Our neighbors, Meg & Allan, just had their bathroom walls - and the kitchen walls below - insulated with a blow-in material.  According to Meg: "It's wet blown foam insulation called Icynene, with an R-value of I think 12, no cancer-causing formaldehyde, and no CO2-producing and ozone-depleting HCFCs found in other insulation. It reduces the potential for mold growth, and is supposed to be good for indoor air quality and for people with chemical sensitivities..." She shared this info in a comment to an earlier post, but this is so exciting that I decided to make sure no one missed it.

 They also had the floor joists in the basement insulated. The total cost was $1.50 per square foot, or $750 dollars.

The information I was able to find on Icynene says that it does not settle over time like other "blow in" insulation foams, so it maintains its R-value (the amount of insulation it provides). It is recommended by the American Lung Association for not contributing to indoor air pollution, and is included in their "Healthy House" program. The "green" specs for the product can be found at their website.

I also found an independent website that offers a lot of information on home energy savings: GreenHomesGuide.

Heating and cooling consume about 44% of a home's energy use.  While insulating the attic gives the biggest bang for the buck, insulating foundation walls can cut your costs by up to 20%.