New affordable community in Santa Rosa a precedent
for attainable sustainable development strategies

Mahonia Glen, an 81,000-square-foot, 99-unit affordable family housing development in Santa Rosa, has successfully leveraged attainable design strategies to achieve Net-Zero energy performance upon completion. A combination of proactive design decisions, commitment to efficient design and construction, and robust communication and coordination across the interdisciplinary project team has demonstrated the accessibility of Net-Zero performance for a housing typology, density, and infill site condition that is familiar across North America’s West Coast.

"We’re thrilled to see our early site and building design efforts pay off with such a high level of energy performance," says Ray Reedy, an associate at PYATOK and the project architect for Mahonia Glen. "More importantly, we now understand that modest efficiency and design measures can bring Net Zero within reach of even those developments with substantial first-cost constraints."

The nine buildings’ placement on the 4.75-acre site and their asymmetrical roof form maximize space and orientation for the development’s photovoltaic (PV) array. The three-story walk-up format using open-air stairs helps minimize construction complexity and avoid the need for energy-intensive elevators. This format also allows for more resident control, enabling the mechanical systems to serve as an important but secondary tool for resident comfort.

Coordination with the mechanical system and plumbing system designs ensured no conflicts with rooftop solar. Other highly-attainable energy-efficient measures include the incorporation of induction cooktops, orientation-specific glazing, and a combination of mini-split heat pumps and through-wall heat pumps.

The "full-roof" PV array is estimated to generate 515 megawatt hours (MWh) annually, overshooting anticipated energy use by about 3%, as modeling by Partner Energy. Energy performance will be verified after completion, move-in, and operation.

The project developer, nonprofit MidPen Housing Corporation, has committed to using sustainable practices and the incorporation in all new construction of superior standards in environmentally-friendly design and materials that exceed California’s stringent energy codes. This early and steadfast commitment, including an atypical up-front investment in full PV coverage, enabled the project to target Net Zero.

Mahonia Glen occupies the site of a former nursery, across from the St. Francis Shopping Center at the intersection of CA-12 and Calistoga Road. The project is currently under construction, slated for completion in August 2024.

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Ray Reedy, AIA, LEED BD+C, Associate | (510) 465-7010