I have already had foam blown into the centers of the cinder blocks, which were hollow. This gave me an R-5. The contractor is talking about attaching the 2 x 4s with tap-con screws. There will be 2 x 6s at the corners of the house, to anchor the vinyl siding. I am getting 1 1/2 inches of foam board glued to the cinder block and then also furring strips which are 2 x 4s with screws. Then 1/2 inch of foam board over the 2 x 4s, for about R-11 for all the boards. Then R-4 insulated vinyl siding over that. The contractor said this will be R-15 total added.