Sheep's Wool - Usually needs to be treated with chemicals to prevent mite infestation and reduce fire risk, although some natural builders use it untreated with success. It has very low embodied energy and performs exceptionally well as an insulation material. Thermafleece is the most common commercial brand available. Thermafleece CosyWool, Thermafleece UltraWool
Flax and Hemp - Natural plant fibres that are available in batts and rolls, and typically contain borates that act as a fungicide, insecticide and fire retardant. Potato starch is added to flax as a binder. Both materials have low embodied energy and are often combined in the same product. Thermafleece Natrahemp, Isonat wood wool panels.
Celulose - A recycled product made from newsprint and other cellulose fibre. It is one of the most favoured materials of natural builders because it can be blown into cavity walls, floors and roofs; used as a loose fill; and is also available in quilts, boards and batts. It contains borate as an additive.
Wood Fibre - Made from wood chips (by-products from the forestry industry) that have been compressed into boards or batts using water or natural resins as a binder. It has very low embodied energy.
Expanded Clay Aggregate - Small fired clay pellets that expand at very high temperatures to become lightweight, porous and weight-bearing. They can be used in foundations as both an insulator and aggregate. They have excellent thermal insulation properties.
Recycled Plastic Bottles - Created entirely from recycled plastic bottles. Thermafleece SupaLoft.
R-value Comparison Chart for Eco Insulation products available at Insulation Shop