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The design team of the award-winning Theresa Passive House utilized the principles of the AIA’s Framework for Design Excellence, in addition to other building performance standards, as a guide for best practices in incorporating sustainable design strategies. Composed of 10 principles that originally stemmed from the AIA’s Committee on the Environment (COTE) Top Ten Award, the Framework for Design Excellence supports a clear vision for an equitable, resilient, and healthy built environment. The intention of the framework is to act as a resource for the designer and client at the initiation of every project, regardless of size, typology, or aspiration. Targets within three of the framework’s categories — Energy, Change, and Discovery — were exceeded within the Theresa Passive House and are detailed as follows.

Design for Energy

Completed in 2020 by Forge Craft Architecture + Design & Hugh Jefferson Randolph Architects, the Theresa Passive House was a pilot project for the PHIUS 2018+ Passive Building Standard. It is one of the first Passive House projects located in a hot, humid climate and is the first project in the South to receive PHIUS Source Zero Certification. At the time of its completion, it received the highest rating by the Austin Energy Green Building and has met the AIA 2030 Challenge by consuming 75 percent less energy than a typical new home. The project utilized WUFI Passive energy modeling software during the design of the project in order to inform design decisions.

Through the Passive House certification process, the project utilized assembly strategies that ensured maximum comfort and efficiency. The building envelope consists of tri-pane windows and continuous insulation, with insulation values that are double the code minimum.

The construction process included on-site verification and testing, including rigorous testing for air-tightness. This project was able to achieve air-tightness levels that are 15 times tighter than code in order to meet the rigorous standard required by Passive House.

The carefully designed HVAC system efficiently delivers fresh, filtered air using a VRF heat pump with dedicated dehumidification and a separate ERV ventilation system.

Design for Change

A team of researchers from The University of Texas at Austin have actively tracked the thermal performance of the Theresa Passive House and compared it to UT’s own research code baseline house. As seen in the above table, the Theresa Passive House surpasses the case study house in regulating internal temperature during a power outage. This shows how structures can be designed for resilience and passive survivability as the climate becomes more extreme and unpredictable. The energy-efficient design strategies adopted by the designers allow the house to maintain a comfortable environment during extreme weather events.

Due to the Passive House strategies adopted within the project (airtight envelope, robust insulation, and careful glazing and shading), the structure acts as its own battery, storing cool energy to reduce demand on the grid. During power outages, the house generates its own power through photovoltaic and battery backup, which can provide 60 percent of the home’s total energy demand.

Design for Discovery

As emerging design professionals, the homeowners intended for the project to be a forum for learning. University of Texas at Austin students attended on-site tours during construction, and lunch-and-learn presentations were given for regional AEC professionals, where installation demonstrations for windows, air-sealing products, blower door testing, and other high-performance products and systems took place.

By means of circuit-level monitoring within the house, the homeowners can utilize dashboards to observe the performance and energy usage of numerous systems — such as the air conditioner and hot water systems — as well as plug loads. This readily accessible data has assisted the homeowners, post-occupancy, in improving the performance of the house when outliers in expected performance are observed.

The Theresa Passive House is a highly successful case study on how the Framework for Design Excellence can be adapted to the residential scale. It illustrates one of the most important features of the framework: that it is specifically designed to be utilized by all projects, regardless of square footage or building type. Created as the defining set of principles for good design in the 21st century, the framework will aid every architect and client in promoting a more sustainable, equitable, and resilient built environment.

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