I have a very large 2600 sq. ft. vented crawl space. I found that I had
accumulating water due to the builder not installing drain tile around
the perimeter of the block wall foundation. I had only one main sump
pump in the corner with varying degrees of slope across the terrain. I
had an outfit come in and install 3 addtional sumps in the low lying
areas and daisy chain them to the main sump. They told me that it would
be cheaper and easier to just seal off the ground from the main floor
overhead. They installed very thick plastic all the way from the sill
plate down the walls to the ground and over the entire ground area
(sealing the seams together). My floors are very, very cold and I would
like to insulate. I am concerned about moisture, obviously, and would
like to know more about the expanding foam insulation. Should I use a
closed cell foam? Will this type of insulation seal in the heat
overhead and not allow moisture/mold issues? Any advice or links would
be helpful. Thanks. BK

could you insulate the underside of the floor, between the joists ?