We bought a two-story brick house with a walkout basement. The entire basement had to be gutted due to a burst water line and the mold and mildew that developed while the house sat empty - even the ceiling had to come down. Although the walls had been insulated with Fiberglass batts, the rim joist had never been insulated. Lots of air leaks at the rim joist, around the windows and around the fiberglass. Louisville Spray Foam Insulation sprayed closed-cell foam from the top of the rim joist/band joist all the way down to the basement floor. The difference is truly amazing! Our house sits very close to the road and before the spray foam application you could hear cars coming down the road long before they passed in front of the house ? now I only hear them when they are directly in front of the house and only when I am standing right at a window. The foam seals it up very tight! The basement has a totally new warm cozy feeling with no cold corners or any lingering dampness. It just doesn't feel like a basement at all now. The foam applicators were careful to mask off areas where there might be overspray, like our brick fireplace, floor and stairwell. They did a good job of cleanup when they were done and we were able I guess what I take away from this process is this: there is no real comparison between fiberglass and spray foam insulation. They may both use "R-Values" to try to explain how well they insulate, but the difference is so much more. The closed-cell spray foam is not just insulation, it is also a vapor barrier that seals every little space. It can't absorb water or get damp or sag over time. Fiberglass is done, part of history. I could never see myself using it again.