Here's a challenge: Design a building that qualifies for silver LEED certification, in two parts, and add it to an existing building. And by the way, the existing building includes a cleanroom, where production has to go on while you're building.

That's the assignment RSP Architects got from Coloplast, the medical-product manufacturer, for a significant addition to their North American headquarters in Northeast Minneapolis.

Builder Kraus-Anderson demolished a couple of buildings to make way for the new construction, but in accordance with LEED requirements, the design called for them to pulverize the debris and use it as backfill instead of hauling it to a landfill. The builder also recycled cardboard boxes, drywall and other materials.

"The typical requirement for LEED is to recycle 50 percent of your construction debris, and we hit 97 percent," says Chris Dokken, project manager for RSP.

They also used regional material as much as they could, with 26 percent coming from vendors within a 500-mile radius. While building the 90,000 square-foot office tower and the 37,500-square-foot production building, both of which had to be designed to fit with Coloplast's existing structure, Kraus-Anderson had to maintain the safety procedures devised for Coloplast employees walking through the construction area. And they had to manage air quality, making sure construction activities didn't add dust or other contaminants to the air, particularly in the cleanroom.

The design called for an open office floor plan and lots of natural light, and for a building that had the same curve in its construction as the river it sat next to. A filtration area along the front of the building captures storm water and filters it back to the soil instead of letting it run into the river.

"The owner wanted it to be a great place where people would enjoy coming to work," Dokken says. "The city was pleased, too, because it's a transitional sort of area that's really starting to come together."