I currently live in a 1 1/2 story cape cod house with 4 inch rafters and a "hot roof". We have some prety bad ice dams during the winter and in the summers the upstairs is a furnace. I need to reshingle the roof and was thinking of having some closed cell insulation sprayed. With the current setup, I believe the best I can achieve is a R level of 20. I was wondering if I were to have the decking removed, add 2" furring strips, and spraying the closed cell insulation 5" deep, I'll get the R level up to 35, but will it be worth the extra cost? The added expenses will be removing the decking, adding the furring strips, redecking, and extra insulation. How noticeable will the living conditions be when comparing the two options?