During the few months that it took to set up the insulation and await shipping and delivery of the metal siding, there were a dozen or so uninvited company in our wall assembly. Conversely just the R15 in a 2x4 wall already meets or exceeds IRC code min for zone https://rockwool-insulation00987.shotblogs.com/rockwool-insulation-things-to-know-before-you-buy-49241863