Ice Box Challenge showcases Passive House standards

NK Architects and Passive House Northwest are in the middle of an experiment in Pioneer Square right now. They’re calling it the Ice Box Challenge: Two 1,200-pound ice blocks were each placed in a small structure earlier this month, one that meets the minimum standard of Seattle’s building code, and the other up to Passive House, or Passivhaus, standards.

On Thursday, after the cubes have been in their little houses for 20 days, they’ll unveil each ice block’s progress. For now, people can stop by Occidental Park to peek their heads in and see how they’re doing.

So far, the ice in the passive structure has melted far less—but the big reveal comes this Thursday, September 28 at 12:15.

Passive House is an energy-efficient building standard, characterized by strong insulation, airtightness, strategic ventilation, and passive heat sources like solar power. The idea is that passive homes reject heat in warmer months and collect heat in colder months for maximum energy efficiency.

Courtesy of NK Architects

Like a cooler, that insulation is allowing the ice cube to melt more slowly.

“The Challenge tells the story of how thoughtful consideration to the building envelope can improve energy efficiency by about 75 percent,” Brittany Porter, a Passive House consultant with NK Architects, told Curbed Seattle. She expects that will be reflected in the side-by-side comparison this Thursday.

“All we will have changed between the two boxes is add a bit more insulation, install triple-pane windows, and use careful, air-tight methods of construction,” she explained. “These are minor upgrades for such a huge benefit, and the sooner more designers and builders recognize the elegant simplicity in that, the sooner it will become the new building standard.”

Passive standards, said Porter, have taken root in Seattle—but are even more common to the north in Vancouver, BC, where the ice boxes made their debut. Vancouver has even rolled out new energy efficient building standards for all construction.

Porter said that NK would love to see Seattle do the same thing.

“The ultimate goal is to make all new construction this efficient, because that’s what it takes to keep the global temperature rise below two degrees celsius,” said Porter, referring to a widely-accepted goal to prevent disastrous global warming. “All sustainable efforts in the built environment are worthwhile but Passive House is the only knight in shiny armor that can make an impact quickly and broadly.”

Courtesy of NK Architects

In Seattle, Passive House construction is voluntary, but we have a few examples. Porter points toward an NK project, Pax Futura, an apartment building currently underway in Columbia City. The project combines Passive House standards with solar panels—plus a couple of extra features, like slidable wood screens that can block western sun exposure during warm months.

Those screens “help protect interiors from overheating while also allowing the tenants to express their participation in this sustainable lifestyle,” said Porter.

The public can walk through Occidental Park in Pioneer Square right now to check out the cubes’ progress—and witness the big reveal this Thursday.

The original version of this article stated that one house was built to King County’s building code when it was built to Seattle’s building code.

• Brittany Porter Dishes on the “Ice Box Challenge” [NK]
• Ice Box Challenge [DiP]
• Pax Futura [CB]