Some of these cladding or roofing units are expensive, especially the sandwich units which contain a middle layer of highly efficient thermal insulator, such as expanded polystyrene or glass fibre .

  • 有些围护墙或屋顶构件造价很高,尤其是夹层式构件。这种构件中间有一层高效能的隔热层,如膨胀聚苯乙烯或玻璃纤维。
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