In Search of Eudaimonia Towards Circular Economy in Buildings—From Large Overarching Theories to Detailed Engineering Calculations

Abstract

The current study seeks to explore the underexamined or potentially under-researched social dimensions of circular economy (CE) in the context of buildings. Utilising a meta-synthesis approach, this paper builds on the two primary theoretical frameworks in the well-being literature: the eudaimonic and hedonic perspectives. The analysis of the selected articles reveals that these frameworks foster distinct modes of interaction and perception concerning one’s environment. A consensus is evident among the studies reviewed, advocating for integrating both eudaimonic and hedonic elements to achieve optimal well-being and happiness. Moreover, some scholars argue that for the attainment of sustainability goals and, by extension, CE objectives, the eudaimonic approach to well-being should be emphasised over the currently predominant hedonic inclinations. The research also attempts to open a discourse between the sometimes rather comprehensive, holistic, and hard-to-quantify dimensions of human well-being and the more logical, measurable, and tangible results-oriented approach towards the built environment. This investigation illustrates how well-designed building elements, aligned with CE principles, can play a pivotal role in fostering both environmental sustainability and human flourishing in the built environment.

1. Introduction

1.1. Emergence of the CE Concept

Circular economy (CE) is a regenerative system that focuses on minimising resource use and waste recovery and plays a pivotal role in promoting sustainable development. According to the Ellen MacArthur Foundation, the concept of CE emerged from several different schools of thought, including industrial ecology, biomimicry, cradle-to-cradle design principles, regenerative design, blue economy, and performance economy. Several of these theories recognised that the accumulated information and knowledge in living systems and nature must be harvested for our human benefit. They suggest that we should observe the rules and patterns in nature and try to align ourselves with these. Human-made designs, systems, technologies, and ecosystems can learn from nature’s patterns (biomimicry), concepts (industrial ecology, regenerative design), and large cyclical events (cradle-to-cradle) that have been around, developing, and gaining perfection via several-million-year evolutionary journeys [1,2,3].

Fundamentally, the CE idea provides a new approach that disconnects from the traditional linear take–make–dispose concept and introduces a circular model, in many aspects attempting to mimic patterns and models from nature. Several CE models were developed indicating the number of circularity levels, the so-called ‘R’ models. The first such model was conceptualised in the 1970s, called the ‘Three R principle’, referring to ‘Reduce, Reuse, Recycle’.

1.2. CE in the Construction Industry and the Critical Review of Existing CE Frameworks

The building and construction industry is one of the world’s largest waste generators. Construction waste accounts for about 40% of the total solid waste generated worldwide, and more importantly, only 20 to 30% of all construction and demolition waste is ultimately recycled or reused.

Recent studies have pointed out that the progression from a linear to a circular approach within the construction industry poses a significant challenge, especially due to the lack of available frameworks. The currently available frameworks concentrate on one or two aspects of construction or building projects but fail to have an overarching, holistic perspective. One of the main reasons for this is the highly complex nature of construction projects: the many elements involved, the number of participants required, the variety of stakeholders with a vested interest in different aspects of the project, and the numerous techniques that need to be used. The currently available CE frameworks are fragmented along the lines of these many facets of the construction and building industry. It is important to mention, however, that alternative approaches are trying to consider the lifecycle management of assets from design to end-of-life, such as prefabrication, design for change, design for deconstruction, reverse logistics, waste management, and closed-loop systems [4,5,6,7]. Research results have identified that the construction and building sector has a strong focus on the linkage of CE to sustainable development; however, the CE’s social and future dimensions are somewhat sidelined [8,9,10]. There has been a significant increase in interest in the applicability of CE on the level of operations, business models, and policy guidance recently; however, the academic community has expressed concern regarding the lack of attention to and research on the related human needs and social impacts [11,12,13,14]. Consequently, this research article aims to investigate the potential role of human well-being in the social aspect of CE in buildings.

1.3. The Connection Between Eudaimonic and Hedonic Well-Being and CE

Recent research has concluded that the study of social CE in buildings is fundamentally the investigation of the architectural impact on human well-being [11]. A circular built environment takes a whole-system approach and is underpinned by the three CE principles: eliminate, circulate, and regenerate. In the view of architecture and buildings, it means the following: (i) buildings and construction processes should use materials as effectively as possible, (ii) buildings should be adaptable and be used for the longest possible time, (iii) buildings should enhance the health of ecosystems and the well-being of building users [15]. Humans, as the third pillar of the triple bottom line (TBL) sustainability model, are key actors, clients, and contributors to the CE in buildings. From the view of CE, it can be suggested that humans (building users) are one of the most important stakeholders of architectural and construction projects. Without the full engagement and cooperation of humans, buildings will not be in service for long, the materials in buildings will be used inefficiently, and these buildings will not enhance health and well-being. Consequently, the research hypothesis of the present paper is that people who feel happier, more comfortable, and content in certain buildings will be more likely to use these types of constructions for longer periods, will be more likely to rebuild these places again and again, and will take more care to maintain them. Without serious consideration of the needs, tendencies, and patterns of the human factor in buildings, the very fundamental principles of CE can be at risk. For humans, the built environment and spaces are something more than the pure physical reality of the built existence, as they are also about meaning, memories, and connections. If people feel unhappy and unwell in certain buildings, then this will fundamentally result in the unsustainability of that building type; hence, these buildings will not be a fit for the CE approach.

The two fundamental schools of thought in the well-being literature in search of human happiness are the hedonic and eudaimonic perspectives. The hedonic approach can be traced back to the Greek word hedone (pleasure in English); however, its key aspiration is to maximise pleasure and minimise pain. Eudaimonia means the state or condition of ‘good spirit’ in Greek. Aristotle uses this term for the highest human good in the older Greek tradition; thus, this is a core concept in Aristotelian ethics [16]. Certain researchers propose that the hedonic approach is sensory and the eudaimonic is moral-based well-being. Correspondingly, hedonic well-being is associated with short high-arousal states, whilst eudaimonic well-being is more like stable, long-lasting low-arousal conditions [17,18,19,20]. In the following sections of the paper, the authors investigate how buildings and architecture can affect eudaimonic and hedonic well-being in humans.

2. Materials and Methods

This research paper seeks to examine the potential influence of different types of human well-being on CE within the building sector and will include a detailed numerical engineering calculation. While extensive studies on eudaimonic and hedonic well-being have been conducted within the disciplines of neuroscience and psychology, there exists a notable paucity of literature pertaining to buildings or architecture. The authors posit that integrating findings across these varied fields necessitates the use of a meta-synthesis methodology.

