The O'Neil Passive House Retrofit

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Located just blocks off the plaza in historic downtown Sonoma, PassivWorks has built the first Certified Passive House™ in California and the first Certified Passive House™ retrofit in the United States. Homeowner Catherine O’Neill wanted a comfortable and environmentally-friendly home. Upon learning the advantages of the Passive House Standard, she decided to create a model home and help set a new benchmark for energy efficiency in America.

Design Challenges:

Constructed in 1960, the ranch house was originally two structures linked by an outdoor covered breezeway. The two existing slabs were uninsulated and at different elevations. The single story, North-facing, ‘U’-shape configuration not optimal for solar access or performance and further limited due to shading by adjacent buildings and trees. Site conditions and zoning required that the existing footprint and foundations remain.

Project Success:

The retrofit transformed this neighborhood eyesore into a near net zero energy, state of the art modern farmhouse "jewelbox" that provides exceptional comfort and durability with energy bills averaging $15/month. Energy savings and predicted performance are confirmed by the Department of Energy and Lawrence Berkeley National Lab which have installed monitoring equipment in the home.


Assembly Details

R-31 Walls
2x4 (existing walls), 2x6 OVE framing (new walls)
3.5" to 5.5" Dense packed blown-in fiberglass
Interior installation chases for wiring and plumbing
3.75" exterior Expanded Polystyrene (EPS)
Forest Stewardship Council (FSC) rain screen siding
R-74 Roof
Unvented cathedral ceiling
15” dense packed blown-in fiberglass
Dropped interior soffits for lighting and ducts
2.5" exterior EPS
R-12 to R-20 Foundation/Floor
0.6” Aerogel w/1.5” EPS Top of Slab Insulation (Floor 1)
4.625” EPS Top of Slab Insulation (Floor 2)
3.75” Rock wool (slab edge)

Air Sealing

Blower Door Result: 0.38 ACH @ 50Pa
Exterior Insulated Sheathing (PERSIST/REMOTE) with Grace Ice & Water Shield®
Mud sill sealed with Protecto-Wrap Super Stick Building Tape®
All penetrations booted
Airtight Drywall
Air admittance valves for plumbing vents

Windows & Glazed Doors

Optiwin 3 Wood
Passivhaus Institut (PHI) Certified
Tilt & Turn and Lift & Slide with multi-point latching hardware
R-9 installed, SHGC 0.52
VT of 70%+
Frames over-insulated w/1.5” EPS
23 % Window to Wall Ratio

Mechanical Systems

UltimateAir RecoupAerator Energy Recovery Ventilator
83 % efficient heat exchange
Solar thermal powered water-to-air coil for space heating
Automated night cooling
4" & 6" insulated rigid metal ducts
Mitsubishi Mr. Slim mini-split heat pump for backup heating
Ecosmart ethanol fireplace insert

Renewable Energy

Solar Thermal
Three 4x6 ft Heliodyne panels
Drainback system to avoid glycol stagnation/deterioration
DHW solar fraction: 69 %
10 Sanyo HIT Power 215 Panels
Fronius IG 3000 Inverter
Estimated annual production: 3,125 kWh

Project Stats

Before: 1,933 sq ft, 3 bedrooms
After: 2,357 sq ft, 3 bedrooms
1st Certified Passive House in California
1st Certified Passive House retrofit in the U.S.
15% extra construction cost for Passive House Standard
Modeled Energy Performance
Total Source Energy: 9,098 kWh/yr (31,050 kBtu/yr)
Heating Site Energy:  1,012 kWh/yr (3,454 kBtu/yr)
Peak Heat Load: 2.033 kW (6,939 Btu/hr)
Cooling Site Energy: 225 kWh/yr (768 kBtu/yr)
Peak Cooling Load: 1.529 kW (5,217 Btu/hr)
Performance Improvement*
80% less source energy than typical CA Home
88% less heating than typical CA home
75% less cooling than typical CA home
*Source: 2004 Residential Appliance Saturation Survey (RASS) Data, California Energy Commission
Renewable Energy
3 Panel (72 SF) Solar Thermal
2.15 ( DC) kW PV system

Energy Monitoring

The O'Neill retrofit was selected by the U.S. Department of Energy's Building america program as a prototype home. To valideate predicted performance and track actual energy usage, the DOE installed monitoring equipment during construction, making all data available online for immediate analysis. In addition, Lawrence Berkeley National Laboratory installed equipment to monitor the electrical loads of the plugs.

