Previously home to a cluster of longstanding vacant buildings and an underutilized public park along the busy thoroughfare of Greenfield Avenue, Union Green aims to fulfill the need for “Missing Middle” housing in West Allis while continuing to bring more residents to work, live, and play in the downtown district. Designed to offer an aesthetic transition between the larger multifamily complexes to the south and the neighborhood of single-family homes to the north, the development's massing is broken into two buildings arranged around a relocated and reconfigured public park. The northern edge of the park is defined by a two-story, eight-unit townhouse building, with each unit featuring its own private entrance off the park. The eastern edge of the park is defined by a three-story mixed-use building with 11 apartment units and a first-floor commercial space.

Echoing the character of the single-family homes to the north, the exterior material palette is comprised of clay brick and a combination of lap, vertical grooved panel, and shake siding. All residential units feature on-site parking, open-concept floor plans, private balconies, and extensive glass to bring the outside into the interior spaces.