Metal Architecture Home

A Well-Formed Beauty

The Hennepin County Library uses unique roof forms to define spaces and create excitement

Hennepin Library 1
Photos: Gilbertson Photography

The Hennepin County Library, Brooklyn Park, Minn., replaces a much smaller 40-year-old library, and does so with a unique winged roof and a lively facade. At 39,000 square feet, the structure provides flexible space that maximizes the staff's ability to create new areas for engagement and learning.

The space flexibility comes from putting all the mechanicals beneath a raised floor instead of overhead. In addition, 300 air diffusers in the floor create an upward air flow that minimizes sound and improves air quality.

Large Vaulted Ceilings

The raised floor also gave designers the freedom to plan three, large vaulted ceilings and a massive vaulted butterfly ceiling in the entryway and southeast portion of the building, all unencumbered by messy plumbing and HVAC installations. The three areas create intimate settings separated from the main portion of the library. The library has seven private study rooms named after types of raw materials such as zinc, iron and slate. The rooms have custom-patterned wall coverings inspired by various cultures around the world. 

The sloped roof forms give the structure a strong identity and provide a clear definition for the main entry. Each form marks a separate area of the main library collections: adult, children and teen. The primary collection was given a living room, which acts as a central gathering point.

"Through the use of a sloped roof, users are able to make a visual and physical connection from their interior experience to the building form," says Jesse Zeien, AIA, project architect at HGA Architects and Engineers, Minneapolis. "The standing seam roof [made of Raleigh, N.C.-based Umicore Building Products USA Inc.'s VMZ panels in 0.8-mm QUARTZ-ZINC] was used in conjunction with the zinc fascia to aesthetically tie the sloped roof forms together with the butterfly roof entry."

Unique Exterior

The building's exterior is just as unique, utilizing an array of building materials including hand-chipped Virginia slate, Holland, Mich.-based Dri-Design custom metal panels made of Umicore Building Products' VMZINC in 1.5-mm QUARTZ-ZINC, and stained cedar siding. Designers selected zinc because it is a fully recyclable material, from construction scrap through end of use.

The varied material selection offers strong contrasts in texture while maintaining a consistent palette across the façade. The metal panel section uses a staggered joint approach that mimics the soffits and integrates with the other materials. With such long façades, the complexity of the material selection and the jointing on the panels breaks up the flatness and provides depth and interest.

"The primary exterior vocabulary of slate, zinc metal panels and sloped roofs are inspired by local residential neighborhoods and world culture agrarian vernacular precedents; influencing a material palette and form which is civic and contemporary; but comfortable and inviting," Zeien says.


Libary Façade

As part of the design process the team explored many sizes and patterns for the metal panel façade. "These studies were reviewed and modified based on supplier input to come up with an aesthetic that fit the design intent and was very efficient based on raw material size, panel spans, framing and manufacturing waste; creating a very cost-effective system that met the design intent without compromises," Zeien says. "The 1.5-mm Dri-Design panels were used to create a largescale rhythm and pattern which related to textiles of world cultures. These larger panels were used to contrast the smaller grain of the hand-split, stacked slate and natural wood siding. The warm, wood soffit of the entry canopy links the interior and exterior through the material as well as the use of pattern and texture."

The continuous zinc fascia aesthetically ties the sloped-roof reading rooms and flat roof library collections together with the butterfly roof entry lobby and canopy. "It was a challenge for the design and construction team to ensure the metal panels tied together the building forms in a cohesive manner," Zeien says. "Through finessing these geometries, relationships from one element to the next, and coordination of final metal panel detailing, it resulted in a continuous roof line that tied all the forms together."

St. Michael, Minn.-based Progressive Building Systems installed all the metal wall, soffit and roof panels for the library. "This was the hardest project I've ever worked on," says Jeremiah Masters, national sales/project manager at Progressive Building Systems. "To meet the design intent, there were a lot of funky angles on this project. The fabrication of the metal panels was the biggest challenge [for us] with all the dimension busts. All the funky angles on this building were the cause of these, but we were able to overcome this with a lot of patience. There was a lot of field measuring, and there was a lot of back and forth between us and Dri-Design."

The design also incorporates two pieces of public art: a hand-welded steel bike rack representing an Ojibwa canoe, and a large mural, which spans across two interior walls. The outdoor space features a community butterfly garden, donated by the library's general contractor Knutson Construction, Minneapolis, and built by Autumn Ridge Landscaping, Sheboygan, Wis.

The project follows the State of Minnesota Sustainable Building Guidelines (B3) to meet the sustainable goal of 60 percent more efficient than a similar building. Several sustainable strategies are undergoing feasibility assessments including ground source heat pumps. Initiatives include a raised-access floor for heating/cooling, efficient air handlers with energy recovery wheel, daylighting with occupancy-sensor lighting controls, all LED interior and exterior lighting, and low-maintenance landscape.

"We see this new library as becoming a center piece for the Brooklyn Park community," says Lance Hornaday, general manager, Knutson Construction. "The spaces, designed by HGA Architects and Engineers, are very unique and offer flexibility to ensure it's an exciting place to continue to visit for years to come. We are extremely proud of the way it has turned out and what it will offer the community."