DIY insulation. Cheap and Green

My wife an I purchased a starter home about 2-1/2 years ago. We believe that it is a sears home from the 1930's a cute little 3 bedroom bungalow with 1 bathroom. When we bought it most of what was done in the 1930's came with it- shallow well, old wiring, steam heat etc. What also came with it were the beautiful upgrades added in the 1970's- shag carpet, textured wall paper and faux wood paneling. No where along the way had insulation ever been thought of, unless you consider the Homasote (http://en.wikipedia.org/wiki/Homasote) that covered all the interior walls and ceilings insulation. Yep, thats right there was not a lick of insulation in this house. We gutted it, re-wired and re-plumbed and de-seventyized the place. Dealing with 2x4 walls and 2x6 ceiling rafters, we opted for open cell spray foam. It was amazing at how fast and efficient it was, and the difference was immediately recognizable. There was also a considerable reduction in outside noise as well. The whole insulation job was about $4,000 for our 1,600 square foot home, considerably more than traditional fiberglass batts or cellulose. However, our home maintains heat very well, and stays cool in the summer as well. Our walls r-value is only 15 and the roof only 27, but the performance seems to be holding its own. Our yearly heating bills are below what others are paying by relative comparison, and we certainly don't feel the need to micro-manage the heat, we also hardly ever have the need for air conditioning.