This article covers the role of WUFI® Passive in passive house design and how to use cove.tool alongside WUFI Passive in pursuit of a Passive House Institute US, Inc. (PHIUS) certification for PHIUS+.
What is WUFI®?
The WUFI® family of software, developed by the Fraunhofer Institute for Building Physics, provides realistic simulation for one- and two-dimensional heat and moisture transfer within wall assemblies. WUFI® is an acronym for Wärme Und Feuchte Instationär—which, translated, means heat and moisture transiency. WUFI® software uses the latest findings regarding vapor diffusion and moisture transport in building materials. The software has been validated by detailed comparison with measurements obtained in the laboratory and on IBP’s outdoor testing field. Different versions of WUFI® can be used for materials, components, and entire building systems. Building component simulations (WUFI® Pro and WUFI® 2D) are assembly-by-assembly modeling tools to evaluate thermal and hygric properties across the assembly. Whole building simulations (WUFI® Plus and WUFI® Passive) address the conditions on the interior of the building, as well as indoor climate simulations and energy calculations.
WUFI® Passive is a building energy modeling tool that is part of the WUFI® family of products. It was developed in collaboration with PHIUS in order to create a tool tailored to North American climates and improve the design process for Certified Passive House Consultants (CPHC).
WUFI® Passive brings energy modeling and WUFI’s hygrothermal analysis together in one tool, using both static and dynamic modeling and compatibility with SketchUp and gbXML importing. One of the critical aspects of WUFI® is its ability to move between static and dynamic modeling and the availability of high-quality reporting. It allows users to validate PHIUS+ criteria, and it is the only accepted method for PHIUS CORE 2021 and ZERO 2021 compliance energy modeling
How does WUFI® Passive relate to the Passive House standard and PHIUS?
PHIUS+ is a calculated standard for building energy performance that incorporates quality insurance inspections and low-moisture risk design solutions. This is the leading building performance certification in North America, and the program certifies the U.S. Department of Energy’s (DOE) Zero Energy Ready Home status, the U.S. Environmental Protection Agency’s (EPA) Indoor airPLUS label, and the RESNET HERS Index score as part of the certification.
You can read more about PHIUS, their certification system, and how cove.tool relates to it here.
WUFI® Passive and cove.tool
WUFI® Passive is commonly used before and after meeting the Passive House standard for design and validation, and it serves as the only accepted compliance model for PHIUS CORE and ZERO 2021. However, cove.tool can fit into the PHIUS workflow alongside WUFI® Passive. For each of the required Passive House design principles, cove.tool allows users to customize inputs and assess the impact on the project’s energy consumption and cost premiums.
After completing design simulation and evaluation in cove.tool, users can export their project from loadmodeling.tool into a gbXML format and import project information into WUFI® Passive in order to validate results to comply with PHIUS+ criteria. Alternatively, if you are not using loadmodeling.tool in your workflow, you may choose to use cove.tool to validate design decisions, and then export your geometry from your modeling software of choice into WUFI® Passive for final validation for PHIUS+. This means that cove.tool can fit into your existing workflow for passive house design so that you can leverage the early-stage design flexibility of cove.tool’s analysis methodology to meet the PHIUS+ space conditioning and source energy criteria.