2.1. Meta-Synthesis Methodology

The meta-synthesis methodology adhered to a standardised protocol, which included a systematic and well-documented search strategy, meticulous extraction, and the classification of relevant information and culminated in an interpretive analysis. The scope of the present research is specifically the well-being aspects of architecture and buildings; however, interestingly, the relevant studies, creating the foundation of the meta-synthesis review, came from diverse academic fields, including psychology, neuroscience, neuroaesthetics, architecture, and design. As the number of research articles resulting from the database searches was rather limited the authors decided to enrich the pool of papers to be reviewed based on the following three principles: (i) using Google’s general search engine to identify potentially relevant documents or projects that might not yet have been found in the academic databases; (ii) including new concepts or phrases in the research that were coming up repeatedly in high numbers in the database search result titles; and (iii) including new books or articles in the research that are relevantand very closely related to search results.

The extended pool of publications reviewed by the authors contained 10 articles and 6 books. A number of these publications were several hundred pages long, containing the conclusions of thirty or more years of research. In the authors’ view, based on the extended number of publications, a focused meta-synthesis review was conducted regarding the very specific topic of architecture and building-related well-being. This comprehensive approach using research results from the most diverse academic fields, such as psychology, neuroscience, neuroaesthetics, architecture, and design, culminated in a synergistic perspective on this topic. Figure 1 below shows the structured explanation of the search strategy.

2.2. Detailed Description of the Meta-Synthesis Review

The systematic search strategy implemented in this study was meticulously detailed. Given the research focus on the aspects of eudaimonic and hedonic well-being within the context of buildings, specific search terms were employed. The phrases ‘Eudaimonia, Building, Architecture’ and ‘Hedonic well-being, Building, Architecture’ were utilised across multiple databases, including EBSCO, Science Direct, Jstor, Proquest, and Google. The authors subsequently reviewed the search results on an individual basis. After reading the articles’ titles and the abstracts, papers that were significantly different from buildings or architecture-related well-being topics were excluded from further evaluation. Although the meta-synthesis approach aims to provide as comprehensive and nuanced a view of the topic as possible, the authors still had to exclude certain papers to maintain the general direction of the research. Consequently, database search results discussing overly specific aspects of well-being, for example, tourism, restaurants, music, AI, the recruitment of healthcare workers, or storytelling were not included in the following meta-synthesis methodology. After the exclusion of these study papers, the number of articles to be reviewed for research purposes was significantly reduced. Owing to the limited yield of results from these academic databases, the researchers also incorporated searches via Google’s general search engine to identify potentially relevant documents or projects that might not yet be extensively documented within the academic literature.

The searches were conducted between 8–15 September 2024 and only included journal or research articles. The search results were the following. The EBSCO database did not have any results with these search entries. The JSTOR search produced 124 results for the ‘Eudaimonia, Building, Architecture’ search phrases, and after reading the titles or the abstracts of these results, 2 articles [21,22] were selected for further review. The JSTOR search for ‘Hedonic well-being, Building, Architecture’ had 66 results, and after reading the titles or abstracts, 1 article [23] was selected for further review. After reading these three selected JSTOR articles, the authors decided to include 2 relevant books [24,25] and an article [26] that further elaborates on the selected 3 articles’ topics. The Science Direct search produced 31 results for the ‘Eudaimonia, Building, Architecture’ phrase search, with 1 article selected [27]; 1 book was added by the author [28], and 156 results were found for the ‘Hedonic well-being, Building, Architecture’ search, with 0 articles selected. The ProQuest search produced 272 results for the ‘Eudaimonia, Building, Architecture’ phrase search with 0 articles selected, and 786 results for the ‘Hedonic well-being, Building, Architecture’ search with 2 articles selected [29,30]. Since the number of the database search results relating to the ‘architecture’ or ‘building’ subject area was very limited, the authors decided to include new phrases that were consistently re-appearing in the titles of the search results. During the ProQuest search, the authors identified that two phrases came up with great frequency in the titles of the search results, namely ‘Positive Psychology’ and ‘Buddhism’. Positive psychology came up 5 times in article titles in the ProQuest ‘Eudaimonia, Building, Architecture’ search and 14 times in the ProQuest ‘Hedonic well-being, Building, Architecture’ search. ‘Buddhism’ appeared 8 times in article titles in the ProQuest ‘Eudaimonia, Building, Architecture’ search and 4 times in the ProQuest ‘Hedonic well-being, Building, Architecture’ search. Altogether, Positive Psychology appeared in 19, and Buddhism appeared in 12 article search result titles. Due to the comparatively high frequency of these two specific phrases, the authors decided to include two more articles and one book that explain the very core concepts of these in relation to well-being [17,31,32,33].

2.3. Meta-Synthesis Review Findings

While the selected articles originated from diverse academic fields, including psychology, neuroscience, neuroaesthetics, architecture, and design, they collectively concentrated on a unified theme: human well-being, specifically eudaimonic and hedonic well-being, each from their distinct disciplinary perspectives. A primary methodological objective was thus to analyse these publications for commonalities or converging themes in their respective treatments of eudaimonia and hedonic well-being. Upon review, the authors identified a recurrent dualistic framework in how these two dimensions of human well-being were described. This framework delineates markedly different modes of perception, understanding, and engagement with the environment. Although some articles focused solely on one type of well-being (either eudaimonia or hedonia), their discussions were consistently relevant and integrative within the broader thematic context established by the other studies.

A collection of these two markedly different approaches associated with the two distinct types of well-being states from the selected publications can be found in

Table 1. Two distinct types of well-being states from the selected publications.

