When “Framework,” Portland’s next iconic building, tops out at 12 stories, it will be the nation’s tallest structure — and one of the tallest in the world — built entirely of wood. But Framework’s most towering achievement may be its stellar environmental performance, including its role in fighting climate change…. Tall all-wood structures once were rare, but now are being embraced by developers in Portland and around the world. They are designed to meet the same fire and earthquake safety performance criteria as comparable steel and concrete structures. But their stellar environmental credentials give them an advantage over other types of structures, according to researchers at the Oregon State University School of Forestry. In a study released in May, OSU researchers attempted to quantify the environmental benefits of wood over other building materials.