LESOSAI: 30 years !!

At a glance

Lesosai is software for the certification and thermal balance calculation of buildings from 1984 containing one or more heated or cooled zones. It is designed primarily for building engineers, HVAC engineers and architects.

The software can be used in the following languages: French, German, Italian and English. It can use many calculation methods, which can be selected one after another. (see "Countries and Standards" below).

New features

  • Lesosai import gbXML file format that is generate by Autodesk Revit, DDS-CAD, Vectorworks, Sketchup (with Plugin) and Archicad. Work with the BIM logic (Building information modeling)
  • Lesosai allows to do the MINERGIE-ECO®, DGNB®, BREEAM, SBNS, SIA2031 and Effinergie labels®.
  • Lesosai includes a wizard that allows you to quickly model a building, ideal for pre-projects and renovation diagnostics. It is now easier and faster !
  • Lesosai includes the module Polysun Inside®, for the simulation, caluclation and dimensioning of solar thermal systems. Lesosai with the modul hourly calculations or with module RT2005/RT2012 France also contain routines for the calculation of photovoltaic systems.
  • Lesosai comunicate with the database MaterialsDB.org and Edibatec
  • Lesosai contains enhanced models of thermal bridges from the SFOE (Swiss Federal Office of Energy) catalogue and communicate with the thermal bridge software flixo energy plus.
  • Lesosai reduces the time taken to create projects: significant financial gains.
  • Lesosai allows to do the labels: Minergie®, Minergie® ECO, SIA2031®, EN 15217, DGNB®, SBNS®, BREEAM®

» Full list of new features

Complete software

Lesosai allows the calculation of environmental impacts of the energy consumption, taking into account the energy used in the building, but also the building's construction materials (Life Cycle Impacts Analysis / Environmental Assessment). This calculation is based on a building life cycle approach, and uses the list of impacts maintained by KBOB (extracted from the EcoInvent database), and the methodology conforming to Swiss Draft Standard SIA2032 (Life Cycle Impacts Analysis complete with ECO+® module).

To calculate the heat transfer coefficient (U-value) we have integrated the software USai, which allows the creation of constructions and materials while controlling condensation. It also allows you to synchronise the database with those of the many materials producers who participate in the materialsdb.org project.

To simulate buildings anywhere in the world, Lesosai includes the meteorological data generator, Meteonorm®. Lesosai include many official meteorological data.

Lesosai can also calculate required heating power, follwing EN 12831 and SIA 384.201by zone or by room. The hourly calculations following EN ISO 13790 are validated with the help of tests follwing EN 15265. Lesosai offers the possibility of calculating the thermal inertia of the buidling by introducing layers of walls (calculation possible under the standard SIA180 and EN ISO 13786).

» Full list of features

Cutting edge software

The developers of Lesosai continually monitor new regulations and standards, and are constantly incorporating new features. The Lesosai user-experience is constantly being optimized to be as quick and easy as possible. The software was developed with support from several institutions and businesses, notably the Solar Energy and Building Physics Laboratory (LESO-PB) of Ecole polytechnique fédérale de Lausanne (EPFL).

» Institutions and Businesses credited


  • RT2012 évaluation (04/02/2016)
    Lesosai a passé avec succès les tests d'évaluation de la conformité aux calculs RT 2012 (moteur de calcul 7.1)
  • Lesosai 2016 build 1001 (02/02/2016)
    Export Polysun:
    - Si Minergie-.P les résultats avec récupération de chaleur sont exportés
    Minergie ECO
    - Lorsque Minergie A/A-ECO est sélectionné, le choix entre A et A-ECO avait disparu. Il a été rétabli
    - Pour Minergie A/A-ECO, les valeurs limites ne sont affichées que si uniquement des zones de type habitat, bureaux et école sont présentes. Les autres types prévus pour Minergie ECO (commerces, salle de sport) ne sont pas valides.
    Calcul horaire
    - Corrigé le calcul du besoin électrique des ventilo-convecteurs
    - Amélioré le rapport
    - Amélioré la gestion de la mémoire
  • Lesosai 2016 est disponible (20/01/2016)
    Lesosai 2016 est disponible à l'achat et au téléchargement. Les principales nouveautés sont:
    * Un nouveau et puissant outil d'optimisation pour les nouveaux bâtiments et la rénovation
    * Minergie ECO 2016 avec la possibilité d'utiliser les valeurs KBOB 2014
    * La nouvelle SIA2024:2015
    * 4 nouveaux calculs horaires de confort extraits de la SIA180:2014
    * ...
    Pour plus d'informations voir notre page web de présentation des nouveautés. nouveautés
    Vous allez recevoir dans les prochaines jours un email avec plus d'informations.
  • Lesosai à la SWISSBAU (05/01/2016)
    Lesosai sera présenté en conférence à la SWISSBAU les jeudi 14 et vendredi 15 à 14h:
    Stand A30 / Halle 4.1
  • Lesosai 2015 build 928 (07/12/2015)
    * amélioré export
    * amélioré les rapports
    * ajouté dépôt SageGlass
  • Nouvelle base de donnée des matériaux (10/11/2015)
    STO SA

» All News

NEW: Lesosai 2016!

Free Download !

Downloads page

Lesosai: » Specifications | » New Features

Why buy Lesosai if I am…
Countries and Standards

Lesosai can perform calcluations under the following standards and performance tests :


  • SIA380/1 2007 and 2009
  • MINERGIE-ECO® Certification
  • DGNB Certification
  • Pre-completing the Minergie® file
  • Exporting ECCB®
  • SIA380/4 Lighting
  • SIA382/2 -SIA2044 Power, energy requirement and operative temperature (air conditioning)
  • SIA380/4 Ventilation
  • Summer overheating
  • SIA384.201 heating power
  • SIA 2031 Primary energy, CO2, air-conditioning (using values from SIA 380/4 and SIA 2024)
  • SIA 2032 Grey energy
  • SIA 2023 window natural ventilation
  • SIA 2028 Official Swiss meteorological stations


  • Calculation of Qh
  • Primary energy and CO2 calculation
  • Energy Passport


  • RT2012
  • RT2005 motor TH-C-E
    (sheet for use)
  • RT refurbishments
  • Ubât, Ubâtréf, Cep, Cepréf, C, Créf, Tic, Ticréf, BBC
  • Standardized reports and XML files
  • Calculations of changes
  • Effinergie Label

And the global calculations methodologies:

  • EN 12831
  • EN ISO 13790, hourly method (heating and cooling needs) and monthly (heating needs)
  • EN ISO 13791
  • Label EN 15217
  • SIA180, EN ISO 13788, EN ISO 6946
  • Building Life Cycle Impacts Analysis
  • PV and solar thermal simulation
Other software and sites
  • USai: Calculation of the U-value follwoing EN ISO 6946 and SIA180, of U-dynamic, and condensation.

  • ECAT: Adapation of Lesosai for the United Kingdom.