List Based on the Comparing Attributes to Profile Human-Centred Design in Architecture—Design for Human Flourishing [23]
Area of manifesting attributes	Comparing attributes
Concept/Mindset	Focus on resolving negative aspects	Focus on inspiring positive aspects
The outcome of the design process	Physical, definite results with direct impact	Immaterial, complex results with indirect impact
Characteristics of design effect	Tangible, real effects	Psychological and emotional effects
Impact level of design	Brief, transient effect with no internal impact	Enduring effect with profound impact
Targeted user group of the design	Limited scope, uniform	Large, extended scope, multifaceted
List Based on Comparing Attributes to Profile Design for Flourishing [27]
Nature of the inner world	More associated with the left hemisphere	More associated with the right hemisphere
Comprehensive perceptual area	Stronger focus on the past (Known information).	Stronger focus on the now (New information).
	Devoid of meaning	Importance of meaning is emphasised
	Detached, common knowledge	Special, individual knowledge and understanding
	Devoid of context	Abundantly contextual
	Fixed, passive	Developing, changing
Respective Parts	Inanimate, determined	Animate, indefinite
	Common, uniform objects	Specific, unique objects
	Unsubstantiated, isolated in space and time	Interrelated, interconnected
	Unequivocal, explicit characteristics	Tacit, implicit connotations
List Based on Comparing Attributes to Understand Analytic and Synergistic Relationality [26]
	Completeness, wholeness as Analytic Relationality	Integrity, wholeness as Synergistic Relationality
The complete—The whole	An array of correlations and connections among different units	Self-fulfilling and self-managing units. Each unit participates and contributes to the formation of every other part
Manifestation of the whole	Based on the particular/specific characteristics of independent, disunited, cooperating units	Based on the fully integral nature of the whole and its intrinsic parts
Units, parts of the whole	Units or parts stay disunited, even if collected and built into the whole. Focus is on the interaction between the units, signifying changes in a few or all the other parts of the whole	Units or parts acquire meaning, and importance because they are part of the whole. Their unique features and characteristics metamorphose into and by the nature of the whole
The ontological view of the whole	Is not an intrinsic concept but a repository of many, complex, connected parts and units. (Consequently, it could be more associated with researchers’ random choices when investigating a few or a selection of these many inter-relational connections). Correspondingly the completeness of the whole is only whole secondarily.	The whole is an intrinsic concept with its parts united integrally together. The coherence and the unity of the parts gain their individuality and uniqueness into completeness/wholeness. The whole and its parts are manifesting as one.

. The first column of this table is more (but not exclusively) associated with hedonic well-being, and the second column is more (but not exclusively) associated with eudaimonia.

From the selected, and the additionally included literature, the two types of well-being approaches and their associations can be enhanced with new concepts, terminologies, and ideas. This extended picture of hedonic well-being at its full capacity is associated with the concepts of fast fashion, branding, retail therapy, and potentially even the hedonic treadmill. The hedonic treadmill theory explains that due to our human nature, our emotional response to the same stimuli decreases or even diminishes with time. Consequently, from the architectural standpoint, continuous change is necessary in the building design to create the same impact. High arousal, big impact, and a very physical or materialistic approach with short-lived and superficial experiences could describe this hedonic approach [34]. Eudaimonic well-being, however, is accompanied by phrases such as thriving, flourishing, or the flow concept from positive psychology [32]. A meaningful life or a life worth living [17], aesthetic experience [25,33], and mindfulness from Buddhist philosophies [31] are also mentioned in association with this. Eudaimonic well-being is most associated with self-realization, self-fulfilment, a meaningful life, a life worth living, and, according to Aristotle, the highest human good in the ancient Greek tradition. Please see Table 1 below containing this extended list of associations with eudaimonic and hedonic well-being based on the added relevant literature.

3. Interpretive Analysis in Relation to Buildings and Architecture

3.1. Hedonic Architecture Example

The epitome of our current XXIst-century hedonic well-being tendencies is our culture of fast food, fast fashion, and fast-moving consumer goods (FMCGs), very often manifested in our attitude to shopping [30]. Correspondingly, the above-mentioned description of hedonic well-being can be most closely associated with the architecture of shopping centres. These buildings are not trying to make a lasting impact on us consumers anymore; however, the brands and fashion trends brought to us by these buildings are influencing our lives greatly in several ways. It is all about looks, impressions, and appearances, which are generally short-lived and changeable. This could be explained by the so-called ‘hedonic treadmill theory’, which explains that material possessions or external circumstances alone cannot sustainably increase or decrease our long-term happiness [34]. Research results indicate that just the pure slowing down of this fast food, fast fashion, and FMCG culture can positively contribute to our well-being [35].

3.2. Eudaimonic Architecture Example

On the other side of this equation are buildings of eudaimonic well-being presenting long-lasting impact, psychological-emotional experience, and timeless classic designs usually associated with aesthetics [25,33]. Further to the associated literature (such as positive psychology, the concept of mindfulness in Buddhist studies, self-fulfilling, and self-realization), one of the most extreme examples of eudaimonic well-being could be the mandala design described by C.G. Jung as ‘the Self, the wholeness of the personality, which if all goes well, is harmonious’ [36], quoted by Kringelbach in his article titled ‘Kalachakra mandala’ [37]. The classical, immortal architectural mandala design can have a truly psycho-emotional impact on humans. The very simplified description of this design in architecture incorporates a stupa building in the middle of the composition surrounded by four gates, called toranas, in the four cardinal directions. The architectural composition aims to help the visitor to gradually lock out and ignore as many distractions of the outer world or everyday life as possible and arrive at the centre with a very focused mental state. Traditionally, the torana gates are the outermost elements of this composition. This is the point where the visitor should start to leave worldly thoughts and worries behind. Interestingly, however, there are academic papers from cognition, brain, and behavioural studies indicating that there is a scientific explanation for this, called the ‘doorway effect’ or the ‘location updating effect’. The studies describe this psychological phenomenon as a short-term memory loss when we walk through a gate or a doorway. We appear to forget about objects, plans, and thoughts that were very important to us just before walking through the door [38]. After the visitor walks through the torana gate, they start to circle around (circumambulate) the stupa building. Traditionally, the central core of the mandala design in architecture is the stupa building. It is not possible to enter a stupa; however, it is strongly associated with the rite of ‘circumambulation’. During the rite of ‘circumambulation’, as the visitor is observing the iconographical representation repeated at each round, they are supposed to gradually leave all distractions of life behind and arrive at the central point with a very focused, meditative state. Metaphorically speaking, the mystical journey starts when the world of samsara, the world of phenomena, is left behind. Bronkhorst, in his paper titled ‘The Mystical Experience’, discusses exactly this point about human mental states [39]; however, most importantly, he claims that it would be a mistake to view mystical experiences as exclusively ‘religious’ or even ‘spiritual’. The process associated with the stupa of gradual detachment and disassociation from everything worldly to achieve the ideal state of consciousness resonates with Bronkhorst’s approach to trying to understand mystic experiences. What Bronkhorst is proposing is that the only claim that can be said about mystical experiences is what these experiences are not. His approach is to suppress or remove factors that contribute to standard consciousness so that we can understand the consciousness of mystical states.

