Warm air holds moisture, and this moisture will condensate it comes into contact with the cold exterior concrete wall. This moisture will collect in your insulation or just freeze as ice or frost on the wall. On a nice day the concrete will warm and the ice will melt and pool on the floor or it will saturate the insulation
What you need is a system that prevents warm air from coming in contact with the cold concrete wall. Think of a cooler on a picnic in the middle of a hot summer day, that white Styrofoam insulation keeps everything cold inside, with no condensation on the outside, now open the cooler and pull out a cold beer and in no time moisture starts to form on the bottle. Glass, Metal, Concrete, these products that are highly conductive and if certain conditions are met will have moisture build up on their surface.
The goal with basement walls is to use a product that will 100% separate the cold concrete from the warm living space.
Spray Foam is the best possible insulation material for this unique area. Closed cell spray foam is perfect for locking out moisture laden air that inherently wants to migrate from your basement living space to behind your wall.
There are two basic types of spray foam insulation: Open Cell and Closed Cell.
Open cell is softer and lighter and incorporates air for the insulator. It's less costly than Closed cell and has half the Rvalue when compared with closed cell foam. Open cell foam will also retain moisture if it gets wet which in a basement is definitely something you want to stay away from. Open cell foam will require the use a separate poly vapour barrier-just like batt insulation. At Red River Spray-On Ltd. we do not spray open cell foam.
Closed Cell is dense and rigid and will not retain moisture. "I'm a huge fan of closed cell spray foam insulation. The best of all insulations on the market is closed cell foam. It wins on all counts-energy efficiency, indoor air quality and environmentally. At 2 inches it's also its own vapour barrier (though you should check with local municipalities. Some inspectors still want to insist on vapour barrier, though they shouldn't.)" - Mike Holmes