This paper investigates the performance of timber-framed walls insulated with straw bales, and compares them with similar walls containing expanded polystyrene (EPS) instead of straw bales. First, thermal conductivity, initial water content, and density of the straw bales were experimentally measured in a laboratory set-up, and the dependence of the thermal conductivity of the dry material on temperature was described. Then, the two insulation solutions were compared by looking at their steady and periodic thermal transmittance, decrement factor, phase shift, internal areal heat capacity and surface mass. Finally, the acoustic performance of both wall typologies was analyzed by means of in situ measurements in two-story buildings built in Southern Italy. The weighted apparent sound reduction index for the partition wall between two houses and the weighted standardized level difference for the façades were assessed based on ISO Standard 16283. The results indicate that the dry straw bales have an average thermal conductivity of k = 0.0573 W/(m·K), and their density is around 80 kg/m³. In addition, straw bale walls have good steady thermal performance, but they still lack sufficient thermal inertia, as witnessed by the low phase shift and the high periodic thermal transmittance. Finally, according to the on-site measurements, the results underline that the acoustic performance of the straw bale walls is far better than the walls adopting traditional EPS insulation. Overall, the straw bales investigated are a promising natural and sustainable solution for thermal and sound insulation of buildings.

Among the several methods investigated over the past few years for the thermal mitigation of buildings in urban areas, green roof systems seem to be one of the most suitable solutions for several reasons, and researchers encourage the further study and implementation of these roofing techniques because of the potential benefits that they offer. So far, intensive, extensive and semi-intensive green roofs are considered to be a better option in terms of both energy efficiency and green area increase. However, there are some aspects that cause green roofs not to be suitable to every application, preventing their use from spreading, such as high maintenance and costs required by these sophisticated systems. Few studies aimed at overcoming the limits of green roofs have hinted at the possibility of implementing hydroponic cultures in green roof systems. This soil-less technology might overcome some issues, such as identifying the suitable substrate to support the growth of the vegetation. This paper aims to provide a systematic review of hydroponic green roof systems (HGRS), based on the rigorous analysis of the evidence gathered from the thorough evaluation of the available literature on the subject, in order to assess their potential use as an alternative to traditional green roofs. The review was carried out by analyzing studies that have assessed the performance of hydroponic green roofs as well as those of comparable systems, such as pond roofs and green roofs. The results of these studies show that HGRS provide similar performances to the above-mentioned systems in terms of the passive conditioning effect, lowering the cooling/heating load of buildings, with slight changes depending on the climatic conditions. However, they offer other significant properties such as higher efficiency in water runoff management, alongside others discussed in this paper, while also requiring minor maintenance. Significant results have been provided; however, gaps in the knowledge have also emerged, and further studies need to be conducted to provide exhaustive information.

Clay has a low environmental impact and can develop into many different products. The research presents two different case studies. In the first, the clay is the binder of raw earth doughs in order to produce clay-bricks. We investigate the effects of natural fibrous reinforcements (rice straws and basalt fibers) in four different mixtures. From the comparison with a mix without reinforcements, it is possible to affirm that the 0.40% of basalt fibers reduce the shrinkage by about 25% and increase the compressive strength by about 30%. Future studies will focus on identifying the fibrous effects on tensile strength and elastic modulus, as well as the optimal percentage of fibers. In the second study, the clay, in form of brick powder (“cocciopesto”), gives high alkaline resistance and breathability performance, as well as rendering and color to the plaster. The latter does not have artificial additives. The plaster respects the cultural instance of the original building. The research underlines how the use of a local (and traditional) material such as clay can be a promoter of sustainability in the contemporary building sector. Future studies must investigate further possible uses of clay as well as a proper regulatory framework.

Nature-Based Solutions offer a concrete opportunity to integrate nature into cities and strengthen their resilience, in response to global challenges related to climate change, biodiversity loss, and water management, which are exacerbated by urban expansion and its impacts on the built environment. This study aims to analyze various European policies and urban greening practices, considering not only some European Union member states but also other cities geographically located in Europe. The main goal is to explore how these solutions are used in various European cities to address environmental challenges and improve urban quality of life. The study highlights the growing role of greening strategies in EU urban policies as key tools to tackle global challenges. It finds that green interventions—such as green roofs, façades, and green urban spaces—offer multifunctional benefits, but their effectiveness relies on integrated planning, strong public–private cooperation, and active community involvement. Key challenges include the limited scalability of these solutions in dense or economically constrained areas and the need for long-term financial and institutional support. Overall, the study highlights that greening is not merely aesthetic but central to building regenerative and climate-resilient cities.

Ecosystems suffer from CO₂ emissions and pollution caused by waste materials, mainly agricultural and industrial, that are dumped in landfill sites. These materials contain aluminosilicates, which are key ingredients for producing geopolymer composite (GPC). While cement, the main component of ordinary Portland cement (OPC), is a highly energy-consuming and polluting material in terms of CO₂ emissions, water absorption, and land depletion, GPC is an emerging building material that can contribute to the sustainability of the construction industry. In this research, bibliometric data on GPCs were collected from Dimensions databases, and a scientometric analysis was performed using the innovative VOSviewer software (ver. 1.6.19). The scope was to examine the development of GPC for construction applications in the context of a circular economy and as an emerging green building material. Using specific query metrics and three keywords (geopolymer, circular economy, and green building materials), bibliometric records were analyzed to identify the articles, authors, and journals with the highest impact. This investigation can help scholars and policymakers in deepening their knowledge in this growing research area. From a societal perspective, this study stimulates geopolymer developments through policies aimed at promoting the circular economy, such as the adoption of green subsidies in research and development (R&D) and production.