Understandably, the potentially very profound architectural impact of the mandala design is not an everyday experience for many of us, and it is not sought by us with great frequency. However, the everyday hedonic experience of material possessions or external circumstances alone cannot sustainably contribute to our long-term happiness. Hence, consequently, many researchers [40] on the topic believe that hedonia and eudaimonia together can result in the highest level of well-being rather than only one of them. On the other hand, they also assume that an imbalance of hedonia and eudaimonia causes frustration and disappointment, leading to lower levels of well-being or ill-being. In this context, two contemporary examples associated with hedonia and eudaimonia from the world of architecture give a very clear picture of their approach to well-being. These two contemporary architectural examples of well-being perspectives are the ‘Hedonic Sustainability’ concept and the ‘Eudaimonia Machine’.

3.3. Contemporary Architectural Approach to Hedonia—Hedonic Sustainability

Hedonic Sustainability was coined by the founder and creative partner of Bjarke Ingels Group (BIG), Bjarke Ingels, in 2011. Although Hedonic Sustainability is itself an oxymoron, Ingels argues that we should put pleasure into our green and sustainable living targets if we want to be successful. His approach can be seen as an experiment to balance out purely hedonic architecture with thoughts of sustainability and caring for nature and our environment [41,42,43]. Ingels further coined the term ‘Hedonistic Sustainability’, suggests that the New European Bauhaus (NEB) [44] could be the response to the merging sustainability and environmental concerns. NEB is looking for beautiful, inclusive, sustainable solutions that respect the diversity of places, traditions, and cultures in Europe and beyond [45]. The importance of circularity is very strongly emphasised in the NEB manifesto. The NEB is an EU policy and funding initiative launched by the European Commission in 2021 that cultivates sustainable solutions for transforming the built environment and lifestyles under the green transition.

3.4. Contemporary Architectural Approach to Eudaimonia—The Eudaimonia Machine

Further to the eudaimonic well-being aspects of buildings, the most notable contemporary architectural approach to the subject is the so-called ‘Eudaimonia Machine’ by David Dewane. Dewane draws on Cal Newport’s book, titled ‘Deep Work’ [46], where the author states that distractions in our life are constant and continuously present; hence, what we choose to focus on and what we decide to ignore make and define the quality of our life. Newport writes that deep work is an ability to be able to focus without distraction on a difficult, intellectually challenging task. The ability to undertake deep work is valuable and rare, but it is the highest state of flourishing. Whilst Newport is a professor of computer science, Dewane is an architect with a background in ecological and socially equitable design. A schematic model of the Eudaimonia Machine based on Dewane below is presented in Figure 2.

Dewane’s adoption of Newport’s deep work theory was the realization that architecture can trigger different mental states purely based on design. He recognised that the key function of our workplace should be the nurturing, development, and synergising of intense brain activity to result in genuine, innovative work results [47,48]. Dewane’s conceptual design, the Eudaimonia Machine, is a single-story, rectangular building containing five rooms containing a linear progression through these five spaces. The gallery (Room Oneis about positive peer pressure. Superficial, informal discussions, and quick information sharing with people from the most diverse areas of interest and background ‘facilitate communication and idea flows’, based on the ‘theory of serendipitous creativity’. In the Saloon (Room Two), the relaxed atmosphere encourages a bit more organised level of socialising and communication. The Office (Room Three), placed in the middle of the arrangement, is described as a typical open-plan office to accommodate ‘shallow work’ in a friendly and collegiate atmosphere. The Library (Room Four), called the ‘hard drive of the machine’ by Dewane, is a quiet space for research and thought gathering. This is the place where deep work begins. The Chamber (Room Five) is a small sound-proof room to cut up distractions and interruptions from the outside world. This is a quiet and isolated place where long-term value and deep work are created. All along these different rooms, Dewane emphasises the importance of involving endusers early, opening wide-ranging discussions with them, and allowing for personalization, which fills the space with meaning, something necessary for deep work. The sequence of these rooms is fundamentally driving us from a very superficial information-sharing and -gathering state to a laser-sharply focused mental state via the gradual exclusion of all unnecessary distracting factors and personalisation.

4. The Quantified Approach to Human Well-Being—The Logical Numerical Engineering Approach

In the previous sections of the paper, further to establishing the fact that a balanced approach is necessary between hedonia and eudaimonia to achieve optimal states of human happiness, it has also been pointed out that slightly stronger attention to the eudemonic tendencies could be advisable due to the currently very dominant hedonic implications.

As described in the second column of

Table 2. The extended list of associations with eudaimonic and hedonic well-beingfrom the selected and the additionally included literature.

An Extended List of Eudaimonic & Hedonic Well-being Associations from Selected and Additionally Included Literature [21,22,23,24,25,26,27,28,29,30,31,32,33,34,35]
It could be more associated with Hedonic well-being in relation to buildings and architecture	It could be more associated with Eudaimonic well-being in relation to buildings and architecture
Analytical	Integrating, synergizing, holistic
Logic	More strongly associated with intuition, creativity
Lifeless, static	Living, evolving
Decontextualised, literal	Richly contextual, symbolic
Short, superficial impact	Long-lasting, profound impact
Tangible, direct physical results	Intangible, psychological-emotional impacts
The focus is on the individual	The focus is on connectedness, relationships
Fast-moving consumer goods trends	Classical, timeless design
Fashion trends	Aesthetic experience
Hedonic treadmill	Contentment
Reducing negative feelings	Stimulating positive feelings
According to certain studies, it could be more associated with the activity of the left brain hemisphere	According to certain studies, it could be more associated with the activity of the right brain hemisphere

, these eudaimonic associations might be more closely related to the right brain hemisphere and a more holistic, integrative, and symbolic approach. In the following section of the paper, as a complementary example, the authors seek to approach human happiness from the ‘other’ perspective.

This view could be potentially more closely associated with the left brain hemisphere and with a more analytical, logical approach providing very tangible physical results, as described in the first column of Table 2. This approach is a logical, numerical engineering methodology using mathematical models.

