Icynene vs straw is a good example of the difficulty in making appropriate choices of "green" materials.   While I don't think that spray foams should be used in new construction, stuffing straw into existing walls for a retrofit/upgrade is not a sensible option and with a limited wall cavity Icynene may be the best alternative for renovation. Even for new construction, straw bales - with their low R-value per inch (≈1.45, about the same as lumber) may not be the best choice.   Besides having no global warming or ozone-depleting installation by-products, Icynene has only a little more embodied energy per cubic foot than fiberglass (not that I would recommend fiberglass for anything), typically less installed embodied energy (since framing bays are not generally completely filled) and better efficiency payback.   Best use of remaining fossil energy and petrochemicals? Not so simple to discern. --- On Thu, 12/11/08, Michelle Smith Mullarkey <[log in to unmask]> wrote: Point taken.  I admittedly was thinking of products like Icynene vs. straw, but it seems fossil fuels really are part of our entire world. On 12/10/2008 6:21 PM, Robert Riversong wrote: --- On Wed, 12/10/08, Michelle Smith Mullarkey <[log in to unmask]> wrote:  Fossil fuel is still used to manufacture and transport the majority of green building products (not natural building products such as straw bales)...   I'm afraid that fossil fuels are used for the production of most straw and since some of it is coming from Canada, there's also transportation costs. "Natural" building materials are not necessarily immune from the environmental costs of other materials.