Keywords

1 Introduction

The world is on the brink of a climate catastrophe, and to limit warming to 1.5 °C above pre-industrial levels, global greenhouse gas (GHG) emissions must decline by 43% by 2030, falling to net zero by 2050 [1]. This is a challenge because more than half the world’s population lives in cities, and accounts for more than 70% of global GHG emissions [1]. Cities are drivers of economic growth, contributing more than 80% of global GDP, however, the rapid and poorly planned urbanization leads to many challenges, including a shortage of affordable housing, high rates of residents living in slums or informal settlements, insufficient infrastructure, limited open spaces, unsafe levels of air pollution, and increased climate and disaster risk [1].

Access to adequate housing has been a challenge for a significant part of Brazilian residents. In 2019, the housing deficit in Brazil was estimated at 5.9 million households [2]. Of the 70.6 million Brazilian households in 2019 [3], 44% were framed with a deficit or unsuitable housing [4]. In addition to the housing deficit, it is necessary to plan the housing provision for a population estimated at 232 million inhabitants in 2040, which means 17 million more inhabitants than in 2022 [5].

Since 2009, with the creation of the National Housing Plan (PlanHab), Brazil has had the Minha Casa, Minha Vida Program (MCMV), which supported the production of around 4.5 million housing units for the population with income of up to 10 minimum wages [6]. The MCMV was a recurrent theme in the Brazilian political scenario and represented a break with previous practices by bringing the issue of housing to the center of the government agenda [7]. The program enables access to housing for the low-income population, historically excluded from financing for home ownership [7]. However, it presents challenges that need to be overcome due to the standardized and large-scale production of housing units, poorly inserted and isolated from the city, contributing to the maintenance of social and spatial inequalities [7, 8].

The development of the MCMV brought other challenges to environmental and urban planning. Apart from equipping houses with solar heaters, justified mostly as a strategy to reduce electricity bills for poor families, and the introduction of sewage collection and treatment in the housing project, MCMV did not follow any environmental policies, since the PlanHab 2008–2023. Housing projects introduced a temporary increase in the consumption of building materials—cement, steel, and bricks made up the bulk of material consumption—with a broad environmental impact. At the city level, it also increased sharply the construction and demolition waste (CDW) generation, causing a significant impact on the environment and even in city-related waste management costs and directly impacting public health management and urban drainage [7]. Additionally, because the housing projects were located mostly on the outskirts of cities it introduced a new vector of urban development, requiring municipalities to reassess and expand the network of community facilities and public services [6], increasing the construction-related impacts.

Nowadays the Brazilian government preparing the PlanHab 2040, which aims to the double challenge, improving housing conditions and urbanization meanwhile mitigating environmental impacts. Besides climate-related policies, circularity can become an important aspect for PlanHab since housing makes up the bulk of construction materials consumption, which represents more than 50% of natural resources and generates about 60% of Brazilian urban solid waste [8, 9]. CE is considered instrumental even for the mitigation of GHG emissions and indispensable for maintaining resource security [9].

The preparation of PlanHab 2040 seeks to create a sustainability agenda for social housing (SH) in Brazil, with objectives and strategies to reduce environmental impacts, increase resilience, guarantee performance, optimize costs, and combat social inequality. For the Brazilian construction industry, these proposals aim to minimize the use of resources and waste generation through the more efficient use of resources, seeking to promote the circularity of materials in the construction value chain. To operationalize these strategies, actions, and indicators are being developed to monitor the progress of the proposed goals, throughout the next PlanHab cycle.

From the perspective of how public policies can encourage the adoption of circular principles in the construction of the built environment, this study presents the proposal of circular indicators in the new 2040 Brazilian Housing Plan. Circular performance indicators are analyzed, aiming to reduce the consumption of construction materials and the generation of CDW. The development of consistent circular indicators will serve as a tool for the formation of benchmarks and performance standards to support decision-making and improve environmental performance during the life cycle of housing units and the quality of life of residents.

2 Background

2.1 Sustainability and Circularity in Social Housing Production

The adoption of the circular economy (CE) is one prerequisite for sustainability. Sustainable housing must present adequate performance, that is, it must be safe, healthy, and comfortable, meanwhile presenting initial and running costs compatible with long-term family income. The total housing cost is frequently neglected in public policies. About 10.4% of the European Union (EU) population cannot pay rent and the costs of housing services (water, gas, electricity) absorb about 40% of income [10]. In Brazil, the excessive rent burden is the main component of the Brazilian housing deficit, corresponding to 52% of the deficit or 3.0 million households [2].

CE is a model that offers the opportunity to reduce resource use, through end-of-life replacement strategies such as reduction, reuse, and recycling of materials in production/distribution and consumption processes. A circular building optimizes the use of resources while minimizing waste throughout its life cycle [11]. It is a business opportunity for innovation and circular value creation for the construction sector [11, 12].