The Organization for Economic Co-operation and Development (OECD), in their most recent publication, titled ‘Built Environment through a Well-being Lens’, designates poor housing conditions, such as dampness, mould, cold, and household crowdedness, as the main reasons globally for poor physical health, undermining mental health and life satisfaction [49]. In recent years, a great number of studies have been published on the connection between the indoor thermal environment and human health.

These studies point out that for the systematic discussion of the specific relationships between the indoor thermal environment and human health, the accurate measurement of these factors is necessary. In the previous sections, the authors introduced large overarching philosophical theories, building on the two fundamental schools of thought in the well-being literature, the hedonic and eudaimonic perspectives, respectively.

The following part of the paper switches from the very large scale to a detailed numerical engineering path. With this change of perspectives, from the macro to the micro, the authors attempt to explore possible correlations between the aspects of human well-being and the numerical measures of the built environment.

Because, according to the OECD publication, the most significant impact on human physical and mental well-being in buildings is associated with dampness, mould, and cold, the authors concluded that a ‘Thermal analysis of building materials’ model would be the most appropriate as a conduit in this approach.

4.1. Thermal Analysis of Building Materials and CE

HVAC systems, providing thermal comfort in our built environment, are responsible for about 60% of total energy consumption globally. The building envelope is considered fundamental to enhancing the thermal performance of structures. Consequently, it is pivotal to minimise the energy consumption of buildings and the associated carbon dioxide emissions towards a sustainable future and CE.

One of the key features of CE is the reuse and recycling of different materials. Recycled materials used in building projects have fundamentally different characteristics and thermal properties than the standard building products. This difference and irregularity require special attention and must be investigated and measured by applying a robust and systematic approach. Thermal analysis methods can help to identify irregularities and ensure that recycled materials meet the product specifications.

Thermal analysis of building materials in CE context is integral to the future of the sustainable construction industry. By focusing on the thermal performance of reused, recycled, and sustainable materials, the construction industry can reduce both operational energy consumption and the embodied energy of buildings, contributing to lower carbon emissions and a more resource-efficient built environment. This approach, combined with advancements in material science and stricter regulatory frameworks, is guiding the construction sector toward a more sustainable and circular future.

4.2. Mathematical Modelling—The Robust, Systematic Approach

The mathematical modelling of building materials’ thermal analysis, particularly within the context of CE, can be structured around key thermal performance indicators such as thermal conductivity, thermal resistance, thermal mass, and U-value. These models quantify how materials behave thermally and provide a framework to compare their performance, especially in recycled or reused materials.

Thermal Conductivity (κ):

Thermal conductivity measures how efficiently heat passes through a material; the lower the value the material has, the better it serves as an insulator.

The general equation for heat conduction is given by Fourier’s Law:

$$Q=-kA{\displaystyle \frac{\Delta T}{\Delta x}}$$

(1)

where

$Q$—heat flux (W);

$k$—thermal conductivity (W/m·K);

$A$—cross-sectional area through which heat is transferred;

$\Delta T$—temperature difference across the material;

$\Delta x$—thickness of the material.

In the context of the circular economy, recycled or reused materials may have different $k$ values due to changes in structure, porosity, or density. Thermal resistance represents the material’s ability to resist the flow of heat. Higher R-values indicate better insulating capabilities. The R-value is related to thermal conductivity by the following equation:

$$R={\displaystyle \frac{1}{k}}\Delta x$$

(2)

For a building element composed of multiple layers of materials, the total R-value is the sum of the R-values of each layer:

$$R_{tot}=R_1+R_2+R_3+\dots +R_n={\displaystyle \sum _{i=1}^n\frac{1}{k_i}\Delta x_i}$$

(3)

Recycled materials with varying thicknesses and thermal properties will influence the overall R-value of the building element. Thermal mass is the ability of a material to absorb and store heat. Materials with high thermal mass can moderate temperature changes in buildings and improve energy efficiency. The thermal mass M of a material can be described by its heat capacity C, which is the product of the material’s specific heat capacity c, density ρ, and volume V:

$$M_t=\rho Vc$$

(4)

where

M—thermal mass (J/K);

c—specific heat capacity of the material (J/kg·K);

ρ—material density (kg/m³);

V—material volume (m³).

Materials like concrete, brick, and water have high thermal mass values, whereas materials like insulation have low thermal mass. In the context of circular economy, reclaimed or alternative materials such as geopolymers, concrete, or recycled aggregates will have different thermal mass properties.

The U-value is a measure of how much heat passes through a building element (such as a wall, window, or roof). It is the inverse of the total thermal resistance:

$$U={\displaystyle \frac{1}{R_{tot}}}$$

where

U—U-value (W/m²·K).

The U-value combines all layers of a building element, including insulation, external cladding, and interior finishes. For example, for a multi-layer wall,

$$U={\displaystyle \frac{1}{\frac{\Delta x_1}{k_1}+\frac{\Delta x_2}{k_2}+\frac{\Delta x_3}{k_3}+\dots +\frac{\Delta x_n}{k_n}}}$$

(5)

A lower U-value indicates better insulating properties. In circular economy practices, materials like recycled insulation, reused bricks, or eco-friendly alternatives would alter the U-value of the building, requiring careful selection to meet energy efficiency targets.

To calculate the total heat loss through a building component, such as a wall or roof, the following equation is used:

$$Q=UA\Delta T$$

(6)

where:

Q—total heat transfer (W);

U—U-value of the building element (W/m²·K);

A—the surface area of the element (m²);

ΔT—temperature difference between inside and outside (K).

This model helps quantify how much heat is lost (or gained) through a particular building material or system, including recycled or reused materials.

The energy performance of materials in the circular economy must balance operational energy savings (due to insulation and thermal mass) with embodied energy (energy required for production, transport, and installation).

The total energy impact of a building material over its lifecycle can be expressed as

$$E_{tot}=E_{em}+E_{op}$$

(7)

where

$E_{tot}$—total energy impact of the material (J or kWh);

$E_{em}$—embodied energy over the material’s lifecycle (J or kWh);

$E_{op}$—operational energy savings (or losses) due to the material’s thermal performance (J or kWh).

Minimising embodied energy and maximising operational energy savings is one of the main goals in a circular economy context. For instance, a recycled insulation material might have lower embodied energy than traditional materials while still maintaining high thermal resistance and low U-values.

The mathematical framework provides a way to quantify the thermal performance of materials, both traditional and those adapted for the circular economy. The equations help assess the impact of using recycled or reused materials regarding insulation efficiency, thermal mass, and overall energy performance, guiding decisions toward sustainable building practices.

