The audience of dedicated urbanists at Vancouver’s Robson Square Theatre was startled earlier this year when the first speaker at a debate about mass timber—which B.C. has been promoting vigorously—said it isn’t the for-sure climate-change silver bullet that everyone likes to think it is. Adam Rysanek, a UBC professor of environmental systems who specializes in energy efficiency, poked hard at the assumption that, because everyone thinks of mass timber as just wood—a plant! that comes out of the ground!—it must be natural and environmentally friendly and surely better than concrete. But Rysanek kept making the point at the Urbanarium debate that those ideas are not fully proven. A study he cited, which aimed to factor in all the uncertainties of carbon emissions in different types of building materials, found there is not a clear answer yet about the differences between mass timber and concrete.