standards. A new column 'Standard' replaces the former columns 'C1', 'C2' and 'C3' (fully compatible with BISCO v12).
    • Implementation of the equivalent thermal conductivities for air voids and layers according to EN ISO 6946.
    • Implementation of the equivalent thermal conductivities for glazing gas layers according to EN 673 (with user-defined gas mix).
    • Introduction of Colour database allowing to quickly adjust frequently used materials and boundary conditions (File → Open Colour Database…).
  • Graphic Output:
    • Revised legend with indication of material names and clustered cavities per EN ISO standard. The colour for each cluster of cavities can be defined by the user.
    • Sun obstacles can be visualized.
    • Triangulation mesh only visible when image has relevant scale.
    • New view: Absorbed Solar Fluxes
    • Improved handling of sun position (rotation by holding mouse wheel, implemented as a ‘view’, not a ‘toggle’, and sun position view saved in .bst file)
  • Report:
    • Irradiation (total, direct, diffuse, ground reflected) as additional output.
    • Max. temperature difference as additional output.
    • Possibility to output temperature results of two colours combined.
    • Colour name indicated in report.
    • List box for easier selection in Report Definition window.
    • Absorbed solar flux and energy (qsol and Qsol) available as output for all colours with interfaces where absorption could occur.
  • Replace Help > How To's with link to website's Knowledge Base (which contains more information).
  • Licence information dialog boxes not shown when calculating from command line.
  • Additional keyboard shortcuts for menu commands.
  • Additional error messages (ill-conditioned system, BMP file problems, diverged ventilation system, simulation start time definition, failed triangulation).
  • Bugfixes:
    • Animations in Graphic Output no longer play as an infinite loop.

Version 4

BISTRA v4.2.01

  • Bugfixes:
    • Automatically switch Tmin and Tmax in Temperature Range dialog box if Tmin>Tmax.
    • Template file Bistra.bst not always correctly read on program start-up.


  • Possibility to assign a fixed sun position (solar radiation perpendicular to bitmap border) as an alternative to a real sun path
  • Improved algorithm for visualizing BC_FREE in graphic output resulting in higher rendering speed
  • Off line activation of software licence keys added
  • Cloud-based licences are automatically activated when opening the application
  • Bugfixes:
    • EQUIMAT always assigned solar reflection factor 0 and solar transmission factor 1


  • Feature 'Unlimited nodes' replaces old 64-bit version
  • Documentation accessible from the BISTRA menu ‘Help’: Manual, How to’s and Tutorials.
  • More documentation (example projects, validation projects and training material) available via the online Physibel Portal (
  • Extended software protection options:
    • Hardware licence key (USB): stand-alone
    • Software licence key: stand-alone, network floating and cloud-based floating.
  • Bugfixes:
    • Numerical error in solar processor for very small values corrected


  • Functions harmonised with BISCO v11.0w: write compressed BMP files; equivalent thermal conductivities (EQUIMAT, TRANSMAT) and convective surface heat transfer coefficients (BC_FREE, BC_SKY, BC_NOSKY) dependent on dominant heat flow direction derived from temperature field (rules CEN_DIR_I, CEN_DIR_E); definition of cavity emissivities; improved radiation simulation in a TRANSMAT cavity at the bitmap border; graphic output of single isothermal line; fill bitmap in graphic output.

  • More clear visualisation of sun path of current day and current sun position (visible or hidden by sun obstacles) above horizontal plane.

Version 3.0w

  • Default data file Bistra.bst with initialisation values for thermal properties per colour.
  • Time dependent functions for thermal conductivity, total surface heat transfer coefficient and convective heat transfer coefficient.
  • Simulation of ventilation flows through different zones following user-defined ventilation paths.  The ventilation volume flow rates refer to time dependent functions.
Presentation BISTRA v3

Version 2.0w

  • Solar processor based on direct and diffuse solar radiation climate files.
    Solar irradiation on (slanted) edges of triangulated object geometry.
    Solar reflection factor based on angle of incidence.
    Solar transmission factor after subtraction of reflection.
  • Definition of north orientation based on 3 rotation angles around 3D rotation axes.
  • Sun obstacles as spherical rectangles on the sky hemiphere (defined by azimuth and altitude coordinates).
  • Sun path visualisation (in animation video).
  • Diffuse solar radiation redistributed using radiosity method.
  • Output of absorbed solar fluxes.