Closing the loop in building services: A systematic review of circular economy applications

Introduction

Addressing environmental challenges remains a paramount priority across all industries. Nonetheless, the built environment continues to pose significant sustainability concerns. This sector is characterised by high energy and resource consumption and substantial waste generation.^1–3 Also, the industry’s greenhouse gas emissions have shown a concerning upward trend, accounting for an estimated 37% of global CO₂ emissions. ⁴ Despite undeniable economic and social benefits, a growing body of research highlights the detrimental environmental impacts of the built environment.^2,5,6 These impacts encompass the entire life cycle of construction projects, often called “cradle-to-grave,” including resource extraction, manufacturing, transportation, construction and end-of-life disposal.

The impact of buildings and their components on the environment can vary. The Building “shearing layers” concept, conceived by Frank Duffy and later popularised by Stewart Brand, offers profound perspectives on the dynamic nature of building structures and their evolution with time. Various layers, including site, structure, skin, services, space plan, and stuff, have distinct lifespans and impacts on sustainability and building performance. ⁷ These layers can then be categorised into fast- or slow-changing based on their frequency of replacement or repair. The building services layer, referred to by Brand as “the working guts”, wears out and changes frequently and can impact the lifespan and overall performance of a building.

The Chartered Institution of Building Services Engineers (CIBSE) ⁸ and The Royal Institution of Chartered Surveyors (RICS) ⁹ categorised building services into thirteen categories (sanitary, disposal, water, ventilation, space heating, air conditioning, and others). However, The American Society of Heating, Refrigerating and Air-Conditioning Engineers ¹⁰ outlined HVAC across five applications (comfort, industrial, energy-related, building operations and management, and general applications). The most common categorisation includes Mechanical, Electrical, and Plumbing (MEP) and Heating, Ventilation, and Air Conditioning (HVAC). Despite their vital functions, building services are responsible for a high proportion of energy consumption and carbon emissions, leading to significant environmental impacts.^11,12 In the UK, for example, the built environment represents 42% of total CO₂ emissions, of which 16% are from operational energy consumption by building services. ¹³ However, various assessments to advance sustainability in the construction industry often neglect building services and focus on building structure and envelope.^14,15

Building services and their components are usually complex, sophisticated, cost-intensive, and encompass numerous materials.^15–17 CIBSE ¹⁸ outlined the commonly used primary raw materials, such as metals (copper, steel and aluminium), plastics (polyvinyl chloride, acrylonitrile butadiene styrene, and polyethene), rubber (rubber, silicone, neoprene, and ethylene propylene diene monomer), adhesives and sealants (epoxide resin, silicones, and acrylics), and insulation (fibreglass, mineral wool, and cellulose).

Building services also require frequent maintenance, repair, and replacement, resulting in higher embodied carbon.^19–22 In new construction, MEP systems can represent 2 to 27% of embodied carbon, reaching up to 75% in retrofit and continuously increasing over the system’s lifespan.^18,23 While the building structure and envelope often have a lifespan of 50 to 100 years, building services have a lifespan of 15 to 25 years, and even less, most times.^24,25 Also, building services represent 30 to 60% of capital cost, sometimes reaching 75% in medical uses and up to 90% of operational costs of buildings.^16,25

In-depth studies on building services’ embodied carbon and environmental impact have outlined the significant adverse effects and recommended a paradigm shift towards a circular economy.^26–28 A Circular Economy (CE) is a regenerative or restorative business concept that replaces the “end-of-life” theory, advances renewable energy, eradicates toxic chemicals hindering reuse, and aims to eliminate waste by intentionally and carefully designing resources, goods, systems, and economic models. ²⁹