There are specific techniques developed to model the thermal properties of insulated walls, such as the Crank–Nicolson and Monte Carlo methods. These approaches allow the modelling of the transient heat transfer through insulation and account for uncertainties in material properties. The Crank–Nicolson method represents an implicit time-stepping method, intended to solve the heat conduction equations, providing accuracy and stability for transient thermal analysis.

For the insulation layer, the heat conduction equation is written as

$${\displaystyle \frac{\partial T}{\partial t}}=\alpha {\displaystyle \frac{{\partial }^{2}T}{\partial x^2}}; \alpha ={\displaystyle \frac{k}{\rho \cdot c}}$$

(8)

where

T(x,t)—the temperature at position x and time t;

α—the thermal diffusivity;

k—thermal conductivity;

ρ—density;

c—specific heat capacity.

The Crank–Nicolson method uses a finite difference approximation that averages the explicit (forward) and implicit (backward) time steps.

For a grid with spatial step size Δx and time step Δt, the discretised form is presented as

$${\displaystyle \frac{T_i^{n+1}-T_i^n}{\Delta t}}={\displaystyle \frac{\alpha }{2}}\left({\displaystyle \frac{T_{i+1}^n-2T_i^n+T_{i-1}^n}{\Delta x^2}}+{\displaystyle \frac{T_{i+1}^{n+1}-2T_i^{n+1}+T_{i-1}^{n+1}}{\Delta x^2}}\right)$$

(9)

$$-{\displaystyle \frac{1}{2}}\alpha {\displaystyle \frac{\Delta t}{\Delta x^2}}{T}_{i-1}^{n+1}+\left(1+\alpha {\displaystyle \frac{\Delta t}{\Delta x^2}}\right)T_i^{n+1}-{\displaystyle \frac{1}{2}}\alpha {\displaystyle \frac{\Delta t}{\Delta x^2}}{T}_{i+1}^{n+1}={\displaystyle \frac{1}{2}}\alpha {\displaystyle \frac{\Delta t}{\Delta x^2}}{T}_{i-1}^n+\left(1-\alpha {\displaystyle \frac{\Delta t}{\Delta x^2}}\right)T_i^n+{\displaystyle \frac{1}{2}}\alpha {\displaystyle \frac{\Delta t}{\Delta x^2}}{T}_{i+1}^n$$

(10)

Considering the temperature vectors at time steps n and n + 1, the equation is written in a matrix form, where the matrices A and B are dependent on the thermal diffusivity and spatial resolution for each layer:

$$A{T}^{n+1}=B{T}^n$$

(11)

$$A=\left[\begin{array}{ccccc}1+r& -{\displaystyle \frac{1}{2}}r& 0& \dots & 0\\ -{\displaystyle \frac{1}{2}}r& 1+r& -{\displaystyle \frac{1}{2}}r& \dots & 0\\ 0& -{\displaystyle \frac{1}{2}}r& 1+r& \dots & 0\\ \dots & \dots & \dots & \dots & -{\displaystyle \frac{1}{2}}r\\ 0& 0& 0& -{\displaystyle \frac{1}{2}}r& 1+r\end{array}\right] B=\left[\begin{array}{ccccc}1-r& {\displaystyle \frac{1}{2}}r& 0& \dots & 0\\ {\displaystyle \frac{1}{2}}r& 1-r& {\displaystyle \frac{1}{2}}r& \dots & 0\\ 0& {\displaystyle \frac{1}{2}}r& 1-r& \dots & 0\\ \dots & \dots & \dots & \dots & {\displaystyle \frac{1}{2}}r\\ 0& 0& 0& {\displaystyle \frac{1}{2}}r& 1-r\end{array}\right]$$

(12)

where

$$r=\alpha {\displaystyle \frac{\Delta t}{\Delta x^2}}$$

(13)

The Monte Carlo method is used to estimate the impact of uncertainty in material properties (e.g., thermal conductivity k) regarding the thermal performance of insulation. By applying this method, the random sampling of uncertain parameters is used to compute multiple scenarios, from which statistical properties like mean temperature and multiple variances are derived.

Assume that the uncertainty in thermal conductivity (k) of the insulation layer follows a normal distribution (with k mean values and standard deviation (σk)). Several random samples are generated considering the k mean values as a specified distribution; for each value, the thermal diffusivity value is calculated:

$$\alpha ={\displaystyle \frac{1}{\rho \cdot c}}\cdot k$$

(14)

Using the Crank–Nicolson, method the heat conduction problem is solved based on α values, obtaining a temperature profile T(x,t) for each sample.

Calculating the mean temperature T(x,t) and variance ${\sigma }_T^2\left(x,t\right)$ across all samples at each position x and time t offer the problem solution to the thermal distribution across the isolated system:

$$\begin{array}{c}\overline{T}\left(x,t\right)={\displaystyle \frac{1}{N}}{\displaystyle \sum _{i=1}^N{T}_i}\left(x,t\right)\\ {\sigma }_T^2\left(x,t\right)={\displaystyle \frac{1}{N-1}}{\displaystyle \sum _{i=1}^N{\left[T_i\left(x,t\right)-\overline{T}\left(x,t\right)\right]}^2}\end{array}$$

(15)

The thermal insulation model, with both transient heat conduction and property uncertainty, is enhanced through these methods, enabling the computing process for temperature distribution statistics, such as mean temperature and temperature variance, to quantify the thermal performance and variability due to insulation property uncertainty. This approach provides insights into both the average thermal response from the insulation and the range of possible outcomes due to the variability in material properties, whilst the specified combination is particularly useful in assessing insulation materials’ reliability and robustness under real-world conditions.

5. Numerical Analysis and Results—A Practical Example of the Mathematical Model

CE emphasises the importance of minimising waste and maximising resource efficiency by reusing, recycling, and regenerating materials throughout their lifecycle. In the construction industry, the thermal performance of building materials directly impacts energy consumption and efficiency, which is a key consideration for both economic and environmental reasons. Thermal analysis refers to the evaluation of how materials conduct, store, and lose heat. This is an important aspect of maintaining energy efficiency and reducing heating and cooling loads in the construction and building sector. The relevant key parameters are the following. Thermal conductivity (TC) quantifies how a material conducts heat, and low thermal conductivity materials (insulators) help to reduce energy loss. Thermal resistance (R-value) refers to a material’s ability to resist heat flow, and high R-values are desirable for insulation. Thermal mass (TM) is the ability of a material to absorb, store, and release heat because materials with high thermal mass can stabilise temperature fluctuations within buildings. The U-value is the overall heat transfer coefficient of a building element (wall, window, etc.), and lower U-values mean better insulating characteristics.

