Tools & Guides

We develop a wide variety of software and other tools to support the design and operation of energy efficient buildings.


General overview of tools, guides, and software developed by the Building Technology and Urban Systems Division at LBNL.

Whole Building

  • Building Controls Virtual Test Bed (BCVTB): A software environment that allows expert users to rapidly couple different simulation programs via middleware for co-simulation, and to couple simulation programs with real time data from testbeds or operating buildings.

  • EnergyIQ: A tool for Low-cost energy and carbon benchmarking and savings opportunity assessment that bridges whole-building benchmarks with investment-grade audits.

  • EnergyPlus: A new-generation building energy simulation program based on DOE-2 and BLAST, with numerous added capabilities.

  • GenOpt®: An optimization program for the minimization of a cost function that is evaluated by an external simulation program, such as EnergyPlus, TRNSYS, SPARK, IDA-ICE, or DOE-2. It has been developed for optimization problems where the cost function is computationally expensive and its derivatives are not available or may not even exist.

  • Labs21: A benchmarking database tool that allows laboratory owners to compare the performance of their laboratory facilities to similar facilities and thereby help identify potential energy cost savings opportunities.

  • Modelica "Buildings" library: A free, open-source library for modeling of building energy and control systems using the equation-based, object-oriented Modelica language. The library enables rapid prototyping of new building systems, development and performance assessment of control algorithms, and analysis of the operation of existing buildings.


  • Radiance: Radiance is a highly accurate ray-tracing software package that is used to evaluate lighting levels and lighting quality from daylight and electric light in virtually any environment. It provides numerical output as well as high quality, photorealistic images of building environments.

Windows and Envelope Materials

  • COMFEN: A tool to analyze and optimize facade options for commercial buildings, capabilities include evaluation of: energy consumptin, daylighting, glare, and thermal comfort.

  • Optics: Calculates the optical properties of glazing systems composed of multiple glazing layers, laminates, and coatings.

  • RESFEN: Helps consumers and builders pick the most energy-efficient and cost-effective window for a given application, for new homes, additions, or as window replacements. It calculates heating and cooling energy use and associated costs as well as peak heating and cooling demand for specific window products.

  • THERM: Used by building component manufacturers, engineers, educators, students, architects, and others interested in heat transfer. It models two-dimensional heat-transfer effects in building components such as windows, walls, foundations, roofs, and doors. It is useful where thermal bridges are of concern.

  • Berkeley Lab WINDOW: Calculates performance of window and shading systems. It can be used to design and develop new products, teach about heat transfer through windows, and help develop building energy codes. It calculates total window thermal performance indices (i.e. U-values, solar heat gain coefficients, shading coefficients, and visible transmittances) for glazing and framing, as well as thermal and solar optical effects of a wide range of interior, between glass, and exterior shading systems.

Legacy Tools