The evolution of CE is founded on various archaic concepts: industrial ecology and symbiosis, cradle-to-cradle, Commoner’s four laws of ecology, performance economy, biomimicry, regenerative design, natural capitalism, and the Slowing, Closing and Narrowing Resource Loops.^1,30 Various frameworks to advance the circular use of resources and waste reduction are emerging, like the four distinct resource loops: narrow, slow, close, and regenerate.^1,31,32 The 4 Rs principles of “reuse”, “reduce”, “recycle”, and “recover” have also emerged and remain dominant across various sectors. ³³ Though noting the use of up to 38 Rs, Reike et al. ³⁴ united diverging perspectives and recommended 10 Rs. Adopting CE implies that resources are preserved and retained in a continuous usage loop, as opposed to the traditional one-off consumption and disposal in the linear economy. ³⁵ Often, the smaller the loop, the less energy and resources are required.

The CE model proffers a solution within the construction sector by promoting recycling and reuse of resources, waste reduction, and energy efficiency. ³⁶ Existing approaches aligned to the application of CE in construction include design for disassembly, passive design, environmental product declarations, recyclability and reusability, urban mining, energy efficiency and zero carbon buildings, life cycle analysis, material passport, buildings as material banks, products-as-a-service, local resources use, waste reduction, and deconstruction.^2,6,37–39 Spanning through the various stages of the building lifespan, these approaches are pivotal to a sustainable and resource-efficient construction industry. McConahey ⁴⁰ emphasised that findings on the global warming potentials of building services must prompt building designers to explore CE principles critically.

While the real-world deployment of circular solutions in building services is minimal, some pioneers have set the pace in their projects and businesses. Grundfos, an HVAC pump manufacturer based in Denmark, has focused on eliminating landfill waste, streamlining its production process, and reducing energy usage and material consumption. ²¹ They implemented a take-back programme on pump circulators to remanufacture and recycle components and reduce waste across seven EU countries.^23,41 In 2022, Grundfos reduced total landfill waste by 32% since its baseline year and collected 64,288 kg of pump circulators. ⁴¹

Another pioneer of CE solutions in building services is L∞P by Daikin, launched in 2019 to recover, reclaim, and reuse refrigerants. ⁴² Reitmeier HVAC Services in the US has also recovered air filters from its clients since 2016 and collaborates with an energy-from-waste (EfW) facility to produce energy from these air filter wastes. ²³ Circular business models have also been explored for building services, such as Philips “light as a service” and Kaer “cooling as a service”.^13,21 In the lighting industry, the shift from conventionally lamped luminaires to energy-efficient light-emitting diode (LED) luminaires resulted in an unmaintainable product with a shorter life span and a complex supply chain. ⁴³ Recognising these unintended consequences, CIBSE ⁴³ developed technical guidance for all stakeholders to advance circularity in the lighting industry.

Though minimal, some research outputs have considered CE in building services.^21,23,27,44 Most related research outputs on CE and building services have focused on life cycle assessments,^{14,26,45–47} embodied carbon,^{15,18,19,47–49} material flow analysis, ⁵⁰ and environmental assessments. ⁵¹ Rabie and Sjöholm ²⁸ examined the adaptive reuse of HVAC components within an office-building case study in Sweden. Stiglmair and Jurkait ⁵² also outlined guidance for engineers to implement cradle-to-cradle in building services design.

However, the application of CE in building services is still nascent and has experienced very little research.^23,27,28 The advancement of CE in building services is constrained by knowledge gaps and the multifaceted supply chain, which mostly requires products and sub-components from third-party suppliers.^21,27 Robust market insights and circular options to replace existing HVAC systems are also not widely available, and stakeholders hesitate to incur the initial capital required to explore new circular solutions. ²³ Essentially, a shift in the supply chain and business model of building services is necessary, and building services is a “golden spot” for implementing CE principles. ²¹

