Answer: FOAMULAR® insulation is a great product for many applications but rigid foams are not ideal for stud cavities. The main issues are productivity during installation and the risk of leaks around the product after installation. Stud cavities tend to have a lot of electrical boxes and plumbing in them that require cutting and piecing the insulation to go around them. This would be very time consuming with a rigid product but fiberglass insulation can easily be cut and tucked around these objects. After installation, there would likely be lots of places where air could leak around the rigid insulation. Fiberglass insulation, by comparison, is made to fit snugly in the space and not allow air to flow between the insulation and the studs.