In 1992, the U.S. Environmental Protection Agency launched a program designed to lower greenhouse gas emissions by encouraging development and use of energy-efficient products. Most people think the ENERGY STAR label applies only to products, but structures are also eligible. An apartment or condo building that’s 15% more efficient than code requirements, for example, qualifies for the rating.
Last year, a 13-story residential building in downtown Detroit earned Michigan’s first ENERGY STAR rating. Only 10% of the project – the foundation and a structural podium that runs from the first to second floors – is cast-in-place. Kraemer Design Group specified precast concrete panels for the rest of the building, interior as well as exterior, because they’d help the project meet ENERGY STAR requirements.
There were other compelling reasons for precast as well.
The building, called 28 Grand for its location on Grand River Avenue in downtown Detroit, isn’t a typical apartment building. The 13-story building contains 218 micro-units, so-called because they’re an average of 250 square feet. Precast’s sound-dampening properties and extremely high fire-safety rating are a bonus for multifamily buildings. Painted concrete walls and ceilings eliminated the need for additional investment in drywall or other interior finishes.
The building’s footprint consumes an entire 8,957-square-foot corner lot, so equipment and materials staging space was virtually nonexistent. The project was on a tight deadline as well. Using precast elements overcame both challenges. Panels were fabricated offsite and shipped per an aggressive schedule that was developed and closely coordinated with the factory. Upon arrival at the jobsite, they were off-loaded directly from the truck and hoisted into place, minimizing the potential for damage.
Precast also satisfied various aesthetic requirements.
To fit in with the neighborhood, the city’s Historic District Commission required punched windows and a masonry façade. The goal of replicating the look of limestone, a commonly used exterior cladding material on many historic Detroit buildings, was achieved via a custom pigment mix and acid finish. Black bricks were cast directly into the panels for the lower two floors to satisfy the design aesthetic while maintaining the quick construction cadence.
The exterior design also reduces the opportunity for water to penetrate the wall assembly, preventing future water damage. The exterior skin is self-supporting, requiring a low number of tiebacks to the main structure; and a gap between the exterior wall and floor slab edge allows for the running of continuous insulation. Thermomass insulated precast sandwich panels were used at strategic locations to minimize thermal bridging. Introduced 30 years ago by Australian company Composite Global Solutions (CGS), the panels incorporate the structure, insulation, vapor barrier, and exterior façade for a seamless installation process. They were shipped in and assembled just like the typical precast panels, only they came from the factory with a layer of insolation between two layers of precast.
With fully furnished studio apartments, extensive amenities, and easy access to downtown Detroit destinations, 28 Grand is the next big thing in city living.
