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


  • Nouveau TRYBA (07/10/2016)
    Lesosai intègre les fenêtres TRYBA pour les calculs Suisse!
  • Nouvelle base de donnée des matériaux (06/10/2016)
  • Lesosai 2016 build 1023 (05/10/2016)
    - importation des ombrages lointain selon Suntag.ch
    MoPec 2014:
    - calcul de la puissance selon la SIA384/3
    - intégration de l'EGID
    - amélioré la gestion: vers bâtiment à la temp. de ...
    - corrigé le problème nouveau RGD et ZNC réel
    Calcul horaire:
    - possibilité de changer les surfaces des locaux par groupes
    - corrigé bug de l'ombrage sur lui même
    - amélioré rapport des constructions
    - amélioré plusieurs écrans
    Calcul horaire:
    - corrigé énergie éch. rot.
    - corrigée calculs éch. rot. absorpt.
    SIA380/1 comp.:
    - amélioré calcul puissance
  • 19.09.2016 (18/09/2016)
    Aujourd'hui 19.09.2016, le bureau de Lausanne reste fermé pour le Jeûne fédéral
  • Lesosai 2016 build 1022 (08/09/2016)
    Normes Suisses:
    - connexion à la base de donnée officielle pour la recherche du numéro EGID et compléter l'adresse
    - Les modèles de ponts thermiques sont crées adaptés aux constructions
    MoPEC 2014:
    - amélioré le calcul et rapport SIA380/4 ventilation
    - corrigé rapport SIA380/1
    - amélioré le rapport
    - corrigé position de la classe dans le label
    Calcul horaire:
    - adapté chapitres 1.1 et 1.2 à la SIA2024:2015 dans le rapport
    - corrigé graphique température
    Fabricants de fenêtres:
    - adapté Lesosai à avoir plusieurs fabricants de fenêtres
    - introduits les vitrages Tryba
  • Formations Lesosai automne - romandie (01/09/2016)
    Cours Lesosai & SIA384.201
    Calorimétrie-dim. chaudière
    Comprendre la norme, définir la ventilation et dimensionner la chaudière, vérifier la puissance pour Minergie P®07.09.2016
    (13:30 à 16:00)
    Lausanne220.- CHF/p.inscription

    reste 4 places
    Lesosai Bases
    collaboration FE3
    SIA380/1, Rapports, Exercices simples13.09.2016
    (08:30 à 12:30)
    Lausanne320.- CHF/p.inscription
    Lesosai AvancéSIA380/1, CECB, MINERGIE®, import gbXML, astuces d'utilisation13.09.2016
    (13:30 à 18:00)
    Lausanne400.- CHF/p.inscription
    Lesosai et le confort thermique
    collaboration FE3
    Application des normes SIA 180 et SIA382/1 version 201415.09.2016
    Lausanne400.- CHF/p.inscription
    flixo energy plus & Lesosai
    Nouvelle formule
    Import-export ponts thermiques entre flixo energy plus et Lesosai. Gestion et exercices ponts thermiques simples et complexes27.09.2016
    (09:00 à 12:00)
    (13:30 à 16:30)
    Lausanne500.- CHF/p.inscription
    Lesosai & SIA382/2 + SIA2044 - besoins chaud/froidCalcul des puissances et des besoins (chaud et froid) selon SIA2044 et SIA382/2.
    (13:00 à 18:00)
    Lausanne400.- CHF/p.inscription

» 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.