CE seeks to close material loops and reduce the environmental footprint of production and waste. In the building industry, this includes a number of principles that promote some specific coordinates. First of all, the principle of reuse and recycling (RR) encourages the use of recycled materials and components that maintain or improve thermal performance. This minimises raw material extraction and reduces energy consumption during production. Another concept is represented by design for disassembly (DD) when buildings are designed in a way that allows for easy disassembly, promoting the reuse of materials without a loss of thermal efficiency. The material lifespan (ML) principle ensures that materials have a long lifecycle and can be used in multiple building projects, which can decrease the need for new materials and associated embodied energy. These principles and new approaches to buildings culminate in the application of building materials, which do not have the commonly known standard characteristics or thermal properties. These reused, recycled, or disassembled building materials will have irregular, inconsistent properties that must be appropriately measured and analysed to be used in CE building projects.

5.1. TheOutline of the Case Study

As a case study example, a thermal analysis exercise is conducted on three commonly used insulating materials: Polyurethane Foam (PUF), Fiberglass (Glass Wool), and Polystyrene. Each of these materials has specific thermal properties that significantly affect the thermal resistance (R-value), energy saving, and overall insulation efficiency. The typical thermal properties of each insulation material are presented in

Table 3. Material properties for numerical analysis.

Material	Thermal Conductivity [W/m·K]	Density (ρ) [kg/m3]	Specific Heat Capacity $\left({\mathit{c}}_{\mathit{p}}\right)$ [J/kg·K]
Cellular Clay Brick (CCB)	0.72	1345	1180
Polyurethane Foam (PUF)	0.02–0.03	30–60	1400
Fiberglass (Glass Wool)	0.04–0.045	12–40	840
Polystyrene (EPS/XPS)	0.033–0.04	15–45	1300

.

Thermal analysis seeks to evaluate how these materials perform in a typical multi-layer wall system. A typical multi-layer wall system is a cellular brick wall that can contain different types of insulation. The different types of insulating materials are presented in Table 3. The first part of the analysis is to identify the key parameters represented by thermal resistance (R-value) for each material, heat flux through the wall over a daily temperature cycle, and energy savings for cooling when insulation is applied. The second part of the analysis evaluates the possibility of retaining heat inside the building during the winter season.

Table 4. Insulation materials and masonry-type wall structure’s properties.

		Thickness [m]	Thermal Conductivity [W/m·K]
External Layer	Cellular clay brick	0.1-0.3	0.72
Internal Layer	Wood/Gypsum	0.025	0.12
Insulation Layer	Polyurethane Foam	0.05–0.3	0.022–0.028
	Fiberglass		1–1.05
	Polystyrene		0.034–0.038

below shows the insulating materials and the masonry-type wall structure’s properties used in the thermal analysis. The principal cases considered for thermal analysis are presented in

Table 5. The principal cases considered for thermal analysis.

Case 1	Case 2	Case 3
Thermal Resistance (R-value)	Heat Flux Analysis	Energy Savings
Analysis for calculation and comparison of the overall R-value of the wall for each insulation type	Analysis of the heat flux through the wall over time using sinusoidal external temperature variation (e.g., day/night cycle)	Estimation of potential energy savings due to insulation
The wall resistance is computed as the sum of the resistances of individual layers	The heat flux (Q) through the wall was estimated using Fourier’s Law	The energy required to maintain a constant internal temperature compared to an uninsulated wall
$R={\displaystyle \frac{d_{brick}}{k_{brick}}}+{\displaystyle \frac{d_{insulation}}{k_{insulation}}}+{\displaystyle \frac{d_{wood}}{k_{gypsum}}}$	$Q={\displaystyle \frac{1}{R}}\left(T_{ext}-T_{\mathrm{int}}\right)$	$E_s={\displaystyle \frac{1}{{\eta }_{cooling}}}\left(Q_{ins}-Q_{no-ins}\right)$

.

Results obtained from the numerical analysis are presented in Figure 3.

If the primary goal of the insulating methods is to retain heat within the building during winter time, then the analysis focuses on minimising heat loss from the building to the colder external environment. The analysis type is crucial for understanding how well the insulation materials can conserve energy for heating purposes, keeping indoor spaces warm despite cold external temperatures (

Table 6. Winter condition assumptions.

Environment Condition	Temperature Range [°C]	Assumption
Internal (T_int)	20:24	comfortable room temperature
External (T_ext)	−5:+5/−10:+10/−20:+20	simulating a typical winter/spring day/night cycle

). The same fundamental principles of thermal resistance and heat flux apply to winter conditions, where the external temperature is lower than the internal temperature.

The thermal resistance values (R-value) were calculated for each insulation material according to the actual conditions, as this value is crucial for minimising heat loss. The simulated conditions are for the heat loss values over a 24-h winter day for a wall insulated with Polyurethane Foam (PUF), Fiberglass and Polystyrene. The corresponding temperature profile for each insulation type is presented in Figure 4.

Further to the new initial condition assumptions, according to the cases presented in

Table 7. Estimated energy savings by comparing the heat loss with insulated and non-insulated walls.

Case 1	Case 2	Case 3
Winter Thermal Resistance (R-Value)	Winter Heat Loss Analysis	Energy Savings for Heating
R-value calculation for each insulation material, while the total R-value depends on the thickness of each material; higher R-values indicate better insulation, which reduces heat loss from the building to the external environment	Minimise the heat flux (Q) from the building to the external environment, since the winter conditions are declared, the internal temperature is higher than the external temperature, and the heat will naturally flow outward	The calculation of the energy saved by comparing the heat loss through a well-insulated/non-insulated wall

, the thermal analysis results of the insulated brick wall system are shown in Figure 5.

The numerical method provides us with a solution to obtain temperature distribution results of the wall structures for each insulation type with three different thicknesses. Figure 6, Figure 7 and Figure 8 below show 3D surface plots for insulated brick walls’ temperature distribution depending on time and insulation thickness.

