Suisse record of 300 m² of solar thermal collectors based on drainback for a large appartments block at Chemin de Mouille Galant in Geneva. They have been modernised in order to reach the passive standard 'Minergie". To acheve this, the insulation has been strengthened, an mechanical ventilation has been placed and the installation of over 300 square meters of solar collectors Optisun 245V has been placed. This is Cooltec, Sunoptimo's partner in Switzerland, who managed the project from design to commissioning. This installation is part of the top-5 largest solar thermal system in Switzerland and certainly the largest in Drainback!