Architectural Designs

What green building system has the best thickness to r-value ratio?

I am designing a hypothetical multi-story building in Toronto, Canada. The site is 15' wide, which means that I need a thin wall with an amazing r-value. I also cannot use wood frame construction. What building system, from exterior to interior, can I use to have the best r-value to wall thickness ratio, while still being able to support 4 stories of concrete slab flooring.

Public Comments

1. Structural steel for vertical support. Metal stud framing with Styrofoam panels, stucco exterior with sheetrock interior. R30 can be done with the sandwich style exterior walls.