Loose-fill pumice, fly ash, and sawdust have been used to construct insulated walls for retrofit or new construction of small residential buildings. Pumice in sandbags was demonstrated as exterior insulation for an existing adobe house in New Mexico. Such houses are rarely insulated because of the cost and difficulty of providing exterior insulation. Prototype stand-alone walls were also constructed using fly ash and sawdust blown into continuous polypropylene tubing, folded as it is filled to form the shape of the wall. Other materials could also be used.