Despite numerous literature reviews on CE in construction, ⁵³ no review studies broadly examine the application of CE in building services and components. A critical review by Seuntjens et al. ⁵⁴ focused on only ventilations in adaptable buildings, excluding many other building services components. Therefore, this paper aims to fill the knowledge gap by examining current knowledge on the application of circular economy to close the resource loop in building services. The paper systematically reviews existing literature to identify the current applications of CE in building services, and identify recurrent barriers and opportunities, key influencers, and map out recurrent strategies for improved application. This review is vital for influencing improved research and industry efforts in this subject area, ultimately advancing sustainable buildings and construction. The paper is organised in five sections. The next section outlines the methodology. This is followed by the analysis of the systematic review which is in two parts; descriptive and thematic. There then follows a discussion that presents a framework and identifies the gap in the research. The paper draws to a close with the conclusions.

Methodology

The study conducted a systematic literature review (SLR) of research outputs in existing databases, as adopted in numerous related research outputs.^55,56 SLR is useful in developing frameworks for future research by analysing and mapping existing knowledge from a large body of literature. ⁵⁷ The preferred reporting items for systematic reviews and meta-analyses (PRISMA 2020) guideline was utilised to search, evaluate and extract the literature metadata for the SLR. ⁵⁸ As an evidenced-based framework, this guideline has also been adopted in numerous SLRs related to circular economy in the building and construction sector.^59,60

Web of Science (WoS) and Scopus were adopted as the primary databases for extracting the existing scientific outputs. Using multiple databases ensures an extensive coverage of bibliometric data, and these two represent the most influential digital databases for scientific research globally. ² Considering that many relevant outputs on circularity in building services exist outside academic and scientific databases, the SLR includes relevant published outputs from external sources. This approach is regarded as best practice ² and will “supplement results retrieved from a citation database with additional publications to reach the desired level of completeness for the study at hand”^{61, p.66}.

The search syntax deployed for extracting the existing scientific outputs includes a combination of keywords related to the research area and adopting various Boolean operators as defined below.

1. Circular Economy AND “Building Services”

A wild card (*) is also attached to some words to ensure the inclusion of their various forms and plurals, and quotation marks and brackets were used to ensure an exact match. The keyword for HVAC adopted only “heating ventilation” based on the notion that the term usage always commences with these two words. The search in both Scopus and WoS was set to be performed within the article titles, abstract and keywords. Even though the advocacy of CE received tremendous attention during the last decade, no year range was applied to the search since CE is rooted in various archaic concepts. The literature search was inclusive, without restrictions on article types, subject areas, or countries of origin. However, only literature published in English language was considered for ease of review and analysis.

A total of 301 publications were retrieved from both databases in June 2024, as shown in the PRISMA flow diagram in Figure 1. Overlapping duplicates (86) from both databases were removed, resulting in 215 publications. 23 publications were also considered for screening from external sources. Before screening using various inclusion and exclusion criteria, this bibliometric data was collated in EndNote and exported to VOSviewer.OPEN IN VIEWER

The network visualisation in Figure 2 displays terms that occur in titles, abstracts and keywords of the bibliometric data selected based on a 60% relevance score of terms with a minimum of five occurrences. The proximity of terms depicts the occurrence relationship, while the size variation represents the frequency of occurrence. Four notable clusters are observed, with “building service” representing the link between all the clusters. While there are many terminologies, only the red cluster visually represents the terms directly relevant to the research focus, indicating that only a few publications in the bibliometric data would be appropriate to the research.OPEN IN VIEWER

Various inclusion and exclusion criteria were then utilised across three screening stages to determine the publication to be included in the SLR. A first-stage manual screening was conducted on the titles and abstracts of all the publications to review the alignment of the publication with the research focus. Only 38 publications aligned with the research focus, as earlier projected by the VOSviewer mapping technique. Many of the publications initially retrieved from the databases used the search syntax in other contexts, such as “circular” representing “round” and building services used in the context of “service life of buildings”. Some other publications, though relating to buildings’ HVAC, focused on regenerated energy, recycled water and reusable fluorinated gases rather than the building services components.

