The Theresa Passive House in Austin

Passive House for Extreme Temperatures



Homeowners in the U.S. can build and improve their homes to be more resilient to increasing climate extremes. We aim to educate homeowners about climate-related risks and opportunities to reduce potential damage to homes and save lives. 


In this series of blogs, we share stories of climate-resilient homes that proved their resilience by withstanding extreme weather events. 


Trey Farmer, an architect in Austin, Texas, lives in such a home that he designed with his wife Adrienne of Studio Ferme in collaboration with their friend and fellow architect Hugh Jefferson Randolph. The Theresa Passive House, one of the first passive house-certified projects in the south, is home to Farmer’s family. Soon after moving in, they experienced two prolonged winter power outages in which the outdoor temperatures were significantly lower than the design temperatures used to design the heating and cooling.  


The house coasted quite well and preserved the indoor heat for much longer than it would have with a regular new construction built to code – as expected for a home designed to the Passive House (PHIUS) standards. In fact, in a simulated power outage during a cold snap, indoor temperatures within homes constructed before 1950 dropped to below 40 degrees Fahrenheit within eight hours. For 2009 code-compliant buildings, the temperature dropped below 40 degrees after 45 hours. Homes with Passive House standard building envelopes and net-zero energy buildings maintained safe indoor temperatures for over six days before indoor temperatures fell below 40°F.


The extra insulation, air tightness, and the ability to store energy allowed the house to maintain comfortable temperatures in Farmer’s home for three days and livable conditions much longer.

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Living in the house for eight years before the renovation, they had experienced several climate events, such as extreme heatwaves, floods, and wildfires nearby, which formed a clear vision of the climate risks they wished to prepare for. Choosing the Passive House Standard supplied solutions to many of these climate issues. 


Unfortunately, most of the framing in the 85-year-old house had significant termite damage and couldn’t be reused. As a result, Farmer rebuilt using a prototype proof-of-concept of the healthiest, most energy-efficient, and most resilient home possible, considering the historic preservation controls in the house’s historic neighborhood.

Climate Resilient Strategies Used in the Theresa Passive House

Farmer’s home was rebuilt to the Passive House standards and designed to perform better than Net Zero. It is exceptionally airtight and insulated, about 10 times tighter than the code in Austin, and double the insulation of a regular construction residential home. Read more about the Passive House Standard and concept here

Farmer specified some of the strategies used in the design and construction of the Theresa Passive House:

  • A fully enclosed and air-sealed envelope to stabilize indoor temperatures at times of extreme heat or cold, even during power outages. The tight envelope also helps preserve indoor air quality and prevents smoke from entering the house during wildfires, while neighboring homes in similar circumstances might need to take measures such as placing towels under their doors and windows to keep the smoke from coming in. 
  • Continuous ventilation through the Energy Recovery Ventilator (ERV) is crucial with a properly sealed envelope, contributing to healthier indoor quality and preventing smoke or other pollutants from entering the house. A combination of these two strategies with a supplemental filtration system and pleated filters ensures the best air quality possible daily and during extreme weather and pollution events.
  • Above-code insulation contributes to maintaining stable indoor temperatures during power outages. The insulation reduces the energy use daily, especially during peak demand, lowering the burden on the grid, which benefits broader societal resilience.
  • A highly efficient HVAC system (see below) and dedicated dehumidification. Dehumidification is popular in Passive Houses in Austin and houses in general due to significant humidity build-up, especially in the shoulder seasons when the HVAC isn’t used much and doesn’t participate in removing moisture. 
  • A battery backup system paired with a PhotoVoltaic Solar system.
  • A standing seam metal roof. This roofing strategy is beneficial for PV installation and rainwater capture and can withstand storm and hail damage, which is common in Austin. A recent hail storm damaged and broke windows of friends’ houses and cars and damaged roofs in the neighborhood. The standing seam metal roof provided confidence that the house could withstand those events.

