Efforts to reduce GHG emissions from several economic sectors have stepped up in recent years as Europe aims to become climate neutral by 2050 [1
]. The building sector receives special attention from the European Commission (EC) in this challenge due to the fact that it represents 40% of annual energy consumption and 36% of corresponding emissions [2
]. By implementing the Energy Performance of Buildings Directive (EPBD) in 2010, the EC established the Nearly Zero Energy Building (NZEB) concept in order to encourage the construction industry [3
]. Since then, a broad range of policies and support measures have been developed, contributing to a more effective implementation of the EPBD [4
] thus serving the clean energy transition and decarbonization of the building sector. A crucial aspect of these measures is the establishment of long-term energy efficient renovation strategies, aiming to turn the existing building stock to NZEBs [5
], while more than 85% of currently constructed buildings will still be standing in 2050, and less than 1% of structures receive energy-related renovations annually [6
]. Through energy efficient renovations towards NZEBs, Europe aims to unlock the significant clean energy transition and decarbonization potential. A key principle for such renovations is the life cycle thinking and circularity, addressing the whole life cycle carbon of buildings to achieve climate neutrality [6
], thus considering both the building operational and embodied energy impacts.
The continuous evolution of the NZEB concept, and its integration in the EU Member States, are also promoted by EU funded projects, under various EU programme frameworks, such as the “Horizon 2020”. Research from EU projects shows disparity across the EU countries concerning metrics for applying the NZEB regulations in the EPBD [8
]; most countries consider the primary energy use, others refer to the minimum Renewable Energy Sources (RES) contribution, whilst only a few integrate environmental indicators, in particular of equivalent CO2
]. Still, the indicators introduced so far, refer only to the operational lifetime of buildings and not to their whole life cycle, despite the fact that the embodied carbon emissions are estimated to be from two to four times greater than emissions associated with operational energy use [11
Embodied energy can contribute to up to 100% of a building’s life cycle in NZEBs [12
], while embodied carbon can accounting for 40% to 70% of a new low-carbon building’s total life-cycle carbon [13
]. Although embodied emissions are connected to materials and processes throughout a building’s entire life cycle, they are predicted to be responsible for 50% of a new building’s overall carbon footprint [14
], with the production stage of building materials and components being the main source of embodied carbon [15
Therefore, to reduce buildings’ total life-cycle carbon emissions, it is necessary to conduct further research on the embodied carbon of the product stage, primarily when it comes to new advanced building elements, which lack the appropriate data. Such research is facilitated by LCA, which is a standardized methodology, based on ISO 14040:2006 [16
] and ISO 14044:2006 [17
]. The methodology is dedicated to measure potential environmental impacts from fabrication until the end of life, including possible recycling related to products, any benefits, trade-offs, and areas for achieving improvements, at a full life cycle perspective [18
]. Human health, natural environment (also known as ecosystems), and natural resources are generally the three areas of protection that are taken into account, as described at the ILCD handbook [18
]. Recently, a lot of research has been performed using LCA as a tool to calculate the potential emissions from NZEBs at a worldwide level (India [19
], China [20
], Europe [21
]), showing the importance of considering a life cycle methodology when evaluating buildings’ actual energy and environmental performance. To enhance the carbon reduction potential, the careful selection of materials and components is required in the context of an integrated design approach. Belussi et al. [22
] reported that innovative materials such as Phase Change Materials (PCMs), aerogels, etc., can be utilized to minimize energy demand, while taking into account the building system’s boundary requirements and the performance-affecting constraints.
It is feasible to develop high-performance NZEB buildings with a careful selection of materials and components and a full set of installations, also including the design phase [23
]. For instance, different types of glazing, including traditional windows, facades, and roofs, can use Phase Change Materials (PCMs). Their use in the glass structure appears to show potential as it can boost the heat storage capacity; allowing the visible radiation to penetrate the interior environment for daylighting, while absorbing the solar radiation and storage it into thermal energy [23
]. Thus, in order to achieve not only energy efficiency but also a high level of thermo-hygrometric comfort, a building envelope’s thermal insulation, an improved glazing, a high air tightness, an elimination of thermal bridges, and a high-efficiency ventilation system, are required [26
However, despite the benefits and the wide research in the field, especially the last years, there are still issues to be addressed (the high cost of encapsulation production; potential variation of thermal storage capacity after several cycles of use; the lack of data concerning the environmental footprint, etc.) and further research has to be carried out concerning PCMs and innovative building materials.