Measuring the actual environmental performance of construction is essential to reducing environmental impacts because it encourages not only building design optimization, and careful selection of material but also procurement of the most eco-efficient supplier for each material improved construction site management or seeking a more efficient building operation scheme [13]. This requires relevant performance indicators, as they represent key components for describing the environmental, social, and economic impacts of buildings [14], coupled with mitigation goals supported by a robust benchmark baseline. It is also required to establishing not only minimum acceptable performance over time but a system to track the aggregated variation of each performance indicator for all housing projects [14].

Environmental performance indicators must have priority, measurability; reliability; comparability, and understandability [13]. Excess of indicators implies a large burden of data collection, and the priority is to reduce the number of indicators that meets the expectations of decision-makers. Measurability to facilitate data gathering at a low cost. Reliability ensures stakeholders trust the indicators, which foster its introduction in actual decision-making. Comparability enables benchmarks and the evaluation performance over time. Comprehensibility is a prerequisite for engagement and for a clear understanding of each indicator by those involved in the construction value chain [13].

2.2 Circularity in Social Housing

The literature consulted on social housing refers mainly to the themes of energy efficiency, climate change, and economic development. The European Energy Package 2030 suggested testing initiatives in public housing to achieve EU targets on energy efficiency, energy costs, and environmental sustainability [10]. Few reviewed studies explicitly examine the circular transition of the housing sector. For the Dutch social housing sector, the implementation of CE is in the experimental phase. In interviews with representatives of social housing organizations in the country, none of the represented associations has completed a circular project so far, but almost 80% of them are carrying out circular pilot projects [15].

In Italy, design solutions to improve the energy and environmental quality of public housing have been carried out with the involvement of inhabitants to define new design strategies and to program long-term sustainability [10]. In Milan, a project for the renovation and revitalization of a neighborhood proposed a functional and social mix of housing, with flexible spaces, green design, renewable energy, CE criteria, and continuous maintenance to drive social revitalization and improve equity, safety, comfort, energy efficiency, and sustainability [10].

Recent experiences on the implementation of circular principles in social housing in Denmark have focused on the development of flexible and adaptable housing, considering the intended lifespan of each of the building layers, optimizing the longevity of the construction, and maximizing the recovery of 90% of material at end of life [16]. The Circular Economy Plan for Housing Regeneration in the United Kingdom developed by KLH Sustainability and Clarion Housing [27] considered a set of activities such as demolition for recovery, products with high-recycled content, supply chain integration, and construction waste management, aiming to eliminate and reduce waste before considering conventional management opportunities such as recycling [17].

3 Research Strategy

The research has a qualitative approach; specifically, we used the case study method, which enables researchers to obtain in-depth and comprehensive information about the phenomenon in its natural context [18]. This research describes the case for the proposal of circular indicators to be included in the sustainability axes of the Brazilian National Plan of Social Housing. The process of proposing the circular indicators included weekly meetings with the academic team from interdisciplinary disciplines and government representatives. The authors reviewed relevant literature and documents and discussed their ideas in an iterative and interactive process (Fig. 24.1). The proposed circular indicators were consolidated after discussion and analysis by the team.

Fig. 24.1
An illustration of the proposed circular indicators includes weekly meetings, bibliographic research, documental research, and discussion and analysis.

Research strategy adopted for the proposal of circular indicators

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4 Possible Indicators of Circularity

4.1 Aspects Related to Housing

The construction sector has a large potential for CE, given the scale of material use, the value contained in buildings, labor intensity, and the long-term effect of measures adopted in buildings [19]. In long-term resource use and waste generation, minimization can be achieved by longer service lives, which keeps materials and resources in use as long as possible. Therefore, the measures to be adopted are based on the incorporation of secondary materials in the construction of buildings and the reduction of wasted resources in the manufacturing/construction process of building products.

Design criteria are particularly important for the built environment because a building is a complex object consisting of different layers with different life cycles, making it difficult to assimilate a single circularity analysis [19]. The building circularity index can change according to the life cycle stage [20]. Whether a building is in the design stage or under construction, one can think of following circular principles, making its design and space flexible and adaptable. This facilitates the reuse or recycling of products and materials used in the building when their useful life ends. For existing buildings, circularity can be improved through requalification and choice of products and materials that are reused, recycled, or that allow better energy efficiency in the building. If a building is at the end of its life, products, and materials can be reused or recycled. Therefore, even if a building is not circular during its lifetime, it can influence and provide opportunities for other buildings to improve their circularity [20].

