Bio-based Insulation Materials Research Articles

Assessment of the Usability of Some Bio-Based Insulation Materials in Double-Skin Steel Envelopes

In this paper, a double-skin steel building-demonstrator, set up using panels of five bio-based insulators and a classical mineral insulating material, is studied. The panels used in the demonstrator are made from industrially manufactured and commercialized bio-materials. To assess the suitability of these panels for use in cold formed steel envelope buildings, their advantages and/or the drawbacks (if any) of the synchronized records of temperatures, relative humidity and thermal flux of each panel are obtained using a system of continuous measurements. Data from 6 months of records in the roof of the demonstrator are used to assess the infield properties of the panels and the seasonal evolution of these properties in relation to the presence of the vapor barrier. The thermal resistance of each panel is determined from these data using two methods: the ISO 9869-1:2014 based on the Heat Flow Meter (HFM) method and an inverse problem identification method. All bio-sourced panels manifest higher thermal resistance than the classical insulation system, whatever conditions of use with or without barrier vapor. The seasonal variations of thermal properties are attenuated when a vapor barrier is used. No risk for water condensation inside the bio-insulations is revealed so far.

Thermal performance and statistical analysis of a new bio-based insulation material produced using grain puffing technique

• Energy performance of a new bio-insulation material prepared from the rice was evaluated. • The three factors of the insulation sample material—sample weight, temperature, and moisture ratio—were optimized. • The optimal sample amount, temperature, and moisture level were identified by the response optimizer. • The thermal conductivity of the newly developed insulation material is found to be appropriate. As energy conservation has become a major issue, the building sector is moving towards low energy consumption and the development of bio-based thermal insulation materials contributes strongly to this approach. In countries with hot climate, like the UAE, thermal insulating materials play an important role in preventing heat gains in buildings. Various insulation materials are available in the market, including inorganic, organic (petrol-based and bio-based), combined materials, and new-technology materials, each of which suffers from harmful environmental impact and high cost. This research aims to identify the most optimal production parameters, including sample weight, temperature, and moisture ratio, for a newly developed bio-based insulation material produced using puffed rice grains. Using the response surface method (RSM) and Minitab software, 15 runs for optimizing the three individual parameters in the central composite design (CCD) were conducted. Their findings indicate that the moisture and temperature have a major effect on the thermal conductivity of the insulation material as well as the puffing ratio. The lowest thermal conductivity value (0.04971 W/mK) of the newly developed material at its natural conditions without the use of any binders or additives was found for the sample weight of 16.5 g compressed to a circular mold of 8 cm diameter, at the temperature of 263 °C, and the moisture level of 16%, which is acceptable when compared with other commercially available insulation materials such as polystyrene.

Material Diets for Climate-Neutral Construction.

The climate crisis is urging us to act fast. Buildings are a key leverage point in reducing greenhouse gas (GHG) emissions, but the embodied emissions related to their construction often remain the hidden challenge of any ambitious policy. Therefore, in this paper, we explored material GHG neutralization where herbaceous biobased insulation materials with negative net-global warming potentials (GWPs) were used to compensate for building elements that necessarily release GHGs. Different material diets, as well as different building typologies, were modeled to assess the consequences in terms of biobased insulation requirements to reach climate neutrality. Our results show that climate-neutral construction can be built with sufficient energy performance to fulfill current standards and with building component thicknesses within a range of 1.05–0.58 m when timber- and bamboo-based construction is chosen. Concrete-based ones require insulation sizes that are too large and heavy to be supported by the dimensioned structures or accepted by urban regulations. Moreover, a time horizon of 20 years is more appropriate for assessing the contribution of material shifts to biobased materials in the transition period before 2050. This paper demonstrates that this is technically feasible and that climate neutrality in the construction sector just depends on the future that we choose.

Hygric Behavior of Viticulture By-Product Composites for Building Insulation.

