Closed Cell vs Open Cell Spray Foam: Which One Is Right for Your Home? Not all spray foam does the same job and choosing the right one depends on what you’re trying to accomplish. Closed cell spray foam has a higher R-value, typically R-6 to R-7 per inch. At around 1 inch, it stops air movement, and at 2 inches, it acts as a vapor barrier. That makes it ideal for areas where moisture control and structural rigidity matter. Open cell spray foam, on the other hand, has a lower R-value at about R-3