Development of low-cost wheat-straw insulation board
Insulation boards suitable for buildings with solid masonry walls that lack cavities necessary for loose-fill insulation have been fabricated and tested for use in developing countries. The boards were made at low density, 80 to 160 kg/m{sup 3}, and have suitable thermal properties for an air-based insulation, with a thermal resistivity of 21 to 28 m{center_dot}K/W [R3 to R4 per inch (h{center_dot}ft{sup 2}{center_dot}{degree}F/Btu{center_dot}in)]. The initial effort focused on straw insulation boards suitable for use in buildings with solid masonry walls that lack cavities necessary for loose-fill insulation. The possible methods of fabrication initially evaluated were (1) containing the straw in panels with wire and battens, (2) pulping the straw, and (3) binding with adhesive. Starch, polyvinyl acetate (PVA), and sodium silicate were evaluated as adhesives for both uncut and shredded straw. Methods of application included spraying, foaming, and dipping, at various adhesive-loading rates. Small samples were formed at a range of densities and tested for structural and thermal properties. All three approaches can succeed structurally and thermally, but are unable to compete economically with existing insulation board. A final batch of boards was made by spraying methane di-isocyanate (MDI), a synthetic resin, into a rotating tumbler that contained shredded straw. The boards, made over a range of densities and resin contents, and using straw with and without the fine particles, were tested thermally and structurally. Good mechanical properties were obtained at resin contents as low as 2% by mass. At densities of 128 and 160 kg/m{sup 3}, the boards had thermal resistivities of 24 to 26 m{sup 2}{center_dot}K/W. The pressure required to compress the 160 kg/m{sup 3} boards to 10% of their original thickness was approximately 100 kPa, and the modulus of rupture in bending was about 340 kPa. Removing the fine particles from the straw improved board strength markedly. The final boards at a density of 160 kg/m{sup 3} and 2 to 4% resin content have an estimated materials cost of $1.22 per unit of thermal resistance (m{sup 2}{center_dot}K/W) per square metre of area (2{cents} per R per ft{sup 2}). This cost is substantially less than either the cost of the expanded polystyrene available in Pakistan or the retail cost of any rigid board insulation sold in North America.
- Research Organization:
- Massachusetts Inst. of Tech., Cambridge, MA (US)
- OSTI ID:
- 20104789
- Resource Relation:
- Conference: ASHRAE Winter Meeting, Dallas, TX (US), 02/05/2000--02/09/2000; Other Information: The full text of this paper can be found in the International Journal of Heating, Ventilating, Air-Conditioning and Refrigerating Research; 5: No. 3, 249-264(Jul 1999); PBD: 2000; Related Information: In: ASHRAE Transactions 2000; Volume 106, Part 1, 929 pages.
- Country of Publication:
- United States
- Language:
- English
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