When the first phase of the Orchards at Orenco affordable housing development opened in Hillsboro last year, it was built to stringent – and expensive – passive house standards. But the developer, REACH Community Development, didn’t think it would be possible to do the same for the second phase because of higher construction costs.

Yet thanks to lessons learned during the first phase and assistance of a national passive house nonprofit, the second phase of Orchards at Orenco not only was completed for less money than the first phase, but also achieved passive house certification.

To meet passive house standards, according to Michael Bonn, a senior associate at Ankrom Moisan Architects, which designed the second phase, a building “must have super insulation, super-efficient HVAC and be super airtight.”

The decision to shoot for passive house certification, Bonn said, was made early in the design phase at the urging of Katrin Klingenberg, co-founder and executive director of the Passive House Institute US (PHIUS). The organization also provided financial help.

No money was budgeted for a passive house consultant on the project, Bonn said, but during the schematic design phase, PHIUS officials ran tests for passive house through their software and filled in as low-cost consultants.

“They really stepped up to help support the passive house campus as an example of what could be done,” Bonn said.

PHIUS was able to provide consulting services “for a nominal fee” because it had received a MacArthur Foundation grant to encourage more affordable housing construction featuring passive house standards, according to Mike Steffen, vice president and general manager of Walsh Construction, the project’s general contractor.

By applying what it had learned in phase one, Steffen said, the phase two team was able to reduce the cost of meeting passive house certification requirements. The total cost of the first phase was $14,565,874, while the cost of the second phase was $13,641,339.

The main cost-saving design change that allowed pursuit of passive house certification was in building orientation and shape. The first phase was an L-shaped building with one wing running east to west and the other running north to south, Steffen said. For the second phase, the massing was changed and the shape simplified.

“In phase two the building is wider and shorter – a simple rectangle shape,” he said.

The newer building is oriented completely east and west, which improves energy efficiency and helps reduce solar loads, he said.

A more efficient design has allowed more units per square foot: 58 apartments per 49,000 square feet area in the second phase, compared to 57 apartments per 57,000 square feet in the first. Bonn said that was possible because the building’s shape allowed for narrower and deeper units without a reduction in floor area.

Space was also saved because the second phase didn’t require a large community room, as the first phase did. Slightly smaller lobbies and entrances at each floor saved even more space.

Because the building’s shape improved the skin-to-volume ratio, Bonn said, less insulation was needed under the slab. Also, exterior wall framing studs could be reduced to 2 inches by 8 inches, from 2 inches by 10 inches in the first phase, and less exterior insulation was needed.

“For the same reason, the walls could be a couple of inches thinner,” he said. “We reduced the cost premium by 8 percentage points, just under $1 million savings while still achieving passive house.”

In addition, a less expensive roof design was used for phase two, Bonn said, even though that made airtightness more difficult to achieve. A flat roof with a parapet was used in the first phase, while a standard, sloping truss roof was used in the second.

That made the project much harder for the contractor, Steffen said, and took a lot of effort.

“It was a real challenge for us when the decision was made to go for passive house,” he said. “It was tricky construction and took a lot of quality control and special inspections with infrared cameras and heat and pressurization.”

To keep in line with passive house standards, triple-pane windows and an HVAC system similar to the one used in the first phase were used in the second, Bonn said. But the better orientation and shape of the second building resulted in more efficiency.

Both buildings feature heavy timber deck framing and American Craftsman-style-inspired sun shades over the windows, three different patterns of shingles and lap siding, Bonn said.

The second Orenco at Orchards building also includes many amenities, including exterior decks on the second and third floors, common laundry rooms, a fitness room and an outdoor playground. Like the first building, it also will have displays in the lobby so that tenants can track their energy use.

“We’re wrapping up installation right now so they can compare, and we hope it creates positive peer pressure,” Bonn said.

A third phase for Orchards at Orenco is being planned, said Ben Sturtz, REACH Community Development’s housing development project manager. Plans call for 19 three-bedroom units in two buildings joined by a sky bridge. Because of that design and the need for bigger apartments, it is unlikely to be built to passive house standards.

“Our goal is to try to continue to build (to) passive house standards,” Sturtz said, “but it will become more of a challenge in the future.”

Orchards at Orenco II

Developer: REACH Community Development

General contractor: Walsh Construction

Architect: Ankrom Moisan Architects

Landscape architect: Walker Macy

Civil engineer: Humber Design Group

Structural engineer: Stone Wood Design Center

Mechanical engineer: PAE Engineers

Third-party certification: Earth Advantage

Owner’s representative: Housing Development Center

Total cost: $13,641,339

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