tsbi3 logo.

Easy-to-use and flexible program when evaluating the indoor climate and energy conditions as well as the designing of the heating, cooling and ventilation plants. tsbi3 is a tool for consulting engineering companies, research institutes and others who need to simulate and calculate the thermal working environment, energy consumption, control functions, energy saving measures in buildings and the utilisation of passive solar energy.

tsbi3 permits calculation on complex buildings with several (in principle indefinitely many) rooms and zones simultaneously. tsbi3 utilises data from all structures in the thermal evaluation. All depending on the complexity of the building and the systems, a total of 200-400 data, which usually are to be taken direct from the project material, must be given.


energy performance, design, retrofit, research, residential and commercial buildings, indoor climate



Expertise Required

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


Approximately 200 licences, of which about 150 in Denmark.


Engineers, researchers and students.


When using the tsbi3 the building is divided into rooms or zones where materials, building component, equipment and systems used are described as follows:
Rooms and zones
The net and gross area, net height, distribution of solar radiation, surfaces surrounding the zone as well as equipment and systems in the zone.
Structures and materials
Description of type, density, thermal capacity and thermal conductivity. Walls, floors and roof constructions are built in layers according to the description of the materials. The structures are joined together with the windows and doors to make entire surfaces stating the orientation and slope. Sunshades are defined in relation to the surfaces.
Equipment and functions
Internal loads (e.g. persons, lighting, equipment, moisture load), natural ventilation (e.g. infiltration, venting), heating 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.
Central and local 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 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).
Default libraries
tsbi3 comes with standard libraries for: constructions (walls, floors, roofs, and internal walls), materials, glass, window frames, people loads, schedules and national constants. The user can choose from these libraries or define new input.
Input interface:
Input is given as texts in a menu-driven DOS based environment.


The user can define any of the calculated parameters (more than 67 for each zone plus data from ambient climate, central ventilation plant (if any) and solar walls (if any) as output on hourly basis, in either. tabular or graphically 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.

Computer Platform

PC-compatible, 486 or higher.

Programming Language

C and assembler.


Analysis of the indoor thermal climate in complex buildings or buildings with special requirements for the indoor climate.


No true geometry, and thereby weak models for airflows. Should not be used for detailed analyses of moisture conditions in indoor air.



Danish Building Research Institute


P.O.Box 119
Hoersholm DK-2970


+45 (45) 86 5533


+45 (45) 86 7535






English version: 30000 DKK (approx. 4.000 euro).
Danish version: 25000 DKK (approx. 3300 euro).
Extended version with module for solar walls: +5000 DKK (approx. 670 euro).
Order directly from the Danish Building Research Institute. There is ongoing work for development of a MS-Windows based successor for tsbi3.