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  • Triple-pane casement operable windows provide further insulation and protection while preserving the historic aesthetic. The location of the windows allows cross-ventilation for passive cooling. 
  • Fire-rated exterior walls abide by Austin’s stringent fire building code. Furthermore, the passive house standards that include the simple design form, the enclosed and airtight envelope, and the metal roof reduce the risk of embers accumulating in nooks and crannies or entering through soffit vents into the attic and igniting a fire. 
  • Under the house runs a watershed that flooded recently. Luckily, the lot is well-positioned and elevated. The landscape’s design ensures minimal water runoff while securing access to and from the house in case of flooding. 


Farmer recognizes a growing interest in resilient homes. The requests usually revolve around specific structural systems for resilience, such as Steel Framed Homes or Insulated Concrete Forms (ICF). Farmer is supportive of novel building strategies but has found the challenge of finding experienced builders for specific systems and the risk of a cost increase has dissuaded most clients from initially looking at those strategies. Furthermore, a specific strategy by itself doesn’t always provide resilient solutions for the building as a whole. 


For example, metal frames with metal siding are strong and durable but act as thermal bridges that allow heat to infiltrate the home. ICFs are considered insulated and fire resistant, but wouldn’t necessarily make a home better withstand fire than a stick-built house properly built with resilience in mind. 

The better approach, per Farmer, is to look at the final goal and the resilience desired and find the optimal solution. For Farmer and his firm, Forge Craft Architecture, and Design, the benefits of the Passive House standard are so great that the firm has decided to design all their custom homes this way and is even applying some of these same principles to large commercial developments.


Climate Resilient Building Materials 

The choice of familiar building materials in Theresa Passive House’s construction was purposeful to prove that building passive houses is achievable and not much different from regular construction. Most of those materials have been frequently used by builders for years, with minor changes. 


Some of the building materials used in this specific project:

  • Hardie artisan siding is an extra-thick siding for better protection that matches the historic profiles of the neighborhood. It's an inflammable, durable, and low-carbon building product, and was acceptable to the local historic preservation group.
  • Zip R systems for sheathing and continuous insulation instead of plywood, Water Resistive Barriers (WRB), and continuous insulation. The zip system is a ubiquitous product with insignificant additional cost.

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  • Rockwool insulation in the roof and walls, mainly to avoid spray foam. 
  • As mentioned, a standing seam metal roof is the best practice, with its durability over time and during hail storms. This roof also has less embodied carbon than a shingle roof, is recyclable, is convenient for installing Solar PV, and is ideal for capturing rainwater. Berridge was picked as a local dealer in Austin.
  • Mitsubishi Variable Refrigerant Flow (VRF) as the HVAC system helps in long-term outages because it can operate with battery backup. It has a two-stage operation, turning on at a very low amperage and only then increasing intensity.

Cost of Climate-Resilient Strategies and Materials

Farmer’s experience with resilience, health, and building science taught him that it doesn’t necessarily take expensive products to build a climate-resilient home, but rather the knowledge to build it better.


Yes, traditional construction is usually less expensive upfront, but considering the reduced energy bills, lower insurance premiums, and less potential damage, building properly has a good return on investment


“And what is the cost of our health and our kids' health and knowing that you got the best indoor air quality, that your house is comfortable and performs well in power outages due to extreme weather events?” Farmer asks. “I think even just the peace of mind is valuable.” 


He shows a slight price increase in the total cost of the Theresa Passive House in Austin. After amortizing the cost increase and deducting the utility savings, the price addition is reasonable, especially considering the resilience, safety, and health benefits.


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One of the larger Passive House projects Farmer is working on is a $3.5 million duplex. The cost of adding Passive House strategies was $75,000, a mere 2% increase, which is a reasonable consideration.


Gaining experience building Passive Houses, Forge Craft has established a best practice and is working with builders and clients who understand the value of resilience and health. Eventually, this also lowers the time and cost of the construction. 


For the time being, higher-end custom homes are the easiest targets for passive housing as the minimal additional cost ends up being just a fraction of the budget. Farmer hopes to use this knowledge and lessons learned to lower the cost of passive house buildings, making it achievable for a wider audience. 


“Our clients are making one of the biggest financial investments of their lives, so we want to give them the best possible house for that investment, the most resilient house in the face of increasingly extreme weather events and wildfires, and the healthiest indoor air quality possible throughout the years,” Farmer says. “We're building the best way we know, we always try to improve, and we're always looking back at what we've done to see what we can do better.” 


