Industry Experts’ Perspectives on the Difficulties and Opportunities of the Integration of Bio-Based Insulation Materials in the European Construction Sector

Abstract

This paper explores the current status of bio-based insulation materials (BbIMs) integration in Europe, through structured online questionnaires. with industry experts. The findings show that the main common difficulties are obtaining European Conformity (CE) marking, high costs, a skills gap, a lack of trained builders, and slow acceptance from industry decision-makers. On the other hand, the main common opportunities are the gradual improvement with certain supportive policies and incentives, the growing environmental awareness, thermal, acoustic, and environmental performance, long-term cost savings and value, and increasing educational initiatives, advertising, and awareness campaigns. The finding also emphasizes the critical role that users and buyers play in the adoption of these materials as a potential driver and barrier. The professionals suggest strengthening environmentally friendly standards, integrating natural materials into construction databases, leading by example, withdrawing subsidies for hazardous waste disposal, providing continuing education, workshops, collaboration among stakeholders, and referencing exemplary projects in France. Further insights on bio-based building materials integration in building information modeling (BIM) practices indicate that the rate of their integration is very low. This research contributes to the scientific literature on BbIMs, by highlighting the barriers to the widespread use of these materials in practice and promoting the drivers of their widespread use. Future research should address more insights from other uncovered countries and the countries with limited insight (The Netherlands, Switzerland, and Portugal) in the current study as well as End-users’ perceptions.

1. Introduction

1.1. Background

The construction industry is one of the most polluting industries in the world, making it a major contributor to global warming and energy consumption. Embodied energy accounts for 10–30% of the total lifetime cost of a building [1]. The production of materials, use, and demolition of buildings are responsible for about 20% of the total environmental impact [2], as they are made from non-renewable resources [3]. In Europe, they are responsible for about 36% of global greenhouse gas emissions and 50% of raw material consumption [4].

Reducing energy consumption and emissions from buildings is one of the current and long-term global goals. Energy consumption typically can be reduced through effective thermal insulation of the envelope components and the adoption of efficient installations. While conventional thermal insulations vary in types and solutions, their embodied impacts negatively affect the environment [5], human health, and well-being [6]. As a promising alternative, BbIMs such as wood fiber, cork, hemp, and straw had many benefits, including carbon sequestration [7] and enabling circularity. Despite the opportunities for widespread use, the market share of renewable insulations, including BbIMs in Europe, is still small in comparison to conventional ones, reaching 2% in 2022 [8] (Figure 1). At the national level, there is a surge in which western Europe countries, in particular, lead the market. For instance, in France, the share of BbIMs produced is expected to reach 13% in 2030 after the Environmental Regulation (RE 2020) and Responsible Building Regulation (RBR 2020), which has been in full effect since 2021 [9]. The example of France shows the pivotal role of national building regulations in promoting the use of certain materials, while conservative regulations can make it difficult to use BbIMs. Therefore, it’s imperative to understand the national regulatory environment and the conditions to produce construction products.

Understanding the dynamics of the building insulation production process in Europe involves knowing the stakeholders involved and the regulations that govern it. Many direct and indirect stakeholders are involved at different levels in the availability of insulation materials, such as government bodies, organizations, suppliers, manufacturers, distributors, contractors, engineers, architects, craftsmen, and customers.

In this vein, European regulations and policies have a considerable impact on directing new construction products toward more sustainable practices and compliance with environmental standards. In fact, the European Union (EU) has implemented several policies and financial frameworks for projects to promote sustainable construction practices due to the significant CO₂ emissions associated with the construction and demolition sector. Key policies include, for example, the Circular Economy Action Plan (CEAP), the Waste Framework Directive (WFD), and the New European Bauhaus (NEB) [10]. These policies affected the construction industry in Europe by being an instrument towards more sustainable and resource-efficient building practices. The first (2015) [11] and the new CEAP (2020) [12] promote further waste reduction, resource efficiency, and sustainable production, among the measures to close the loop of the product lifecycle. Meanwhile, WFD [13] sets out the definitions and requirements for waste management following the waste hierarchy. The NEB initiative, on the other hand, promotes linking technology, art, culture, and social inclusion in the built environment. These policies are aligned with the benefits of using bio-based construction materials.

However, according to a report [14], bio-based construction materials are not explicitly recognized and mentioned in the EU National Energy and Climate Plans and the National Long Term Renovation Strategies documents, except in the case of France. Nevertheless, wood-based products are widely considered in the policies of EU member states, while cork is a notable national product in Portugal [14].

To enforce better building practices, new construction products are regulated by the ‘Construction Products Regulation’ (CPR) under Regulation (EU) No 305/2011, which has been fully in effect since July 2013 [15]. “The Regulation’s main objective, like that of the earlier Construction Products Directive (‘CPD’), is to make the single market work better and improve the free movement of construction products in the EU, as provided for in Article 8(4) of the CPR, by laying down harmonised conditions for their marketing” [15]. In compliance with the CPR, the construction products get the CE Marking, which involves multiple steps and documentation (Figure 2). Those steps depend on the category of the products as set by the CPR [16]. If the product is covered by the harmonized European standard (hEN), the manufacturer must submit the Declaration of Performance (DoP) and then label the product with the CE marking. If the product is not covered or doesn’t fall within the scope of any hEN then the manufacturer, voluntarily, may issue a European Technical Assessments (ETA), which is based on European Assessment Document (EAD) [16]. The latter is the harmonized technical specification issued by the Technical Assessment Body (TAB). The CE marking will be affixed after applying the Assessment and Verification of Constancy of Performance (AVCP) system provided for by the EAD [16]. It should be noted that “The CE marking only proves that the product performance has been assessed as required by existing harmonised technical specifications” [15]. However, the requirements depend on the national regulations various EU member states, in which the manufacturers are responsible for the specifications declared [17].

