Bio-based Insulation Materials Research Articles

Exploring the thermal conductivity of green filamentous algae natural fibre: an experimental investigation

Abstract The use of non-renewable resources in thermal insulation has significant environmental impacts. Another major problem faced by the ecosystem is the invasive growth of water weeds. Making sustainable products from waterweeds helps to prevent its overgrowth that disrupts the balance of the ecosystem. This study explores the viability of Green Filamentous Algae (GFA) as an eco-friendly thermal insulation material. GFA was collected from water bodies, cleaned, and processed into two forms: untreated (UTD) and alkali-treated (TD). Experimental investigations were conducted to evaluate the physical properties of GFA, including density, self-ignition temperature, water absorption, moisture absorption, flammability, and thermal conductivity. Results show that the untreated GFA had a density of 402.52 kg/m³, while the treated GFA exhibited a slightly lower density of 392.32 kg/m³. The self-ignition temperature for both untreated and treated GFA was measured between 275°C and 280°C. The water absorption capacity was higher in treated GFA (654.7%) compared to untreated (493.83%). Moisture absorption capacity was 15.14% for untreated GFA and 17.47% for treated GFA. Flammability tests revealed a burning rate of 20.026 mm/min, placing GFA in the combustibility classification 1 (CC1). Thermal conductivity values were found to be 0.308 W/mK (UTD) and 0.273 W/mK (TD), making treated GFA a promising candidate for sustainable insulation applications. This study demonstrates the potential of GFA as a bio-based insulation material and highlights future improvements to enhance its moisture resistance and thermal performance.

Addressing the Difficulties and Opportunities to Bridge the Integration Gaps of Bio-Based Insulation Materials in the European Construction Sector: A Systematic Literature Review

Bio-based insulation materials (BbIMs) represent a potential alternative to conventional insulations, with their characteristics that favor a negative-carbon built environment. However, their use may face challenges that could prevent them from being used on a large scale in certain countries. The current study aims to provide focused insights into the practical difficulties and market opportunities for the application of BbIMs in Europe through a systematic literature review (SLR). The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were used as the basis for the conduct and reporting of this review. A keyword search was performed in Web of Science, Scopus, and ScienceDirect databases to select peer-reviewed English-language articles. HubMeta web tool was used to organize the selection process. The quantitative visualization of the literature was made by the Bibliometrix R package V4.1.4. Data were manually extracted and clustered in an Excel sheet. The review included 28 studies that have revealed interrelated insights. Difficulties range from regulatory and policy limitations and variability in performance, such as microbial growth and inconsistency in the behavior of materials under different conditions, to cost barriers. However, there are promising opportunities, including policy incentives and material performance benefits such as improved energy efficiency and indoor air quality. This research contributes to the literature by providing focused insights into the practical difficulties and market opportunities for the application of BbIMs in Europe. Research gaps and future perspectives point to the need for more field validation experiments, exploration of alternative production processes, and expanding life cycle assessment scopes to optimize their integration and performance. Stakeholders’ perceptions were made with a small sample in certain countries. Stakeholder perceptions were conducted with a small sample in some countries, so insights from stakeholders are needed to confirm or correct current findings.

Development of a multifunctional bio-based insulation material with corncob and silica aerogel

Bio-based insulation materials with superior comprehensive properties are crucial to building energy conservation. This study aims to develop a multifunctional bio-based insulation material that integrates good insulation, mechanical strength, and waterproofing. In this work, using corncob as the raw material, foamed geopolymer as the binder, silica aerogel and silicone oil as additives, a novel bio-based insulation material was prepared. Moreover, the effect of corncob size, silica aerogel content and silicone oil content on the microstructure, density, thermal conductivity, compressive strength, water absorption, moisture absorption and water contact angle properties were discussed. The results showed that, a desirable bio-based insulation material with a corncob size of 20 mesh, silica aerogel/geopolymer mass ratio (A/G) being 1.71 %, silica aerogel/ silicone oil mass ratio (A/O) being 0.2, is recommended, of which the thermal conductivity is 0.111 W/(m.K) with the compressive strength being 2.2 MPa, the density being 350 kg/m3, the water absorption being 7.1 %, the moisture absorption being 9.4 % and the water contact angle being 133°. With a simple preparation process, low cost and low energy consumption, this bio-based insulation material has good application prospects in buildings. Meanwhile, the preparation method of bio-based insulation materials proposed in this study provides new ideas for the development of multifunctional insulation materials in the future.

