Is there much of a practical difference between different brand names of insulation? Just wondering, because I found a building supply store that sells something called Certainteed for a much cheaper price per square foot (same R-values and facing type) than the Owen-Cornings insulation at Home Depot or the Johns Manning insulation at Lowes. I'd like to know whether the extra cost at Home Depot and Lowes is actually paying for a better product, or is it just paying for a pretty brand name or the higher overhead costs or profit margins of the retail stores.