In a world increasingly aware of the environmental cost of the current production/ consumption model, the use of sustainable practices to reduce our environmental impact as a society becomes imperative. One way to reduce this impact is to increase the reuse of materials that are considered, by current definitions of ”waste”, at their end of life. End-of-Life Household Materials (EoLHM) can be defined as household waste materials that still possess exploitable properties, thus making them suitable for reuse. There are several studies in the literature that address the recycling of these materials. When it comes to their reuse, unfortunately, only a limited number of studies are available. This paper aims to fill this gap by investigating the possibility to convert EoLHM, such as clothes or packaging, into low-cost thermal insulating materials for the improvement of the indoor thermal comfort in buildings, especially for households at risk of suffering from energy poverty. For this purpose, a comprehensive literature review and a qualitative analysis of both commercial and EoLHM are proposed. Commercial thermal insulating materials analysis is used as a reference to measure the performance of EoLHM. Important aspects to be considered when choosing suitable EoLHM for a smart conversion and reuse are also investigated. The most important outcome of this investigation is the comprehension that the conversion of EoLHM into insulating material is possible, and it implies a direct reduction in waste production, with environmental benefits and positive social implications. However, some aspects such as adaptability, life expectancy, collection and storage are, at present, in need of further thinking and development to make the EoLHM reuse and re-conversion processes viable on a large (neighborhood/city) scale.

From a construction point of view, neighborhoods with residents living at or below the poverty threshold are characterized by low energy efficiency buildings, in which people live in acoustic discomfort with no viable options for home improvements, as they usually can not afford the materials and labor costs associated. An alternative to this is to use low-cost insulating elements made of non-conventional materials with acceptable acoustic properties. Given that household materials at their end-of-life (EoLHM) are free of costs and available also to the more disadvantaged population, they can be used to build acoustic panels for such contexts. This approach embraces several benefits since it reduces the amount of waste produced, the footprint deriving from the extraction of new raw materials and, by highlighting the potential of the EoLHM, discourages the abandonment of waste. In this paper, the acoustic properties of EoLHM, such as cardboard, egg-cartons, clothes, metal elements and combinations of them, are investigated by means of the impedance tube technique. The measured sound absorption coefficient and transmission loss have shown that EoLHM can be used for the realization of acoustic panels. However, since none of the analyzed materials shows absorbing and insulating properties at the same time, EoLHM must be wisely selected. This innovative approach supports the circular economy and the improvement for the living condition of low-income households.

From a circular economy perspective, the acoustic characterization of steelwork by-products is a topic worth investigating, especially because little or no literature can be found on this subject. The possibility to reuse and add value to a large amount of this kind of waste material can lead to significant economic and environmental benefits. Once properly analyzed and optimized, these by-products can become a valuable alternative to conventional materials for noise control applications. The main acoustic properties of these materials can be investigated by means of a four-microphone impedance tube. Through an inverse technique, it is then possible to derive some non-acoustic properties of interest, useful to physically characterize the structure of the materials. The inverse method adopted in this paper is founded on the Johnson–Champoux–Allard model and uses a standard minimization procedure based on the difference between the sound absorption coefficients obtained experimentally and predicted by the Johnson–Champoux–Allard model. The results obtained are consistent with other literature data for similar materials. The knowledge of the physical parameters retrieved applying this technique (porosity, airflow resistivity, tortuosity, viscous and thermal characteristic length) is fundamental for the acoustic optimization of the porous materials in the case of future applications.