I was researching various kinds of insulation for our new home a few months ago and found out that the best most environmentally friendly insulation is polyurethane spray foam.  It is a great cavity wall insulation which is just what we needed.  I uncovered information about this kind of insulation that really impressed me.  I have serious allergies, and it is perfect for me since it reduces airborne fibers, dust and allergens better than any other insulation.  The biggest plus I found is that it saves me so much more on my utility bills.  So far, our bills have been low and I have yet to discover any drafty places in our home.  I have been recommending this insulation to all my friends.