1) Download the software

Download Lesosai !

This is the full version, including all the modules. » Spécifications

Download Lesosai 32bit
Download Lesosai 64bit*

Save the file, then install it on your computer

2) Try the software

A) Use the DEMO version:

No time limit,
but restricted functionality.

B) Use the TEST version:

No limit to functionality,
but a time limit of 10 days.

»See 'Terms of Use', below

3) Buy the software

Order the software via the internet with or without modules.

Pay-it when you want !

» Prices

» Order on line

Versions of Lesosai

Lesosai 2020 is the current version. It downloads as a single, complete version. It can serve as a DEMO version, not limited in time. It is possible to order a free TEST version, with full functionality, limited to 10 days use. The modues and certain functions are automatically activated with the purchase of a license from within the software itself.

Current version only Date Version File
Lesosai 2020 : SIA380/1 (2007, 2009, 2016), Minergie®, Minergie-ECO®, SIA 2028, export CECB®, Luxembourg, SIA380/4, SIA387/4, RT2012 (motor 8), RT2005, SIA2044, DLGs 311 (2010), USai, SIA382/1, SIA382/2, EN12831, EN13790, EN13791, DGNB, SNBS, SIA180 25.02.2020 2020.0 build 1501 Download 32bit
Download 64bit*

* Module Polysun Inside and module RT2005 aren't compatible with the version 64bit

Previous versions are available for existing customers.

Previous versions Date Version File
Lesosai 2019 (available only to those with an existing license) 24.01.2020 2019.0 build 1425 Download 32
Download 64
Lesosai 2018 (available only to those with an existing license) 31.01.2019 2018.0 build 1224 Download 32
Download 64
Lesosai 2017 (available only to those with an existing license) 02.02.2018 2017.0 build 1125 Download
Lesosai 2016 (available only to those with an existing license) 10.06.2017 2016.0 build 1034 Download
Lesosai 2015 (available only to those with an existing license) 19.12.2015 2015 build 928 Download
Lesosai 7.4 (available only to those with an existing license), RT2012 (moteur 6.3) 29.01.2016 7.4 build 875 Download
Lesosai 7.3 (available only to those with an existing license) 19.06.2013 7.3 build 790 Download
Lesosai 7.2 (available only to those with an existing license) 03.01.2013 7.2 build 753 Download
Lesosai 6.0 (available only to those with an existing license) 09.11.2010 6.0 build 551 Download
Lesosai 5.7 (available only to those with an existing license) 05.05.2008 5.7 build 357 Download
Lesosai 5.6 (available only to those with an existing license) 25.04.2008 5.6 build 351 Download
Lesosai 5.0 (available only to those with an existing license) 17.02.2005 5.0 (138-270) Download

Update information (News) 2019, 2018, 2017, 2016, 2015 (in french)

Information Update 7.0 (in french)

Updated information: 6.0

Updated information: 5.6/5.7

Updated information: 5.0

DEMO version and TEST version: Terms of Use

After installing Lesosai, there are two ways in which to test the free software and its features:


DEMO version

Upon installing the software, you have access to the DEMO version.

This version is not limited in time, and contains only the basic version. It does not include the following features:

  • creation
  • backup
  • printing
TEST version

You can request a TEST version, àlicense from the Order online.

This version is limited to 10 days and provides access to all the features and modules, without exception.

Several sample projects are included, for use during testing.




Eco-Sai is software for calculating the thermal conductivity (U-value) and risk of condensation within a wall. It helps to check whether the composition of a wall can induce harmful condensation. It also enables the rapid modelling of several solutions to renovate the facades, and to control the U-value.


Materialsdb is a tool for exchanging information between the manufacturers of materials and calculation software in the field of building physics. Funded by the manufacturers, the use of this integrated data base software is free.