In addition, LCA results for these types of building panels are not publicly available and it is the first time they are openly presented. In what concerns LCA of thermal insulation sandwich panels for building façades, regarding the materials examined in this study, very few studies were found in literature, which mainly assess environmentally individual materials of sandwich panels, without considering the assembly as a whole [27
]. This could be either the reinforced concrete, the polymer matrix, or the core insulation material.
When it comes to the LCA of thermal insulation materials for buildings, numerous studies were found in literature. However, recent literature review shows significant issues on the methodology followed, as well as a lack of transparency on the methodology implementation, within the LCA framework [30
In this context, the present study performs preliminary LCA concerning the product stage of two new advanced building components, to quantify and evaluate the respective environmental impacts, with the intention of producing NZEBs with reduced embodied carbon. These two new components are: the multifunctional composite sandwich (MCS) and the composite panel made of textile reinforced concrete layers and cellular lightweight concrete cores (TRC/CLC), purposed for façade elements, and providing improved thermal insulation. This study aims to environmentally assess the building components as a whole assembly and provides detailed LCI data for the product stage of innovative materials, as well as methodology transparency, to facilitate follow-up research on the field.
For both demos, the design and the materials used are based on the circular economy perspective considering environmental, economic, and social effects along their value chain. Thus, it is expected to present improved CO2 emissions and lower cost in comparison with the respective conventional alternatives. However, in this study such a comparison is not presented, since the two demos that are examined do not reach yet the appropriate Technological Readiness Level (TRL) in order to be considered commercial and be able to compare with the benchmarking. This study provides a preassessment concerning the advanced building components focused on their production phase, including their innovative materials and processes. This assessment could support the decision-making during the production phase, as well as the respective mitigation actions, reducing the CO2 emissions and the environmental impact in a component level. In addition, it is crucial to be mentioned that the produced data (presented below) are currently missing both from the literature and the commercial data bases (e.g., Ecoinvent) and would be a valuable reference/inventory for following studies in the field, since the availability of life-cycle data (especially in the initial stages of materials’ production/manufacturing) provides the opportunity to perform relevant changes in order to reduce the total environmental impact of a final product or system.
4.1. General Introduction
The LCIA results for the building components under investigation are shown in the following figures as staked 100% graphs for all the impact categories covered. For reasons of confidentiality, results are presented in a normalized form in advance. The material and energy inputs and outputs for each component under consideration are shown in the legends.
4.2. Results for MCS
presents the LCIA results for the standard MCS panel. The GWP of the product stage of the MCS panel is 169 kg CO2
eq per m2
. According to the environmental hotspot analysis, the electricity required for the MCS manufacturing represents the largest share for most of the impact categories addressed, contributing to climate change by 64%. As shown at the LCI of the MCS (Table 4
) concerning the energy inputs required for manufacturing, it is noticed that the preparation of the resin does not present high energy demands; in contradiction to the general exhaust, operating during the rest of the manufacturing process, which is time-consuming, including hand layup applications as well as vacuum assisted lamination lasting for over 12 h. However, the MCS manufacturing is planned to be upscaled, moving from time-consuming hand laminations to fast automated ones, therefore crucially reducing the operation time of the mechanical ventilation.
The other climate change contributors are the mortar with 27.5% and the XPS with 7.7%. The resin, the resin catalyst, and the glass fiber do not show significant contribution to any of the impact categories assessed, as their amount is very small in the total MCS panel mass. In addition, the generated waste does not significantly affect the impact categories assessed. It is also noticed that the mortar plays a crucial role in mineral, fossil, and renewable resource depletion, with a contribution of 88%. In particular, the mortar examined is lime mortar, mainly containing limestone, the most widely used crushed rock, the mining of which directly leads to the scarcity of mineral resources.
