Remodeling a cathedral attic space of a 1904 home. Rafters are 2x6, but 5.75" wide. The area is mostly roof, because it is a double gable, but the end walls are high (12') Previous owner in the 70's put in 3 1/2 inch figerglass/kraft paper R-11. The attic floor/2nd floor ceiling was insulated in 2004. This winter, I measured the temperature and it hardly went below 50. Not bad for a house in Milwaukee. The remodeled space will be used as an artist studio and plan on using an electric space heater to warm it up when it is being used. (there is one radiator for a servants bedroom that gets some heat, BTW) I know the R value is a third of what is recommended by Wisconsin Energy for new construction but can't justify to myself the added cost of removing the R-11 and replacing it with physio board. I'm 59, and may not live until the end of the payback period. (I'm assuming physio board is the only product that will make the roof R-38 as there is only 5.75 inches and they are steeply pitched (9/12). Any suggestions or comments?