One possible approach to reducing the environmental impacts associated with the building sector is the development and use of bio-based building materials. The objective of this study is to determine the water properties of bio-based insulation materials, derived from winegrowing co-products, which promote energy efficiency. The water performance of these new bio-based materials is based on the measurement of the moisture buffer value, the sorption isotherm, and the water vapor permeability. Four by-products are analyzed: stalks, grape pomace, crushed stalks, and skins; they are combined with a potato starch binder. The performance of these composites is compared to two other bio-based composites (hemp/starch and beet pulp/starch). The stalk/starch composite can be classified as a hygroscopic and breathable material with excellent moisture retention capacity.

Integration of Bio-based Insulation Materials as a Contribution to the Biological Transformation of Production Technology

In the context of a circular economy, the adoption of biological principles and materials play a decisive role in the transformation to a more sustainable production technology. Ecologically harmful materials such as polystyrene (so-called Styrofoam), for example, has properties for thermal and acoustic isolation. This material has therefore been used in production machinery to control thermal issues and improve product quality. Here, the use of renewable and biodegradable materials can ensure these measures have a minimal environmental footprint while maintaining the intended functionality.This paper serves to open-up opportunities and define requirements for the integration of bio-based isolation materials in production machines. For both thermal and acoustic issues, the place of implementation and the choice of insulation material, as well as its shape and composition, determine the ability to isolate over the required temperature range. In addition, coatings and surface functionalization offer possibilities for using bio-based materials even under demanding process conditions. Concluding, the experimental approach on the effectiveness of bio-based insulation materials within a machine tool is presented. The technologies presented in this work have been developed by the participating Fraunhofer institutes.

Hygrothermal properties of advanced bio-based insulation materials

Hygrothermal performance of buildings is one key element to the sustainable design, health, and comfort of the indoor environment. Building sustainability depends on all associated lifespan stages, from building design and material production to demounting and waste management. Many building materials are unsustainable in terms of their environmental impacts. One approach to reduce environmental impacts associated with buildings is the development and application of bio-based building materials. The aim of this study was to determine the hygrothermal properties of bio-based thermal insulators that promote energy efficiency and contribute in decreasing environmental impacts of buildings. Here, the hygrothermal properties of eight new peat-, recycled paper-, wood shaving-, and feather-based insulation materials were assessed. Measurements of these material properties will improve understanding of the energy efficiency, permeability, and sustainability of new buildings, building retrofits, or both. Data on these new materials will provide the necessary parameters to develop a hygrothermal dynamic numerical model. The studied bio-based materials appear to provide sufficient hygrothermal performance, which is comparable with conventional insulation materials with minimum embodied energy.

Thermal Characterization of a New Bio-Based Insulation Material Containing Puffed Rice

Although many advanced insulation materials have been recently developed, very few are eco-friendly and their production requires a substantial amount of energy and complex manufacturing processes. To address this issue, a bio-based thermal insulation material was developed using short- and long-grained puffed rice. A set of experiments was subsequently carried out to identify the best rice type and the optimal range for the most influential parameters (sample amount, temperature, and moisture level). Our findings revealed that short-grained rice exhibited greater puffing ability and was thus adopted in further material optimization experiments. These assessments indicated that the most optimal thermal conductivity of the insulation material and the highest puffing ratio was attained at 12–15% moisture, 260–270 °C temperature, and 15–18 g sample weight. The thermal properties, including thermal conductivity and fire reaction, and thermal performance of samples obtained using these parameters were similar to those of common insulation materials.