As electricity is the main contributor to most of the environmental impact categories assessed, including climate change, which is the basic focus of this study in terms of embodied emissions, a sensitivity analysis was performed considering different electricity grids of Europe to examine the influence of different electricity mixes in the climate change impact of the MCS. Apart from the Portugal grid that was already considered, the electricity mix of Norway was examined as highly decarbonized, that of Malta as slightly decarbonized and the European as an average, using the Renewable Energy Sources (RES) share for year 2019 [50
The datasets used from Ecoinvent reflect the share of electricity technologies valid for the year 2016, and have been extrapolated from 2017 to 2019 with the uncertainty adjusted accordingly. The sensitivity analysis, presented in Figure 4
, illustrates that the decarbonization level of the electricity grid considered plays a significant role in the environmental impact of climate change. If the Norway grid is selected, with a Renewable Energy Sources (RES) share of 74.41% of gross final energy consumption, the climate change of the MCS goes from 169 kg CO2
to 66 kg CO2
, leading to a reduction in the climate change impact of 60%. On the other hand, when the Malta grid is selected, having a RES share of 8.23%, the climate change of the MCS goes to 274 kg CO2
, leading to an increased impact by 62%. Thus, climate change is very sensitive to the RES share of the electricity grid considered and the respective impact decreases as the decarbonization levels of the electricity mixes increase. This analysis implies that when performing a LCIA it is important to consider the local electricity manufacturing conditions, rather than use European or other averages, for increased accuracy in the results. In addition, decarbonization paths of electricity grids are expected to be intensified during the next years, which will contribute to the mitigation of climate change.
4.3. Results for TRC-CLC-TRC
presents the LCIA results for the standard TRC-CLC-TRC panel. The GWP of the product stage of the panel is 313 kg CO2
eq per m2
. According to the environmental hotspot analysis, the CF mat represents the largest share for all the impact categories addressed, contributing to climate change by 90.6%, followed by the concrete for TRC with 6.1% and the CLC with 3.3%.
When investigating closer the CF mat, it is noticed that the electricity required is the main environmental contributor to all impact categories assessed, followed by the CF, while the epoxy resin burden is considered negligible (Figure 6
). Particularly for climate change, electricity has a share of 58% and CF a share of 41%. Finally, a closer look at the manufacturing of the CF, reveals again that the electricity required is the main environmental contributor to all impact categories assessed, (Figure 7
), with a share of 95% to climate change.
4.4. Comparison of Materials
The comparison of the two panels examined with respective conventional alternatives in terms of environmental impacts, would be of high interest and added value in this research; however, this is not included in the present study, since the two panels are still under development and do not yet reach the appropriate Technological Readiness Level (TRL), so as to enable comparisons with commercial products. Furthermore, the two panels examined are not compared to one another, since they present different thickness and targeted U value, as well as they are planned to provide different functionalities.
Nevertheless, comparisons concerning the materials of the panels are also of high importance, since they can reveal any alignments or diversions compared to similar material alternatives. In this context, the CLC of the TRC-CLC-TRC panel is selected to be presented for an indicative comparison with other insulation foam concretes from literature, in terms of climate change potential, considering the importance of this material operating as a thermal insulator. Table 11
illustrates the Global Warming Potential (GWP) of the CLC and other foam concretes in literature, considering the product stage (A1–A3) [51
], showing that the CLC examined in comparison to other foam concretes is aligned in terms of climate change potential.
