A Banner Project For Sustainable Design

The Banner Bank Building in Boise, Idaho, was conceived and designed not just as the most sustainable building in town, but also as a cost-efficient stigma breaker that shows how green design doesn't necessarily have to drive up costs. The $24 million, 11-story, 195,000-sf office building was constructed on a brownfield site in downtown Boise and incorporates hundreds of sustainable features that added no additional costs or construction time.

In all Banner Bank uses 65% less electricity than a comparable office building and 80% less water. It will deliver a 32% return on investment in its green technologies for a price that's comparable to other 11-story office buildings in Boise.

The design team, led by architects from the local office of Omaha, Neb.-based HDR, strived to create “efficient synergies” that would deliver both a LEED Platinum rating and a building that cost only $128/sf. The owner/developer, Gary Christenson, became a sustainable design convert and praised the team for finding new, less expensive ways to incorporate such green features as geothermal heat and computer-controlled lighting.

In the design stage the team, including the owner and a tenant advocate, planned how to create a floor plate that eliminated interior columns, which would have inhibited the design of tenant fit-outs. The structural engineers from KPFF recommended castellated beams (which are cut and re-welded so they are deeper and lighter) commonly used in airport and warehouse projects. The beams typically cost 25-30% more than conventional beams, but because their strength allowed the design team to reduce the amount of concrete and rebar in the project and eliminated the need for interior steel columns and field welding, overall costs were reduced. Since air flows freely through the holes in the beams the building required only one smoke detector per floor, saving the cost of 400 smoke detectors and $100,000 in first costs.

“There are interesting components that any LEED project can incorporate,” said Dan Murphy, PE, LEED AP, a Building Team Awards judge.