Integrating Energy Modeling: Designing with WUFI Passive Software

February 20, 2019


WUFI® is a family of software products that have made a big impact on the way we design high performances buildings. The software allows realistic calculation of the transient heat and moisture transport in walls and other multi-layer building components exposed to natural weather. This gives us valuable information that can inform every decision of a project. If integrated into the design process at an appropriate time, WUFI is an invaluable tool in the hands of a Passive House designer.

WUFI® Passive is an acronym for Wärme Und Feuchte Instationär—which, translated, means heat and moisture transiency. This particular version of the software emerged from a partnership between Fraunhofer Institute of Building Physics and Passive House Institute U.S. and it is tailored specifically to the design and certification of Passive Houses. In a dynamic interface it gives the designer real time changes in building heat and moisture performance throughout the day, week, month or year. As well as presenting live on the screen, a customizable summary report can be generated which visualizes the data in a concise and clear way.

By creating an energy model early in the design process, the design team can iteratively test different conditions, materials, assemblies, mechanical systems and shading conditions until the design goals are met. The energy model report breaks these components down to subcategories so the design team can better make adjustments to optimize the building performance.

For example, the report page in the image above examines the balance of transmission losses vs. solar gains of all the windows in the project. In this case, WUFI® Passive sub-divides the windows into orientations so that we can examine the balance for each elevation as they all have different solar conditions. Here we can see the same project modeled with ASHRAE 90.1 minimum windows (bottom) alongside the project modeled with a high performance wood window (above, circled).

The 3D visual interface of WUFI Passive allows for creation of ‘cases’ to look at iterative models side-by-side. Each ‘Case’ displays the performance results caused by iterations of geometries, dimensions, products, assemblies and windows and door specifications. This information becomes invaluable in the process of optimizing a project by determining the biggest impact for the least amount of effort.


John Loercher
John Loercher
John is an instructor for the Passive House Institute U.S., Secretary of the Passive House Alliance - Hudson Valley chapter and Owner of…

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