When it comes to BbIMs, unlike traditional insulation, these products often lack reference standards due to their different properties and performance. For wood fiber insulation products, the hEN 13171 has been developed, but not for other natural insulations [14,18]. Hence, the process seems long and may differ depending on the national additional requirements and administrative process.

1.2. Literature Review

The literature has pointed out several difficulties related to policies and regulations, material performance, and cost [19,20,21,22]. National building standards can be a barrier or a driver due to these materials’ characteristics and the need to adapt them to the built environment [20]. Some BbIMs, except those made from waste [23], may have an adverse effect on eutrophication and land usage since they compete with food production [23]. Given some countries’ construction standards and a lack of government regulations and incentives for BbIMs [24], the type of insulation material is less important, i.e., the most thermally efficient materials are preferred [23]. Regarding the installation techniques and performance of BbIMs, several factors can impact their effectiveness in different climatic conditions [24]. The need for thicker walls, material heterogeneity, mechanical properties, flammability, and microbial growth are significant concerns that can affect the overall performance of BbIMs [21,22,25,26,27]. Cost is another major factor influencing the wide use of BbIMs, as they are generally more expensive than conventional insulation [25]. The economic feasibility of these materials depends largely on the availability of production, installation, and labor expenses [19,25]. On the other hand, promising opportunities exist, including policy incentives such as the bio-economy directive [28] and material performance benefits such as improved energy efficiency [29] and indoor air quality [30].

However, literature on various Bio-based building materials contains few studies that have specifically reported on stakeholders’ perspectives in specific countries for certain materials: Sweden [31], Nordic region (Finland, Sweden, Norway) [32], and the United Kingdom (UK) [33].

In this regard, Markström et al. (2016) investigated Swedish architects’ and contractors’ perceptions and their attitudes towards bio-based building materials through semi-structured interviews. The barriers to the wide integration of these materials in Sweden include a lack of supportive incentives, technical knowledge, and cultural backgrounds. A positive attitude towards the use of biobased building materials was evident among architects, while contractors showed a more conservative attitude [31].

Maniak-Huesser et al. (2021) analyze the policy gap in promoting timber construction in Finland, Sweden, and Norway by conducting semi-structured interviews and a literature review. The policy was identified as a potential barrier and driver, in addition to the challenge of complying with fire resistance requirements and the high price. Moreover, addressing social and political challenges to improve the timber market calls for collaboration among stakeholders [32].

Dams et al. (2023) addressed challenges and opportunities of upscaling bio-based construction materials through semi-structured interviews with industry professionals in the UK. The authors point to several integration challenges that have hindered the widespread use of biobased materials, including a lack of knowledge among professionals and concerns about their durability. While initiatives such as Greenbelt planning and crop growth subsidies could promote the wide use of bio-based construction [33].

These studies provided insightful perspectives on the national scale for the already covered countries. However, the current study aims to address the integration of BbIMs in practice at a broader European scale, aiming to fill the existing research gap. To address this gap, it draws on 18 stakeholder experiences from European countries, including Italy, France, Germany, Spain, Portugal, Switzerland, and The Netherlands, through online questionnaires. This approach provides deep insights into the real-world integration of BbIMs in the European construction industry.

The research questions for this study are thus defined:

Q1: What are the in-situ challenges and opportunities for integrating bio-based insulation materials for construction in Europe?

Following the introduction, the structure of the paper is as follows: Section 2 outlines the methodology, Section 3 presents results and Discussion—which includes background of participants (Section 3.1), Integration difficulties and opportunities (Section 3.2), and Future Perceptions (Section 3.3).

2. Materials and Methods

The questionnaire was designed in line with the objectives of this research; a comprehensive and focused understanding of BbIMs integration in the field at the European level. Structured questionnaires with open-ended answers were chosen to gather insights, with the same predefined questions in the same order for all respondents.

These questionnaires were conducted by sending invitation emails between January and March 2024. Conducting this kind of survey was due to the language barrier and to make it more convenient for respondents to fill out the questionnaire at their convenience and their own pace. This survey is exclusively for architects, manufacturers, suppliers, distributors, and contractors. 101 Emails in total were sent to publicly available contacts of stakeholders, initially from Italy, France, Germany, Spain, Portugal, Belgium, Austria, Switzerland, and The Netherlands. The contacts were searched on search engines and were identified based on the criterion that they use or provide BbIMs in their projects. The emails included a descriptive introduction to the authors, an overview of the research and the questions, a link to access the online questionnaire, and the authors’ contact information for any additional questions by the respondents. Due to language differences across Europe, to make it easier for the respondents, the questions were translated from English into several languages, including Italian, French, German, Spanish, Portuguese, and Dutch. It should be noted that the term “natural insulation materials” is often used in the field, so it was used in the questionnaire instead of the more academic term “bio-based insulation materials”. Then, a few reminder emails were sent to improve the response rate, especially in countries where no one responded.

The questionnaire consisted of four main sections with responses in a free-text field format. Before that, there is an introductory section, which defines the research context, research sections, target participants, and a declaration of anonymity and confidentiality. It should be noted that after sending several emails to different parties, the questions do not contain any identification of the respondents. Therefore, the first section contains four questions that aim to know the respondent’s background: country, role or which target belongs to, years of experience in the field, and some biobased materials that they use in their projects or provide. The second section contains six questions dedicated only to difficulties. This includes policy, market availability, cost and financial, material performance, customer acceptance, and finally a question about the respondent’s opinion on what they consider to be the most influential difficulty. Similarly, the same structure is followed in the third section about opportunities, with six questions. The fourth section included two questions about future perceptions regarding recommendations for best practices and the level of integrating BbIMs in BIM, respectively. The latter question aims to assess how BbIMs are being incorporated into BIM workflows to improve the application and management of low-carbon materials data. Figure 3 presents the workflow and outcomes of this research.

