At TE Studio we are fortunate to attract some pretty incredible people. With this project, we were commissioned by a couple from South Minneapolis to bring their mid-30s home into the 21st century of performance. This project became the first certified Passive House Retrofit (EnerPHit) in a cold-climate, and the first Passive House in the Twin Cities.
Based on the the fact that it is located in Minneapolis and the Passive House Institute’s EnerPHit moniker for retrofits, the clients coined this home the “MinnePHit House”.
An EnerPHit design brings many significant changes to an existing building—most noticeably to the envelope, or those bits that separate inside from out. TE Studio provided the design for this new high-performance winter coat, as well as the architectural exercise of adding 3 bedrooms, 2 baths, an open kitchen, living and dining area, a mudroom, and a home-school room to the program—all within a modest 800 square foot addition for a total of only 2,000 finished square feet. To compliment the high-performance design, we selected sustainable materials and construction methods, such as wood framing and cellulose insulation.
The basement was insulated inside and out; a new slab poured on top of insulation. Above grade walls were air-tightened and added on to with i-Joist framing to provide cavities large enough for high R-values. The structurally unfit roof was replaced all together with modern trusses and loose fill cellulose insulation. As a result, the heating demand was reduced to only 3.8 kW [12.9 kBTU), or about three hair dryers going at the same time to provide adequate heating on the coldest day of the year. Through diligent design and execution, airtightness was improved from a staggering 8.5 ACH50 [2,100 CFM50] during the initial test to a final reading of 0.65 ACH50 [196 CFM50]—well below the prescribed 1.0 ACH50 target.
A whole-house heat recovery ventilation system with an efficiency rating of over 90% provides fresh air 24/7. The existing in-floor heating system was recycled and extended to heat the home. The same boiler also delivers domestic hot water. A minisplit air conditioner was installed to provide on-demand cooling and dehumidification.
This project demonstrates the amazing potential of a high-efficiency retrofit design for existing homes in a cold climate. TE Studio combined mindful recycling of valuable components with careful designs for assemblies and layouts that build on sustainable practices and methods for a building that outperforms code-compliant new construction by a huge margin to become one of North America’s first EnerPHit projects, and indeed the first certified Passive House retrofit in a cold climate anywhere. At the same time, this design is complementary to the building’s origins and works within the surroundings of its urban setting in an established Minneapolis neighborhood.
The project was extensively covered in Spaces Magazine’s August/September 2013 “Eco-Chic” issue.