Technical Performance Overview of Bio-Based Insulation Materials Compared to Expanded Polystyrene

The energy efficiency of buildings is well documented. However, to improve standards of energy efficiency, the embodied energy of materials included in the envelope is also increasing. Natural fibers like wood and hemp are used to make low environmental impact insulation products. Technical characterizations of five bio-based materials are described and compared to a common, traditional, synthetic-based insulation material, i.e., expanded polystyrene. The study tests the thermal conductivity and the vapor transmission performance, as well as the combustibility of the material. Achieving densities below 60 kg/m(3), wood and hemp batt insulation products show thermal conductivity in the same range as expanded polystyrene (0.036 kW/mK). The vapor permeability depends on the geometry of the internal structure of the material. With long fibers are intertwined with interstices, vapor can diffuse and flow through the natural insulation up to three times more than with cellular synthetic (polymer) -based insulation. Having a short ignition times, natural insulation materials are highly combustible. On the other hand, they release a significantly lower amount of smoke and heat during combustion, making them safer than the expanded polystyrene. The behavior of a bio-based building envelopes needs to be assessed to understand the hygrothermal characteristics of these nontraditional materials which are currently being used in building systems.

建筑物的能源效率有充分的文献记载。然而，为了提高能源效率标准，围护结构中所包含材料的蕴含能也在增加。像木材和大麻这样的天然纤维被用于制造对环境影响小的隔热产品。文中描述了五种生物基材料的技术特性，并与一种常见的、传统的、基于合成材料的隔热材料，即发泡聚苯乙烯进行了比较。该研究测试了材料的导热性、透湿性以及可燃性。木材和大麻毡隔热产品的密度达到低于60千克/立方米时，其导热性与发泡聚苯乙烯处于同一范围（0.036千瓦/米·开尔文）。透湿性取决于材料内部结构的几何形状。由于长纤维相互交织且有空隙，蒸汽在天然隔热材料中的扩散和流动量比基于多孔合成（聚合物）的隔热材料多达三倍。天然隔热材料的着火时间短，易燃性高。另一方面，它们在燃烧过程中释放的烟雾和热量明显较少，这使得它们比发泡聚苯乙烯更安全。需要对生物基建筑围护结构的性能进行评估，以了解这些目前在建筑系统中使用的非传统材料的湿热特性。