3. Results and Discussion

3.1. Background of the Participants

Several experts, producers, suppliers, distributors, architects, and contractors responded to the survey with a total of 18 respondents (out of 101 invitations sent). The overall response rate was 28% for producers, 23% for architects, 22% for distributors, 23% for suppliers, and 23% for contractors. Figure 4 shows the number of field experts who responded and the distribution of their respective roles per country. Their professional experience ranged from 10 to 50 years in their area of expertise, which validates the results despite the small number of respondents in some countries such as Portugal, Switzerland, The Netherlands, and France. The large experience of the respondents also reflects the fact that although biobased insulation has been around for years, its use still faces difficulties in some countries. The variety of insulation types they provide, such as hemp, wood, straw, and cork, emphasizes the availability and variety of insulation on the market.

Table 1. Background of the participants with their respective roles, years of experience, and used/provided.

Participants	Role	Years of Experience	Insulations
IT01	Manufacturer	10	Hemp fiber panels, hemp wood blocks, hemp insulating plasters
IT02	Manufacturer	18	Hemp and lime bio-composite materials
IT03	Architect	20	Hemp Panels, EPS, Jute Panels
IT04	Distributor	15	Cork panels and granules, hemp mats
IT05	Architect	12	Straw, cork, hemp, rice husks
ES01	Distributor	12	Structural wood panels with straw insulation
ES02	Architect	15	Wheat, barley, rice straw, wood fiber, recycled cotton, cellulose, natural cork.
ES03	Architect	25	Straw, cork, cellulose, wood fibers
ES04	Architect	20	Bales of straw, wood fiber, and recycled cotton.
DE01	Distributor	20	Wood fiber products, hemp products, sheep’s wool products
DE02	Supplier	30	Hemp, wood fiber, cellulose, cork, reed
DE03	Distributor	30	Cellulose (flakes), wood fiber, hemp, flax
DE04	Supplier	18	Straw
FR01	Architect	25	wood, straw, earth, thatch, cellulose wadding, algae
FR02	Architect	-	Straw, wood, hemp
NE01	Contractors	35	wood fiber, straw bales, straw panels
CH01	Architect	10	Straw, wood fiber
PT01	Manufacturer	50	Expanded Cork Agglomerate

shows the background of the participants with their respective roles, years of experience, and materials used/provided in detail. Each participant was assigned a code to ensure anonymity.

3.2. Integration Difficulties and Opportunities

3.2.1. Regulations and Policy

Italy

The manufacturing of building materials in Italy is regulated by CAM regulations, also known as “Criteri Ambientali Minimi” [34], which aim to promote sustainable production practices. These regulations align with other policies, such as mandatory green public procurement [10], encouraging market stimulation to improve the quality of products [35]. However, according to the insights, Italian BbIMs manufacturers face different challenges in meeting the CAM regulations. The manufacturer IT01 highlights the challenge of obtaining CE marking for new BbIMs, which is mandatory under the latest CAM regulations released in 2022 [34]. Due to the lack of a UN reference standard for some BbIMs, obtaining ETA certification is a time-consuming and expensive process through the Italian Technical Assessment Body (ITAB), as noted by IT01. Architect IT03 reports that ITAB penalizes natural panels that contain non-recycled plastic fibers; these materials cannot be certified if these fibers exceed 10%; however, recycled polystyrene is accepted.

Similarly, IT05 (Architect) points to a systematic bias in the certification process, i.e., it is easier to obtain CAM certificates for highly polluting materials such as reinforced concrete and steel than for environmentally friendly materials such as straw. This discrepancy suggests that the current certification system is leaning towards conventional building materials and does not adequately recognize the environmental advantages of biobased products. In the same context, IT03 recognizes the intent behind regulations that advocate for sustainability, but points to challenges in their implementation, stating: “Regulations are pushing for sustainability (see CAM and public works), showing a way, following it is another thing”. Further, IT04 (distributor) critiques the deception of the true scope of current policies, noting that even synthetic materials with questionable sustainability qualities have been accepted as sustainable products. Similarly, IT05 criticizes current policies and calls for a radical reform of standards to truly support eco-friendly materials. Thus, stakeholder feedback reveals an aligned perspective across the different roles on the effectiveness of the regulatory framework in promoting sustainability. Therefore, while in Italy, there is a regulatory framework that includes ways to promote sustainability, actual support for BbIMs appears inconsistent and challenging. All the respondents’ experiences point to the need for more transparent, effective policies and real support that align regulatory practices with sustainability goals.

Spain

In Spain, participants dealing with BbIMs had different experiences due to the regulatory environment. According to ES01 (distributor) and ES04 (Architect), there are no explicit regulatory challenges in their use, suggesting an unrestricted market for these products. However, there are still obstacles, especially in the testing and certification procedures. ES02 (Architect) emphasized the difficulties of obtaining certified fire-testing for components and obtaining EU labels for natural materials that have not undergone industrial processing, indicating procedural hurdles that may hinder the deployment of sustainable insulation solutions. Furthermore, ES03 (Architect) identified a significant organizational barrier: Building permits are obtained depending on built-up areas, which disproportionately affects buildings that use thicker natural insulation materials such as straw. This also leads to increased expenses due to thicker walls. Despite some current constraints, the respondents believe that the Spanish regulatory environment may evolve to better encourage the use of BbIMs. Addressing current barriers related to certification and building codes may pave the way for the widespread use of eco-friendly materials.

