Rob-
BEopt, developed by the National Renewable Energy Laboratory, is designed specifically to do cost-benefit tradeoffs for insulation strategies. It can be downloaded for free at http://beopt.nrel.gov/. BEopt also will provide a tradeoff for insulation levels versus solar photovoltaic systems. That is, at some relatively high insulation level, it is more cost effective to spend your money on a PV system than to continue to add more insulation. BEopt is the optimizer program, and it calls one of two other U.S. Dept. of Energy programs as the computational engine. I find the file system a little awkward, but otherwise, it seems to work well.
If you want to do things more manually, I like to use REScheck, which was developed by the U.S. Dept. of Energy's Pacific Northwest National Laboratory. It only computes UA, the sum of U x A for each element in the house, where U is the conductivity, and A is the area for each element. To compute the energy use, that must be multiplied by the heating degree days and cooling degree days (converted from days into hours), and an accounting must be added for the heat losses due to infiltration. I am working on the details for my web site, but it is not there yet.
Also, check out the links at: http://www.residentialenergylaboratory.com/links.html. |