Commercial Passive House Retrofit

901 23rd Avenue in Northeast Minneapolis started out in life as a custom-designed clinic building for Dr. C.E. Arlander and K.A. Sodergren. Desgined by Architect Irwin E. Engler in 1953, it was completed and first occupied in 1954. Exactly 60 years later, Stephan Tanner and Tim Delhey Eian purchased the building to make it the new home for this architecture studio. The building was originally designed with the sleek lines of mid-century modern architecture and built to last. What it lacked was performance and it was in desperate need of some TLC. TE Studio/ Intep to the rescue.

A Commercial Retrofit with Passive House Components


Project period



TE Studio/ Intep


Tanner Construction

Walking the Walk

As designers of high-performance projects we decided to leverage our skills in a demonstration of retrofitting with Passive House components for our own offices. Working with the existing building stock is inherently sustainable. Enhancing it to highest levels of performance is our civic duty.  On August 1, 2014, the building was officially reopened with the help of our local Northeast community, friends and family, invited guests, as well as Northeast Minneapolis Council Member Kevin Reich and Swiss Honorary Consul Rudolf Gutmann.


The Transformation

Within a little over 3 months, the interior was gut-renovated with new “green” surfaces throughout, spades of performance were added, the energy and carbon footprints lowered by a huge margin, and the flow and usability improved to suit the new use as an office building. Exterior walls were upgraded to an R-value of 38; aluminum storefront windows were replaced with triple-pane Tanner Windows from Germany, a Zehnder enthalpy exchange heat-recovery ventilation system was installed, and the two separate heating and cooling plants were consolidated into a single unit. All lighting was replaced with LED—lowering the installed lighting load from 12,500 to an amazingly low 860 Watts: a 93% improvement over baseline! Hella‘s exterior motorized shades complete the picture of performance enhancements and the end result is nothing short of spectacular.

The Results Are In

The retrofit with Passive House components nets energy performance 78.9% below the median comparable office buildings in the area. The fiscal payback on energy improvement measures is just a few short years. The investments in increased comfort, enjoyment, and a clear environmental conscious provide immediate returns. 901 23rd Avenue NE sets a new bar for office buildings and demonstrates that a holistic approach yields massive performance and carbon footprint reduction. It is proof that we can meet today’s carbon-action plans cost-effectively to provide both environmental leadership, as well as fiscal responsibility and reward.

Key Features

  • Retrofit with Passive House components
  • Triple-pane high-performance windows with high solar-heat gain (53%), clear glazing and installed U-factor of less than 0.17 BTU/(h SF F)
  • Exterior, motorized shading
  • Super-insulated walls R-38
  • Balanced  heat-recovery ventilation with enthalpy exchange
  • On-demand hot water system
  • “Green” materials throughout


  • 21.3 Site EUI (kBtu/ft²)
  • 30.3 Source EUI (kBtu/ft²)


Retrofit with Passive House components

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