Germany

Stakeholders using BbIMs in Germany face significant regulatory challenges, particularly those associated with fire safety and thermal conductivity regulations. DE01 (distributor) indicates that deliberate misinterpretation of thermal conductivity often requires the use of larger product bodies, complicating the application process. Regarding fire safety, building insulators must comply with DIN EN 13501-1, where they must be rated in European Class E or higher to be approved [25]. All Respondents DE01, DE02, DE03, and DE04 indicated that the stringent fire safety regulations limit the use of natural insulation materials. Although these regulations ensure resident safety by restricting the use of non-compliant materials, they also emphasize the importance of further research. There is a need to enhance the fire safety properties of bio-based insulations using natural agents, which could broaden their use in construction without compromising safety and environmental impacts. Despite these challenges, there are emerging opportunities that can overcome these difficulties. DE01 discusses the initiative under the promotional program of the German Investment Bank (KfW) that includes the “Quality Seal of Excellence for Sustainable Construction” (QNG) [36], which aims to promote climate-friendly construction practices. However, the effectiveness of this seal is questionable because it is also awarded to conventional manufacturers, placing synthetic materials (often considered hazardous) on the same rating scale as natural insulation materials, according to DE01. DE02 (supplier) highlights the Bavarian Wood Construction Subsidy Program [37], which supports the use of wood in core structural elements, although it is limited to large properties. DE03 (distributor) and DE04 (supplier) also mentioned subsidies and incentive support, including Environmental, Social, and Governance (ESG) criteria, that are designed to promote the use of sustainable building materials. The regulatory environment for the integration of bio-insulation, in particular, highlights the challenges of balancing strict regulations alongside subsidies and incentives for sustainable building practices in Germany. Further optimization of both policies and insulation performance is needed to ensure fair competition for BbIMs.

France

Both respondents FR01 and FR02 indicated that the regulatory environment in France is mostly supportive of BbIMs, and there are no specific barriers, reflecting a proactive approach towards environmental sustainability in construction. Specifically, FR02 stated that regulations have not only become more flexible but are actively encouraging the adoption of bio-based materials. There are regulatory opportunities that are seen as key drivers for promoting energy efficiency and sustainability and explicitly favor materials that contribute to these goals. FR01 and FR02 note the importance of the RE2020 [38] and the new carbon emission thresholds that will be applied by 2025, 2028, and 2031, depending on the type of building [39]. France’s focus on developing its own building regulations to support bio-based materials is indicative of a national commitment to reducing the environmental impact of the construction sector [9]. The RE2020 regulation and carbon emission thresholds, in particular, demonstrate a forward-looking approach that sets increasingly stringent requirements that incentivize the use of materials that are not only energy efficient but also environmentally friendly. This regulatory framework not only enables the wider adoption of BbIMs but also sets a benchmark for other countries aiming to create a less carbon-built environment.

The Netherlands

For the Netherlands, contractor NE01 identified a challenge in the certification process, noting that the certification of several bio-based building products is disorganized. This would indicate an organizational gap that could hinder market entry or wider adoption of these sustainable materials. In terms of opportunities, NE01 notes that there are subsidies available, such as “Building Balance” [10], which aim to promote the use of Bio-based raw materials. However, there is concern that some of these funds may not reach the targeted projects, implying inefficiencies or mismanagement in the subsidy distribution systems.

Switzerland

The respondents from Switzerland (CH01) indicated that they do not perceive significant difficulties or opportunities associated with the implementation of BbIMs. This may reflect a lack of effective support for the adoption of low-carbon building materials. However, in fact, there are several initiatives and standards in place to promote sustainable building practices. For instance, there are subsidies and mortgages sponsored by banks for homeowners who construct buildings adhering to Minergie standards [40]. Specifically, the Minergie ECO label supports the use of sustainable practices and materials, which promotes healthy, circular, and ecological building methods [41].

Portugal

In the context of implementing measures for the “Long-Term Strategy for the Renovation of Buildings” also known as ELPRE (which stands for “Estratégia de Longo Prazo para a Renovação dos Edifícios”), the official journal of Portugal considered the use of recycled and bio-based materials [42]. However, similarly to Switzerland, the respondents from Portugal (PT01) indicated that they do not perceive significant difficulties or opportunities associated with the integration of BbIMs.

Figure 5 summarizes key policy and regulations-related difficulties and opportunities for BbIMs according to respondents for all countries.

3.2.2. Availability in the Market

Italy

Based on the respondents’ experiences, several factors have impacted the availability of BbIMs in Italy. IT01 stated that they do not see a lack of availability. However, IT02 highlighted that the absence of specific incentives for renewable building materials and insulation has hindered the wide availability of bio-based materials. IT03 explained that the introduction of the 110% superbonus created confusion in the construction market. Superbonus 110% is a tax deduction for the expenses related to the renovation and optimizing the energy efficiency of existing buildings [43]. IT04 added that this bonus led to an increased demand for conventional materials during the period of concessions. Furthermore, IT05 pointed out that the mandatory CAM certifications under the Superbonus schemes favored less environmentally friendly materials like EPS, PUR, and XPS over more sustainable options like straw bales, thus directing public funds towards polluting materials. On the positive side, IT01 emphasized the excellent performance and comfort BbIMs, which have raised awareness among end users about their benefits. This growing awareness, particularly regarding issues such as health, living comfort, and the durability of materials, is significant. All respondents shared the idea that increasing environmental consciousness, especially among younger generations, is driving demand for healthier and more natural living environments. This collective insight sheds light on the potential and need for significant availability of bio-based materials in the market. Hence, the BbIMs market in Italy faces some organizational and market challenges. However, customers’ increasing environmental awareness and preference for sustainable and comfortable living environments are indicative of future expansion opportunities and the potential to overcome barriers.