Hygrothermal assessment of three bio-based insulation systems for internal retrofitting solid masonry walls

The present project investigated the hygrothermal performance and risk of mould growth in solid masonry walls retrofitted internally with three diffusion-open bio-based insulation materials (two loose-fill cellulose and one hemp fibre), installed in test containers with controlled indoor climate. Focus was on bio-based insulation materials, as these are upcoming due to necessary CO2 reductions and because the hygroscopic properties of bio-based materials are different from traditional insulation materials like mineral wool therefore, some manufacturers claim a vapour barrier is unnecessary, even in relatively cold climates. The project was a large experimental study in two reefer containers with reconfigured facades, in which solid masonry walls with embedded wooden elements were constructed. The study focused on the conditions in the masonry/insulation interface and in the embedded wooden elements. The effect of hydrophobization and different indoor moisture loads were also investigated. Moreover, the bio-based insulation systems were compared with a wall insulated with the traditional mineral wool and vapour barrier system. Relative humidity and temperature were measured at several locations in the test walls for 1 year and 9 months. Measurements show that exposed masonry walls retrofitted internally with diffusion-open bio-based insulation materials resulted in unacceptably high moisture levels (>80% RH over longer periods). Lower moisture levels were observed when the internal insulation was combined with hydrophobization against wind-driven rain, but unacceptably high moisture levels still occurred (60%–70% in summer and 95%–100% in winter in the interface). Hydrophobization reduced the moisture levels in the interface and embedded wooden elements only in walls facing southwest, which is the direction with the most wind-driven rain. Mould growth tests showed no growth in the interface in walls insulated with cellulose insulation (mycometer surface value <25). Meanwhile growth was found in all four walls insulated with hemp fibre matts (mycometer surface value >400).

Mycelium-wood composites as a circular material for building insulation

In Europe, buildings account for 40% of the energy consumption and produce 36% of CO2 emissions. Renovation could be a great tool to decarbonize the building stock since it allows for a decrease in the operational energy required for buildings and is less material-consuming than new construction. Further benefits are brought by the usage of bio-based insulation materials that can drastically reduce embodied emissions and transform structures into factual carbon sinks. This study focuses on a particular kind of biogenic material, mycelium-wood composites, consisting of organic matter bound by the root structure of fungal organisms. This innovative insulation material was compared with traditional ones for the renovation of the building stock, with a focus on vertical components like walls in the Helsinki metropolitan area. To characterize mycelium-wood composites, density and carbon content information were gathered from the samples realized in the Politecnico di Milano MaBa.SAPERLab, while the production processes were included in a SimaPro model to obtain the GWP value. Different scenarios were then defined by two variables: the renovation rate of the building stock and the market penetration of mycelium-wood composites. For each scenario, the overall GWP and CO2 stored values were calculated. Results show the great potential of the innovative material that grants carbon storage in the building stock that could even surpass the amount stored in the 32,500 ha of forest in the area. However, this possibility is heavily influenced by factors independent of the type of insulation used that should be further investigated.

Characteristics of Insulating Panels Realised from Coconut Palm Fibres for Low-Temperature Thermal Insulation

In recent years, there has been growing interest in issues relating to pollution and energy consumption, and the resulting regulations have led the construction sector to focus on thermal insulation. The application of bio-based insulation materials can help to minimise the environmental impact of buildings by reducing energy demand both during construction and over the lifetime of the building. Agroforestry biomass plays an interesting role, as its use can reduce greenhouse gas emissions. The aim of this work is to produce insulating panels from agroforestry by-products for low-temperature thermal insulation applications. The insulating panels in this study are produced from coconut palm fibres and their thermophysical properties are determined. They were produced using a human-motricity press and the temperature rise was controlled using the hot-tape method. Characteristics such as calorific value and modelling of temperature rise as a function of time to calculate thermal conductivity, thermal effusivity and diffusivity were determined. The calorific value varies from 3668.0 to 4135.0 and from 3742.0 to 4186.0 cal.g-1 when the moisture content is 11.28 and 10.61%, respectively. The thermal conductivity, effusivity and thermal diffusivity are 0.4 W.m-1.K-1, 760.30 J.m-2.°C-1.s-1/2 and 2.73.10-7 m.s-1, respectively. In view of these results, coconut fibre represents a potential precursor to produce insulating panels.

