Passive-House Remodel in A Historic Neighborhood
A century-old bungalow is renovated to maintain its original character while achieving Passive-House certification.
Synopsis: Architect Trey Farmer and his wife, Adrienne, an interior designer, took their 1914 Craftsman-style home in Austin, Texas, and renovated it into a Passive House certified build. Located in a National Register Historic District, the house had to fit into the neighborhood. The two wanted to keep as much of the existing structure as possible, while creating a healthier indoor environment. Consulting with other professionals in the area, Trey and Adrienne made upgrades such as adding insulation, installing a balanced HVAC system, and adding a modern addition to increase square footage while maintaining a traditional facade.
Just outside of downtown Austin, Texas, our 1914 Craftsman-style home is a case study for Passive House renovation, achieving PHIUS+ 2018 Certification and PHIUS+ Source Zero Certification in a hot, humid climate. This renovation fulfilled both a personal and professional mission. My wife, Adrienne, and I bought the house more than a decade ago after falling in love with the neighborhood. We were always thinking about what it could be and planned to update it. Given my experience as an architect at Forge Craft Architecture + Design, and with Adrienne’s emphasis on healthy and sustainable interiors at her firm, Studio Ferme, we saw this as our opportunity to demonstrate the possibilities for a small, healthful, high-performance home.
Together, we improved the building envelope, which lacked insulation; added square footage with a modern addition; and created a flexible floor plan that matched our young family’s lifestyle while maintaining the integrity of the historical structure. Electrification is a priority for any Passive House project, so we also added a 6.3kw PV array and battery backup.
Starting from “scratch”
The house is located in a National Register Historic District, so we wanted to keep as much of the existing structure as possible. We met with a friend who oversees Preservation Austin to talk through our proposed changes. The plan was to save all the framing, but once the siding came off and we saw the extent of the water and termite damage, the plans changed. What remains of the original structure is the porch and columns (the piers were redone in the ’80s).
Starting from near scratch allowed us to transition from 2×4 framing to 2×6, offering a deeper cavity for insulation and truer walls. We also had to address a foundation that was 2 in. out of level. New piers were installed to support the addition as well as level what remained of the existing structure. Steel shims were used to make up the difference on existing piers.
To help meld the existing and the new, we worked with local architect Hugh Jefferson Randolph, who specializes in contemporary additions to historic homes (see “Adding on to historic homes,” below). By replacing the back half of the floor plan with a modern addition, we added 50% to the square footage, from 1400 sq. ft. to 2100 sq. ft. We dialed in the floor plan with a focus on openness and flow. We also added a light well in the kitchen and other architectural details, such as different ceiling planes to define spaces without adding more interior walls, and we mixed in full-height windows and other modern details for a cohesive aesthetic throughout.
Investing in the envelope
After living for 10 years in a 100-plus-year-old home with no insulation in the walls or floor and insufficient fiberglass batts in the roof, we made insulation a key priority. We wanted to avoid spray-foam insulation within the interior of the home because of its environmental impact and our concern with indoor-air quality.
Bedrooms: 3 Bathrooms: 2-1⁄2
Size: 2210 sq. ft. Cost: $375 per sq. ft. (incl. screened porch)
Completed: 2022 Location: Austin, Texas
Architect: Forge Craft Architecture + Design
Builder: CleanTag LLC
Mineral-wool batts were used for cavity insulation in both the walls and the roof. Mineral wool has a higher R-value per inch than fiberglass, and it retains its shape better than fiberglass or cellulose. Zip System R-Sheathing was used for the roof and the walls because of its integrated rigid insulation and water-resistive barrier. We were already over existing setbacks before the sheathing went on, so this was an all-in-one solution that allowed us to “hide” continuous insulation behind the sheathing to achieve our insulation goals.
Keeping the original front porch was important to maintain the historical facade of the home, but connecting an older porch to new construction is challenging when it comes to air-sealing. I knew it was a weak point in the air barrier when the initial blower-door test came in at just under 1 ACH50. To achieve the required 0.6 ACH50 airtightness for a Passive House, I reached out to a friend who installs AeroBarrier, which involves a sealant distributed through the air while the house is pressurized by a blower door, effectively sealing existing gaps and leaks in the envelope (for more, see “Is There an Easier Approach to Air-Sealing,” FHB #296).
The next blower-door test came in at 0.3 ACH50. This was a significant improvement from the pre-renovation result of 16 ACH50. Not only did we drastically improve the home’s performance, but we created a home designed with sustainability, health, and well-being in mind.
Adding on to historic homes
There is no right way or wrong way to approach an addition. Each project is different; no formula fits all. When working with a historic home or one in a historic locale or with a more traditional facade, there are two options. The first is to integrate the addition into the existing architecture. The original home and addition become one, with no visible interruption between. The second approach—the one we took with Trey and Adrienne’s home—is to create purposeful juxtaposition, where each architectural element stands between the existing and the new.
When planning the addition to this Craftsman-style home, we worked closely to create a plan that included a modern addition. (A modern addition has a confident presence, which can complement and amplify historical architecture.) We didn’t want to make changes to the things that worked. While much of the original house was torn down, we liked the front elevation, given the historic nature of the neighborhood.
We approached the project from the perspective of preserving what works and changing what needed to change based on the goals of the homeowners. It was about retention and addition for the overall betterment of the house. Despite the need to start from scratch on much the structure, the main house remained with some modifications. Square footage was added with the addition.
The homeowners wanted an open-concept interior. Older homes tend to have divided floor plans with spaces clearly delineated with walls. Because the interior needed to be reframed, there was an opportunity to open the floor plan to suit the family’s way of living. Trey and Adrienne didn’t want a true great room because it wouldn’t work in the context of their modestly sized home.
The kitchen, dining room, and living room are visually defined using architectural features. The light well in the kitchen indicates division without walls, and it brings in abundant natural light that amplifies the space. Variation in the ceiling planes creates subtle separation between each space. Using these cues effectively designates areas of the home without impacting sightlines.
The right windows in the right place
Upgrading windows in any 100-year-old home should help with R-value and add instant curb appeal. We chose triple-pane windows for their high performance, but our stylistic needs varied throughout. We ended up mixing and matching three different styles of Marvin windows. Traditional-style windows keep the front facade looking historically accurate, while a more modern style of window matches the aesthetic of the contemporary addition at the back of the home. We used a more cost-effective option in less visible areas without sacrificing performance.
We kept the new windows the same size and in the same location as the original windows, and all sills line up between the old and new windows. The contemporary addition features floor-to-ceiling windows with a brake-metal trim crafted from thin sheets of metal bent to fit or contour around the window. This minimal trim aesthetic offers a modern profile and makes the most of downtown views.
For the specifics of the HVAC system on this home, see Designing an HVAC System for a Passive House.
Photos by Leonid Furmansky, except where noted. Drawings by Christopher Mills.