I've ingested about every piece of information regarding foam insulation and my head hurts as there doesn't seem to be a clear answer. I had two companies come by and got two different options. One is an open cell 8" and another for 3" of closed cell. I live in Zone 5 (NY) to be exact and have duct work and an air handler located in the attic. The reason the one installer recommends open cell is due to locating a roof leak faster than closed cell foam. The closed cell installer claims its a superior product. What do you guys think? Especially those of you who live in my zone and had one of these types of systems installed? I'd greatly appreciate some real people input rather than those of sales people at this point.