Housing affordability pertains to the capacity of a given household to pay their rent or mortgage in relation to their financial means. Considering the criticism of the concept when viewed as a strict ratio rule between income and housing expenses (Hulchanski, 1995), it may be useful to focus on the relational nature of the concept and as a way to analyze the relationship between different processes. As Whitehead (2007, p. 30) contended, affordability is a composite of three main parameters: (1) housing cost, (2) household income and (3) direct state interventions (or third-actors) playing on the previous two factors, for instance by improving one’s capacity to pay through direct payments or by reducing housing costs through subsidized housing. Considering the current trend towards unaffordability in European cities (Dijkstra and Maseland, 2016, p. 96), the concept is particularly useful to understand the interplay of factors that both favour rising housing costs—through financialization (Aalbers, 2016), gentrification (Lees, Shin and López Morales, 2016), and entrepreneurial urban policies (Harvey, 1989)—with those that enable the stagnation of low- and middle-incomes, namely Neoliberal globalization (Jessop, 2002) the precarization of work and welfare policy reforms (Palier, 2010). The “hard reality” behind one’s home affordability can therefore be construed as the result of a complex interplay between large-scale processes such as those enumerated above, behind which lie the aggregated behaviours of a multitude of actors; from the small landlord to the large investment firm seeking to speculate in global real-estate markets, from the neighborhood association protecting tenants from evictions to national governments investing (or divesting) large sums of money into housing programs. The conceptual strength of affordability lies in its capacity to scrutinize a wide range of complexly interconnected phenomena, which ultimately affect greatly everyone’s quality of life.    

The discussion on housing regimes dates back to e neo-institutional turn in policy research which occurred during the 1980s. This literature viewed institutions not so much as “formal” entities but more as the culmination of conflicting power relations, market dynamics, and ideology. The study of these dynamics could, in turn, be used to understand the variegated development of post-war welfare states, as exemplified by Esping-Andersen’s seminal Three worlds of welfare capitalism (1990). Kemeny defined the housing regime as “the social, political, and economic system of housing supply, distribution, and consumption, which determines the housing market opportunities of a certain period” (1981, p. 13). His framework follows the logic of the historical and institutional structure of society. Kemeny (2006) argues that, due to the central role of real estate in modern capitalism, housing systems follow similar paths, albeit with  different logics. Studying the emergence of regimes of a different nature between countries, he distinguished between unitary and dualized housing regimes, based on their rental-market systems, that is: (a) countries with an open private sector but with a firmly regulated public sector are characterized by a dual rental market; and (b) societies where the private and public sectors are strictly regulated have a unitary rental market. In dualist countries (primarily the Anglo-Saxon ones), homeownership is commonplace, while in countries with an integrated/unitary system (such as Germany, Netherlands, and Scandinavian countries) renting is a realistic and even competitive alternative to ownership. Kemeny highlighted that the dominance of homeownership is not organically developed but is socially and politically constructed. The above conceptualization of housing regime based on the functioning of rental market systems does not mirror the (Foucaultian) political and conflictual approach of Clapham, for whom a housing regime stands for a “set of discourses and social, economic and political practices that influence the provision, allocation, consumption [of housing] and housing outcomes in a given country” (2019, p. 24). He views policy as an arena where actors “negotiate and bargain” through discursive processes (Ruonavaara, 2020b). Clapham clearly distinguishes regime types from housing regimes. Regime types are useful for categorization since they can function as a baseline for comparative studies. However, “every housing regime is unique”(Ruonavaara, 2020b). Because of the complexity of the concept, Clapham (2019, p.17) proposes a three-stage analysis for housing policy (Figure 1). Ruonavaara (2020b) finds Clapham’s approach nuanced but too general and broad, which – according to him - makes it less applicable. On the other hand, Hegedüs (2020) considers Clapham’s (2002) housing pathway reasonable, as it describes housing provision forms as a result of interactions. In line with Clapham, he argues that “interventions within the housing system can only be understood in the context of interactions between different housing market actors” (Hegedüs, 2020, p. 569). Consequently, an analysis that only focuses on the rental sector would lead to narrowed interpretations with low explanatory power. More recently, Ruonavaara provided a new definition of housing regimes, which combines the elements of previous theories. He defined housing regime as a “set of fundamental principles according to which housing provision operates in some defined area (municipality, region, state) at a particular point in time” (2020a, p. 10). These principles are present in discourses, institutional arrangements, and political interventions. All actors have certain principles when operating in the system of housing provision at a given time and place. Housing regimes can be considered as the “principles of operation” (Ruonavaara, 2020a). In this sense, the housing regime concept faces challenges in its ability to represent an effective analytical tool for today’s housing systems. For Stephens (2020), it is necessary to rethink housing regime as a way to find middle-range theories given that current accounts of neoliberal convergence (Aalbers, 2016; Clapham, 2019) barely manage to explain the role of regime path-dependences in continuing to shape variegated housing outcomes.