Impact of Insulation using Bio-sourced Materials on the Thermal and Energy Performance of a Typical Residential Building in Morocco

Among the measures to be taken to design and construct buildings with envelopes that are more energy-efficient, sustainable, and environmentally friendly is thermal insulation using a very wide range of insulating materials, either synthetic or of natural origin or derived from biomass. The present work represents a thermal and energy study aimed at improving the thermal comfort levels and energy requirements of a typical residential building located in the city of Al-Hoceima, Morocco. To this end, a series of numerical simulations were carried out using TRNSYS software to assess the impact of applying three bio-based insulation materials, namely hemp wool, wood fiber, and expanded cork, in the wall layer of the building. Different insulation scenarios were studied to make a choice that would ensure optimum comfort in the building with low energy demand. The results of this study show that insulating the roof with 8 cm of hemp wool contributes to energy savings of up to 36.7% and 35.2% for cooling and heating demand respectively. In thermal terms, improvements in the temperature inside the building have been achieved: in January, the maximum temperature recorded is 20.94°C, while in July, the maximum temperature is around 26.80°C.

Hygrothermal Properties and Performance of Bio-Based Insulation Materials Locally Sourced in Sweden.

In recent years, there has been a paradigm shift in the building sector towards more sustainable, resource efficient, and renewable materials. Bio-based insulation derived from renewable resources, such as plant or animal fibres, is one promising group of such materials. Compared to mineral wool and polystyrene-based insulation materials, these bio-based insulation materials generally have a slightly higher thermal conductivity, and they are significantly more hygroscopic, two factors that need to be considered when using these bio-based insulation materials. This study assesses the hygrothermal properties of three bio-based insulation materials: eelgrass, grass, and wood fibre. All three have the potential to be locally sourced in Sweden. Mineral wool (stone wool) was used as a reference material. Hygrothermal material properties were measured with dynamic vapour sorption (DVS), transient plane source (TPS), and sorption calorimetry. Moisture buffering of the insulation materials was assessed, and their thermal insulation capacity was tested on a building component level in a hot box that exposed the materials to a steady-state climate, simulating in-use conditions in, e.g., an external wall. The tested bio-based insulation materials have significantly different sorption properties to stone wool and have higher thermal conductivity than what the manufacturers declared. The hot-box experiments showed that the insulating capacity of the bio-based insulators cannot be reliably calculated from the measured thermal conductivity alone. The results of this study could be used as input data for numerical simulations and analyses of the thermal and hygroscopic behaviour of these bio-based insulation materials.

Strategies for robust renovation of residential buildings in Switzerland

Building renovation is urgently required to reduce the environmental impact associated with the building stock. Typically, building renovation is performed by envelope insulation and/or changing the fossil-based heating system. The goal of this paper is to provide strategies for robust renovation considering uncertainties on the future evolution of climate, energy grid, and user behaviors, amongst others by applying life cycle assessment and life cycle cost analysis. The study includes identifying optimal renovation options for the envelope and heating systems for building representatives from all construction periods that are currently in need of renovation in Switzerland. The findings emphasize the paramount importance of heating system replacements across all construction periods. Notably, when incorporating bio-based insulation materials, a balance emerges between environmental impact reduction and low energy operation costs. This facilitates robust, equitable, and low-carbon transformations in Switzerland and similar Northern European contexts while avoiding a carbon spike due to the embodied carbon of the renovation.

