ESP-r (Environmental Systems Performance – Research) is an advanced tool for simulating the energy and environmental behaviour of buildings, developed by the University of Strathclyde, in Glasgow. Its approach is based on an integrated model capable of representing heat, air, moisture, light and electrical energy flows with high spatial and temporal resolution. This versatility allows the analysis of complex interactions between different building systems, offering a holistic view of energy performance.

The software is designed for Linux environments, although it can also run on Windows via Cygwin, and is distributed under an open licence, making it accessible for research, consultancy and training. ESP-r uses a finite volume conservation method, transforming building geometry and operating conditions into equations solved dynamically according to climate, occupancy and control systems. Its ability to integrate multiple domains makes it ideal for detailed studies, from energy efficiency to thermal comfort.

It also provides installation resources, documentation and an active community that supports its ongoing development. Thanks to its rigorous and flexible approach, ESP-r has become a benchmark in building and energy system simulation.