Thermal conductivity of different bio-based insulation materials

To achieve the zero-waste goal as well as sustainability, the use of the raw materials, especially those from nature, and wood in particular, has to be smart, meaning that the resource has to be used to its full potential. Since wood-based industry is associated with high intensity and the generation of a relatively large amount of residues, those residues should be used for the production of useful products, otherwise they will easily be classified as waste and afterwards used as a source of energy. To present a possible solution for wood residues like wood chips, wood particles and bark, we investigated the possibility of using wood and bark residues as constituents for the production of single layer insulation panel with a target thickness of 40 mm and target density of 0.2 g·cm-3. Thermal conductivity was determined using the steady state principle at three different temperature settings. The average thermal conductivities were determined between 49 mW·m-1·K-1 and 74 mW·m-1·K-1. The highest values were determined at boards made from bark, which also had the highest density (0,291 g·cm-3), while the lowest thermal conductivity was observed for boards made from spruce wood particles.

Natural Building Materials for Interior Fitting and Refurbishment-What about Indoor Emissions?

Indoor air quality can be adversely affected by emissions from building materials, consequently having a negative impact on human health and well-being. In this study, more than 30 natural building materials (earth dry boards and plasters, bio-based insulation materials, and boards made of wood, flax, reed, straw, etc.) used for interior works were investigated as to their emissions of (semi-)volatile organic compounds ((S)VOC), formaldehyde, and radon. The study focused on the emissions from complete wall build-ups as they can be used for internal partition walls and the internal insulation of external walls. Test chambers were designed, allowing the compounds to release only from the surface of the material facing indoors under testing parameters that were chosen to simulate model room conditions. The emission test results were evaluated using the AgBB evaluation scheme, a procedure for the health-related evaluation of construction products and currently applied for the approval of specific groups of building materials in Germany. Seventeen out of 19 sample build-ups tested in this study would have passed this scheme since they generally proved to be low-emitting and although the combined emissions of multiple materials were tested, 50% of the measurements could be terminated before half of the total testing time.

Humidity-Dependent Thermal Boundary Conductance Controls Heat Transport of Super-Insulating Nanofibrillar Foams

Summary Cellulose nanomaterial (CNM)-based foams and aerogels with thermal conductivities substantially below the value for air attract significant interest as super-insulating materials in energy-efficient green buildings. However, the moisture dependence of the thermal conductivity of hygroscopic CNM-based materials is poorly understood, and the importance of phonon scattering in nanofibrillar foams remains unexplored. Here, we show that the thermal conductivity perpendicular to the aligned nanofibrils in super-insulating ice-templated nanocellulose foams is lower for thinner fibrils and depends strongly on relative humidity (RH), with the lowest thermal conductivity (14 mW m−1 K−1) attained at 35% RH. Molecular simulations show that the thermal boundary conductance is reduced by the moisture-uptake-controlled increase of the fibril-fibril separation distance and increased by the replacement of air with water in the foam walls. Controlling the heat transport of hygroscopic super-insulating nanofibrillar foams by moisture uptake and release is of potential interest in packaging and building applications.

Mussel shells: A canning industry by-product converted into a bio-based insulation material

The canning industry in Galicia produces 25 thousand tonnes of mussel by-product (i.e. unconsumed shells) per year, having a significant environmental impact. Mussel shell becomes suitable for different uses after undergoing heat treatment such as poultry feed or bedding, etc. However, other end uses for this by-product must still be explored. Building insulation material (for instance expanded polystyrene, extruded polystyrene, polyurethane, etc.) has a significant harmful effect on the environment, which is especially seen when analysing its entire life cycle (use of large amounts of energy and water for production, difficulty recycling or reusing waste in the event of demolition or refurbishment, etc.). The aim of this research is to prove the feasibility of using mussel shell as a building solution. Mussel shell has been found to have thermal and acoustic characteristics suitable for using it as building insulation material. Mussel shell confined inside an enclosed space (e.g. a wooden box) has a thermal conductivity similar to that of a light conifer wood, so it can be considered a material with low thermal conductivity. Furthermore, several acoustic studies indicate that a section of confined mussel shell displays a behaviour similar to that of commercialised insulation material. The embodied energy of mussel shell as a loose-fill material is similar to that of other bio-based insulation materials. The main goal of this paper is to demonstrate that it is possible to design mussel shells building solutions, that actively participate in environmentally responsive architecture.

