Building a net zero energy home is often seen as an expensive luxury reserved for wealthy homeowners. However, a Seattle couple proved that net zero energy buildings can be surprisingly affordable. Eric Thomas and his wife Alexandra Salmon purchased an infill lot in Seattle’s Ballard neighborhood and constructed a 1,915-square-foot three-bedroom home that produces as much energy as it consumes on an annual basis. Their total project cost, including the lot, came to $417,000 — roughly the same price as a nearby townhouse on a shared lot built around the same time. The key was careful planning, smart material choices, and a design philosophy that prioritized building envelope performance over expensive mechanical systems.
Published originally by GreenBuildingAdvisor in January 2012, this case study remains highly relevant today as homeowners across the country seek practical strategies for reducing their carbon footprint without breaking the bank. The approach taken by Thomas and Salmon demonstrates that net zero construction is achievable in urban infill settings using readily available technology and standard construction techniques.
Site Selection and Project Cost Breakdown
The couple started by purchasing an infill lot in Seattle’s Ballard neighborhood for $180,000. Infill lots — vacant parcels within already developed areas — offer several advantages for net zero construction. They typically have existing utility connections, reduce urban sprawl, and allow homeowners to stay within desirable neighborhoods. The total project cost of $417,000 breaks down as follows:
| Cost Category | Amount |
|---|---|
| Infill lot purchase (Ballard neighborhood) | $180,000 |
| Construction and materials | $237,000 |
| Revised plans and engineering | < $5,000 |
| Total project cost | $417,000 |
| Federal PV tax rebate (30%) | Applied to PV system cost |
The construction cost of approximately $125 per square foot is remarkably competitive for the Seattle market. Thomas noted that their net zero home cost about the same as a nearby townhouse on a shared lot completed around the same time. This price parity with conventional construction is a powerful argument for why net zero energy buildings 2 can appeal to a much broader demographic than just wealthy early adopters.
The design came from Zero-Energy Home Plans, a company based in Coupeville, Washington, founded by Ted Clifton. The plans were specifically created to bring building performance close to net zero while minimizing construction costs — a balance that many green building projects struggle to achieve.
Structural Insulated Panels and Envelope Performance
The home’s shell was built using structural insulated panels (SIPs), a construction system that provides continuous insulation and reduces thermal bridging compared to traditional stick framing. SIPs consist of a foam core sandwiched between two structural boards, typically oriented strand board (OSB). The system delivers several benefits for net zero construction:
- Continuous insulation without thermal breaks at stud locations
- Rapid installation that reduces on-site labor and construction time
- Superior airtightness compared to conventional framing
- Structural strength that can handle seismic and wind loads common in the Pacific Northwest
The exterior walls achieved an R-26 thermal resistance value with all drywall and siding in place. The roof was built with 10.25-inch SIPs providing R-41 insulation. Under the slab, 4 inches of extruded polystyrene (XPS) was installed, with perimeter XPS extending down to a depth of 2 feet around the stem wall. This comprehensive insulation strategy created a well-sealed thermal envelope that minimizes heat loss during Seattle’s cool, damp winters.
The airtightness testing yielded impressive results: only 0.56 air changes per hour at 50 Pascals pressure difference (ACH50). For comparison, the standard new home in the United States tests at roughly 5 to 7 ACH50, while ENERGY STAR certified homes target 3 to 4 ACH50. Achieving 0.56 ACH50 places this home in the same league as Passive House construction, demonstrating that SIP-based envelope systems can deliver exceptional performance without exotic materials or techniques. For more details on how this project achieved such results, the case study by Seattle homeowners who built an affordable net zero energy house provides additional construction insights.
Triple-Glazed Windows and Solar Gain Management
Windows are often the weakest link in a building’s thermal envelope, but Thomas and Salmon selected high-performance triple-glazed units from Vancouver-based Vinyltek using Cardinal LoE-i81 glass. These windows deliver impressive specifications that contribute significantly to the home’s overall energy performance:
| Window Performance Spec | Value |
|---|---|
| Center-of-glass U-factor | As low as 0.12 |
| Visual light transmission | Up to 63% |
| Solar heat gain coefficient (SHGC) range | 0.15 to 0.51 |
| Glazing type | Triple-glazed with LoE-i81 coating |
The variable solar heat gain coefficient — ranging from 0.15 to 0.51 depending on window orientation — is a critical design feature. Windows on the south side can capture passive solar heat during winter months while windows on other orientations minimize heat gain to reduce cooling loads. Ted Clifton, founder of Zero-Energy Home Plans, commented that the window technology has advanced to the point where builders can place glass wherever they want without sacrificing envelope performance. This flexibility in window placement opens up architectural possibilities that were previously constrained by energy concerns. Those interested in the broader principles behind these choices can explore net zero buildings design principles, technologies, and strategies for energy independent construction.
