Building Simulation applications (BSA) 2015 was the second IBPSA-Italy conference on building performance simulation to take place at the Free University of Bolzano, from February 4th to 6th 2015. The main topics dealt with were: detailed modelling of phenomena and components, integrated and non-energy performance analysis, optimization techniques for high performance buildings and retrofit, and development and validation of new tools. The principal mission of the International Building Performance Simulation Association (IBPSA) is to promote and advance the practice of building performance simulation in order to improve the design, construction, operation and maintenance of new and existing buildings. IBPSA-Italy is the Italian regional affiliate, a non-profit-making association, which includes researchers, developers and practitioners acting on the topic of building performance simulation. IBPSA-Italy was founded in January 2011 and has now more than 140 members including university professors, researchers, professionals, software developers and students.