Usually the only cost effective RB is in the form that comes pre attached to the sheathing and you have duct work in the attic. You would be better off by interrupting the thermal bridging of the 2x8s with foam sheathing below the rafters or preferably on top of the roof sheathing. You also need 30 lb felt for roof applications.

Usually the only cost effective RB is in the form that comes pre attached to the sheathing and you have duct work in the attic. You would be better off by interrupting the thermal bridging of the 2x8s with foam sheathing below the rafters or preferably on top of the roof sheathing. You also need 30 lb felt for roof applications.

Radiant barrier only works when there is an air space and a ventilated attic. Your project, being living space in an a actual attic area, would not be able to utilize a radiant barrier. The only way to get the code required insulation for a residential space is to lose some headroom and use spray foam to get the required R value. Otherwise, that is going to be one HOT living space that even AC won't help much. And it'll cost a pretty penny to try to cool as well.

Ditto 30 pound roofing felt.

You've posted about quite a few issues with this build that do not meed residential code standards. I'm curious as to why you wouldn't want to at least meat the minimum required standards for safety, comfort, and energy efficiency. Especially when there are so many opportunities to design something that exceeds code standards and performs so much better for safety, comfort, and energy efficiency.

Thank you letting me know about the thirty pound roofing felt. Story and a half homes have been around for a very long time. Aside from insulating the eight inch deep spaces between the rafters I'm not sure what more I can do. Please explain.