1. Introduction
There is a global problem of housing the poor. It has been estimated that there is an annual population increase of approximately 83 million people in the world; hence, there will be roughly a total population of 8.9 billion by the year 2050 [
1]. A study conducted in Europe shows that people find it difficult to afford to buy a house. Normally, the cost of housing in urban areas often outweighs household income. Additionally, housing assets are a source of wealth, and has impact on spatial inequality, and could be a potential determinant to intergenerational discrimination within a society [
2]. Sustainable and affordable housing is a hot button topic for researchers from both developed and developing countries. It has been realized that housing for the poor and low-income earners should be paramount to the academic and policymaker [
3]. Less developed countries are putting much effort into ending housing problems due to their growing populations [
4].
The policies on housing, in the case of Nigeria, was first initiated and developed by their British colonial masters. The policies were formulated as an adaptation of British housing policies and were not only separationist in nature but also not sustainable. Many attempts have been made by the government to elicit and initiate national housing policies since the country’s independence. Unfortunately, the problem of housing persists, and it is on the rise [
5]. Housing projects have been executed in significant towns and cities in Nigeria, but are inadequate to meet the demand for housing. With a population of over 180 million, the Nigerian government needs to formulate workable policies and housing programs to provide decent housing for the growing masses. By 2020, there will be a housing deficit between 17 to 20 million housing stock. The housing problem in Nigeria can be described from both the supply and the demand perspectives. Although the government has invested enormous capital on expanding housing supply through National Housing Programmes, it has yielded little or no result on housing supply.
According to the background, which describes the housing situation, the authors find that current housing stock is not in the best living conditions for human habitation. Thus, it is not only inadequate but also deteriorating and overcrowded. Meanwhile, the National Housing Programmes in place lack continuity and consistency and are impacted by political interference and nepotism [
5,
6,
7]. There is a proliferation of slum populations in town and cities in Nigeria because it is difficult for the general masses to afford or rent decent housing (
Table 1 and
Table 2). The average income of a civil servant is grossly inadequate due to the enormous disparities in income. As of 2018, the least paid individual (national minimum wage) in a month is N18,000 (USD 50), and the average monthly wage is about N43,200 (USD 120) [
8,
9]
It is gainsaying that housing policies and programs initiated by the government do not employ sustainable strategies that are realistic, affordable, and acceptable by end-users. It is also not unusual to find empty and abandoned houses in the city center. Hence, the government has not only worsen the housing crisis but also failed to satisfy the desired housing needs sustainably over time [
10,
11]. A study by Ibem and Azuh supported the fact that weak sociopolitical structure and institutional frameworks are the banes of failed housing policies and its implementation mechanisms [
12]. Additionally, corruption is a huge stumbling block in housing delivery and procurement processes [
13]. More so, Ihua et al. associated poor housing quality and housing management services, which eventually result in time and cost overruns, with bad estate and project management practices [
14]. Furthermore, Adekunle et al. described, with sharp empirical pieces of evidence, the connection between respiratory-related diseases in children and the quality of air in a house [
15].
The study aims to establish a process of assessing success criteria to achieve a sustainable housing model from the household viewpoint. To achieve this aim, the objectives of the study are to evaluate economic, social, and environmental success criteria from the end-users’ perspective, and to validate and rank the evaluated success criteria as presented in
Figure 1. The city of Abuja, the administrative capital of Nigeria, was chosen as the study area. Furthermore, it is a model city with a defined master plan, having several public and private housing estates (pilot housing schemes and programs) that are usually scaled up and duplicated across the nation. It is centrally located geographically, making it a melting pot for different groups of people with varying socio-economic and religious-cultural backgrounds living together. Furthermore, the survey of the study will be validated by surveying respondents from heads of households who are government employees.