Impacts of test methods on the assessment of insulation materials’ resistance against moulds

Bio-based insulation materials have been increasing in the construction market, however, these materials must prove their resistance to moulds. This research project aimed to compare two test methods to assess the resistance against moulds of two bio-based insulation panels and a mineral conventional panel artificially contaminated with Aspergillus niger spores. Test specimens were assessed applying a reference test method and a method developed in this work. The two methods consisted in four steps: 1) preconditioning of test specimens at 26 °C and 85 ± 5% of relative humidity during 1 week, 2) inoculation of test specimens, 3) incubation of test specimens at 26 °C and 85 ± 5% of relative humidity during four weeks and, 4) growth assessment by visual inspection and CFU counting. The difference between the methods is the contamination technique, which is a liquid inoculum for the reference method and a dry aerosolization of fungal spores for the new method. A dry aerosol was used because is a more realistic way on how materials get contaminated in realistic conditions and avoids the introduction of water into the system and in consequence, the modification of water activity (Aw). Materials presented different behaviours concerning visual and quantitative assessments according the test method employed, highlighting the difficulty establishing a standard test method to assess bio-based materials resistance to mould growth. The results showed that an evaluation only by a visual inspection may lead to misinterpretations of the results. Variability in the results may have been due to the differences in the inoculation techniques of the test methods and the heterogeneity of the materials composition and the anti-fungal product distribution within them.

Technical Performance Overview of Bio-Based Insulation Materials Compared to Expanded Polystyrene

The energy efficiency of buildings is well documented. However, to improve standards of energy efficiency, the embodied energy of materials included in the envelope is also increasing. Natural fibers like wood and hemp are used to make low environmental impact insulation products. Technical characterizations of five bio-based materials are described and compared to a common, traditional, synthetic-based insulation material, i.e., expanded polystyrene. The study tests the thermal conductivity and the vapor transmission performance, as well as the combustibility of the material. Achieving densities below 60 kg/m3, wood and hemp batt insulation products show thermal conductivity in the same range as expanded polystyrene (0.036 kW/mK). The vapor permeability depends on the geometry of the internal structure of the material. With long fibers are intertwined with interstices, vapor can diffuse and flow through the natural insulation up to three times more than with cellular synthetic (polymer) -based insulation. Having a short ignition times, natural insulation materials are highly combustible. On the other hand, they release a significantly lower amount of smoke and heat during combustion, making them safer than the expanded polystyrene. The behavior of a bio-based building envelopes needs to be assessed to understand the hygrothermal characteristics of these nontraditional materials which are currently being used in building systems.

Production of Bio-based Polyol from Oxypropylated Pyrolytic Lignin for Rigid Polyurethane Foam Application

A recent trend in ecofriendly product development is the use of added-value lignin residues. This study aimed to assess the potential use of pyrolytic lignin (PL) for producing rigid polyurethane foam (RPUF). For this purpose, PL was recovered from bio-oil using water as extraction solvent. The PL was then subjected to oxypropylation in the presence of KOH and under mild temperature and pressure (482 K; 14 Bar). FTIR and hydroxyl number quantification was used to confirm and assess the occurrence of oxypropylation reaction. Thus, oxypropylated lignin (OL) was successfully used to produce RPUF. Results revealed a lignin recovery yield of 30 ± 4% relative to the bio-oil weight. FTIR and NMR showed that the PL retained its aromatic structure after pyrolysis cracking. The weight ratio obtained after oxypropylation was 50/50/5 lignin/propylene oxide/KOH with a hydroxyl number of 703 mg KOH/g. Gradual substitution of polyol with OL ranged from 10 to 50%, and the ensuing foams were characterized in terms of chemical, physical, and morphological properties. Modulus of elasticity and insulation performance of 20% OL-based foam increased by 17% and 5.5%, respectively, compared to the commercial rigid polyurethane foam (CRPUF). SEM micrographs for OL-based polyurethane foams showed smaller cell structure, which is desirable for increasing rigidity. These findings demonstrate the potential use of pyrolytic lignin in the manufacturing of high performance biobased insulation materials.

