Question: what building materials are environmentally friendly?
Answer: Recycled Steel. Utilises steel already in existence for structural use in a home. ... 
Bamboo. Bamboo is increasing in popularity as a building material. ... 
Sheep's Wool. ... 
Straw Bales. ... 
Precast Concrete. ... 
Earth. ... 
Plant-Based Polyurethane Rigid Foam.