New Homes team helps Verdant Apartments become the first Phius+ certified multifamily building in St. Paul
Back in March 2020, construction began on the Verdant Apartments, an 82-unit building in the West Side Flats neighborhood of St. Paul. These apartments set out with the goal of building environmentally conscious, affordable, and accessible housing for St. Paul residents. CEE’s New Homes team was brought in to help the project achieve Passive House Institute U.S. certification (Phius+). Achieving the Phius+ certification identifies the building as meeting a rigorous level of energy efficiency while also creating comfortable indoor living spaces. The basic principles of a Passive Building include continuous insulation and thermal-bridge-free enclosure (to keep warm air inside when it's cool outside and cool air inside when it's hot outside), airtightness and balanced ventilation with heat and moisture recovery, solar radiation control with high-performance windows, and moisture control based on proper design, selection, and installation of mechanical systems.
To help the building reach a Phius+ certification, the New Homes team provided energy recommendations early in the building process. There were multiple key energy efficient features that contributed to reaching Passive Building energy efficiency standards. One standout feature of this building is its super airtight construction. During final testing, the entire 93,010 square foot building had 3200 cfm50 total air leakage, which is tighter than many existing single-family homes. Many weatherization features were also incorporated during construction including double-framed walls to prevent thermal bridging and lower the risk of moisture damage in the walls, triple-pane windows, and an energy recovery ventilation system that provides 7,000 cfm of fresh air to living spaces while extracting the moisture, stale air, and indoor pollutants. Additionally, the building has water loop heat pumps in each unit to heat and cool the building, high thermal efficiency condensing water heaters providing hot water to units, and all Energy Star appliances rated.
In addition to providing recommendations, CEE’s in-house Phius+ rater, Jake Selstad, performed testing and verification throughout the construction process to ensure the building was on track to receive desired certifications. This testing included frequent insulation inspections, mid-construction blower door tests to ensure effective airtightness of building assemblies, air leakage tests of the HVAC ductwork, and assisting with testing and balancing the whole building energy recovery ventilation unit. Near the end of construction, CEE performed final testing and verification to ensure the project met or exceeded all performance targets of Phius+ certification, including the whole building leakage threshold and critical ventilation rates.
After wrapping up final testing, the next step for certification was submitting for third-party verification through the RESNET and Phius quality assurance teams. Once the verification process was complete, the Verdant Apartment buildings achieved Phius+ certification, as well as Energy Star Multifamily New Construction, EPA Indoor airPLUS, and DOE Net Zero Ready Homes certifications. Additionally, the building received a Home Energy Rating System (HERS) score of 33, which is 70% more efficient than the average HERS reference home. The accolades for this project didn’t stop with energy certifications either, this project also won the Best Affordable Housing project of 2023 at the Phius Passive Projects Design Competition.
CEE’s New Homes team works on a variety of projects, from large multifamily buildings to single-family homes, to help builders and homeowners achieve their energy efficiency goals. Learn more about CEE’s new construction services and energy rating options here.