Housing can be perceived as consisting of two inseparable components: the product and the process. The product refers to the building as a physical artefact, and the process encompasses the activities required to create and manage this artefact in the long term (Turner, 1972), as cited in (Brysch & Czischke, 2021). Affordability is understood as the capability to purchase and maintain something long-term while remaining convenient for the beneficiary's resources and needs (Bogdon & Can, 1997). Housing Affordability is commonly explained as the ratio between rent and household income (Hulchanski, 1995). However, Stone (2006, p.2) proposed a broader definition of housing affordability to associate it with households' social experience and financial stability as: "An expression of the social and material experiences of people, constituted as households, in relation to their individual housing situations", ….. "Affordability expresses the challenge each household faces in balancing the cost of its actual or potential housing, on the one hand, and its non-housing expenditures, on the other, within the constraints of its income." Housing costs signify initial and periodic payments such as rent or mortgages in the case of  homeowners, housing insurance, housing taxes, and so on. On the other hand, non-housing costs include utility charges resulting from household usage, such as energy and water, as well as schools, health, and transportation (AHC, 2019; Ezennia & Hoskara, 2019). Therefore, housing affordability needs to reflect the household's capability to balance current and future costs to afford a house while maintaining other basic expenses without experiencing any financial hardship (Ezennia & Hoskara, 2019). Two close terminologies to housing affordability are  “affordable housing” and “affordability of housing”. Affordable housing is frequently mentioned in government support schemes to refer to the housing crisis and associated financial hardship. In England, affordable housing is still concerned with its financial attainability, as stated in the UK Government's official glossaries: "Housing for sale or rent, for those whose needs are not met by the market (including housing that provides a subsidised route to home ownership and/or is for essential local workers)", while also complying with other themes that maintain the affordability of housing prices in terms of rent or homeownership (Department for Levelling Up Housing and Communities, 2019). The affordability of housing, on the other hand, refers to a broader focus on the affordability of the entire housing market, whereas housing affordability specifically refers to the ability of individuals or households to afford housing. In the literature, however, the term “affordability of housing” is frequently used interchangeably with “housing affordability,” despite their differences (Robinson et al., 2006). The "affordability of housing" concerns housing as a sector in a particular region, market or residential area. It can correlate affordability with population satisfaction, accommodation types and household compositions to alert local authorities of issues such as homelessness (Kneebone & Wilkins, 2016; Emma Mulliner et al., 2013; OECD, 2021). That is why the OECD defined it as "the capacity of a country to deliver good quality housing at an accessible price for all" (OECD, n.d.). Short-term and long-term affordability are two concepts for policymakers to perceive housing affordability holistically. Short-term affordability is "concerned with financial access to a dwelling based on out-of-pocket expenses", and long-term affordability is " about the costs attributed to housing consumption" (Haffner & Heylen, 2011, p.607). The costs of housing consumption, also known as user costs, do not pertain to the monthly utility bills paid by users, but rather to the cost associated with consuming the dwelling as a housing service  (Haffner & Heylen, 2011). “Housing quality” and “housing sustainability” are crucial aspects of housing affordability, broadening its scope beyond the narrow economic perspective within the housing sector. Housing affordability needs to consider "a standard for housing quality" and "a standard of reasonableness for the price of housing consumption in relation to income" (p. 609) (Haffner & Heylen, 2011). In addition, housing affordability requires an inclusive aggregation and a transdisciplinary perspective of sustainability concerning its economic, social, and environmental facets (Ezennia & Hoskara, 2019; Perera, 2017; Salama, 2011). Shared concerns extend across the domains of housing quality, sustainability, and affordability, exhibiting intricate interrelations among them that require examination. For instance, housing quality encompasses three