At new Bell Museum, designers turn to a new process to make building look natural

Designers of the Bell Museum + Planetarium at the University of Minnesota's St. Paul campus want the new facility to be as natural as possible.

When completed in the summer of 2018, the $79.2 million complex will showcase the state's natural history — and be made out of it.

About 40 percent of the new museum's exterior is covered with locally sourced, thermally modified timber, or "cooked wood" as it has been dubbed. Designers believe the project is the largest commercial-scale use of thermally modified white pine in the country.

"It's a beautiful wood, white pine," said Dave Dimond, a principal at the Minneapolis office of architecture firm Perkins+Will, which designed the new museum.

"The challenge always has been that you can't use pine outdoors – that it has to be protected by the weather," Dimond said. "This is a really new and exciting way to use white pine in a way it's never been used before."

About 21,000 square feet of white pine will be finished being installed this month on the outside of the museum located near Larpenteur and Cleveland avenues near the State Fairgrounds. A portion of the bottom half of the building is clad with steel from the Iron Range.

"The architecture speaks to the story of Minnesota and nature in Minnesota. … White pine is an iconic timber species from Minnesota," said George Weiblen, interim scientific director and curator of plants at the Bell Museum.

The white pine comes from state forest land in Cass Lake, located about 30 minutes from Bemidji, that has been certified by the international nonprofit Forest Stewardship Council for being responsibly managed. One of the focuses for researchers at the Natural Resources Research Institute (NRRI) at the University of Minnesota Duluth is how to help strengthen Minnesota's forestry industry in an environmentally sustainable way. Thermally modified wood is one of the products the group is studying.

"One of the cool ways to grow the economy in northern Minnesota is to start looking at renewable resources," Dimond said. "Rather than cutting down trees permanently, grow them sustainably and selectively cut them so that the forest remains. … This is what got us excited about white pine, since it is native to Minnesota and does have some significant sustainable forest."

The process of "cooking" wood originated in Finland and while Europe has been experimenting with it for years, the process has had limited use in the United States, said Kelly Bartz, president at Duluth-based Arbor Wood Co., which sourced the wood and the local kiln needed for the museum project.

Arbor has been selling thermally modified wood for about four years, though it normally focuses on hardwoods like ash and red oak instead of pine, which is a softwood.

For the museum project, Arbor Wood selected Palisade, Minn.-based Superior Thermowood of Minnesota. About 8,000 board feet or enough wood to fill half a semitrailer truck was slowly heated in the kiln until it reached about 100 degrees Celsius. The heat cooks out the moisture and natural sugar that can cause wood to decay and attract insects. The heat is then spiked to 210 degrees Celsius so that the cellular makeup of the wood is changed, and it makes it less susceptible to water. The wood is cooled down with the addition of steam and is provided with some much-needed moisture so that the wood is not too brittle. The result is a wood that can withstand the elements without needing any other type of finishing. The entire process can take four to five days.

Several partners were needed to make the museum project work, including Cass Forest Products, the sawmill that harvested the pine, Woodline, the sawmill that prepared the thermally modified white pine for installation, and McGough, the construction company responsible for building the museum and installing the white pine.

"This innovative way that Perkins+Will has come up with the siding for the Bell Museum is definitely intriguing to us," Bartz said. "Now the supply-chain challenges that we had in the beginning, that's all figured out. We have resources and it is kind of interesting to work with something like white pine that's indigenous to Minnesota and is a newly-revitalized resource."

After 75 years on the U campus in Minneapolis, the old Bell Museum closed in December and will reopen next year on the St. Paul site.

Besides the wood siding, other natural elements are featured at the museum. There will be rain gardens to help reduce stormwater runoff from the parking lot. There will also be a pollinator garden and other native plant landscaping as well as solar panels on the roof.