When it came to the design of the Kiln Apartments in Oregon’s North Portland neighborhood, GBD Architects aimed high. Just how high? Consider this: the Passive House certification the architects are pursuing will require energy performance approximately 65 to 75 percent better than Portland’s already industry-leading code requirements. And, if certified, the 18,000-square-foot building will become one of the largest mixed-use buildings in the country to achieve the standard. “This represents the next leap forward in terms of energy performance,” says architect Agustin Enriquez, a principal at GBD Architects, who adds that with ample wood and natural light, the 19 units were designed to feel “less like apartments and more like well-crafted, single-family homes.” Here’s a breakdown of the building’s energy-saving solutions.

Program 19 apartments, ground-floor retail space
Size 18,000 ft2
Completion 2014 Certification Passive House (expected)
Cost Withheld

CLIENT Edlen Family
Architect GBD Architects
Civil Engineer TM Rippey
Structural Engineer KPFF Consulting Engineers
MEP Engineer Solarc
Landscape Architect Lango Hansen Landscape Architects
General Contractor Lorentz Bruun

Glazing & Doors
HH Windows & Doors
HRV Ultimate Air
Water-Based Radiators Myson
Building Insulation Blanket Dow Corning

Because Passive House focuses on how much energy is used per square foot per year, buildings must have an ultra-high-performing building envelope. The first step for the Kiln Apartments, according to Enriquez, was creating a continuous air barrier to seal the building, reducing airflow in and out. Comprising the building’s exterior skin is an uninterrupted layer that dramatically reduces air infiltration and improves interior temperature consistency. Next came heightened levels of insulation—double the typical R-values for the walls (R-52), foundation (R-21), and roof (R-70). “If the air barrier acts as the metal skin of a Thermos,” Enriquez says, “then the insulation acts as a Styrofoam cooler holding the Thermos.” In addition, triple-pane, European-style, tilt-and-turn windows minimize any potential weak links in the building skin.

One of the greatest benefits of Passive House design is an extremely low annual energy demand, which provides significant savings on operational costs. Thanks to passive solar gain, Enriquez anticipates that the vast majority of heat will come from the building’s many south-facing windows. Sunshades were installed like visors above these deeply inset south-facing windows to help reduce heat gains from high-angle summer sun while allowing in the lower wintertime sun. Any remaining heat demand will come from wall-mounted, hot-water radiant heaters served from solar-thermal roof panels. (On days when the water isn’t hot enough, a gas-fired boiler will kick in to offset the solar hot-water array.) Enriquez estimates that these systems will reduce space-heating costs by 70 percent.

To avoid thermal breaks where the windows' metal sunshades attach to the wall, the architects specified a thin-profile, flexible insulation by Dow Corning. Providing 100% fresh air to each unit, air-handles with heat-recovery wheels recapture up to 90% of heat that typically would be dumped outside.

To avoid thermal breaks where the windows’ metal sunshades attach to the wall, the architects specified a thin-profile, flexible insulation by Dow Corning. Providing 100% fresh air to each unit, air-handles with heat-recovery wheels recapture up to 90% of heat that typically would be dumped outside.

The Kiln Apartments’ exterior skin was designed to eliminate thermal bridging where heat transfer could reduce energy efficiency. During construction, infrared imaging was used to identify unintended thermal bridging. A vulnerable area was discovered where the 18-inch metal sunshades were bolted to the wall above the windows, creating a thermal break that bypassed four inches of exterior rigid insulation. “Picture a zipper on a jacket—no matter how warm the jacket is, that metal is going to be cold if it makes direct contact with the skin,” Enriquez says. To remedy this, the team worked with Dow Corning to specify the HPI- 1000 Building Insulation Blanket, a thin-profile, flexible material that delivers insulation with a per-inch R-value of R-9.8. “It was cut to fit the sunshade attachment area,” says Dow Corning’s Paul Wisniewski, “creating a thin ‘gasket’ that keeps the metal from touching the wall sheathing and conducting heat directly from the framing.”

A central air-handling unit, the UltimateAir 2000DX, provides balanced ventilation—an equal quantity of supply and extracted exhaust air—to and from each apartment 24/7, providing an average of 0.64 air changes per hour. During the winter, a 100-percent outside-air system would incur a significant energy penalty to bring the cold outside air up to room temperature. “Most conventional HVAC systems provide the small quantity of code-required fresh outside air and mix it with a large quantity of return air recirculated from inside,” Enriquez says. At the Kiln Apartments, the ventilation system provides 100-percent outside air to the apartments using a heat-recovery wheel in the air-handler that captures most of the heat in the exhaust air and transfers it with the fresh air; the system recaptures up to 90 percent of the heat that would otherwise be dumped outside.

Not all of the building’s energy efficiencies are about high-performance systems—some of it comes down to smart design that also may help increase occupant health. To reduce total energy consumption from the use of the building’s elevator, the architects got creative. “As a four-story building, we needed an elevator, but we decided to find a way to encourage residents to use the stairs instead,” Enriquez says. That meant designing the stairs to be as inviting as possible. Rather than the drab, dimly lit stairwell often found in multistory buildings, the Kiln Apartments’ staircase is visible from the exterior and features site-specific artwork and ample, operable windows, all of which encourage residents to skip the elevator and make the walk up.