A new load-bearing insulation material made of cattail
Due to the special structural properties of cattail (typha) building materials can be produced offering a combination of insulation and strength, which is unique on the market. The leaf mass of typha is especially suited due the structure of the plant. The leaves have a fiber-reinforced supporting tissue filled with soft open-cell spongy tissue providing for amazing statics and an excellent insulating effect. The newly developed magnesite-bound typha board has a high strength and dynamic stability despite a low thermal conductivity of about 0.055 W/mK and can solve energetic as well as static problems. This innovative building material possesses a lot of additional positive properties: renewable building material with a very high resistance to mould growth; good protection against fire; simple processability with all common tools; low energy consumption in production and its recyclability. The first practical application of this material has been within the restoration of an old half-timber-framed building. With the typha board as infill of the timber frames and as an additional inside insulation layer an extremely slender exterior wall construction with wall heating is realized. Due to the simple processability and inherent stiffness the material could be adjusted to the irregular inclined walls. The suitability of the wall structure has been investigated over a measuring period of 1.5 years. The U-value of the whole building (infill and timber construction) is about 0.35 W/m²K. The low level of moisture applied by the mortar and plaster dried out fast to a constant moisture contents in the wooden supports of below 20 M.-%. The magnesite-bound typha board is also applied successfully for interior insulation of masonry as well as for a modern wood-frame construction. Altogether, the entire insulation procedure based on typhapanels comprises an effective solution in terms of building physics and especially for historic preservation.