ESP-r logo.

General purpose simulation environment which supports an in-depth appraisal of the factors which influence the energy and environmental performance of buildings. The ESP-r system has been the subject of sustained developments since 1974 and in 2002 converted to the GNU Public License.

ESP-r has the objective of simulating building performance in a manner that: a) is realistic and adheres closely to actual physical systems, b) supports early-through-detailed design stage appraisals, and c) enables integrated performance assessments in which no single issue is unduly prominent.

ESP-r attempts to simulate the real world as rigorously as possible and to a level which is consistent with current best practice in the international simulation community.

By addressing all aspects simultaneously, ESP-r allows the designer to explore the complex relationships between a building's form, fabric, air flow, plant and control. ESP-r is based on a finite volume, conservation approach in which a problem (specified in terms of geometry, construction, operation, leakage distribution, etc.) is transformed into a set of conservation equations (for energy, mass, momentum, etc.) which are then integrated at successive time-steps in response to climate, occupant and control system influences. ESP-r comprises a central Project Manager around which are arranged support databases, a simulator, various performance assessment tools and a variety of third party applications for CAD, visualisation and report generation.

In keeping with the philosophy of linking ESP-r to other modelling systems, users can now export to EnergyPlus an ESP-r model with materials, constructions, surfaces (all three and four sided surfaces as well as those including one window or one door - more complex surfaces are omitted). Boundary condition attributes are translated and the parent/child relationship between opaque and transparent surfaces established. The exported models usually pass the EnergyPlus parser with no errors or with minor warnings. Currently, approximate optical properties are established and schedules are not yet included. We anticipate updating the geometric filters to match the EnergyPlus V 1.2.1 release (October 2004) as well as including casual gain schedules in the near future.


energy simulation, environmental performance, commercial buildings, residential buildings, visualisation, complex buildings and systems


ESP-r has been extensively validated. See Strachan P A. 2000. 'ESP-r: Summary of Validation Studies', ESRU Technical Report, University of Strathclyde, Glasgow. for more information.

Expertise Required

Understanding of thermo-physical processes in buildings, environmental systems and controls.


Hundreds of users, primarily in Europe and Asia.


Engineers, researchers, architects, energy consultants.


Building geometry can be defined either using CAD tools or in-built facilities. ESP-r is compatible with the AutoCAD and ECOTECT which can be used to create a building representation of arbitrary complexity. Models can be exported to other assessments tools such as TSBI3 and Radiance. Constructional and operational attribution is achieved by selecting products and entities from the support databases and associating these with the surfaces and spaces comprising the problem. Models can be further attributed to account for temporal shading and insolation patterns, explicit radiation view factors, facade-integrated photovoltaic modules, temperature dependent thermophysical properties and CFD domains. As required, component networks can be defined to represent, for example, HVAC systems, distributed fluid flow (for the building-side air or plant-side working fluids) and electrical distribution systems.

Simulations: With ESP-r functionality follows description - simple models and operating regimes composed in a few minutes can be extended, in steps, to encompass the simultaneous solution of fabric (1/2/3D), air flow (network and/or coupled, transient CFD), electrical power, embedded renewables, plant system components, indoor air quality and lighting assessments via Radiance. Building and flow simulations can be undertaken at frequencies of one minute to one hour and system simulations can be from fractions of a second to an hour.


Results analysis modules are used to view the simulation results, undertake a variety of performance appraisals and explore the interactions between assessment domains. Tools are provided to enable the construction of an Integrated Performance View which summarises performance over a range of relevant criteria. Changes to the model parameters can then follow depending on these appraisals. The range of analyses is essentially unrestricted and data can be exported to other analysis and graphing tools.

Computer Platform

Sun-Solaris, Silicon Graphics: Sparc5 or newer, 96+MB memory.
Linux (Redhat/ Mandrake/ SUSE etc): Pentium or newer, 128+MB memory.
Mac OS X 10.1 or newer, 128+MB memory.
Windows NT/2000/XP (graphic mode running under Cygwin), Pentium or newer, 128+MB memory. Windows NT/2000/XP (console application for batch processing), Pentium or newer, 128+MB memory.
Disk requirements: ~12MB source distribution, ~200MB executables/libraries/example problems, 50-500MB user project folders.

Programming Language

C and FORTRAN (F77 or F90) Compiles with most Unix and Linux compilers, GNU compilers and MINGW.


ESP-r is flexible and powerful enough to simulate many innovative or leading edge technologies including daylight utilisation, natural ventilation, combined heat and electrical power generation and photovoltaic facades, CFD, multi-gridding, and control systems. An active user community and mailing list ensures a quick response to technical issues.


It is a general purpose tool and the extent of the options and level of detail slows the learning process. Specialist features require knowledge of the particular subject. Although robust and used for consulting by some groups, ESP-r still shows its research roots.



Department of Mechanical Engineering


University of Strathclyde
James Weir Building
75 Montrose Street
Glasgow, Scotland G1 1XJ
United Kingdom


+44 (141) 548 3986


+44 (141) 552 5105




ESP-r is available a GPL license and is available for free download.

Support agreements available (contact ESRU).

See web page for information on training. A listing of simulation capabilities is available here. Users can browse the source code through a cross-referenced page.