Dynamic assessment of the thermal performance of hemp wool insulated external building walls according to the Moroccan climatic zoning

Abstract This paper deals with the assessment of the dynamic thermal performance of Moroccan external walls. Firstly, based on the quadrupole method, the thermal capacity and thermal resistance of an uninsulated brick wall were calculated for different thicknesses of the brick layer. The optimum brick thickness chosen corresponds to the one that maximally enhance the thermal inertia and thermal resistance. Afterwards, the brick wall was externally insulated with hemp wool, a bio-based insulation material. For an hypothetical lifespan of 20 years, and based on the life cycle cost analysis, annual heating and cooling requirements, optimum insulation thicknesses, energy savings and payback periods were calculated for all wall orientations and considering the six climatic zones of Morocco. It was found that the optimal brick thickness was equal to 0.20 m and the optimal insulation thicknesses vary between 1 and 6 cm for the different climatic zones and the different wall orientations. Moreover, a comparison with the minimum technical specifications fixed by the Moroccan thermal regulation showed that our results allow the reduction of annual heating and cooling requirements by a minimum percentage of 56% for the city of Ifrane, and a maximum percentage of 79% for the city of Marrakech. Finally, annual greenhouse gas (GHG) emissions were also calculated and it was found that they can be decreased, with the use of optimum thicknesses of hemp wool, by a minimum of 32% for the city of Ifrane and a maximum of 75% for the city of Errachidia.

Towards a model for circular renovation of the existing building stock: a preliminary study on the potential for CO2 reduction of bio-based insulation materials

In the context of strategies for mitigating the impacts of climate change within European cities, increasing attention is being paid worldwide to the use of urban green infrastructure which, in addition to the potential for improving the quality of the urban environment, allow significant amounts of CO2 to be removed from the air. However, considering the peculiarities of the dense European cities, most of the available surfaces in urban areas are the perimeter walls of buildings of considerable age that are in urgent need of measures to upgrade their energy performance. Based on this premise, this paper investigates the potential for CO2 storage resulting from the application of energy retrofit solutions using biogenic insulating materials. Starting from the analysis of the demand for insulation materials necessary for the energy requalification of the residential existing building stock in 28 European countries, following the renovation target fixed by EU, the research analyses, through the adoption of a dynamic LCA approach, the environmental benefits of bio-based materials compared to traditional solutions. The use of these materials, especially if they are fast-growing - as the study shows - offers several advantages in terms of climate change mitigation by reducing the energy needs and CO2 emissions of the existing building stock and increasing carbon storage capacity within cities. The results of this study are intended to provide a robust database on which to build a model of circular building renovation that takes into account the environmental long-term effects of measures for increasing energy efficiency of buildings.

Energy performance and thickness optimization of hemp wool insulation and air cavity layers integrated in Moroccan building walls’

Interest in the use of bio-based materials for thermal insulation of buildings has been increasing in recent years. Indeed, the integration of these materials into building envelopes will simultaneously reduce energy use and greenhouse gas (GHG) emission rates. In this context, the thermal performance of bio-based insulation materials is studied and compared to that of conventional insulation materials. However, the majority of these studies, concentrated especially in Europe, lack economic analysis. Cultivated for centuries in Morocco, the use of hemp in the building industry is very limited. The aim of this study is to assess the use of hemp as insulation material for Moroccan external building walls located in Meknes, a city characterized by the Mediterranean climate Csa. Firstly, time lag and decrement factor are investigated in order to assess the dynamic thermal behavior of an external multilayer wall insulated with hemp wool. Afterwards, based on a life cycle cost analysis (LCCA), optimum hemp wool thickness, energy savings and payback period are determined for an analysis period of 20 years. Using a computer program developed in Matlab, an implicit finite difference method is applied to solve the 1D heat equation and investigations are carried out for different wall orientations. It was found that highest optimum insulation thicknesses are provided by east and west orientations (5 cm) followed by the southern and the northern ones (4 and 3 cm, respectively). In addition, an air gap layer is introduced to the optimal insulated multilayer wall, and a third investigation is conducted. The optimal air gap thickness is determined based on the analysis of various thermal parameters such as Prandtl, Rayleigh and Nusselt numbers, conduction, convection and radiation heat transfer rates. For all wall orientations, optimum air gap thickness was found equal to 1.3 cm. Annual GHG emissions were also calculated and it was found that they can be decreased by about 71% with the use of optimum thicknesses of hemp wool and air cavity insulations. Finally, a comparative study with the recommendations set by the Moroccan thermal regulation is conducted. The findings showed that our investigated configuration would be more efficient from thermal, economical and environmental points of view.

