CoDyBa  logo

CoDyBa is a design tool on classical PC for buildings dynamic performance simulation. It is intended for design offices, teaching, and research organizations. The new CoDyBa version is called KoZiBu. A prototype can be downloaded for free.

CoDyBa is used to analyze dynamic hygrothermal performance of building elements when subjected to any kind of climate conditions. The tool helps the user conduct studies of heating and cooling strategies, air conditioning or ventilation options, and insulating materials. The main objective is to forecast the energy consumption, temperature, and humidity evolution range.

It enables the user to estimate the instant heating or cooling powers needed to maintain a given set point, or to calculate the indoor temperatures when the heating or cooling system is insufficient. Humidity is treated the same way. CoDyBa can be used to investigate the energy performance of buildings of almost any type and size. In addition to performing peak load calculations necessary for mechanical equipment design, CoDyBa also estimates the annual energy performance of the building. For more details, see the samples.

CoDyBa is based on bricks assembled to form a complex building with its equipment. Through the graphical interface, users construct a model of the building's geometry using basic elements (air volumes, walls, windows). With the interface users can add internal loads and HVAC-systems into the created model of the building and perform thermal calculations.

The building main screen is like the Windows Explorer.

An accurate building description is provided via a graphical interface, which includes a building tree, similar to Windows Explorer. The building tree is used to describe the general building structure. Users can choose to display different hierarchies of information, zone level, etc. Within the interface, each entity is associated with a graphical representation that the user can manipulate via "copy", "paste", and "drag-and-drop".

The input entities are currently used by professionals; the calculation models are treated in a transparent manner.

CoDyBa has no limit on air volumes number (thermal zones). It can simulate buildings of any size. The only real limit is the time used to input data. Screen Shots


Energy simulation, energy efficiency, building performance, renewable energy, comfort, thermal analysis, indoor air temperature, dynamic simulation.


The BESTEST benchmark (International Energy Agency) was passed successfully (see report in pdf format). This benchmark is the most precise and the most reliable which exists. Then CoDyBa can simulate the performance of 155 buildings in the BESTEST protocol and in almost all the cases matched the performance of other reference energy programs.

Expertise Required

Understanding of thermophysical processes in buildings is desirable. Engineering background is helpful to analyze calculation results. One day of training is desirable, but not necessary for those familiar with building modeling (no training courses are required). CoDyBa is designed for nonexperts on simulation methods, but has an advanced level appreciated by simulation experts.


More than 50 (in France and other countries).


Engineers, researchers, architects, energy consultants (architecture/engineering firms, utilities, equipment manufacturers); students of engineering and architecture.


The basic data are the building geometry and constitution: air volumes, walls (with the materials of layers and the surface parameters), windows (possibility for solar masks). The main parameters are the climate (several meteorological files for French cities are supplied), internal loads (from lighting, people, equipment), regulators (powers and set points for temperature, humidity, and ventilation). Virtually everything is defaulted but modifiable. The user adjusts descriptions using fill-in menus.


A number of results graphs may be viewed and printed. These graphs can compare selected alternatives or selected hourly variables to find information about energy use. All results graphs can be exported to other packages such as Microsoft Excel or Word for customized report generation. The user chooses the desired graphical output for each entity or for the whole building. The following graphical outputs are available (as hourly time function): - Building: sensible and latent powers (sum of all air volume powers). - Air volumes: sensible and latent powers, indoor air temperature, resultant temperature (average of air and wall temperatures), air relative humidity. - Surfaces: absorbed direct and diffuse solar fluxes, surface temperature (useful for thermal comfort evaluation). - Windows: transmitted direct and diffuse solar fluxes, sunlit fraction, direct and diffuse transmission coefficient, global transmission coefficient g. - Regulators: power. CoDyBa produces input summary reports that may viewed on-screen or stored as rtf files.

Computer Platform

PC-compatible, Windows 95 or higher, Pentium processor with 20 Mo of RAM is recommended

Programming Language

The software has been built in an Object-Oriented Programming language : C++ (use of a hierarchy of classes to represent the building).


No limitation in the numbers of air volumes (thermal zones, see sample 1), simplicity of use, ease of input data, multi-zone calculation, computational speed.


Equipment is modeled very simply (maximum power, set point, activity). Lack of global input of building data.



Centre de Thermique de Lyon, UMR CNRS 5008


Département Génie Civil et Urbanisme
INSA de Lyon, Bât. Freyssinet
20, Av. A. EINSTEIN 69621 Villeurbanne Cedex





The single-zone version is free (download) and can be used as demo version. Special price for Department of Education and training organizations: ½ * Base price.