A second stage screening of the title, abstract and conclusions was conducted to decide on publications to be retrieved. The screening ensured that the publication had a strong connection or recommendations regarding building services and circular economy. 17 publications were excluded. A third-stage screening retrieved the full text of all the 21 articles included. A quick scan-through was done by searching for “building services”, “mechanical, electrical, and plumbing”, “MEP”, “heating, ventilation”, or “HVAC” to understand the exact use cases of these search syntax within the full article of the publications. Two publications with no full text available as of the review were excluded. Eight publications did not fulfil the inclusion criteria, resulting in only 11 publications in the SLR.

At stage 3, 14 other relevant publications on circularity in building services previously identified from websites, journals, and universities were considered. Snowballing was also conducted to identify relevant articles that did not appear in the database search by reviewing the references and citations of all included. Nine publications were identified for screening via references and citations. Observation revealed that some of these articles were initially omitted from the database syntax search because of the word choice, such as “technical services” and “comfort systems”. A total of 23 publications were therefore considered from external sources for screening. The full text of these publications was retrieved and reviewed to examine relevance to the research focus. Five articles did not fulfil the inclusion criteria and were excluded. Some excluded publications outlined the technicalities of how new building services components function in adaptable buildings. After in-depth screening, only 18 articles from external sources were included in the SLR.

The retrieval and screening of all the bibliometric data in three stages for the systematic literature review is outlined in the PRISMA flow diagram in Figure 1. While the study is believed to represent the existing body of knowledge on the focus area, the research was conducted within the limitation of the availability of relevant literature, scientific databases and sources, language restrictions, and time constraints.

Results

The analysis of the SLR is presented in two categories. The descriptive analysis outlines the results identified from the bibliometric data of all the publications included in the SLR. This analysis is essential for contextualising the systematic review procedure and the thematic outcomes. ⁶² The thematic analysis outlines various research axes based on patterns and parallels.

Thematic analysis

The thematic analysis of the literature identified four key themes. The first theme identified the recurrent limitations and barriers identified by the various publications. Based on similarities and affinity, the limitations and barriers are categorised into four axes: technical, economic, legislative, and organisational. 79% of the literature mentioned technical barriers, 72% included economic barriers, 55% outlined legislative barriers, and 59% mentioned organisational barriers.

The second theme examines the opportunities for implementing circular building services. 76% of the literature identified the opportunities and benefits of implementing CE principles within the building services sector. The third theme considers the role of various stakeholders across the building services supply chain. The six major key influencers are noted in the literature. Their frequency of occurrence includes clients (31%), manufacturers (45%), designers – architects and planners (55%), MEP engineers (28%), developers and contractors (45%), and policymakers (14%).

The fourth theme outlines the various strategies outlined across the literature to advance/enable CE applications in building services. These strategies are categorised under nine axes based on similarities. These include design (76%), business model (55%), policy (31%), product information (31%), warranties (24%), life cycle costing (17%), digital technology (24%), education (17%), and collaboration and transparency (17%). Table 1 outlines the exhaustive list of all the identified publications for the SLR and their corresponding opinions on the four key themes from the findings.

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Table 1.

Summary of findings from publications included in the systematic literature review.