Characterization and Thermal Evaluation of a Novel Bio-Based Natural Insulation Material from Posidonia oceanica Waste: A Sustainable Solution for Building Insulation in Algeria

Natural bio-based insulation materials have been the most interesting products for good performance and low carbon emissions, becoming widely recognized for their sustainability in the context of climate change and the environmental impact of the building industry. The main objective of this study is to characterize a new bio-sourced insulation material composed of fibers and an adhesive based on cornstarch. This innovative material is developed from waste of the marine plant called Posidonia oceanica (PO), abundantly found along the Algerian coastline. The research aims to valorize this PO waste by using it as raw material to create this novel material. Four samples with different volumetric adhesive fractions (15%, 20%, 25%, and 30%) were prepared and tested. The collected fractions underwent a series of characterizations to evaluate their properties. The key characteristics studied include density, thermal conductivity, and specific heat. The results obtained for the thermal conductivity of the different composites range between 0.052 and 0.067 W.m−1.K−1. In addition, the findings for thermal diffusivity and specific heat are similar to those reported in the scientific literature. However, the capillary absorption of the material is slightly lower, which indicates that the developed bio-sourced material exhibits interesting thermal performance, justifying its suitability for use in building insulation in Algeria.

Thermally Future-Proofing Existing Libyan Housing Stock with Biobased Insulation Materials and Passive Measures: An Empirical and Numerical Study Using a Digital Twin

Thermal refurbishment and retrofitting building envelopes with passive measures such as the optimisation of opaque and transparent fabric performance may play a key role in reducing cooling and heating load and promoting building energy efficiency. Furthermore, to reduce the embodied carbon impact of the building, the refurbishment measures need to consider the use of low-carbon building materials. This paper investigates ways to thermally future-proof typical Libyan houses using biobased materials. Several typical Libyan houses were monitored for one year to investigate the heating and cooling energy use and to thermally retrofit the building envelope. A digital twin was created in the DesignBuilder software using the real building data of one building for digital model calibration. Finally, multi-objective optimisation was carried out with low-impact biobased materials for insulation, including camel hair, sheep wool, and date palm fibre as well as using other optimisation variables such as shading and glazing types. The study reveals that thermally upgrading the building roof and wall with insulation materials and upgrading the windows with energy-efficient glazing and local shadings can achieve a reduction in cooling load from 53.51 kWh/m2/y to 40.8 kWh/m2/y. Furthermore, the heating load reduces from 19.4 kW/m2/y to 15 kW/m2/y without compromising the standard annual discomfort hours.

Cost and Carbon Intensity Analysis of Different Bio-based Insulation Materials across European Countries

Cost and Carbon Intensity Analysis of Different Bio-based Insulation Materials across European Countries

Innovative Thermal Renders Incorporating Oyster Shells for Sustainable Insulation

In accordance with current sustainable development objectives, it is intended to implement innovative and sustainable solutions at economic, environmental, and functional levels, boosting the construction sector to increasingly contribute to society. Expanded cork is an alternative to sand aggregate in improving the thermal insulating properties of renders. In addition, other materials can be incorporated as aggregates in an attempt to contribute to both the improvement of the physical characteristics that the render must fulfil as well as the improvement of thermal behaviour (if possible). In this sense, bio-based materials generated by the aquaculture sector, such as oyster shells, can contribute as a bio-based insulation material for thermal renders. In this study, thermal natural hydraulic lime mortars were produced from a mixture of expanded cork (EC) insulating aggregate and oyster shells (OSs). The percentages of replacing EC by OSs were 20, 30, 40, and 50%. The tests were carried out in fresh and hardened states. The studied mortars presented a thermal conductivity and compressive strength of 0.151 W/(m·K) and 0.63 MPa, respectively. The most interesting performance between thermal conductivity and compressive strength was for the composite with 50% of each bio-based material. The potential of incorporating oyster shells as a bio-based insulation material could contribute to a sustainable blue circular economy.

Emission rates of bio-based building materials, a method description for qualifying and quantifying VOC emissions

Biobased insulation materials offer opportunities to use vapor-open building constructions. Such constructions allow direct interaction between the biobased material and the indoor environment. This interaction raises questions about indoor air quality concerning volatile organic compounds (VOCs). This study presents results for the VOC emissions from biobased materials. It consists of two parts: 1) qualification of VOC emissions (compounds) from several biobased and non-biobased building materials, and 2) quantification of VOC emissions (emission rate) from expanded cork (biobased), particle board (semi-biobased), and EPS insulation. By quantifying the emission rate, the exposure to the released VOC emissions at room temperature in a standardized room can be compared to health limit requirements. Gas chromatography and mass spectroscopy (GC–MS) is used to derive the individual VOC emissions and the Total Volatile Organic Compounds (TVOC) from these materials. For qualification, two different sampling techniques are used in which temperature is introduced as a variable to investigate its effect on the type of compounds emitted. For quantification, the toluene equivalent approach is compared to the group equivalent approach. From the analyses it is concluded that temperature has an effect on the type of VOC compounds emitted from (biobased) materials. Results from the quantification indicate that expanded cork and particle board emit no harmful substances at a level that can affect human health. For EPS insulation, elevated levels of benzene were found to exceed healthy limits. The toluene equivalent approach for quantifying the emission, generally, underestimates the rate as compared to the more accurate group equivalent approach.

