1. Soybean-based spray foam: Although it has a similar R-Value, soybean-based foam does not contain MDI. Biobased and Demilec are two of the leading manufacturers of soy-foam.
2. Castor oil-based Icynene: This additional form of chemical-free insulation is even a spray foam, but without MDI.
3. Cotton denim batting: Denim insulation is typically produced in sheets from recycled clothes or industrial materials. It works similarly well to spray foam, but can cost about double and is not quite as easy to install. For new construction, however, this green alternative to spray foam has a lengthy life span.
4. Sheep's wool insulation: Like denim, this green alternative to spray foam cannot be blown into walls, but is a chemical-free alternative to traditional foam insulation.
Read more about green alternatives to spray foam from Fairfield Citizen.