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The impact of the temperature dependent thermal conductivity of insulating materials on the effective building envelope performance

机译：隔热材料的温度相关导热系数对有效建筑围护结构性能的影响

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Constant thermal conductivity values of insulating materials are typically used in building design and assessment. However, the thermal conductivity depends on many factors, such as on the temperature and moisture content. Linear temperature-dependent laws have been occasionally proposed for inorganic fibrous materials such as fiberglass or rock wool that exhibit a decreased thermal conductivity (better performance) at low temperatures. However, the petrochemical-foamed insulating materials such as the polyisocyanurate, have less regular temperature dependent behaviors with a poorer performance at both extremely cold and warm temperatures. This means that the use of constant thermal conductivity values results in actual building envelope performance different from the design predictions, with increasing building energy consumptions, greater risks of condensation issues, and decreased occupants' comfort. This paper aims to quantify the impact of the temperature dependency of the thermal conductivity in exterior walls and flat roofs. Experimental results over a large temperature range (from -20 degrees C to +60 degrees C) for different insulating materials were used in hygrothermal simulations in both continental and humid temperate climates. Common insulating materials were taken into accounts, such as fiberglass, rock wool, polyisocyanurate, and extruded polystyrene. The increase in the energy fluxes from common building envelopes once the effective thermal conductivity was considered resulted below 10% for walls and as high as 70% for roofs, especially in the cold weather. Finally, a hybrid insulation system constituted by two layers of different materials, i.e. a polyisocyanurate and a rock wool is investigated. (C) 2017 Elsevier B.V. All rights reserved.
机译：绝缘材料的恒定导热系数值通常用于建筑设计和评估中。但是，热导率取决于许多因素，例如温度和水分含量。对于无机纤维材料，例如玻璃纤维或岩棉，偶尔会提出线性温度相关定律，这些无机纤维材料在低温下会降低热导率（更好的性能）。但是，石油化学发泡的绝缘材料（例如聚异氰脲酸酯）具有不太规律的温度依赖性行为，在极冷和极热温度下的性能都较差。这意味着使用恒定的热导率值会导致实际的建筑围护结构性能与设计预测有所不同，从而导致建筑能耗增加，出现凝结问题的风险增大，并降低了乘员的舒适度。本文旨在量化外墙和平屋顶中导热系数对温度的影响。在大陆性气候和潮湿温带气候的湿热模拟中，使用了不同保温材料在较大温度范围（-20摄氏度至+60摄氏度）下的实验结果。考虑了常见的绝缘材料，例如玻璃纤维，岩棉，聚异氰脲酸酯和挤塑聚苯乙烯。一旦考虑了有效的热导率，普通建筑物围护结构的能量通量就会增加，导致墙体低于10％，屋顶高达70％，尤其是在寒冷的天气下。最后，研究了由两层不同材料即聚异氰脲酸酯和岩棉构成的混合绝缘系统。 （C）2017 Elsevier B.V.保留所有权利。

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