The ThermoWood process that NRRI is introducing to Minnesota will make Red Pine a durable building product. Here, it is shown as a wood siding.
The ThermoWood process that NRRI is introducing to Minnesota will make Red Pine a durable building product. Here, it is shown as a wood siding.
As far back as 900 B.C., the Vikings of Norway kept fence posts from rotting by burning the surface of the wood.
The best ideas, it seems, stand the test of time.
Today, NRRI research on heat-treating Minnesota red pine could mean that regional window and door manufacturers don’t have to truck in wood from the western U.S.—with additional environmental advantages, as well.
As many homeowners know, wood exposed to moist air expands and contracts, causing painted surfaces to peel and crack. Covering the wood with vinyl is an option, but it can be expensive. The wood can also be chemically treated, but toxic chemicals are not a good option for the environment.
Intensive research over the past 15 years in Finland by VTT Technical Research Centre and the Institute of Environmental Technology resulted in an industrial scale heat-treatment process called Thermowood. Now, Pat Donahue, NRRI forest products co-director, is bringing this tried and true idea to Minnesota with funding from the USDA Wood Utilization Research Program.
“The window and door industry came here because of the availability of white pine,” Donahue explained. “But when the white pine was gone they’ve had to ship it in from the west. If this industry can get their wood locally again, it would have a very positive economic impact.”
Here’s the basic process: the wood is heated in a two-part process to 374° – 482° F while being protected with steam. Once it is “cooked,” the wood is more stable in changing humidity, has improved thermal insulation properties, and is decay resistant.
Donahue is sending Minnesota red pine to Finland where the wood will be thermally treated. It will then be shipped back to NRRI for testing to specific window and door industry standards.
“Red pine has a lot of sticky resin in it,” he said. “This process fully cures the resins so the wood doesn’t bleed. It eliminates the hemicellulose, or sugars, where decay gets its foothold in wood. When the lignin in the cellulose wall softens, water’s ability to affect the wood is greatly reduced.”
With new housing construction down 25 percent from 2006 to 2007, related industries are also feeling the pinch. Donahue hopes this wood treatment process will help Minnesota’s window and door manufacturers stay competitive in a slow economy.