Cost-Effective Passive House for Multifamily: Lessons from EcoFlats at Log City – GreenBuildingAdvisor

By Karuna Eberl | December 3, 2025

This is part 2 of a four-part series discussing the new multifamily Phius Zero project in upstate New York. You can read part 1 here.

The largest Phius Zero apartment complex in the country, EcoFlats at Log City, is slated to finish its first phase of construction in early 2026. Its design incorporates three main green goals: achieving Phius Passive House Zero certification, minimizing embodied carbon, and creating healthy, comfortable housing.

That would be an ambitious task for any 168-unit multifamily housing project, but EcoFlats is taking the challenge to the next level by adding the budgetary goal of market-rate rents. That means they’re having to find ways to go green without throwing in extra money.

“With sustainability there is absolutely merit to trying out expensive things that are pioneering, and I’ve learned a lot from projects like that,” says Jesse Schwartzberg, founder of Black Mountain Architecture. “But this is exciting, to have to come up with sustainable solutions that don’t cost more. Necessity is the mother of invention, right?”

EcoFlats is under construction in Amsterdam, New York, and is the brainchild of David Bruns and the Bruns Realty Group. The team, which includes Black Mountain Architecture, builder Ballston Mourningkill Associates, and others, has been collaborating for 10 years. EcoFlats marks its third green market-rate project—and first Phius Passive House objective.

In this blog, we’ll share specifics on their solutions for creating a high-performance building envelope, including the foundation, exterior walls, roof, and windows. In the next blog we’ll clarify the definitions of their goals, plus highlight the other systems and designs that are making those possible.

Design process: Tight collaboration and creative on-site problem-solving

In some respects, the EcoFlats team has had to invent the playbook on financially accessible green building—and that has presented a constant stream…