What is the point of diminishing returns?
Brian writes from Freeport, Maine: “The insulation chart for my area of the country shows that i should have R49 in the attic- I currently have R-38. I can add R11 this fall but I am wondering if there is any return on investment for adding R19 vs the R11 called for. What is the point of diminishing returns? What % of heating costs should I expect to receive for adding either thickness- I read 15% for the R11 which would get me to R49 in total. My walls have R19 and I have double paned low-E windows.” Answer: R-49 is a minimum recommendation for attics in your area as determined by the U.S. Department of Energy. I do not have cost-to-benefit information for such an upgrade because home heating and cooling costs are impacted by so many variables. Also, the savings for any given R-value will vary depending on whether you are installing the product alone or adding it to existing insulation. Whatever the estimated payback period, it will only get shorter if home heating and cooling costs c
