The left-most column has R-Values of insulation, starting at R-8 and going up in increments of 4. The next column shows the amount of heat flow reduced by the insulation, showing the diminishing return as a percentage. The next columns show the increased cost; for each increment, the cost increases 30 cents per square foot. Using the improved energy efficiency (the next column), the chart shows a calculated savings per year for insulation above R-8. The final column shows the years it would take for the insulation above R-8 to pay for itself via savings; for R-12, it is 53 years. For R-16, 64 years; for R-20, 71 years; for R-32, 107 years.