I asked the contractor I have chosen the questions that were listed here

https://www.greenbuildingadvisor.com/question/contract-specs-for-ducted-mini-split-install

or at least the front half questions.

He said that code is R-8 for the insulation on the ducts, and there would be a $600 upcharge for R-12. 

That seems like a lot of money (especially since he’s already asking for $400 extra for the duct blaster test, which they hire an outside contractor to do).

The attic runs about 2 degrees hotter than the currently unairconditioned upstairs in the summer, as we have 2 inches closed cell foam against roof-deck/gable walls plus r-23 rockwool and 1.5 inch polyiso furring on rafters. (4a climate)

Sometimes it does get to 90 degrees upstairs.

We are not initially planning to use this system for heat, though we are buying the Daikin Aurora so it could more or less keep up with the need in the winter if we one day added minisplits to the downstairs and stopped using our natural gas boiler/radiator system.

In the winter, when it’s 32 degrees outside at 8 a.m., the attic is in the upper 50s as the second floor is 63 degrees.

So — how much difference would there be in our power draw be if we upgrade to R-12?  If we don’t pay them, is there a a diy solution to add r-4? (We did do the furring and cut/placed the rockwool, because of course amost none of our rafters were standard widths, and drywalled the gable ends, so we are somewhat handy)