A Review of Natural Bio-Based Insulation Materials

Within the context of climate change and the environmental impact of the building industry, insulation materials contribute to improving the thermal performance of buildings, thus reducing energy demand and carbon emissions during the operation phase. Although most of them are responsible for significant carbon emissions during their production, bio-based insulation materials can provide good performance with low carbon emissions. This paper aims to investigate natural insulation materials’ properties and environmental impacts through a literature review. Due to the growing importance of Environmental Product Declarations (EPDs) on specification requirements, many manufacturers already disclose environmental data related to their products, allowing for a comparison between thermal insulation solutions. In academic research, embodied environmental impacts are not as explored as physical properties. In addition, from the analysis of results, it is possible to conclude that the characterization of the physical properties of this type of material is normally focused on thermal conductivity. Nevertheless, most studies overlook other important parameters of these materials, such as the thermal capacity, lifetime, and environmental impacts. This is something that is necessary to overcome in future developments to allow for a comprehensive comparison between the properties of different (conventional and bio-based) insulation materials.

Evaluation of the seasonal variation of VOC surface emissions and indoor air concentrations in a public building with bio-based insulation

The use of bio-based insulation materials is widely spreading in buildings. Due to their organic load, they can be an important source of Volatile Organic Compounds (VOCs). This study is among the first that evaluates the spatial and seasonal in-field VOC surface emissions from bio-based and conventional building structures as a whole, in a French public building insulated with wood wool. In addition to surface emissions, measurements of VOC concentrations in indoor air were taken. Results showed that a spatial difference (up to 5 times) in VOC emissions was observed due to the inhomogeneity of the surface. Moreover, the cardinal orientation of building structures with the same constitution induced a difference (up to a factor 30) in emission rates due to the exposure to different hygrothermal conditions. The variation in temperature and relative humidity between seasons led to higher summer VOC emissions and indoor air concentrations. In addition, indoor VOC concentrations were shown to be higher at night compared to daytime due to the decreased ventilation rate. Furthermore, an interesting approach was developed in this study to have a primary overview of the impact of surface emissions on indoor VOC levels. Results confirmed that the three bio-based walls have no significant specific VOC emissions at high rates compared to the floor and the ceiling. Bio-based insulations showed no impact on microbial indoor air concentrations during the two seasons. Moreover, no detected VOCs could be attributed to microbial development as they were also emitted from building materials.

Thermal performance assessment of double hollow brick walls filled with hemp concrete insulation material through computational fluid dynamics analysis and dynamic thermal simulations

Thermal insulation is the most widely used solution to reduce the energy consumption of buildings. In order to minimize the cost and time needed to build an insulated wall as well as to decrease greenhouse gas emissions, this manuscript proposes to incorporate a bio-based insulation material into the air cavities of hollow bricks constituting the external walls of buildings. Therefore, the aim of this paper deals with the assessment of the thermal performance of Moroccan external building envelope constituted of double hollow brick walls filled with hemp concrete and separated by a 5 cm air layer thickness. Three configurations composed of three types of hollow bricks were studied (8-, 12- and 16-holed bricks). Firstly, using numerical simulations based on a two-dimensional Computational Fluid Dynamics (CFD) method, a parametric study was conducted in order to determine which of the three configurations meet with the requirements imposed by the Moroccan thermal building regulation. In terms of thermal resistance R and thermal transmission coefficient U, results have shown that double brick walls with 12 and 16 hemp concrete filled holes were the only configurations meeting the requirements of Moroccan Thermal Regulation. Afterwards, the study was revolved at a whole building scale and a dynamic thermal simulation considering various internal parameters was performed using TRNSYS software. Furthermore, an economic and environmental analysis was conducted and a comparison with Moroccan thermal regulation shows that our results perfectly meet the requirements of this regulation and are more efficient from thermal, economic and environmental perspectives. Finally, the insulation technique used in this investigation can be widely applied around the World and similar thermal performances can be achieved for the case of different regions characterized by the same Mediterranean warm climate considered in this paper.

