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Purpose: Bio-based insulation materials can have a significant impact in achieving net zero target in the construction sector. However, they face challenges due to lack of data on environmental performances and professional perception, hindering their proliferation. This study aims to combine scenario-based and dynamic analyses of environmental performances to provide comprehensive environmental information on bio-based thermal insulation materials. The goal is to empower professionals with robust information, facilitating informed decisions and promoting the selection of bio-based materials. Methods: Data on manufacturing, use, recyclability, and technical performance of eleven commercially available natural insulation materials were collected from the literature to create a Life Cycle Inventory (LCI). For each material, a scenario-based life cycle assessment (LCA) was conducted by modelling variation in manufacturing, transportation, end-of-life and material properties, using the UK as the primary case study. Materials were compared to three non-bio-based insulation materials by ranking the thirteen environmental impact categories in EN 15804(2013) + A2(2019) to give an exhaustive overview of their potential benefits and burdens. Additionally, a dynamic LCIA was performed to implement in the analysis both short-and long-term emissions, exploring the impact of biogenic carbon. Results: The scenario analysis highlighted that recycled cotton and hemp fibre insulation have the lowest impact across all impact categories, attributed to their sustainable manufacturing processes and minimal impacts at the end-of-life stage. The dynamic LCIA demonstrated that recycled textile insulation has the lowest impact both in the short-term (prior to waste disposal) and the long-term (post-waste disposal), regardless of the chosen end-of-life scenario. Furthermore, it indicated that cotton and hemp fibre have a negligible impact on global temperature changes, achieving a net-zero effect in the short-term and close-to-zero impact in the long-term. Conclusion: The novelty of this paper lies in its comprehensive investigation of the environmental impacts of bio-based thermal insulation materials, employing multiple tools to enhance generalizability. These results will support decision-making by providing data ranges to help practitioners identify the most environmentally friendly insulation materials. Additionally, they offer insights into how similar products compare within that range, driving progress in the built environment towards net-zero emissions. Whilst the full dataset and evaluation methods are illustrated through a UK-based case study, this method can be adapted for specific scenarios and projects, due to the transparency of data and methods. This research significantly influences the built environment and promotes net-zero targets within the sector.

Circular economy principles can be applied to the construction sector to reduce use of resources, energy consumption and wastes. Bio-based construction materials are particularly suitable to circular building design. Advantages of bio-based materials include: (1) a renewable supply chain, (2) often fast-growing, (3) recyclable or used as fertilisers/compost and (4) can sequester carbon. In this paper, the design of three circular bio-based wall panels is presented. The three panels were designed to be disassembled, and innovative bio-based materials, such as mycelium, sheep’s wool and cellulose were implemented in the walls. The wall assemblies were tested in a large environmental chamber to assess whether the panels achieved high insulating performances. Monitoring results showed that the three panels have excellent thermal properties. In parallel, life cycle assessment (LCA) of the bio-based construction materials applied in the three panels was undertaken to assess the sustainability and circularity of the selected materials. LCA results showed that some of the materials, such as sheep’s wool and flax, do have a low carbon footprint. However, there are uncertainties around the carbon footprint of other bio-based materials (e.g. fungi-based products), as information on the manufacturing process and associated emissions are not always available. This paper provides an overview of the applicability, advantages and challenges of innovative and sustainable technologies in buildings to achieve net-zero targets and to apply circular economy model of construction in buildings.

Construction projects using emerging bio-based materials have been realized over the past ten to fifteen years within Europe. Bio-based buildings utilize properties of natural materials to regulate internal environments, particularly fluctuations in temperature and relative humidity. Despite individual exemplar projects demonstrating functional performance and long-term operational cost savings, there hasn’t been a proliferation of commercial or domestic bio-based projects. With a growing shift towards circular economy construction, bio-based buildings could be readily adopted to meet this development. This study evaluates barriers faced by bio-based materials, making the upscaling of production and a breakthrough into mainstream construction challenging. Evaluation was achieved through senior professionals with experience in bio-based construction participating in semi-structured interviews based on core categories of finance, knowledge, and policy. Challenges include the upscaling of production by manufacturers of emerging materials, inconsistencies in life cycle assessment, material certification and accreditation, vested interests in the construction industry, and concerns regarding initial costs, availability, and knowledge of products. Potential solutions for upscaling bio-based construction are identified and include increased case studies, positive legislation, regional economic regeneration, the wellness agenda, long-term economic sustainability, and engagement with established construction companies. This insight has informed the procurement process, material evaluation, and adoption of policy.

Buildings are subjected to the indoor environment, especially in non-controlled climates. Temperature and humidity variations might effect or even damage materials sensitive to moisture. For this reason, it is important to understand the response of hygroscopic materials to variable indoor environmental conditions. Existing methods looked into the dynamic sorption capacity of materials, by analysing the impact of only humidity fluctuations, with temperature usually considered non-influential or non variable. However, temperature fluctuations may impact the moisture capacity of the materials, as materials properties might substantially vary with temperature. Moreover, in existing protocols, the humidity variations are considered to be varying under square wave fluctuations, which may not be applicable in environments, where the indoor is influenced by daily and seasonal climate variations, which presents more complex fluctuation. In this study, a simulation method that can predict the impact of environmental condition on materials under simultaneous temperature and humidity fluctuations was developed. Clay and gypsum plaster were analysed in the numerical model and results were then validated with experimental data. Materials were subjected to either sinusoidal and triangular temperature and RH variations and different cycle time intervals. The investigation of sinusoidal and triangular environmental variations pushed to a better understanding of materials response to different environments and to the improvement of the simplified model. The development of a simplified model can realistically predict the potential future impact of climate changes on buildings without the use of complex and memory demanding computational methods.

Hygroscopic finishing materials can be used to moderate indoor humidity levels; they have the capacity to adsorb and release moisture from and to the surrounding air, depending on the indoor relative humidity levels. To determine the moisture buffering properties of materials several protocols have been introduced. However, testing procedures are based on a time-response method, where humidity variations are under a square wave function and temperature remains constant. Therefore, the ability of these methods to simulate material behaviour under real conditions, where cyclical humidity variations are more gradual, and temperature is variable, has been called into question. The aim of this study is to perform a standard moisture buffering test, by substituting the step-variation method, with a sinusoidal humidity function at different temperatures. Clay has been used to perform the tests in a climatic chamber, where a small increase of relative humidity have been set, in order to obtain a quasi-sinusoidal curve. The relative humidity variation are limited by low humidity (33% RH) and high humidity (75% RH) and temperature variation between 18 °C and 28 °C. Materials tested present a lag in the response to the peak relative humidity to peak mass gain, which suggests an alternative way to consider the rate of sorption and the moisture storage function. The significance of the paper is to develop a laboratory test that can be more readily compared with the behaviour real buildings, which operate under more of a sine waveform