Author	Type*	Country	Outline	Barriers	Opportunities	Key influencer	Strategies
Webb et al. 64	JA	UK	Article	α γ	√	θ	ν π τ
Webb et al. 63	CP	UK	Article	α β	√	λ	ν π τ
Thomson et al. 65	JA	UK	Survey	α β γ ε	√	ζ κ λ	τ
Thomson et al. 66	CP	UK	Article	α β γ ε	√	ζ κ λ	π
Webb et al. 67	JA	UK	Framework	α			τ φ
Olnhoff and Martin 68	B	UK	Guideline	β γ ε	√	η μ	π ρ
Addis 69	B	UK	Guideline	α β γ ε	√	η θ λ μ	ν σ τ
CIBSE 22	B	UK	Guideline	α β γ	√	η θ	ν π σ φ
Afify 70	JA	USA	Opinion	α β		ζ θ	ν
Croxford et al. 21	TR	UK	Case study	α β γ ε	√	η θ	ν π ρ φ ψ
Ciugudeanu et al. 71	JA	Romania	Case study	α ε			ν
Jurkait and Stiglmair 72	CP	Germany	Review	β ε	√	ζ η θ κ λ	χ
Stiglmair and Jurkait 52	B	Germany	Guideline	β ε	√	ζ η θ κ	ν π σ
CIBSE 13	B	UK	Guideline	α β	√	η θ λ	ν π ρ ω χ ψ
UKGBC 73	TR	UK	Guideline	γ	√	ζ η θ λ	ν π ω
CIBSE 43	B	UK	Guideline	α γ ε	√	ζ η θ	ν π ρ σ τ φ χ
Oosting 27	TR	Netherlands	Opinion	α β γ ε	√	η	ν π σ
Chai et al. 74	JA	China	Framework	α γ		λ	ν
Loreau et al. 75	CP	Greece	Case study	α	√	κ
Loreau et al. 50	CP	Belgium	Case study	α β ε	√		π σ
Seuntjens et al. 54	JA	Belgium	Review	β		θ κ	ν π ω
Theißen et al. 14	CP	Netherlands	Case study	α γ ε	√	θ μ	ν σ ω φ
Lundgren et al. 76	JA	Sweden	Case study	α β ε	√	θ λ	ν π ψ
Mohamad et al. 77	CP	Malaysia	Case study	α β γ ε		λ	ν ρ
Patil 23	T	Netherlands	Interview	α β γ ε	√	ζ η θ κ λ	ν π ρ σ ω φ ψ
Zainal Abidin 78	CP	Malaysia	Case study	β			ν
Kaarmila 79	T	Finland	Case study	α β γ ε	√	η θ	ν ρ φ χ
Pichlmeier and Lindner 44	JA	Germany	Case study	α β	√	θ λ	ν ρ σ χ
Rabie and Sjöholm 28	T	Sweden	Case study	α β γ ε	√	ζ η κ λ μ	ν π ρ τ ψ

*JA: journal article; B: book; CP: conference paper; TR: technical report; T: thesis; α: technical; β: economic; γ: legislative; ε: organisational; ζ: clients; η: manufacturers; θ: designers; κ: MEP engineers; λ: contractors; μ: policymakers; ν: design; π: business model; ρ: policy; σ: product information; τ: warranties; ω: life cycle costing; φ: digital technology; χ: education; ψ: collaboration.

Discussion

The discussion of the SLR result is structured into three segments. The discussion of the descriptive analysis is presented, followed by the discussion of the various themes identified in the literature. In conclusion, the research gaps identified from the literature are also outlined.

Conclusion

The systematic literature review has outlined the current state of knowledge on closing the resourcing loop in building services, which is a component for ensuring comfortable and safe internal building environments. The review identified the current application of CE in building services, recurrent barriers and opportunities, key influencers, and strategies for improved application. After a 3-stage literature screening from two databases and external sources, 29 publications were included in the review. While this review offers an exhaustive evaluation of the state of knowledge regarding the application of circular economy in building services, the limitation to only literature published in English may have excluded relevant articles. Also, while the addition of publications from external sources enriched the review, relevant literature may have been omitted due to the requirements to define exclusion and inclusion criteria when conducting a systematic review.

The findings from the review indicate that while the adoption of circularity in building services has attracted attention in recent years, the research efforts within this industry are still nascent, especially when compared to the research on broad CE applications in construction. Exploratory research and guidelines are the highest publication outputs, representing the need for pragmatic solutions. The concentration of research within Europe can be attributed to public policies and legislation driving market demand and need. Even though building services are characterised by a complex supply chain, most solutions for advancing CE within the broad construction sector also apply.