Bio-based insulation materials and model predictive control of active cooling systems in machine tools

The adoption of biological principles and materials plays a decisive role in the conversion to sustainable production technologies. Measures for the biological transformation of a machine tool were implemented following the example of warm-blooded animal, which automatically control their core temperature and, depending on their habitat, possess an insulating layer of fat. In this work, thermal insulation measures were implemented on machine tools using renewable materials and their effects were evaluated.Insulation materials of petrochemical origin such as polystyrene (Styrofoam) were replaced by alternatives made of mycelium with comparable heat insulating properties. On the lower machine bed, a slowdown of the cooling rate was observed after application of insulation materials at external temperature drops. The insulation between the machine bed and the control cabinet was also found to reduce tool centre point (TCP) displacement. This cost-efficient measure reduces the error during the process and the effort required to correct the linear axes and to heat and cool the machine.To homogenize the temporal and spatial temperature profile of machine tools, a control system was developed to compensate for thermally induced errors by means of adaptive active cooling. Therefore, a model predictive control using an embedded artificial intelligence (AI) model to forecast the structural temperature development was implemented. Through a hybrid training database combining experimental and simulative data series, a both flexible and precise determination of the thermal system behaviour could be achieved. On a real production machine, the active cooling system is divided into five individually controllable and adjustable cooling circuits. This approach allows cooling the machine structure according to time and local demand to minimize thermally induced TCP displacement under variable operating conditions.This paper serves to define and evaluate possibilities and requirements for the integration of bio-based insulation materials and control algorithms for homoiothermic conditions in production machines.

Applying life cycle assessment with minimal information to support early-stage material selection

Traditional life cycle assessment (LCA) is too data intensive and time consuming to be used during typical building design processes. Conducting an LCA during the building design process therefore requires simplifications and assumptions. Such “screening LCAs” are quicker and can be used with less data but introduce greater uncertainty. Unfortunately, uncertainty is not reflected in standard deterministic LCA calculations, which produce single-point values in LCA results. Thus, in this study, data quality scoring has been incorporated into a screening LCA to produce probabilistic predictions of environmental performance based on limited data. The approach has been applied during the design process of a bio-based wall panel designed for a circular economy. A combination of ecoinvent and material data sheets were used to analyse a wide range of novel bio-based insulation materials. The screening LCA analysed global warming potential and identified a short-list of promising materials that were then subjected to a detailed LCA for further consideration in the design. The method uses publicly available information and can be applied at material or building-element level. The method thus helps designers estimate environmental impacts without hindering the design process.

Impact of fibre orientation on the hygrothermal properties of straw bale insulation

This paper presents findings from a research project that aimed to develop the use of wheat straw bales as non-load bearing building insulation with a new prototype insulation product. Demands for more sustainable construction products, with lower net carbon emissions and improved thermal performance, have grown in recent years. There is an increasing recognition that bio-based insulation materials, including hemp, wood fibre and straw, can provide more sustainable alternatives to current insulation products. Straw bales, produced as an agricultural co-product from cereal production, can be used directly in construction. However, both the bale sizes and orientation of straw fibres in these agricultural bales are sub-optimal for most construction uses, and have become a barrier to wider adoption. This paper reports on the technical development and characterisation of a prototype insulating product produced from wheat straw, in which both the bale size and straw fibre orientation has been produced to optimise insulation performance. Thermal conductivity and hygric performance studies are presented for the prototype bales, characterising improvement in performance from optimising straw fibre orientation. Optimising orientation of the straw fibres in bales has successfully reduced thermal conductivity, compared to conventional agricultural bales, by 38%, allowing similar reductions in insulation thickness for an equivalent performance. Furthermore, by optimising the orientation of the straw fibres a reduction in water vapour permeability, moisture buffering, and moisture infiltration by as much as 76%. This research will support opportunities for greater uptake of a novel bio-based insulation materials into mainstream construction.