The circularity percentage is calculated by taking the weighted average of the circular inflow and outflow of material (Fig. 24.2). Key considerations in measuring this circular flow are monitoring the type of material, the percentage of materials reused and recycled, and the recovery of materials at end of life. There is no standardized methodology and existing circular indicators are being discussed. Therefore, benchmarks, standards, and key performance indicators must be defined [20]. The circular inflow is the mass of non-virgin or sustainably sourced renewable materials used in the building. The circular outflow is calculated by multiplying the potential recovery factor by the percentage of materials recovery after the end of the product/building life [20].

Fig. 24.2
An illustration depicts the material flows within a building. It includes the circular inflow of secondary and renewable sources, social housing, circular outflow, linear inflow of non-renewable virgin sources, percentage circular index, linear outflow of non-renewable products and waste streams, and landfill incineration.

Scheme of linear and circular material flows within a building (adapted by WBCSD [20])

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The mass of the materials used in a building is an important consideration in measuring circularity, but not the only one. Additional variables must be considered, such as how materials were transported and how the building was constructed [20].

4.2 Material Demand Indicators

Material demand (MD) is the sum of the materials necessary to produce a given dwelling, including waste in its entire production chain, divided by the housing unit (t/HU) (24.1). MDt is the total demand for materials; Mi is the mass of primary materials in the product i; HU is the number of housing units in a project, or it can be the built area of the house/project.

$${\textit{MD}}_{t}=\frac{\sum i{M}_{i}}{\textit{HU}}$$
(24.1)

Within the same construction technology, the environmental impact and the cost are approximately a function of the mass of materials used, so dematerialization improves the performance of this indicator. Lower construction mass will imply less demolition waste. The mass of a material is important information on the production process, and easy to measure, and understand. From the builder's perspective, the main goal of the intensity of materials is to reduce the mass of the building, and, therefore, the indicator can be expressed in kg/m2 [21]. Compared with a proper benchmark it allows to track of construction dematerialization.

Amount of secondary material in the housing unit (t/HU). Circularity requires substituting virgin raw materials with secondary materials. The use of renewable or secondary (reuse or recycling) and end-of-life materials are an option to reduce the demand for natural resources. Therefore, the total material demand can be expressed as the sum of primary and secondary raw materials, and the total material demand of a housing unit can be expressed as Eq. (24.2).

$${\textit{MD}}_{t}=\frac{\sum i{M}_{p}+\sum i{M}_{s}}{\textit{HU}}$$
(24.2)

Mp is the mass of primary materials in the product i; Ms is the mass of secondary materials. This indicator is used to monitor progress towards a CE in secondary raw materials. The indicator measures both a country’s ability to produce secondary raw materials and its effort to collect waste for recovery [22].

Demand for renewable material used in the housing unit (t/HU). Total material demand can also be disaggregated into materials from renewable and non-renewable sources (24.3). Renewable materials comprise cultivated or native biomass from sustainably managed areas. Non-renewable materials include metallic and non-metallic minerals, petroleum (used as a raw material to produce plastic), and native biomass from areas of unsustainable management, that is, areas managed with an intensity greater than that necessary for the recovery of the forest [13].

$${\textit{MD}}_{t}=\frac{\left({M}_{p,ren}+{M}_{p,nren}\right)+{M}_{s}}{\textit{HU}}$$
(24.3)

Mp,ren is the mass for renewable primary materials in the product i; Mp,nren is the mass for non-renewable primary materials.

Circularity index (%), considers the amount of primary renewable and non-renewable, and secondary material (24.4). Values can range from 0 to 1. Higher values represent a higher roundness rate.

$$\textit{IC} = \frac{{\sum M_{s,} + \sum M_{p,ren} }}{{\sum M_{p,ren} + \sum M_{p,nren} + \sum M_s }} \times 100.$$
(24.4)

4.3 Waste Generation Indicator

Amount of waste generated at the end of construction of the housing unit (m3/m2 or t/m2) (24.5). WG is the waste generation rate (mass or volume/HU); Wi is the amount of waste generated during construction (mass or volume); HU is the housing unit.

$$\textit{WG} =\frac{\sum Wi}{\textit{HU}}$$
(24.5)

In Brazil, the generation of waste at the end of a building is regulated by Law No. 12,305/09, which provides for the National Solid Waste Plan [23], and CONAMA Resolution No. 307/02, which establishes guidelines for the management of civil construction waste. In addition to separating waste by class, the creation of a Construction Waste Management Plan is required for large generators, establishing the necessary procedures for sorting, storing, transporting, and disposing of the waste generated in an environmentally appropriate destination.

5 Discussion

Consistently measuring circularity and adopting a standardized approach are important to enable stakeholders to understand the level of circularity of their buildings and determine actions to improve their performance, accelerating the shift towards a sustainable built environment [20]. The main advantages of a circular assessment approach are to pay more attention to the renewability of the input resources, focus more on the use phase and the possibility of reapplying products, and introduce the assessment of the potential recoverability of the product at the end of its useful life [19].

