THis is what is happening at Northfield Community Middle School. See Glenn Robbins' blog (http://connectedleadlearner.blogspot.com/2015/08/goodbye-hallways-and-welcome-to-idea.html).
Hallways in a school building make up to 30% or more of unused space. Learning spaces don't only have to take place inside the classroom. Bulletin boards can be repurposed and used to spark creativity and for design challenges.