Building Energy Software Tools
Formerly hosted by US Dept. of Energy    


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EFEN is a next generation energy analysis tool using EnergyPlus simulation engine and intelligent building generator. It is packaged in a user friendly program suitable for quick analysis in early stages of design, comparative energy analysis of different fenestration options and prediction of the whole building energy use, and prediction of the size of HVAC equipment.

EFEN is also very useful in early stages of design when decisions are made about the placement and type of fenestration products, building orientation, overall building shape, prediction of the whole building energy use and prediction of the size of HVAC equipment.

More info can be found here:

Expertise Required: 

EFEN does not require expertise for simpler models, so it can be used by students, but it also allows expert users freedom to do in-depth analyses and model various special cases.


EFEN uses custom project file format (.efm) to store user settings for different projects.


EFEN produces reports in various formats and with customizable content elements.


- Simple, comprehensive UI which provides ease of use and steep learning curve
- Optimized models for fairly quick simulations
- Ability to control various details in overall models
- Customizable reports

United States
Major Capabilities: 
HVAC System Selection and Sizing
Free To Try
Last Software Update: 
12 March 2015
Last Entry Update: 
03 October 2015
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