Spray foam insulation is not difficult to install once you have been trained in the more technical aspects of its application. There are a few details to which you must pay close attention, however. One of these is the thickness of the foam.
Code Regulation Conflicts
Generally, the thickness of spray foam is determined by building codes in the area. The minimum recommended thickness is set by determining the needed R value based on climate zone. There are two different organizations which make recommendations based on thickness -- the International Energy Conservation Code (IECC) and the International Residential Code (IRC). Since the IECC makes recommendations based on insulation needs and the IRC makes theirs based on fire hazards, you often end up with two different recommendations. Luckily, the IRC allows contractors to use a thickness determined to be safe as per ASTM guidelines.
The ASTM Guidelines
Although the ASTM guidelines use 4 inches as a baseline safety recommendation, they do allow for greater thicknesses so long as the thickness has been fire tested in its end-use configuration. NCFI has performed this testing in conjunction with the Southwest Research Institute, with important findings regarding thickness.
Based on our testing and approval by ASTM, we are able to recommend a maximum spray foam insulation thickness of 8 inches in walls and 12 inches in ceilings. Of course, the thickness you should use will depend on your building project and the climate in your area.
If you have questions about the right thickness of spray foam for your project, or how to go about calculating this figure, don't hesitate to contact NCFI Polyurethanes. We're your go-to source for polyurethane spray foam materials, training, equipment and more.