Spain

Spanish respondents have expressed varied perspectives on the availability and market conditions of bio-based materials, highlighting both challenges and opportunities. Respondent ES01 reported no availability issues, while ES02 noted the absence of significant difficulties in the European market but identified some challenges within the national market, with the exception of some products with a strong presence. They also mentioned the limited availability of cork, controlled by a few manufacturers or distributors, and the rarity of materials like straw and wood, compounded by insufficient funding for expensive technical experiments. ES03 observed that while demand remains stable, there are disadvantages in the distribution network and a lack of skilled installers. Additionally, ES04 pointed out that these products are non-standardized, contributing to the challenges of the wide availability. Conversely, the respondents also identified several opportunities for bio-based materials. ES01 cited increased demand driven by comfort, energy efficiency, and environmental awareness. Similarly, ES02 and ES03 emphasized the growing importance of energy efficiency and ecological concerns, with ES03 specifically noting increased public awareness about energy savings. ES04 highlighted the sensitivity of private customers and the emergence of a new generation of technicians within the administration as key opportunities for the bio-based materials market. Therefore, BbIMs can be deployed in the Spanish market to meet the potential demand by having professionals with sufficient skills and standardized products that are easily accessible.

Germany

All respondents emphasized that biobased materials are usually available in sufficient quantities, indicating strong supplies; however, other respondents pointed out some challenges. For example, DE03 points out a notable difficulty regarding the cost-effectiveness of bio-based materials compared to conventional alternatives, highlighting price as a significant factor that could influence buyer decisions. In terms of opportunities, several key points were highlighted. DE01 mentioned that the German population is increasingly addressing the issue of hazardous substances in traditional materials themselves. This shift is due to a growing awareness of the harmful nature of traditional insulation materials, which are often considered hazardous waste. Consequently, there is a growing preference for safer bio-based alternatives. DE02 emphasized the role of advertising in promoting these materials, which can help educate and attract more consumers. DE03 also pointed out the material performance advantages and sustainability benefits of bio-based materials, which could serve as key selling points to environmentally conscious consumers. However, despite these advantages and growing awareness, the market penetration of renewable raw materials remains limited in Germany. According to the latest statistics from 2019 (Figure 6) [44], the sales share of renewable raw materials in the German market is relatively small, constituting only 9% of the total in comparison to fossil and mineral insulations. Within this segment, cellulose accounts for 32%, and wood fiber makes up 58% of the sales. This indicates that while there are promising signs and opportunities for bio-based materials, their current market share remains modest.

France

In France, market conditions are exceptionally favorable for bio-based insulations. In 2020, It comprised approximately 8% of the building insulation market [45], as shown in Figure 7. After the implementation of the RE2020, 27 million square meters of bio-insulation were installed, i.e., an estimated 87% increase since 2016 [46]. The participants provided further confirmation of the current status of bio-based materials in France. According to FR01, there has been no observable decrease in the availability of these materials, which aligns with the national low-carbon strategy aimed at promoting sustainable practices. Furthermore, FR02 noted that there are no longer any obstacles in France regarding the use of bio-based materials. This improvement can be attributed to the effective organization of various sectors, which has streamlined the integration and utilization of these eco-friendly materials through industry collaborations that facilitate the production, distribution, and use of bio-based materials.

The Netherlands

Respondents indicated that the artificially high prices of these materials are a major barrier to their widespread adoption in the Netherlands. However, on an optimistic note, respondents pointed to a growing public awareness of environmental impacts and the climate crisis. This growing awareness represents a huge opportunity for the adoption of biobased materials, as more people are becoming aware of the need for sustainable and eco-friendly options. Thus, while high costs are a challenge, the growing environmental awareness among the Dutch population could drive demand and support the market for biobased materials.

Switzerland

For Switzerland, statistics on the market share of bio-based materials are difficult to find. Nevertheless, CH01 (Architect) indicated that there are no apparent issues regarding the availability of BbIMs. However, when it comes to opportunities, the respondent admits to uncertainty and lack of knowledge about growth within the Swiss market. This may indicate that although the market is not facing direct challenges, there is no clear vision of growth opportunities or emerging market directions in the Swiss context.

Portugal

The initiative of ELPRE [42] may promote the further use of bio-based materials, but still the high prices compared to conventional alternatives impacted the wide availability as highlighted by PT01 (Manufacturer of Expanded Cork Agglomerate). The opportunity for increasing the acceptance and use of bio-based materials in Portugal is linked directly to the growing concerns about environmental awareness (PT01).

Figure 8 summarizes the key availability of BbIMs in the market-related difficulties and opportunities according to respondents for all countries.

3.2.3. Techniques and Performance

Italy

IT01 and IT02 emphasized that there were no major issues with the technical performance of BbIMs, indicating their satisfaction and affirmation of the effectiveness of using these materials. Instead, IT03 indicated that technical performance challenges are related to particular installation techniques. Installers often do not have the time or motivation to learn the new techniques required for materials such as hemp panels, which can involve distinctive skills such as drilling (IT03). This implies a skills gap that should be addressed through extensive training. Similarly, T04 highlighted the need to comply with insulation installation requirements, particularly moisture protection, to ensure that the insulation meets performance requirements. On the same line, IT05 (Architect) expands further with a nuanced view that the effectiveness of natural construction materials relies heavily on the technical expertise of designers and the tailored application of these materials, stating (translated from Italian): “the difference between making an eternal natural house and making a rotten natural house lies in the technician who designs: the difference is the in-depth technical expertise, the knowledge of the natural materials and their protection and employment needs, how they work synergistically. If you use the classical design mentality and use natural materials only to replace conventional classical packages, you will make rotten packages: you need a way of designing the packages and stratigraphies”. Hence, IT05 argues that the use of natural materials requires a shift from traditional design practices to avoid issues such as mold growth, which underlines the need for specialized design approaches for these materials.

