Building insulation is commonly realized using materials obtained from petrochemicals (mainly polystyrene) or\ud from natural sources processed with high energy consumptions (glass and rock wools). These materials cause\ud significant detrimental effects on the environment mainly due to the production stage, i.e. use of nonrenewable\ud materials and fossil energy consumption, and to the disposal stage, i.e. problems in reusing or\ud recycling the products at the end of their lives. The introduction of the concept of “sustainability” in building design\ud process encouraged researches aimed at developing thermal and acoustic insulating materials using natural\ud or recycled materials. Some of them, such as kenaf or wood fiber, are already commercialized but their diffusion\ud could be further improved since their performance is similar to the synthetic ones. Others are currently under\ud study and their development is only at an early stage. The goal of the paper is to report a state of the art of building\ud insulation products made of natural or recycled materials that are not or scarcely commercialized. Comparative\ud analyseswere carried out considering in particular thermal characteristics in terms of thermal conductivity, specific\ud heat and density. Data on the acoustic performance of the materials were also reported. Life Cycle Assessment\ud data were finally collected, in order to put in evidence the environmental advantages of these materials.\ud Particular attention was paid to researches focused to exploit local materials and even industrial byproducts,\ud since these approaches respectively limit transportation and disposal impacts

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Acoustical sustainable materials, either natural or made from recycled materials, are quite often a valid alternative to traditional synthetic materials. The production of these materials generally has a lower environmental impact than conventional ones, though a proper analysis of their sustainability, through Life Cycle Assessment procedures, has to be carried out. Airborne sound insulation of natural materials such as flax or of recycled cellulose fibres is similar to the one of rock or glass wool. Many natural materials (bamboo, kenaf, coco fibres) show good sound absorbing performances; cork or recycled rubber layers can be very effective for impact sound insulation. These materials also show good thermal insulation properties, are often light and they are not harmful for human health. Furthermore, many of these materials are currently available on the market at competitive prices. There is however a need to complete their characterization, both from an experimental and a theoretical point of view, and especially to propose a standard and unique procedure to evaluate their sustainability. The paper presents an updated survey on the acoustical properties of sustainable materials, both natural and from recycled materials, including mixed and composite materials and systems such as green roofs and green walls, and is completed by a wide selection of recent related bibliography.

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