The results of the above thermal analysis combined with the 3D temperature distribution plots show the numerical approach to tracking and investigating thermal properties of potentially reused, recycled, or disassembled building materials with irregular or inconsistent thermal attributes. The accurate and robust measurement of the thermal performance of reused, recycled, or disassembled building materials is a necessity to achieve CE in buildings and for the attainment of human well-being.

5.2. Indoor Temperature and Human Well-Being

The relationship between indoor temperature and well-being has been internationally recognised, and the WHO Housing and Health guidelines provide practical relevant recommendations [50]. The categorical cut-off point at 18 °C was chosen as there is no demonstrable risk to human health from air temperatures between 18–24 °C. The first systematic WHO review focused on the following priority health outcomes: (i) respiratory morbidity and mortality, (ii) all-cause mortality in infants, (iii) hospital admissions, (iv) cardiovascular morbidity and mortality, and (v) depression. The second systematic WHO review focused on (i) respiratory morbidity and mortality, (ii) cardiovascular morbidity and mortality, (iii) hospital admissions, (iv) all-cause mortality, (v) depression, and (vi) high blood pressure. Based on these two systematic WHO reviews, the issued guideline recommendation regarding 18 °C as a safe and well-balanced indoor temperature is strong, and the guideline recommendation regarding the efficient and safe thermal insulation of new housing and retrofitting in old housing is conditional.

In view of these WHO guidelines, and considering the fact that recycled materials have significantly different, irregular thermal properties, a very robust and systematic thermal analysis of the building envelopes is imperative.

This numerical engineering approach using mathematical modelling and following guidelines and standards is fundamentally different from the large overarching theories of eudaimonia. Although these two perspectives are very diverse and almost contradictory to each other, still, only the combined complementary application of these together can lead to synergistic results.

6. Discussion

Dewane’s chosen title, the ‘Eudaimonia machine’, is an oxymoron. The concept of eudaimonia is almost contrary to a machine, just like with Ingels’ title selection, where hedonism and sustainability are conflicting theories. The use of oxymorons in the titles attracts attention but also adds depth and complexity, evoking critical thinking. Consequently, Dewane’s approach can be seen as an experiment on how to bring eudaimonic well-being architecture into our mundane everyday work–life. Similarly, Ingels’ suggestion could be viewed as a proposal to make our hedonic, profane daily chores more sustainable, meaningful, and long-lasting. Dewane and Ingels both realised the need to create an architecture that integrates both eudaimonic and hedonic well-being tendencies. However, researchers such as Ehrenfeld, McGilchrist, Hutchinson, Csikszentmihalyi, and Chatterjee [24,25,28,32,51] offer further insights into this intricate balance between these two types of human well-being. They argue that our world is currently too focused on hedonia, which to a certain extent can be associated with a very logical, numerical approach producing purely physical, tangible results, while eudaimonia is insufficiently represented in the design of our buildings, environments, and life in general. As a result, human well-being, the sustainability of our buildings, and the broader environment are increasingly compromised.

7. Recommendations

To achieve true sustainability and align with CE objectives in buildings, the suggestion is to renew focus on the eudaimonic aspects of well-being—such as aesthetics, symbolism, long-lasting impacts, and timeless designs—without dismissing the hedonic. A careful balance between these aspects is necessary for achieving optimal human health and happiness within buildings and for making them truly sustainable and applicable to CE. In line with the principles of CE, which emphasise patterns in nature and harmony with natural systems, architecture and building design should mirror our inherent ways of perceiving and responding to the world. This is where the practical application of materials and design strategies can directly influence both human experience and environmental impacts. This is achievable with the direct involvement of the stakeholders from the very early design stage, during the whole design and construction process, and until the post-occupancy evaluation.

Looking at the logical, numerical, and more technical complementary approach to human well-being concerning buildings, and following the findings of the OECD publication, it is pointed out that one of the most important factors of human physical and mental health is thein-house thermal comfort. Consequently, the systematic and robust thermal analysis of the building envelope and wall structures containing recycled, reused materials with significantly altered properties can optimise energy efficiency in buildings, reducing both the environmental footprint and heating or cooling energy demands. Brick walls, when properly insulated, can enhance thermal comfort, contributing to a healthier living environment while lowering energy consumption—thus serving the dual purpose of improving occupant well-being (hedonic) and contributing to sustainable, long-lasting, and energy-efficient architecture (eudaimonic). Such design strategies align with the CE’s goals of reducing waste, improving material efficiency, and fostering a more sustainable, resilient built environment. When building systems like these are considered, the architecture of a building moves beyond mere function and form, becoming a conduit for deeper environmental and human flourishing.

8. Conclusions

The present paper investigates the social or human well-being aspect of the CE in buildings, a subject area still considered relatively unexplored by the academic community. The methodology used was a meta-synthesis approach, examining the limited available literature through the lens of CE in buildings. From the selected research papers, two distinct perspectives emerge concerning the association of eudaimonic and hedonic well-being with buildings and architecture. These perspectives differ significantly in terms of perception, approach, and overall interaction with our surrounding world. Researchers across various fields studying human well-being agree that both eudaimonic and hedonic tendencies play crucial roles in achieving optimal human happiness and well-being. Two contemporary architectural theories, ‘Hedonic Sustainability’ and the ‘Eudaimonia Machine’, are discussed as examples. Both theories emphasise the importance of balancing these two factors of human well-being in modern life. Researchers suggest that the hedonic well-being approach is currently too dominant in our built environments and everyday life. Therefore, greater awareness and emphasis on eudaimonic well-being are essential to meet our sustainability and CE objectives.

Furthermore, besides these very large-scale, comprehensive theories, which can be more closely associated with the right brain hemisphere, holistic, symbolic, synergistic, and contextual perspectives, the authors of this paper found it important to open an avenue towards a complementary, more nuanced, numerical, and logical approach that according to certain researchers is more closely associated with the left brain hemisphere. This second pathway seeks to shed light on human well-being from the logical engineering perspective using mathematical models, following building codes, guidance, and standards. Further to the findings of a recent OECD publication and WHO guideline, the thermal analysis of building materials, as an example, or conduit, within a CE context can provide a more thorough approach to sustainable construction whilst also contributing to human health and well-being. Effective thermal analysis ensures that materials are chosen and utilised to maximise energy efficiency, minimise waste, and extend the life cycle of resources, whilst they provide one of the most fundamental criteria for homeliness, warmth, and human well-being. This combined approach contributes to the more comprehensive overall well-being of occupants by providing comfortable, energy-efficient living spaces while promoting environmental stewardship.