Iowa City Nest is Named 2023 Phius Design Competition Winner

The Iowa City Nest, a new single-family Passive House designed by Sol design + consulting, has won the 2023 Phius Passive Projects Design Competition in the Single-Family category. The Phius Design Competition seeks to recognize the best passive projects in North America and beyond.

The Iowa City Nest is a new construction Passive House on an infill lot in Iowa City. It was designed to be a cost-effective, contemporary home, and was largely shaped by the constraints of site context and passive design strategies. The house presents a low profile to the street to blend in with the scale of its neighboring houses. The second story is only visible from the rear, creating the illusion of a single-story home.

“We are honored to receive this award from Phius,” said Sanyog Rathod, President and CEO of Sol design + consulting. “This project presented a unique opportunity for creative design with a constrained site. Balancing stringent passive house performance requirements was no easy feat as we sought to preserve existing trees, fit into the neighborhood, and create a warm, inviting design.”

Some key passive house strategies of the home include:

• Thick layers of cellulose insulation in walls (R-50) and roof (R-85)
• Compact design minimizes envelope heat loss
• Exceptional air-tightness (0.6 CFM per square foot of enclosure)
• Balanced, fully ducted ventilation with heat recovery
• Large south-facing windows and overhang depth optimized for passive solar gain & summer shading
• Efficient plumbing layout minimizes heat loss in the plumbing system
• 6.2kW rooftop solar array provides 100% of site energy needs annually

The design process utilized early-stage performance analysis with Sefaira and SketchUp to guide design decisions, which evolved into detailed models in WUFI and THERM as the design developed. As a result, the building form, fenestration, shading, and details all serve dual purposes of architectural expression and passive house performance. For example, the inset at the unconditioned garage was the natural result of peeling back the thick insulation blanket that covers the rest of the house.

The materials were carefully selected in order to reduce embodied carbon, promote healthy indoor air quality, and minimize ongoing maintenance. Some of the key material decisions included cellulose insulation in walls and the roof, engineered wood siding, metal roofing, and low-emitting wood floors.

“This achievement would not be possible without the fantastic homeowners and their vision for the first Passive House in Iowa City.” said Sanyog Rathod. “We share this award with them.”

Sol design + consulting worked closely with the builder Oak Tree Homes and the homeowners on this project. You can learn more about the project here.