The house volunteers are working on in East Missoula is part of the organization’s first effort to build with insulated concrete forms. They look like giant white foam Legos that are stacked on each other. The blocks reduce the amount of wood used to build a house and are a test to keep building costs under $200,000.

“And more importantly, I think what it does is it gives us another arrow to add to our quiver, so we can do stick build, we can do [insulated concrete forms],” Harp says.