Thanks for the replys. Forgot to add that the firm that wants to do closed cell + fiberglass said it was a code requirement to cover the foam with what he called a code approved ignition barrier. I thought that any foam rated E-84 was OK by itself. Comments? One question I need to ask is why not just spray 4 inches of closed cell and be done it with. That should provide at least R-25. Compared to the inefective R-11 that was in there it would be a big improvement. One reason this may not be practical is it may require two passes as I'm not sure you can apply closed cell at a 4 inch depth in one pass due to excess heat generation and risk of self ignition. Two passes would add to the cost and most likely push it well above the open cell. As for converting the crawl space into a mini basement, I think the jury is still out on that one. If not done correctly I think the consequences are worse than leaving it the way it is now. I also think the cost would be much higher since you still have to insulate the foundation walls and completely seal the volume from the ground.

Try www.buildingscience.com/ for information about vapor barriers. Another good source for local building advice might be your state land grant university. I do not know anything about your floor finish. I guess you will cringe when I mention pre-finished flooring, but keep reading ;-) The spaces between the boards lets moisture through. With finished in place floors (poly finishes) you have a good vapor barrier. I guess that you understand the "sandwich" prohibition now. If you have a vented crawl space, off gassing will primarily be through the crawl. Ignition is a good question. I am afraid that I do not know much about fire and foam. I know that it burns and that crawl spaces raise fire insurance so it is a good thing to look into. Any kind of covering over the underside of your floor is going to increase the risk undiscovered or delayed discovery of rodent and insect damage. That includes batts, foam or boxing-in with rigid insulation. I do not know if there is any hard information about the relative risks of each method. The rigid insulation alternative is not one that has been addressed in this thread yet. It would be less expensive than foam, if DIY, but it is a lot of work. It has to be taped very well. You could take a hybrid approach and cover selected areas with foam board -- under the most troublesome plumbing areas for example. When you get done with that, you foam the rest. Low density foam pulls out pretty easily. I do not know about high density. You would just have to spray some more in after you make repairs. The problem would be finding the stuff that you need to fix. I would considerer tagging stuff before foaming if it will be covered by foam. You could use durable plastic tags in some color code. If you have a leak, water will run right through low-density foam. I do not think that is so with high-density foam. One important feature of spray foam is the air-sealing capacity. Batts will not do that. That is the problem with it where I live in the humid Gulf South. Air gets around batts even when freshly-installed. It is even worse when it sags. Humid air hits the cool floor, water condenses and does not dry well. Floor rot happens. Even with the best batt installation, the joists become the coolest thing under the house. Condensation happens there and then rot happens. These things worked great before AC existed, but not anymore.

The recommended max curb height for zero entry shower is no more than 1/2", and the Kerdi shower LT pans for my dimensions are designed to be about 1 7/16" thick/high. If I could create a recess of about 1 1/2" into the floor, I could drop in the pan and it would be nearly even with the bathroom floor. Then I would have a 1/2" high curb right where it transitions from shower to bathroom floor, just to provide a little more water barrier. Another option for the floor is to cut out both layers of 3/4", add blocking on the sides of each joist, and recess the 3/4"plywood so it is level with the top of the joist. This would provide a 1 1/2" recess. My architect's concern is that the pan would be resting on top of both joists and recessed plywood sections, and it would not provide even support to the pan. Bruce

This "bora-board" product is 2-2/12" thick, closed cell polyurethane, treated with borate to retard termites. My main concern with the foam is whether there is any downside to having to remove it sometime in the future. Contractor #1 raises this point, but I'm not sure it's really valid.