I am building a home in Omaha, Nebraska - cold winters and hot, usually dry summers. I have a choice between putting up half inch oxboard sheathing covered with Tyvek and then lap siding, or putting up 3/4" Dow Styrofoam insulation in place of the sheathing and Tyvek. The Tyvek and sheathing option costs a little more, seems sturdier, and appears to be what the higher end homes get. My builder thinks the Styrofoam is the better way to go - he indicated it will have much better insulation qualities. Which has the better "R" value? Which option will provide best overall performance?