levels of consideration: (1) the dwelling itself as a physically built environment, (2) the household attitudes and behaviours, and (3) the surroundings, encompassing the community, neighbourhood, region, nation, and extending to global circumstances (Keall et al., 2010). On the other hand, housing sustainability embraces the triad of economic, social, and environmental aspects. The shared problems among the three domains encompass critical aspects such as health and wellbeing, fuel poverty and costly long-term maintenance  proximity to workplaces and amenities, as well as the impact of climate. Health and wellbeing Inequalities in health and wellbeing pose a significant risk to social sustainability, mainly in conditions where affordable dwellings are of poor quality. In contrast, such conditions extend the affordability problem posing increased risks to poor households harming their health, wellbeing and productivity (Garnham et al., 2022; Hick et al., 2022; Leviten-Reid et al., 2020). An illustrative example emerged during the COVID-19 pandemic, where individuals residing in unsafe and poor-quality houses faced higher rates of virus transmission and mortality (Housing Europe, 2021; OECD, 2020). Hence, addressing housing affordability necessitates recognising it as a mutually dependent relationship between housing quality and individuals (Stone, 2006). Fuel poverty and costly long-term maintenance Affordable houses of poor quality pose risks of fuel poverty and costly long-term maintenance. This risk makes them economically unsustainable. For example, good quality entails the home being energy efficient to mitigate fuel poverty. However, it might become unaffordable to heat the dwelling after paying housing costs because of its poor quality (Stone et al., 2011). Thus, affordability needs to consider potential fluctuations in non-housing prices, such as energy bills (AHC, 2019; Smith, 2007). Poor quality also can emerge from decisions made during the design and construction stages. For example, housing providers may prioritise reducing construction costs by using low-quality and less expensive materials or equipment that may lead to costly recurring maintenance and running costs over time (Emekci, 2021). Proximity to work and amenities The proximity to workplaces and amenities influences housing quality and has an impact on economic and environmental sustainability. From a financial perspective, Disney (2006) defines affordable housing as "an adequate basic standard that provides reasonable access to work opportunities and community services, and that is available at a cost which does not cause substantial hardship to the occupants". Relocating to deprived areas far from work opportunities, essential amenities, and community services will not make housing affordable (Leviten-Reid et al., 2020). Commuting to a distant workplace also incurs environmental costs. Research shows that reduced commuting significantly decreases gas emissions (Sutton-Parker, 2021). Therefore, ensuring involves careful planning when selecting housing locations, considering their impact on economic and environmental sustainability (EK Mulliner & Maliene, 2012). Moreover, design practices can contribute by providing adaptability and flexibility, enabling dwellers to work from home and generate income (Shehayeb & Kellett, 2011). Climate change's mutual impact Climate change can pose risks to housing affordability and, conversely, housing affordability can impact climate change. A house cannot be considered "affordable" if its construction and operation result in adverse environmental impacts contributing to increased CO2 emissions or climate change (Haidar & Bahammam, 2021; Salama, 2011). For a house to be environmentally sustainable, it must be low-carbon, energy-efficient, water-efficient, and climate-resilient (Holmes et al., 2019). This entails adopting strategies such as incorporating eco-friendly materials, utilizing renewable energy sources, improving energy efficiency, and implementing sustainable water management systems (Petrović et al., 2021). However, implementing these measures requires funding initiatives to support the upfront costs, leading to long-term household savings (Holmes et al., 2019). Principio del formulario Furthermore,  when houses lack quality and climate resilience, they become unaffordable. Households bear high energy costs, especially during extreme weather conditions such as heatwaves or cold spells (Holmes et al., 2019). Issues like cold homes and fuel poverty in the UK contribute to excess winter deaths (Lee et al., 2022). In this context, climate change can adversely affect families, impacting their financial well-being and health, thereby exacerbating housing affordability challenges beyond mere rent-to-income ratios.