SBI logo.

Package of easy-to-use and flexible programs for evaluating the indoor climate and energy conditions as well as the designing of the heating, cooling and ventilation plants. The BSim package comprise the programs: SimView (user interface and graphic model editor), tsbi5 (simultaneous thermal and moisture building simulation tool), XSun (dynamic solar and shadow simulation and visualisation), SimLight (daylight calculation tool), SimDXF (CAD import facility) and SimPV (building integrated PV-system calculation).

Furthermore there are export facilities to external tools: Be06 (Danish compliance checker), Radiance (advanced light simulations), boundary conditions for CFD simulations, visualisation in tools using DirectX input files.

Screen Shots


building simulation, energy, daylight, thermal and moisture analysis, indoor climate


The thermal simulation core has been validated in the IEA (International Energy Agency) Task 12 / Annex 21 "Empirical validation of thermal building simulation programs using test room data" activity. Any additions to the program since then have been validated individually by external experts.

Expertise Required

Users must have some general knowledge on building design and how buildings behave thermally in order create the building model.


Approximately 650 licences, of which most are in Denmark and Germany, but there are also users in Canada, Mexico, New Zealand, Japan, France, Sweden, Norway, and Iceland.


Engineers, researchers and students.


When using BSim the building is divided into rooms, some in thermal zones. Only rooms in thermal zones will be simulated dynamically, the rest can be used in other applications. The following groups of information are needed: materials, building component, equipment and systems.

Rooms and thermal zones

The geometry of the rooms are created in the model graphic editor or imported from CAD drawings. Room or rooms are attached to thermal zones by drag and drop in the tree structure of the model.

Constructions and materials

Description of type, density, thermal capacity, thermal conductivity, and PCM (phase change material) properties. Walls, floors and roof constructions are built in layers according to the description of the materials. All materials and constructions are defined in a database and attached to the model as defaults in one operation or one by one by drag and drop from the database.

Systems and functions

Internal loads (e.g. persons, lighting, equipment, moisture load), natural single and multi zone ventilation (e.g. infiltration, venting), heating (floor/construction and/or radiator) and cooling radiators, and ventilation systems. All such "systems" are defined by the physical component as well as how it is controlled and when in function.

Ventilation plants

Supply and exhaust fans as well as total pressure rise and total efficiency. Units of heat recovery, heating and cooling coils, and humidifiers. Together with the control strategy chosen, these data form the base for calculating the power demand and energy consumption necessary for running the ventilation plants.

Automatic control strategies

Are defined for each individual ventilation plant, e.g. changes in temperature, volume flow, moisture content, readjustment between winter and summer periods. Differentiation is made between data of the physical components of the plant (in the company catalogue) and the control function (automatic or manual equipment).

Climate data

BSim uses climate data in binary format, but has a built-in function for converting text formatted hourly data to the binary format. This function can automatically convert climate data files in EnergyPlus/ESP-r weather format.

Default libraries

BSim comes with standard libraries for: constructions (walls, floors, roofs, and internal walls), materials, glass, window frames, people loads, schedules and national constants. The connection between the model and the libraries is handled by drag and drop operations in the building model. The user can choose from these libraries or define new input.

Input interface

Input is given as properties of the individual objects or directly in the graphical representation of the model.


The user can chose any of the calculated parameters for each construction layer, each thermal zone plus data from ambient climate, as output on hourly, weekly, monthly or periodical basis, in either tabular or graphic form. The variables can also be presented in "sum" graphs or tables. Finally the energy balances for each zone or the whole building can be shown. Outputs can be copied (graphics or numbers) for presentation in other programs.

Computer Platform

PC equipped with an Intel Pentium processor (min. 800 MHz) or compatible. Operating system: Windows NT version 4, SP3, Windows 2000, Windows XP, or Windows Vista.

Programming Language

MS-Visual C++.


Analysis of the indoor thermal and moisture climate in complex buildings or buildings with special requirements for the indoor climate. Simultaneous simulation of energy and moisture transfer in building constructions. Multi zone natural air flow simulations. Intuitive graphic user interface.

The Danish Building Research Institute is continuously updating BSim to accommodate changes and developments in the building industry.


No standardized result reports. No possibility batch processing of simulation models at this time – typical simulation time for an average model is though only a few minutes on an up to date computer. No support of geometrical input from CAD tools in IFC file formats –this facility is presently being developed.



Danish Building Research Institute,


Aalborg University
Dr. Neergaards Vej 15
Hoersholm DK-2970


+45 4586 5533


+45 4586 5533




Check for price and ordering information, and publications related to BSim.