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Building Energy Savings and Cost Analysis (BESCA)

BESCA (Building Energy Savings and Cost Analysis) is a whole building energy analysis and thermal load simulation program that engineers, architects, and researchers use to model energy use in buildings. Modeling the performance of a building with BESCA enables building professionals to optimize the building design to use less energy. BESCA models heating, cooling, lighting, ventilation, and other energy flows. BESCA includes many innovative simulation capabilities: time-steps less than an hour, modular systems and plant integrated with heat balance-based zone simulation, multizone air flow, thermal comfort, water use, natural ventilation, and photovoltaic systems.

Based on a user’s description of a building from the perspective of the building’s physical make-up and associated mechanical and other systems, BESCA calculates heating and cooling loads necessary to maintain thermal control setpoints, conditions throughout a secondary HVAC system and coil loads, and the energy consumption of primary plant equipment. Simultaneous integration of these and many other details verify that the BESCA simulation performs as would the real building.

The following is a representative list of BESCA capabilities:

  • Integrated, simultaneous solution where the building response and the primary and secondary systems are tightly coupled (iteration performed when necessary)
  • Sub-hourly, user-definable time steps for the interaction between the thermal zones and the environment; variable time steps for interactions between the thermal zones and the HVAC systems (automatically varied to ensure solution stability)
  • ASCII text based weather, input, and output files that include hourly or sub-hourly environmental conditions, and standard and user definable reports, respectively
  • Heat balance based solution technique for building thermal loads that allows for simultaneous calculation of radiant and convective effects at both in the interior and exterior surface during each time step
  • Transient heat conduction through building elements such as walls, roofs, floors, etc. using conduction transfer functions
  • Improved ground heat transfer modeling through links to three-dimensional finite difference ground models and simplified analytical techniques
  • Combined heat and mass transfer model that accounts for moisture adsorption/desorption either as a layer-by-layer integration into the conduction transfer functions or as an effective moisture penetration depth model (EMPD)
  • Thermal comfort models based on activity, inside dry bulb, humidity, etc.
  • Anisotropic sky model for improved calculation of diffuse solar on tilted surfaces
  • Advanced fenestration calculations including controllable window blinds, electrochromic glazings, layer-by-layer heat balances that allow proper assignment of solar energy absorbed by window panes, and a performance library for numerous commercially available windows
  • Daylighting controls including interior illuminance calculations, glare simulation and control, luminaries controls, and the effect of reduced artificial lighting on heating and cooling