It has been recorded that one half of the world’s population are residents in urban centers, and it was further predicted that it would increase two-fold by the year 2030, which will lead to increased human activity. However, this increased urban activity will exacerbate the greenhouse gas effect of the earth’s atmosphere, thereby leading to increased heating of the earth, known as global warming. Furthermore, it was projected that by 2030, OECD countries would need an 80% share of global energy in their cities to meet its energy demand for economic growth. Consequently, we can see that not only the cities significantly contribute to the problems of climate, but also will be negatively impacted by its effects, socially and environmentally.
Climate change not only impacts the urban area economically but also impacts the fabric of the city’s social structure. When impacts of climate change disrupt livelihoods, it leads to displacement of the populace and then poverty. Also, social vices such as crimes and civil conflicts will be widespread; hence, people will no longer feel safe. More so, these social calamities usually cause a health issue that has to do with mental instability. Likewise, skin diseases could be derived from exposure to heatwaves as a result of the heat island effect. Thirdly, buildings are generally vulnerable environmentally from the impacts of climate change due to factors of vulnerability, from the volume of impact to its level of exposure. Mostly, urban areas are located in coastal regions and the riversides, which make them vulnerable to the impacts of climate change. Some of the environmental impacts include urban flooding, a rise in the sea level in coastal cities, heat waves due to the heat island effect, hurricanes, and typhoons [
16]. Empirical pieces of evidence have proven that buildings contribute immensely in exacerbating the effects of global warming. Therefore, in accordance to the United Nations Climate Change conferences and the Kyoto agreement, member countries have signed a resolution to act accordingly with combined efforts and objectives to tradeoff between cutting down or reducing the emissions of greenhouse gasses into the atmosphere by adopting sustainable means of development [
17].
Against this backdrop, the United Nations Sustainable Development Goals (SDG) resolved to tackle global urban problems such as reducing poverty, enhancing good health, available and affordable renewable energy, sustainable cities and communities, climate change, and finally, building strong institutions. Thus, this resolution has given governments, particularly of the less developed countries, the thrust to pursue all avenues to meet these goals. The study, therefore, provides a significant contribution to research in developing a multiple success criteria model for achieving sustainable and affordable housing [
18].
There is no universally accepted definition of sustainable and affordable housing. There have been many attempts to define it by several authors and researchers from deferent fields and disciplines. It is also important to note that empirical studies have shown that professionals and academics in the housing sector differ in opinion on what constitutes success criteria for achieving sustainable and affordable housing. A framework of success criteria is limited but highly significant, and the approach of its development is drawn from inputs from different professionals of different disciplines [
19].
To describe and distinguish between the concepts of sustainability and affordability in housing, first, some definitions of sustainable and affordable housing will be highlighted as proposed by researchers. Research by Adabre and Chan attempted to define sustainable and affordable housing by trying to link sustainability and affordability in housing as a means of enhancing household and stakeholder satisfaction, by reducing housing operation cost, the time factor, affordability and quality of housing [
20]. In another study, sustainable, affordable housing is the development and maintenance of housing, to support and satisfy general human needs, and preserve the environment now and for the future. The housing should be qualitative, marketable, and affordable throughout its life cycle [
21].
The UN habitat describes sustainable and affordable housing from the policy perspective as “sustainability housing development (along the four dimensions of sustainability—environmental, social, cultural and economic) that impacts the environment and climate change, durability and resilience of homes, economic activities in housing and their links with the wider economy, cultural and social fabric of communities, and…poverty alleviation, social development, and quality of life.” [
22].
Furthermore, Ibem and Azuh proposed a definition that sustainable and affordable housing “… is the adoption of a housing and neighborhood environment, housing quality, affordability, quality of life, maintaining cultural heritage and technical feasibility” [
12]. On the contrary, Jiboye argued that sustainable and affordable housing is the optimal utilization of limited resources to provide housing for the masses as well as for future generations [
8,
9,
10,
11,
12]. Also, Mitlin and Satterthwaite propounded that sustainable and affordable housing is improving the health and safety of residence; it should be affordable, secure, water and energy-efficient, connected to infrastructure, social amenities, resilient to natural and human-made disasters, and lastly, meeting the people’s needs and choices. Thus, it should be functional, durable, and employ sustainable and affordable housing designs to optimize the use of utility throughout its life cycle [
23].