The proposed indicators are multiscale and can be used at the level of buildings, suppliers, a city, or globally. They were designed for SH but can be used in other buildings, even if they are not part of public housing policies. In addition, they can be used both for new developments and for the requalification of existing homes and neighborhoods, which is a circular strategy. The application of the indicators suggests a reduction in the mass of construction and waste generation. Dematerialization, reduction of losses and residues, reuse, and recycling increase in the intensity of use and useful life, and use of less energy-intensive materials are strategies for the efficient use of materials and allow reductions in GHG emissions.

The majority of the indicators are related to the inflow of materials and one to the outflow of materials, aiming to obtain a balance of input and output of materials during the construction of a housing (Fig. 24.3). These indicators focus on increasing circularity in the incoming flow of materials, as they are metrics that facilitate the introduction of circular principles and encourage the development of the secondary materials market. In Brazil, CE in the construction industry is still in its infancy, and there is no CE regulation in government urban projects. Still, there is a lack of robust regulation that facilitates the reuse of salvaged building components in new construction projects [15].

Fig. 24.3
A flow chart depicts the summary of the balance of input and output materials. It includes material demand, renewable and non-renewable primary materials, secondary materials, maintenance, repair, reuse, materials bank, demolition and disposal, deconstruction, short-life products, and waste.

Summary of the input flow of materials and output of waste in a dwelling

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Addressing circularity at the ‘exit’ of the flow of materials, that is, at the very long building service life, increases the uncertainties both in estimating the possibilities of reinserting materials into production chains and in the real benefits of circular practices, such as recycling [9]. In addition, it requires a systemic change in the housing design stage and design plans for the deconstruction and recovery of materials at the end of the building's service life. The potential environmental benefits will happen in the future if users keep with the building project. Therefore, solutions that increase environmental loads during construction must be well-pondered. An efficient housing project must prioritize the adaptability of spaces to accommodate the different needs of users over time. Strategies such as modular construction, use of materials following the respective technical standards, and design for deconstruction must be an integral part of the projects [24]. Besides, in the construction stage, waste can be avoided through the construction process and integrated and efficient management of the flow of materials and labor at the construction site.

The implementation of circular indicators is important for planning and incorporating efficiency measures in buildings and for consolidating public policies that encourage the construction of more sustainable buildings. Commitment and support from the top management and CE legislation are the main enablers of the development of Dutch social housing [15]. In addition, a lack of incentives or requirements at a national scale can also make it difficult to apply sustainable practices, even where public policy exists SH providers can also be hindered by restrictive or absent funding requirements, inappropriate competing policies, or organizational barriers [25]. It is also necessary to overcome problems arising from the scale both in the supply of products and in the training of human resources, as well as the objective limitations of cost and production chain [26]. Therefore, the responsibilities of each party must be assigned [26].

The quantity of built stock is important, but more so is its quality, as better buildings and infrastructure will last longer, require less maintenance, and serve users’ needs longer, resulting in an overall reduction of the burden on the environment. Housing needs to evolve towards a system based on circularity, in which building materials are used, reused, adapted, and rebuilt, considering economic and environmental rationality in decisions. It is worth mentioning that residents of housing units, normally, do not have the perception of the potential for the circularity of their dwellings. Communication projects and user awareness is essential for the effective implementation of the CE, especially in the requalification activities carried out by the residents themselves.

6 Conclusions

The study presents the proposal for circularity indicators for social housing in Brazil. The indicators will help to introduce circular principles in the new 2040 Housing Plan, based on the creation of a sustainability axis, that provides adequate housing conditions and promotes the quality of life of the population, at an affordable cost, while reducing impacts on the environment throughout the life cycle of the house.

As the CE gains momentum, governments and construction companies must prepare for their transition based on metrics about their circular performance and associated risks and opportunities. To do this, buildings need a universal and consistent way to measure their circularity. Public governance has shown few efforts on circular policies on social housing and focusing on the energy system. The adoption of these indicators in social housing demonstrates the concern of a social governance policy engaged with sustainable development, in addition to being a way of accelerating the implementation of circular principles in the construction industry.

The proposed circular indicators are directed towards the entry of material flow into housing, favoring the use of secondary and renewable materials in construction chains. In the material flow output, the total waste generation during the construction/renovation of the house was considered. The main issue considered is the efficient use of materials, through dematerialization and efficient management of resources during the housing construction process.

The study has limitations related to the research strategy. The inclusion of different stakeholders of the construction value chain in the meetings could contribute to the circular indicators proposals. In future research, it is suggested to monitor the acceptance and application of the indicators in SH projects, as well as to analyze the creation of new indicators aimed at the output of the material flow with a more interdisciplinary team. The creation of housing scenarios with different circularity indices, through numerical modeling, can be a strategy for the dissemination and awareness of the importance of dematerialization in social housing.