Daylighting design software

an extensive illustrated lexicon – calculation of relevant values – precious advice – easy handling

cd cover lesodial

Author : B. Paule

Leso-DIAL has been further developed and now replaced by the software DIAL+, which includes the same user-friendly interface but offers greatly extended possibilities and a European climate data base (other climates on demand). DIAL+ is distributed by the EPFL Spin-off company ESTIA.

The Software

Leso-DIAL gave architects relevant information regarding the use of daylight at the beginning of the building design process.


  • Calculation of daylight factor values on the work plane.
  • Appraisal of the daylighting sufficiency:
    According to the lighting requirements, Leso-DIAL estimates the time during which artificial lighting can be switched off (Swiss climate).
  • Diagnosis and advice on how to optimise the daylighting performance.
    Based on fuzzy logic rules, the diagnosis facility of Leso-DIAL indicates the possible weak points of your design.


  • User-friendly (developed by an architect …)! No learning time – no specialist knowledge needed.
  • Graphic, linguistic or numerical description of photometry and geometry – input adapted to the uncertainties of the early design stage.
  • A Lexicon is accessible from any stage of the design. About 100 terms of the lighting vocabulary are presented in a richly illustrated way.
  • The quickness of the whole procedure is particularly well adapted to the testing of various configurations.
  • In the current version of Leso-DIAL, up to 30 openings and atria can be taken into account, and the user has at his disposal an integrated database of case studies.

Related PhD thesis

“Application de la logique floue à l’aide à la décision en éclairage naturel”, Bernard Paule, 1999


Computer : PC 486 or more
Memory : RAM : 16Mb, Disk space : 10 Mb:
System : Windows 3.11, Windows’95, Windows NT

For very complex geometry or photometry, we recommend the “Adeline” Software.
This software is only suited for central European climates. Other climates and additional functions: DIAL-Europe

Further information : leso-pb[at]epfl.ch