Considering the aforementioned indicative comparison regarding the CLC thermal insulation material, its production stage does not present any climate change draw back, concerning other similar foam concretes from literature. However, when the whole TRC-CLC-TRC panel is considered, the increased energy demands for the manufacturing of the carbon fibers must be tackled, in order to minimize the respective embodied emissions. Thus, future work includes the equipment upgrade of the manufacturing pilot line, as well as the use of lignin fibers instead of carbon fibers, to balance energy-material emissions. Moreover, the project research is focused on the integration of silica or/and cellulose aerogels into the CLC, to further improve thermal conductivity. As for the MCS panel, its manufacturing process is planned to be upgraded in the near future, while different material compositions are examined by the manufacturing partner; so, the mass values and energy demands of the final composition validated will be updated accordingly. It is also worth mentioning that not all the life cycle stages of the panels have been assessed in this study. Since the burden of embodied emissions lies at the product stage (A1–A3) already examined, it is expected that a full life cycle analysis of the products, including end of life scenarios with credits of reusability and recyclability, will balance the total embodied emissions of the panels across their value chains, if compared to conventional similar building alternatives.
Building systems, materials, components, and product availability, have all significantly expanded in recent years. The innovative design and construction techniques that make buildings stronger, safer, longer-lasting, environmentally friendly, and more effective have been made possible by these technological improvements. Thus, building owners and decision-makers have a variety of options to choose what better fits their needs when looking into new technologies and components that can enhance and improve their facilities. However, opportunities to improve building performance and gradually decrease both operating costs and environmental footprint are often missed because innovative, less-known technologies do not receive significant attention. Building owners, operators, and design experts, can compare multiple innovative technologies and choose the best suitable to accomplish a certain goal by using research studies produced by EC-funded projects, particularly the Research Innovation Actions (RIA).
Materials for thermal insulation are crucial for decreasing buildings’ energy costs and consumption, making them a key-player towards climate change mitigation and green energy transition. Energy and CO2 balance, environmental compatibility, and the likelihood of material recycling or disposal, each contribute significantly to the environmental evaluation. LCA offers structural engineers the opportunity to incorporate environmental factors in the decision-making of buildings, promoting a more efficient use of resources throughout the whole life cycle of a building, and minimizing the environmental impacts of construction activities. However, it is difficult to decide whether a technology or a material/component is environmentally friendly. This is feasible upon the availability of a wholistic and careful analysis that takes into account all the respective parameters. Thus, established research findings of LCA on novel components and/or materials can assist in the protection of the environment through the development of new building structural components, products, and manufacturing techniques.
This paper focused on the preliminary Life Cycle Assessment (LCA) of two advanced multifunctional building components aiming to achieve lower embodied emissions in NZEBs. For the two panels examined, results indicated electricity demands in manufacturing as the main contributor at the product stage to all the environmental impact categories for the TRC-CLC-TRC panel, and to all the environmental impact categories, apart from mineral, fossil, and renewable resource depletion, for the MCS panel. This impact category is highly affected by the mortar integrated in the MCS panel, as this is lime mortar, the mining of which directly leads to the scarcity of mineral resources. Since the GHG emissions highly depend on the electricity grid source, energy efficiency measures and cleaner electricity grid mixes can have a significant influence on the environmental performance. Despite that, comparisons between the two panels or with conventional sandwich panel alternatives cannot be performed, as explained above. An indicative comparison of the CLC as insulation material, integrated into the TRC-CLC-TRC panel, with other foam concretes from literature was presented, indicating that its climate change potential does not diverse from other insulator alternatives. Thus, CLC can consist of a promising candidate for further thermal insulation building assemblies.
The main challenge identified during this research work was the lack of easily accessible Life Cycle Inventory (LCI) data that can be used in decision-making by practitioners, end users, and researchers. However, the above limitation, even considered as crucial for the research accomplishment, was tackled through the development of real-data detailed LCIs, achieved by intensive iterative communication with the respective manufacturing partners. When it comes to comparisons of building materials and components, it is important to mention that special attention should be paid to the consistency between LCA methodologies, system boundaries, and functional units. In addition, properties and functionalities should also be considered for high-quality comparison results. To this direction, a detailed description of the manufacturing processes included in the system boundaries, detailed LCIs along with proxies and assumptions, as well as material/component properties like U values, should be mentioned in literature and databases.