Several technical advantages were emphasized, including durability, fire resistance, aeration, excellent thermal properties of hemp blocks (IT01), significant carbon reduction potential (IT02), and thermal and acoustic resistance (IT04). Additionally, natural materials offer end-of-life benefits, notably no waste disposal or disposal issues (IT03). Furthermore, historical examples such as the “Fachwerkhaus” (Half-timbered houses in Germany) and traditional adobe structures are referenced to demonstrate the durability of these materials across different countries (IT05).

Spain

ES01 and ES04 denied the existence of significant technical challenges. Participants from Spain, similar to those from Italy, indicated that performance failures could only occur due to poor design and installation (ES02 and ES03). ES02 asserted that haphazard construction, with its implementation and design errors, may lead to the stigmatization of bio-based materials despite their benefits. ES03 highlighted specific issues related to interstitial condensation, citing the lack of availability of suitable materials for certain applications, such as the sealing of caissons for prefabricated elements. “These materials exist in France and in many other European countries but have not made it here due to the lack of descriptors due to the lack of knowledge of technicians and low regulatory requirements” (ES03). In line with the scientific literature, the significant performance advantages of bio-based materials emphasized by the participants include excellent thermal and acoustic properties, low environmental impact, health benefits [6], energy efficiency [29], waste minimization [48], fire resistance [49], CO₂ sequestration, and improved indoor air quality [30].

Germany

As discussed earlier, it seems difficult to produce BbIMs with specifications that meet Germany’s fire protection requirements (DE01) and low thermal conductivity coefficient threshold (DE03), along with moisture resistance (DE04). What makes bio-insulators better as an alternative to conventional insulators is the ease of disposal of building materials at the end of their life cycle, the possibility of storing CO₂ (DE01), excellent thermal insulation in summer, excellent indoor climate, all contributing to sustainability (DE03). In particular, hemp has excellent durability and is used even in ship storage, pipe sealing, and other applications (DE02), and the positive effects of using hemp in construction outweigh the negative effects associated with its production, use, and disposal (DE04).

France

FR01 and FR02 reported no technical difficulties and no major issues affecting the performance of BbIMs. Rather, the benefits were emphasized that biobased materials are durable and greatly enhance indoor comfort due to their phasing and moisture-regulating properties (FR01). These features make bio-based insulation particularly useful in climates where maintaining a stable indoor environment is difficult, especially during summer (FR02).

The Netherlands, Switzerland, and Portugal

In the Netherlands, NE01 states that there are few well-trained professionals, which may affect the performance of bio-based insulation.

In Portugal and Switzerland, neither technical difficulties nor issues affecting the performance of bio-based insulation have been reported. Straw in Switzerland is seen as a better alternative because it is an excellent local insulation, healthy, and 100% recyclable (CH01).

Figure 9 summarizes key techniques, performance-related difficulties, and opportunities for BbIMs according to respondents from all countries.

3.2.4. Finance and Cost

Italy

All respondents stated that all-natural products tend to be more expensive, even though they are agro-food processing waste (IT01, IT02, IT03). The high costs can be mainly due to the low availability of raw materials (IT04). For example, IT02 mentioned that the location of industrial hemp cultivation and processing to produce hemp-based insulation affected the price because they imported the raw material (hemp) from France. Furthermore, in new construction, the costs are comparable. In renovation, they are higher because of the high cost and the demanding nature of using natural plasters, according to IT05.

Spain

In Spain, BbIMs are less accessible, making them more expensive and alienating the customer due to the installation process (ES02). These higher costs are partly due to increased floor space and supply difficulties, which lead to an arbitrary increase in the cost of installation bids due to a lack of knowledge or competence (ES03). While these products are generally more expensive, straw bales are an exception as they are cheaper (ES04). However, despite the higher costs, there are business opportunities due to the lack of competition in this market (ES01). Additionally, the value of these insulators increases over time, as they are typically used in development projects that far exceed current regulatory requirements—requirements that are expected to become much stricter in the near future (ES04).

Germany

Similar to the other countries, BbIMs in Germany remain significantly more expensive for several reasons. Their market share is low due to the subsidized production of traditional building materials and the lack of qualified craftsmen (DE01, DE04). Since BbIMs cannot be mass-produced, their price cannot be reduced, and the processing of raw materials is sometimes more complex and expensive (DE01, DE03). However, raising the price of CO₂ could help lower the price of these insulators, according to DE02. Additionally, renovation costs are lower because the insulations are more durable, and disposal costs are reduced, as they are not classified as hazardous waste (DE03). This aligns with the principles of waste management and the circular economy, enhancing their value and sustainability (DE04).

France

The price of BbIMs is still higher (+20%), as reported by FR02. However, FR01 offers a different perspective, denying high prices. This divergence of views, therefore, calls to consult additional references to obtain an adequate understanding. As shown in Figure 10, the cost per square meter for bio-based, synthetic, and mineral insulation materials in France, while many BbIMs cost more, straw is the least expensive of all insulators and provides a cost-effective alternative [45]. Therefore, it cannot be generalized that all BbIMs are expensive, but the price varies depending on the material and the geographical environment where they are produced. However, while straw is the cheapest, it requires a large thickness of 32.5 cm for a thermal transmittance coefficient (U) of 0.20 W/m².K, making it impractical in some urban projects. Hence, it can be said that BbIMs are still more expensive than the other insulations, accounting for around 40% based on the ref. [45], surprisingly, despite the favorable regulatory environment and the increased demand following the implementation of RE2020 in France.

