We have a poured foundation and I'm in the process of replacing the 2x3 walls around the perimeter. I'd like to tighten up the house a bit and get the maximum R value in the walls. I was wondering if it would be a good idea to erect 2x4 walls and inch or two from the cement and then have spray foam insulation put in? The idea of paying for 2x6's to do the whole basement isn't very high on my list of fun things to do. Should I put in some 2x6's to maintain the spacing from the wall? Should I put up plastic sheet, or would the foam adhere better to the cement? It has been painted in the past, but has peeled in many areas.