foam insulation expands to 100 times its volume to fill cracks and crevices and minimize air leakage. It carries an R-value of 3.6 per inch. The product also is available in a pour-fill variation that expands upward to 60 times its original volume; it will not expand outward and damage the wall. The pour-fill version has an R-value of 4 per inch. 800.758.7325. www.icynene.com.