The Netherlands, Switzerland, and Portugal

The Netherlands, Switzerland, and Portugal are grouped together in this section due to their related experiences with the cost of straw bale construction. Unlike in France, NE (contractor) stated that straw bale construction is expensive. However, cost efficiencies can be realized through sequential construction. This is also observed in Switzerland and Portugal. Although the initial cost may be a barrier, individuals who choose straw bale construction, particularly self-builders, are often convinced of its benefits (CH01).

Figure 11 summarizes key finance and cost-related difficulties and opportunities of BbIMs according to respondents for all countries.

3.2.5. User/Buyer Acceptance

Italy

The difficulty of the wide integration of BbIMs in the Italian industry is centered around knowledge gaps and industry readiness rather than end-users’ acceptance. Both IT01 and IT02 express that the obstacle lies in the lack of knowledge about these materials and the slow acceptance process within the construction industry. IT03 further emphasizes that “the first difficulty is the cost. The second is installation. However, those who use it are happy afterwards”, once these obstacles are overcome. IT05 further specifies that it is not consumers but construction companies, municipal technicians, public authorities, and other industry professionals who are reluctant to adopt natural materials, suggesting an administrative challenge within the construction industry itself.

Spain

Respondents indicated that cultural perceptions by users (end-users; occupants) and buyers (decision makers) and the practical challenges hinder the acceptance of BbIMs. It is indicated that there is a cultural issue where there is a prejudice that natural materials are thought to be vulnerable and not durable (ES01, ES03). Despite these difficulties, those who are aware of its benefits really want to use it (ES03), as people are aware of the pollution caused by the production of fossil and mineral materials (ES04).

Germany

The challenge in the German industry is centered on the lack of technical knowledge and awareness among decision makers and consumers, so it cannot be said that there is widespread acceptance of this practice. There is a lack of knowledge among many stakeholders in the construction industry, including craftsmen, end users, architects, and planners, about the benefits of BbIMs and their proper installation, along with poor advertising of the advantages of natural insulation, cost issues, and lack of effective communication (DE01, DE02, DE03, DE04). These challenges are aligned and reflected in the findings of a recent study [50] about consumers’ experiences with bio-based construction materials in Germany, highlighting limited availability and poor positioning of bio-based products in local hardware stores, alongside a general lack of awareness and knowledge among both consumers and salespeople. As DE02 also highlighted, the study [50] suggests using all means of advertising and education campaigns to promote the acceptance and appreciation of the benefits of BbIMs.

France

In France, the biobased insulation market shows exceptionally favorable views from buyers and consumers, as evidenced by the feedback from respondents FR01 FR02. There are no major acceptance barriers remaining; “everyone is involved” (FR02). Hence, there is a collective commitment to sustainable building practices and acceptance of BbIMs.

The Netherlands

In the Netherlands, the main challenge in adopting BbIMs is unfamiliarity (NE01) among users and buyers. This lack of familiarity probably results from a lack of awareness of the benefits that these materials provide. Although the number of respondents from the Netherlands in this study was only one, and there is no literature on end-users’ and decision-makers’ insights, looking at real-life examples, there are several promotion practices for bio-based building materials. For example, an educational initiative was made by the research group “Biobased Building” from Avans University of Applied Sciences and HZ University of Applied Sciences, which provides informative lectures to share knowledge with industry companies and students [51]. Furthermore, with a collaboration between experts, they have developed a bio-based building knowledge bank [52]. Another regional initiative, Zuid-Holland Province, commissioned a report that explores the potential for biobased construction in the region [53].

Switzerland, and Portugal

The respondent from Switzerland (CH01) did not identify any specific barriers or drivers in regards to users’ and buyers’ acceptance due to uncertainty about growth within the Swiss market.

Instead, PT01 (manufacturer) highlighted that the main difficulty is to convince users and buyers to understand the cost/benefit factor in terms of the naturalness and environmental friendliness of the products for the long term.

Figure 12 summarizes key user and buyer acceptance-related difficulties and opportunities of BbIMs according to respondents for all countries.

3.2.6. The Most Potential Key Factor Affecting BbIMs Implementation in the Construction Industry

In this regard, the participants were asked to mention the most influential opportunity and difficulty in their opinion. As shown in Figure 13, in terms of difficulties influencing the use of bio-based materials, the most significant factor is User/buyer acceptance (38.46%), followed by Finance and Cost (30.77%), Policy (15.38%), and both Materials performance and Market, each at 7.69%. In terms of opportunities influencing the use of bio-based materials, the most significant factors are User/buyer acceptance and Materials performance, each at 37.50%, followed by Market (12.50%), and both Finance and Cost and Policy, each at 6.25%.

Notably, User/buyer acceptance is the most frequently mentioned factor as both a difficulty and an opportunity for the wide implementation of BbIMs in the construction industry, each at around 38%. This reflects the critical role that users and buyers play in the adoption of these materials as a potential driver and barrier. As highlighted previously by the participants, buyers are seen as the main barrier. In comparison, end-users are seen as a key opportunity due to their appreciation of the material’s positive impacts. The significant influence of Finance and Cost as a difficulty, which is considered the next most influential factor, suggests that user/buyer acceptance is closely linked to the high cost of BbIMs. Both users’ and buyers’ willingness to adopt these materials is often contingent on their initial cost and investment payback.

