Sustainable thermal insulation

One solution for sustainable thermal insulations is straws. What makes straws so good at keeping the warm air inside is the fact that it is very airy, and what actually serves as insulation is the air located between the straws, not the straws themselves. This material is sustainable because for farmers and in agriculture, straw is considered to be a waste, thus it is usually disposed, but in construction it is given a new use. Upcycling materials this way is a very sustainable manner of treating non-renewable materials, guiding after the principle cradle-to-cradle, not cradle-to-grave.