Heating, Cooling, and Hot Water Systems
The home uses a Unico UniChiller air-to-water heat pump that serves both the radiant in-floor heating system and the domestic hot water system. This integrated approach consolidates two major energy loads into a single efficient piece of equipment. In Seattle’s marine climate, the system operates at a minimum of 212% efficiency in winter while delivering 120-degree domestic hot water. A standard electric water heater supplements the system when additional hot water capacity is needed.
The radiant in-floor heating distributes warmth evenly throughout the living space and operates at lower water temperatures than forced air systems, which improves the heat pump’s coefficient of performance. This combination of low-temperature distribution and high-efficiency heat generation is a hallmark of well-designed net zero homes. Key system components include:
- Unico UniChiller air-to-water heat pump for space heating and domestic hot water
- Radiant in-floor heating throughout the main living areas
- Electric water heater as a backup for domestic hot water
- Fantech CM3000 high-efficiency particulate air filter for makeup air distribution
- Panasonic motion-sensor bath fan for bathroom ventilation
- Remote-mounted kitchen range hood fan rated at 206 CFM
The ventilation system is designed with a single synchronized control for both the range hood and bathroom fan, ensuring balanced airflow throughout the home. The Fantech CM3000 filter serves as an air inlet that distributes makeup air to bedrooms and main living areas whenever the bath fan is running, maintaining healthy indoor air quality without compromising the home’s airtight envelope. For homeowners considering similar approaches, understanding affordable net zero energy house design strategies and construction methods can help in selecting appropriate mechanical systems.
Photovoltaic System and Net Zero Performance
A 6.3-kilowatt photovoltaic system was installed on the roof to generate electricity for the home. According to the project team’s calculations, this PV array is sufficient to bring the house to net zero energy on an annual basis. During the initial months of operation, the system produced a 1,000 kWh power credit that could be drawn on during the darker winter months when solar generation decreases. This net metering arrangement is essential for achieving annual net zero performance in climates with significant seasonal variation in sunlight.
The couple qualified for a 30% federal tax rebate on the PV installation, which substantially reduced the upfront cost of the solar system. This incentive, available at the time of construction, demonstrates how government policies can accelerate the adoption of renewable energy systems in residential construction. The economic calculation for net zero homes depends heavily on these incentives, and prospective builders should research currently available federal, state, and local programs before finalizing their budgets.
Several factors contributed to the system’s sizing and performance:
- Roof orientation and tilt optimized for Seattle’s latitude (47.6 degrees north)
- No shading from surrounding buildings or trees on the infill lot
- Energy-efficient envelope reducing total electrical load before solar generation
- Net metering agreement with the local utility allowing annual energy accounting
Those seeking a more net zero energy buildings guide covering system sizing and financial analysis can find additional resources on sizing PV arrays for different climate zones and household energy profiles.
Lessons Learned and The Future of Net Zero Housing
After living in the home for approximately three months, Thomas and Salmon reported few complaints and plenty of satisfaction. The only notable issue was vibration from the heat pump compressor traveling through the pipes, a problem they planned to resolve with rubber mountings. Beyond this minor adjustment, their experience was overwhelmingly positive. Thomas emphasized that net zero building does not need to cost significantly more than building to code, and that the long-term operating savings make it substantially cheaper over the life of the home.
Their project offers several takeaways for homeowners and builders considering net zero construction:
- Start with the envelope. Investing in a well-insulated, airtight building shell reduces energy demand before specifying any mechanical systems or renewable generation equipment
- Use proven building systems. SIPs, triple-glazed windows, and air-to-water heat pumps are established technologies that do not require custom engineering or exotic materials
- Plan for orientation. Window selection with variable solar heat gain coefficients allows strategic passive solar design without compromising envelope performance
- Leverage incentives. Federal and state tax credits, rebates, and net metering policies can significantly improve the financial feasibility of net zero projects
- Compare against real alternatives. When Thomas compared their home’s cost to a nearby townhouse, the net zero option was price-competitive while offering far superior energy performance
The Ballard project serves as a replicable model for net zero urban infill housing. It demonstrates that with careful design, sensible material selection, and a focus on building science fundamentals, net zero energy homes can be built at costs comparable to conventional construction. This is not a technology problem waiting for a breakthrough — it is a design and education challenge that projects like this one help solve. For a broader perspective on how this project fits into the larger landscape of high-performance construction, exploring green building certification programs including LEED, ENERGY STAR, Passive House, and net zero certification programs provides context on performance verification and quality assurance pathways available to homeowners.
As more homeowners recognize that net zero construction does not have to be the exclusive domain of the wealthy, projects like Thomas and Salmon’s Seattle home will pave the way for broader adoption. The key ingredients — a well-insulated SIP envelope, high-performance windows, an efficient heat pump, a properly sized PV system, and a realistic budget — are all available today. What remains is the willingness to apply these tools thoughtfully and the determination to demonstrate that net zero can be affordable for everyone.