3.3. Future Perceptions

3.3.1. Recommendation for Best Practices to Promote BbIMs in the Industry

Strengthening the application of environmentally friendly standards is necessary to solidify the practice of reducing carbon emissions in the construction sector (IT02). Firstly, emphasis should be placed on minimizing CO₂ emissions during the production process and promoting long-term carbon storage solutions (DE02). Secondly, it is necessary to integrate natural materials into official construction databases (ES04), taking into account their cost and environmental impact. In addition, the public construction sector should lead by example in its commitment to sustainability (IT03, ES04). To achieve this, the withdrawal of subsidies for products that require disposal as hazardous waste should also be advocated (DE01).

Continuing education and hands-on workshops are essential. Therefore, training courses should be offered to promote familiarization with bio-based materials and their benefits (IT01, ES03, DE01). Emphasis should be placed on training craftsmen to maximize the efficient use of natural materials (NE01). Additionally, building strong links between builders, technicians, and manufacturers promotes and ensures the efficient use of bio-based materials (ES02). Instead of relying on improvisation (IT05), thorough research and consultation with experts should be encouraged. Furthermore, detailed information and tailored solutions for different construction situations should be provided (DE03).

Regulations and successful practices that are already being applied in the French industry can be benchmarked. For example, comprehensive resources such as the French Straw Guide (CH01) can be referred to. In addition, reference can be made to exemplary projects and initiatives in France that have successfully applied bio-based materials. These references provide valuable insights and proven strategies for integrating BbIMs into the construction industry.

Figure 14 summarizes the recommendations of the respondents for best practices to promote the integration of BbIMs in the construction industry.

3.3.2. The Current State of BbIMs Integration in BIM Practices within the Sector

BIM is a crucial key for implementing sustainable construction practices. While BIM is essential across various aspects of supply chain management, this section specifically discusses and seeks insights into the data acquisition of properties of BbIMs. Data acquisition of specific private properties of construction materials and related environmental metrics can be a time-consuming process in detailed design stages [54]. Various roles are involved in this process, including manufacturers and architects.

The literature [54,55] highlights various strategies and tools to facilitate life cycle assessment (LCA) through BIM environment. These strategies include, for example, conducting LCA within BIM using plugins and integrating environmental metrics into BIM Objects [54]. Hence, more specifically for bio-based materials, handling the missing data in the default BIM material library on the required layers and components can be more complicated unless it is provided by the manufacturers and published on public platforms. This challenge points to the necessity of collaboration among stakeholders. An exemplary initiative addressing this issue is the European UP STRAW program, which provided detailed straw BIM objects, making them easily accessible for industry professionals [56].

Speaking of participant insights, they were asked about the status of incorporating BbIMs into BIM practices within their industry or company. These insights may give only a small glimpse into the varying levels of enhancing the data acquisition of bio-based materials through BIM practices. The heat map in Figure 15 visually represents the integration levels of BbIMs in BIM practices across different countries and roles. The integration level values are set from 0 to 5. The color-coded scheme includes Red (0) for no integration or no experience. Yellow (1) for low integration. Blue (2.5) for medium integration. Green (5) for high integration. The values are combined with the indication of the different roles: Manufacturers (M), Architects (A), Distributors (D), Suppliers (S), and Contractors (C). This combination allows for a detailed understanding of how different roles can contribute to the integration of BbIMs in BIM practices. Different countries and roles show distinct patterns, reflecting diverse levels of engagement with BIM workflow. It can be argued that manufacturing companies are the key starting point for providing public materials library. However, according to the research results, one manufacturer (IT01) shows no integration (0), while another (IT02) shows an integration level (2.5). In contrast, the manufacturer from Portugal (PT) shows a high level of integration in BIM (5), which reflects different levels of expertise. In general, there is still a lack of awareness of the importance of BIM practices among manufacturers, architects, suppliers, distributors, and contractors.

4. Conclusions

The study provided a focused understanding of BbIMs’ integration difficulties and opportunities on a European scale. Through conducting online questionnaires, the experiences of 18 experts from Italy, France, Germany, Spain, Portugal, Switzerland, and The Netherlands on policy and regulations, availability in the market, techniques and performance, finance and cost, and user and buyer acceptance are conveyed.

The findings identified the main common difficulties in Italy, Spain, and The Netherlands, such as the lengthy process of obtaining CE marking due to a lack of reference standards and the shortage of qualified labor, which may present performance failures. The high price is due to several reasons, including lack of raw materials, labor and production costs, lack of accessibility, and lack of financial and regulatory support. Nevertheless, in France, despite a favorable and explicit regulatory environment since 2020, BbIMs is still more expensive (+40%) than conventional insulation, except for straw, as it’s still a niche market.

Meanwhile, the main drivers are the progressive improvement with certain supportive policies such as bank investment and regional initiatives, the growing environmental awareness among users, thermal, acoustic, and environmental features, long-term cost savings and value, and increasing educational initiatives, advertising, and awareness campaigns.

The industry experts recommended best practices, including strengthening the application of environmentally friendly standards, integrating natural materials into official construction databases, promoting education and hands-on workshops for builders, and referencing exemplary projects and initiatives in France. The study also identified a low integration rate of BbIMs in BIM practices, with a lack of awareness among industry stakeholders.

This research contributes significantly to the scientific literature on BbIMs by highlighting the barriers to the widespread use of the material in practice and promoting the drivers of its widespread use.

Future research should address the limitations of this study by exploring more insights from the other uncovered European countries, as well as from the countries with limited insights explored in this study (The Netherlands, Switzerland, and Portugal). Therefore, some findings from this study may not be fully applicable to other countries. Additionally, further exploration of end-users’ perceptions is recommended.