A Southwest Minneapolis real estate developer hopes to build Minnesota’s first ultra-energy efficient Passive House-certified duplex on a vacant East Harriet lot. Buildings built to Passive House requirements use very little energy for heating and cooling while meeting high standards of year-round comfort.

The three-unit project will include a carriage house apartment built over a new detached three-car garage on the property. The carriage house unit will conform to the U.S. Department of Energy’s Zero Energy Ready Home program, another set of exacting environmental standards, Heirloom Properties co-owner Jim Kumon said.

A “passive” mini-community

Kumon and Faith Cable Kumon, Heirloom Properties’  co-owner, are no strangers to sustainable development in Southwest Minneapolis. They’re the folks behind The Sundial, a 12-unit apartment building about 10 blocks east on 37th Street.

Like The Sundial, the Kumons’ East Harriet development will be all-electric, insulated and air-sealed far beyond code requirements, and wired for rooftop solar panels. The 5,350-square-foot Passive House Duplex will have three parking spots wired for EV charging. The Sundial intentionally omitted onsite parking.

The new up-down duplex will have two three-bedroom, two-bathroom units and the carriage house will be one-bedroom, one-bathroom.

“The goal is to sell [at market rate] to an owner-occupant” that lives in the duplex’s ground floor and rents out the other two units, Kumon said. Kumon declined to estimate the property’s eventual selling price, but said “all things are possible in Southwest Minneapolis” when it comes to real estate pricing.

The backend of the Passive House Duplex. Image courtesy of Heirloom Properties

“You have a set energy budget”

The Passive House Duplex’s above-and-beyond energy efficiency means the future owner and tenants will enjoy very low heating and cooling costs.

The Passive House concept is built on the idea that, based on the local climate, building size, and number of occupants, “you have a set energy budget that you can’t go over,” Kumon said.

To qualify as a true Passive House, a building must meet a slew of strict criteria for energy usage and airtightness. For example, the typical Passive House building has “four to five times less air leakage” than structures built to current code, Kumon said.

“You’re trying to subtract rather than add, so you don’t have to run the heat or air conditioning in the first place,” he said.

Because they’re so airtight, Passive House buildings tend to be more comfortable on very hot and cold days despite using less energy for active heating and cooling. What heating and cooling the buildings do need is generally delivered by highly efficient electric heat pumps, which are basically air conditioners that can run in reverse to provide heating in cold weather.

Per official Passive House guidelines, a certified building’s living space, built as is, can’t exceed 25 degrees Celsius (about 77 degrees Fahrenheit) more than 10% of the year, the temperature in a given room can only vary by 2 degrees Celsius between the head and ankles of a seated person, and the “perceived temperature” at various locations within a room can only vary by 0.8 degrees Celsius.

These and other requirements give Passive House buildings greater comfort flexibility than standard buildings.  

“Frankly, some buildings built to [current codes] are not that comfortable, Kumon said.”

It can be done in Minnesota

A smattering of super-efficient, all-electric multifamily residential and mixed-use buildings are planned across the Twin Cities, including multiple structures in a 1,000-unit development on a former St. Paul golf course and a 32-unit proposal from Footprint Development that’s moving forward in Southeast Minneapolis now that the Minneapolis 2040 plan is back on track.

But the Passive House Duplex will be the Twin Cities’ — and possibly the state’s — first Passive House-certified two-unit building, Kumon said. The lack of comparable projects stems in part from broad skepticism among real estate developers and construction professionals that residential buildings can comfortably and cost-effectively endure Minnesota winters without gas furnaces or boilers.

One durable myth is that air-source heat pumps stop working in cold weather, Kumon said. Newer models work efficiently at temperatures well below zero, and even modestly-sized units are more than capable of keeping well-insulated and sealed buildings like Passive House Duplex comfortable in the dead of winter, he added.

“You can calculate how much heat each [residential] unit needs and as long as the equipment is sized to handle that, you’re fine,” Kumon said. In smaller, super-tight units, like Passive House Duplex’s planned carriage house apartment, Kumon said it’s more common for the heat pump to be too powerful for the space’s needs.

Heirloom Properties said they are “testing the waters” on a potential crowdfunding effort to help finance the project. Federal regulations prevent Kumon from sharing much about the crowdfunding campaign beyond what’s publicly posted, but he characterized the initiative as vital to the project’s financing prospects.

“We are getting enough support that it looks like it’s actually going to happen,” Kumon said.

Heirloom Properties went public with its plans for Passive House Duplex ahead of a possible crowdfunding campaign in part to “find people with shared values [who are] willing to invest in thought process and outcomes,” Kumon said.

“We’ve already met a lot of like-minded people we didn’t know at all,” he added. “We can do [real estate] projects as a community without having to rely on the same-old capital sources.”