Four key themes were identified from the review, including barriers and opportunities, key influencers, and strategies for advancing and enabling circular building services. Based on the similarities, the barriers were categorised into four axes: technical, economic, legislative, and organisational. The technical barriers are mainly product obsolescence, rigorous maintenance, performance gaps, lack of standardised methods, and complex retrofitting processes. The need for technical modifications and possible increased energy consumption that building services components may exhibit when reused were also identified. Also, when conducting life cycle assessments, building services are sometimes omitted or represented in simplified manners because of the complexity of manual calculations and lack of granular information. Economic barriers were also identified as part of the limitations for circular building services. The high cost, logistics impact, low volume, and short lifespan of building services products often inhibit circularity. The absence of a secondary market and no clarity of financial incentives also pose economic barriers.

Stringent performance standards and policies often result in legislative barriers. Older building services frequently fall below the necessary targets for energy efficiency, thermal comfort, and energy consumption. The absence of performance-based specifications, standardised environmental auditing, and clear policy guidance exacerbates these issues. Organisational culture and entrenched practices and mindsets also hinder circular building services. The lack of knowledge sometimes results in clients and professionals restricting the implementation of circularity. An apathy towards environmental issues and the fragmented supply chain also hinders. The need for committed professionals across the building services supply chain remains a deterrent to applying a circular economy.

Beyond these barriers, the review identified various opportunities for implementing a circular economy. Implementing circular practices should minimise waste, reduce demand for virgin materials, lower emissions, and enable resource-efficient construction. Economic benefits are also envisaged, like reducing capital cost and price volatility risks and ensuring long-term resource availability. New business models are also expected to emerge, unlocking market development and economic opportunities. Deploying digital technologies for circularity also ensures effective manufacturing, construction, operations and lifecycle information management.

While a collaborative effort is required across the entire supply chain, six professionals are considered key influencers for circular building services. Clients and building owners are pivotal for creating the demand and spurring necessary commitments across the supply chain. Manufacturers can influence innovations through product design, policy alignment, resource efficiency, and reducing product emissions. Design teams, comprising architects and planners, are essential to the most critical stage to influence circularity. MEP engineers are regarded as the most reliable in implementing circular economy by ensuring the necessary evaluation of functionality and legislative compliance. Contractors, both for installation and demolition, can ensure on-site implementation and effective deconstruction. Legislators create the enabling environment through policies and incentives.

The review developed a framework for advancing circular economy in building services, integrating the nine strategies identified with existing principles and building blocks. Strategies like design for disassembly, passive, and modularity must be adopted during the design stage. Service-based business models, such as leasing, product-as-a-service, and renting, would ensure that products remain within the manufacturer’s supply chain, and they assume responsibility for maintenance and recycling. Policies and regulatory frameworks must not contradict circularity objectives but encourage and incentivise. Systems, like material passports and labelling, must be adopted to provide insights into history, environmental impacts, and product reuse potential. Warranties and performance guarantees build trust and confidence for reused products.

Other strategies included in the framework include detailed life cycle cost assessments to evaluate building services products’ long-term value and environmental impacts. Adopting digital technologies is also vital to facilitate data-driven collaboration, track usage, connect demand and supply, and store life cycle data for efficient operations and management. Educating stakeholders and raising public awareness is essential; this responsibility also lies with professional bodies. Finally, collaboration and transparency between all stakeholders are necessary for advancing the shift to a circular economy. The strategies outlined in the framework are pivotal for enabling circular building services.

Various research gaps identified from the review offer further areas of concentration and evaluation. Guidelines are required to enable the reuse of existing building services. Evidence-based research into deploying new business models is essential to increase adoption. Empirical research on deploying multiple digital construction technologies to enable a circular economy in building services is also vital. Ultimately, new skills, shifts in mindset and holistic solutions are required to advance and enable the application of circular economy in building services.