The Project Team

Homeowner: Cathy O’Neill

After spending 25 years working Wall Street as an institutional trader, Cathy O’Neill closed her office in April 2010 and set out for a retirement life full of family, friends and plenty of long walks with her beloved dog, Max. Cathy wanted a home that was reminiscent of her childhood farmhouse, but that would also be an heirloom and sustainability statement for future generations. She started researching the Passive House concept and together with a team of enthusiasts, they’ve made history as California’s first Certified Passive House and the country’s first Certified Passive House retrofit. Her favorite thing about her passive house is that it doesn’t look like a prototype, or some “geeky” architecture experiment. It is a beautifully appointed, comfortable farmhouse with a sophisticated, modern interior that suits her lifestyle. She loves that guests can come over, sit at the table, and not even realize there is something different about the house. But, by virtue of being a passive house, Cathy’s home is on the vanguard of energy efficiency and sustainable living in the United States. It is, in Cathy’s words, a smart and small answer to some very big problems facing the world today.

Builder: Rick Milburn
PassivWorks, Inc.

Born in Salt Lake City, UT in 1969 and raised in Southern California, Rick grew up with an innate talent and interest in the process of building. His first job in the trades at the age of thirteen was followed by years of mentoring by seasoned building professionals through summer positions and later apprenticeships. During his formative years, he had the privilege of serving in the United States Marine Corps and, with the support of his parents, the G.I. Bill and a hammer to earn his way, he graduated with a B.S. from the University of California, Davis. In 1996, he had the opportunity to move to the Napa Valley and start his own company. He's been building in Northern California ever since with one goal in mind - "Better Buildings.” Rick is passionate about sustainable building. He is the first builder in California to become a Certified Passive House™ Consultant, is a Certified Green Builder, and a Certified Photovoltaic Installer.

Architect: Jarrod Denton
Signum Architecture

Jarrod grew up in the Pacific Northwest, immersed in activities that brought intimate contact with a variety of natural environments. Intellectual curiosity and a propensity for travel moved him along concurrent paths which found their intersection in architecture early-on. Jarrod is licensed in architecture in California and Hawaii. Most of his work has been accomplished in Northern California. In 2010 Jarrod opened his own firm, Signum Architecture. The O’Neill residence was Jarrod’s fifth collaboration with builder Rick Milburn.

PHPP: Graham Irwin
Essential Habitat

Graham has been working in the construction industry as a builder, designer and consultant since 1991. Long committed to sustainability, Graham recognized the value and enormous potential of the Passive House Standard immediately and was one of the first Passive House Consultants trained in the US. Graham's firm, Essential Habitat, provides sustainability consulting, analysis and design assistance to architects, builders and property owners with an emphasis on Passive House methodology. He presents and lectures regularly on energy efficient building and climate change response and trains Passive House Consultants in support of the Passive House Institute US (PHIUS).

Landscape Architect: Jennifer Chandler
Chandler & Chandler

Jennifer Chandler is a California native, raised in the Napa Valley. She received her B.A. from Reed College in Oregon and her Masters degree in Landscape Architecture from Cornell University. After working on the East Coast for three years, she returned to California and worked for Jack Chandler & Associates. In 1997, she formed her own company, Jennifer Chandler, Landscape Architect, in Napa. Jennifer has a particular interest in community projects which allow local residents access to the larger landscape via parks and trails - projects for which she frequently volunteers her time and effort. She is an avid cyclist, hiker and photographer, with a deep appreciation of the natural world.

Interior Designer: Jann Blazona
Jann Blazona Interior Design

Jann Blazona knows that in the end it's as simple as this: your home should make you happy. Launching her career in 1983 after studying at the Art Academy in San Francisco, Jann has designed interiors from Napa Valley to the foot of the Austrian Alps. With a portfolio so diverse, you might expect to see a wide range of aesthetics within her body of work. Instead, her highly involved, simple style that took root three decades ago has grown as beautiful and nuanced as the oak trees that surround her Glen Ellen farmhouse. Her sensibilities are loyal to those same trees, as she handpicks reclaimed wood for flooring or works with local artisans to craft custom pieces using native materials.

Landscape Designer: Dave Dexter
Dexter Estate Landscapes

Dave Dexter founded Dexter Estate Landscapes in 1985, following his strong interest in plants and gardens. With a background in wholesale nursery production and management of soil products business, he has both a degree in plant biology and environmental studies and planning from Sonoma State University. Away from work and family you might find him on a fairway or at a 49er game.

Energy Monitoring:

David Springer/Alea German
Davis Energy Group for the Department of Energy's Building America Program

Jeremy Fisher/Brennan Less
Lawrence Berkeley National Lab