I am in the process of getting solar for my home. The system cannot be installed on the current tile roof with no plywood decking underneath (tiles hang on skip sheathing). Plywood needs to be there. I am not going to just take off the tiles and put the plywood in and then replace the same tiles. Too old. (44 yrs). So I am getting quotes for installing a composition shingle roof. I am going crazy because in order to get ventilation from the eave area up to a new ridge vent,  there is no way they are going to get the code R49 or R38 value in the 8 inch rafter area and leave some room in that cavity for  a +1 inch air space. I read the article on the three things that you can do to use less R value. But, not quite sure if I can stretch what I have to fit into those criteria. So what do people do when they need to get a new roof without having to pay thousands of dollars to meet some code requirements that can’t be met unless their is major building work to be performed? There is no way we can afford that on top of the regular cost of a new roof. What do people do when they are confronted with this situation? Help!