Trey Farmer

Trey Farmer is a Principal and Partner, Chief Sustainability Officer at Forge Craft Architecture. The firm focuses on housing, primarily but not exclusively. They work with emerging technologies such as modular and 3D printing, building, and structural systems to push the boundaries of the art and science of design. As mentioned, the firm has committed to designing all custom homes to meet Passive House Standards. The firm also specializes in affordable housing, working extensively with mission-driven nonprofits. For example, the firm currently works with an organization that provides housing to young adults exiting the foster care system who would otherwise be at risk for homelessness. Resilience is wrapped into all projects, and they are working diligently to nudge multifamily projects closer to Passive House certification.


Farmer’s motivation is to build better. He joined the architecture arena as a sustainability advocate. He enjoys what he does and feels lucky to be able to accomplish only projects he can truly get behind. Thinking about the infinite number of projects he will participate in his lifetime, he wants to ensure those are the best projects possible. 


Sharing the Climate Resilient Design Knowledge

Farmer does his best to share what he knows to create positive impacts in the building community locally and beyond. He’s cultivated a network of individuals who attempt the same so they can learn from one another, share what's working and what's not, and move the needle on low-carbon, healthier, and more resilient buildings.

Farmer shares his knowledge on Passive House and resilient buildings at several levels:

  • Participates in the Urban Land Institute (ULI)’s Climate and Resiliency Strategic Council. The council is developing a report for the City of Austin, looking at broader climate resilience and adaptation causes and effects and appropriate mitigation and adaptation measures that the city can incentivize and implement. 
  • Serves on the Resource Management Commission for the City of Austin. This commission advises the city council in developing and reviewing city plans and programs in the area of alternative energy technologies, renewable energy sources, and energy and water conservation. The Commission is additionally exploring programs around incentivizing passive houses and looking at climate-resilient strategies such as battery backup for the grid to help with resilience during power outages.
  • Contributes to the Passive House National Policy Council.


Farmer believes that public/private/nonprofit collaboration is key to creating change at the scale necessary to safeguard a more resilient, sustainable future for all.


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Overcoming Challenges

The Theresa Passive House in Austin was constructed by Clean Tag, a custom home-building company and carpentry crew. The company had experience with a Building Biology Standard project through which they gained healthy-building knowledge and skills. The main challenge was to educate them about creating a super-airtight envelope. It took effort and numerous lessons learned, but the builders were interested and excited to learn more about Passive House. 


This project further proved that cooperation and coordination with trades from a very early stage in a Passive House project was vital, as was the early involvement of mechanical consultants and installers and the ongoing involvement of the design team throughout the installation. As this project type was new to many of the trades, going forward, Farmer and Forge Craft aim to continue to build a stable of experienced builders who come from building science, care about health, and support the notion that cost is one of several priorities.


Final Thoughts

Farmer keeps his optimism amid a complex industry urgently in need of a major change. He looks at challenges as opportunities and focuses on learning from past successes that lead to more manageable tasks in the future. 


The Theresa Passive House proves that with proper climate adaptation strategies, a structure can perform well and protect its occupants during extreme weather events. While it’s difficult to predict every future climate threat we’ll face, changing the way we think about designing our homes remains our best hope of both reducing our impact on the built environment and protecting homeowners in a warming world.


This project was ultimately a testament to the power of collaboration and a shared vision for the future. There is no substitute for working with local, skilled Architects, Designers, Engineers, and Contractors who understand the macro and microclimate, environmental risks, and solutions, and contribute to building a climate-resilient economy. While building codes (mandatory) and certifications (voluntary beyond code excellence) help reach climate adaptation, trustworthy knowledgeable professionals make sure those goals are met.


Farmer shares his acquired knowledge for the benefit of other homeowners, leads the way, and showcases his home, proving that homes can be comfortable, beautiful, and safe, even in the face of a changing climate.


Please share with us more climate-resilient homes, solutions, and professionals so we can grow climate-resilient communities. 

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