According to the 1987 World Commission on Environment and Development, the Brundtland Commission report, the most famous definition of sustainability is the development that meets the needs of the present generation within the available scarce resources and carrying capacity of the environment without endangering the needs and carrying capacity of future generations. Hence, sustainable and affordable housing is housing that manages and coexists within the limitations of available scarce resources, at the same time preserving and conserving these resources for future needs.
However, there is less reliable research conducted within the Nigerian context involving the contribution of the low-income household, which constitutes the demand side of the housing market, as part of the decision-makers in evaluating and validating sustainable and affordable housing success criteria. Therefore, the motivation for this study is to fill that gap and to enhance the decision-making process for policymakers to achieve sustainable and affordable housing for low-income households in Nigeria.
2. Materials and Methods
A document content analysis was undertaken, and a structured, close-ended questionnaire, as presented in
Appendix A, was distributed in the course of the study. A qualitative analysis to retrieve secondary data from extant literature must contain sustainability criteria, factors, and constituents in housing [
24]. Therefore, success criteria that are profound, distinctly described, and frequently put forward by the documents were generated. Hence, 17 success criteria were generated, as shown in
Figure 2 and
Figure 3, and further collapsed to 8 distinct success criteria by combining closely related criteria, which were used as variables to be analyzed (
Table 3).
Data collected was evaluated by expressing the feelings and opinions of success criteria within a scale of 1 (very weak) to 5 (very strong). The sample group comprised of civil servants working in Abuja. This sample group has expressly indicated their need for housing from their monthly contribution of a percentage of their earnings into the National Housing Fund. The questionnaire survey utilized a Google online form to collate data from the demand side via emails, online links, and other social media outlets. The National Bureau of Statistics reported the population size of federal civil servants employed by the government as 67,000 workers. The sampled population size needed for the study is 262, determined under a confidence level of 95% and at a confidence interval of 6.04. Only 51 respondents engaged in the survey, which is 19% of the sampled population. According to Blaike, it is factual that most research work seldom achieves a whole or a part sampling group or unit [
25]. There are other scholarly opinions about the rate of response, which ranges between 10% to 95%. For example, Akintoye and Fitzgerald suggested that for a research survey that involves personal contacts, the response rate is 95%, and for responses via mail, it is between 20% to 40% [
26]. However, the Survey gizmo suggested that response rates from electronic mails (emails and other social media platforms) regarding surveys on public opinion are between 10% to 15% [
27].
The respondents were made to evaluate the multiple success criteria based on their feelings and perspectives as to the level of importance of eight success criteria, namely, affordability in housing, accessibility of housing, technology in housing, acceptability in housing, community participation in housing, security in housing, adaptability in housing development, utility in housing development.
Analysis of data acquired was conducted using the Microsoft Excel data analysis tool for measurements of central tendencies, correlation, and ANOVA. Therefore, it is essential to do a reliability test for the data collected to prove the validity and significance of the result derived from the study. Therefore, ANOVA was utilized to get the significant
F and
p-value; thus, data less than 0.05 has a significant difference from other paired variables. Therefore, the correlation analysis in
Table 4 shows the
r-value, sometimes known as the Pearson correlation coefficient, indicating the strength of the criteria to each other. The output of the correlation analysis shows that Adaptability and Utility have the strongest means of association with each other, with the coefficient
r-value of 0.82. The second in the strength of the association is the criteria Community and Utility. Additionally,
Table 5 shows that ten paired success criteria that are statistically significant and reliable with a significant
F and
p-value less than 0.05. It shows that the data collected is valid, unbiased, and has statistical significance.