The difference between a building insulated with closed cell foam and one with fiberglass batting is like going outside on a 45 degree day with a shirt and a wool sweater on when there is no wind or moisture you are comfortable and cozy. Add wind and it goes right through the sweater and shirt and you get chilled. Then you add rain and you are wet and cold and almost hypothermic. But if you went out on that same day with a rain jacket with a hood over the wool sweater and shirt you would be dry and warm because the jacket would mitigate the wind and rain.
The first example is the house with the fiberglass batting it does not close all the air spaces and absorbs water. The second example is the closed cell insulation which is water impermeable and seals all the air spaces off so you stay comfortable. In addition, closed cell insulation has an R factor of 7 per inch while fiberglass has one of 3 to 3.5 per inch.