Why not wool batts?goodshepherdwool.comexpensive, but they sure look cosy
Thanks so much to whoever posted this. I was considering wool insulation of some sort, and after working with the "free" found rigid foam I realize I never want to work with it again. I highly recommend people look into insulation like what Good Shepherd Wool is offering. I have no personal experience with their product, but in retrospect I think it's worth saving money to get sustainably harvested insulation. This is an issue I'm very curious about and encourage readers to post links to things you recommend here so I can advise my friends and consider for my own future projects.
FROM FRIEND: There are alternatives to polyurethane foam insulation. Before the invention of plastic foams and fiberglass there were a number of materials used as insulation for walls of houses. There are houses in New England built in the 1700s that were insulated with dried seaweed. A friend of mine remodeled such a house a few years ago and found that the over 200 year old seaweed insulation showed no signs of deterioration. Shredded redwood bark was often used in California. I remember when I was about 10 years old that a cousin built a walk in cold storage room at his ranch and used shredded redwood bark for insulation. The bark was sold in bales in an as removed form from saw logs. The supplier had available for rent a portable shredder that was taken to the jobsite to shred the redwood bark slabs into a fibrous fluff that was then packed into the wall cavities. Straw, wood shavings, sawdust, and shredded paper were also sometimes used but had less resistance to mold, rot, rodent damage, bug damage and fire compared to redwood bark. Expanded Mica, sometimes called Vermiculite, was another material that was used which was fireproof as well and rot and bug proof. So, there are alternatives to foam but foam does a better job in most cases.