Optimisation of bio-based building materials using image analysis method

Wetting of bio-based mortars — the affinity of the biofibres and earth to the water — can have a strong impact on the flow, but the microscale physics and macroscopic consequences remain poorly understood, not helping in the material optimisation. This research analyses the influence of casting on biofibres dispersion in bio-based insulation materials at the macro-level and evaluate changes on hygrothermal behaviour if fibres and casting change. Earth-based blocks reinforced with 3% weight content of barley straw, hemp shiv and rice husk fibres were produced with 5 and 4 cm thickness using two casting methods. The 5 cm blocks were unstabilised and compacted; the 4 cm blocks were moulded and stabilised with gypsum and air lime. The approach is to implement a developed method of image analysis to elucidate the inherently 2D pore-scale mechanisms and help explain the striking macroscopic displacement patterns that emerge. The results indicate that production variables have a significant directionally dependent impact on the physical properties of cast bio-based materials. This means that the Image analysis can be used for quality control towards the optimisation of the bio-composites. Thermal conductivity and ultra sound velocity are affected by fibres distribution inside bio-based materials. The shape of ultra sound distribution from direct and indirect methods enhance the anisotropy of the bio-based materials with different composition and casting methods.

Dynamic behaviour of bio-based and recycled materials for indoor environmental comfort

Abstract UK construction industry contributes 120 Mt of waste every year. Bio-based building materials may be a solution for this problem, as they combine re-use and recycling abilities together with hygroscopic characteristics, leading to buildings energy savings. For the first time, the dynamic response to hygrothermal changes of bio-based materials is examined in terms of Moisture Buffering Value (MBV), dry/wet thermal conductivity, microstructure, density and latent heat through daily cycles. It is shown that MBV is a useful tool for characterisation but needs to be combined with the shape of the change in mass of the final hygrothermal cycle. Mastering this is required to obtain significant improved indoor environment quality in buildings. Ten samples of bio-based insulation materials and one thermoplastic recycled polymer were analysed (wool, hemp, saw mill residue, wood, straw, cork and polyethylene terephthalate). Saw and wool are the most promising, as materials exhibit dynamic response to hygrothermal changes. Only half the amount of samples revealed equivalent efficient moisture transfer to be able to desorb the adsorbed quantity of water. Latent heat of vaporisation and condensation tests led to the conclusion that samples of wool and saw mill residue can qualify as bio-based materials for ‘green’ panels.

Bio-Based Products

Communicating the related environmental benefits of bio-based products to consumers represents a key component of their market uptake. In this regard, the use of ecolabels ISO 14024 Type I play a crucial role. This article identifies and analyzes different criteria proposed by ecolabels for conducting a sustainability assessment of bio-based products considering its entire lifecycle. A comparison of the selected criteria with existing indicators ruled out by the SDGs is proposed. Through expert consultation, the suitability of existing ecolabel criteria for bio-based products has been tested for four applications of biobased products: food packaging from PLA; biobased automotive components; bio-based mulch film; and bio-based insulation material.