Maximum Insulation in Thinnest Wall
I live in downtown Toronto (Zone 6), Canada. I’m building a brand new addition to an existing 1888 brick house, on a narrow 17′ wide lot. I’m interested in getting the best thermal performance (R40) within the thinnest assembly (11″ wide) so here is my idea:
From inside to outside –
2×4 wood stud framing with
3.25″ of high density spray foam (R21)
5″ Roxul Mineral Wool (R20)
1″ wood battens or alternately 6″ thermally broken z-girts
metal cladding (I am hoping to use a flat seam metal panel of some sort.)
Any thoughts would be much appreciated. I want to make certain that I haven’t missed any major holes with the thinking. I’ve been reading this forum for a little while now and am impressed by all the curiosity, knowledge and wisdom.
Also, do you think I need a vapour barrier, considering the spray foam acts like one? If so, should I locate it under the drywall?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part