Project – Biophilic and Passive Cooling Design Strategies for Thermal Comfort In Low-Rise Residential Buildings in Hot and Dry Climate Regions

CHAPTER ONE

INTRODUCTION

1.1 Background to the Study

Climate change, urban heat stress, and rapid urbanization have intensified the need for climate-responsive residential building design in hot and dry regions. Rising global temperatures are particularly evident in Sub-Saharan Africa, where climatic variability is placing additional stress on already vulnerable housing conditions. In Nigeria, the situation is even more pressing due to population growth and urban expansion, which have led to the construction of poorly designed buildings that are often unable to provide adequate thermal comfort. Adamawa State, located within the Sudan–Sahel ecological zone, exemplifies this challenge. The region is marked by prolonged dry seasons, intense solar radiation, dusty winds, and significant diurnal temperature variations, all of which directly affect the indoor climate of residential buildings.

In this climatic context, low-rise residential buildings dominate the built environment. However, many of these houses are constructed with lightweight, thermally inefficient materials such as cement blocks, corrugated roofing sheets, and unshaded windows. Such materials have high thermal conductivity, allowing for rapid heat transfer into living spaces during the day and insufficient cooling at night. In addition, poor planning of building layouts, limited vegetation, and lack of shading worsen the problem, leading to elevated indoor temperatures that compromise occupant comfort, health, and productivity. For vulnerable groups such as children and the elderly, the impacts of heat stress are especially severe.

Globally, biophilic design has emerged as a promising approach to improving environmental quality and human well-being within built environments. Rooted in Wilson’s (1984) biophilia hypothesis, which suggests that humans possess an innate affinity with nature, biophilic design introduces natural elements into the built environment through vegetation, daylighting, water features, natural ventilation, and the use of organic materials. Scholars such as Kellert (2008) and Browning, Ryan, and Clancy (2014) argue that these features not only improve mental health and social well-being but also reduce perceived thermal stress by creating environments that align more closely with human physiological needs.

Similarly, passive cooling strategies represent a vital design approach for hot-dry climates. These strategies utilize architectural techniques such as proper building orientation, thermal massing, natural ventilation, shading devices, and the integration of courtyards to minimize heat gains and maximize cooling potential. Unlike mechanical cooling systems, passive strategies are cost-effective, environmentally sustainable, and adaptable to local contexts. Seminal works by Olgyay (1963) and Givoni (1994) demonstrate that buildings designed with passive principles can maintain comfortable indoor conditions even under extreme outdoor temperatures, making them highly suitable for regions such as Adamawa.

In Nigeria, traditional architecture historically integrated both biophilic and passive cooling principles. Buildings were often constructed with thick mud walls that provided high thermal mass, small window openings that minimized solar gain, shaded verandahs, and internal courtyards that encouraged cross-ventilation. Trees and vegetation were strategically planted around homes to provide shade and reduce glare. However, with the advent of modern materials and Western-style construction, many of these features have been abandoned. Today, most residential developments prioritize cost, speed, and aesthetics over climatic suitability, resulting in thermally uncomfortable living environments.

The consequences of this shift are multifaceted. Occupants increasingly rely on fans, evaporative coolers, and air conditioners to maintain thermal comfort. While these mechanical systems provide temporary relief, they significantly increase household energy consumption, contribute to greenhouse gas emissions, and impose financial burdens on families in regions where electricity supply is often unreliable. In Adamawa State, where income levels are generally modest and access to uninterrupted power supply is limited, reliance on such systems is unsustainable. The result is a cycle of energy poverty and discomfort that undermines the quality of life for many residents.

Recognizing these challenges, there is a growing academic and professional interest in revisiting climate-responsive design strategies that combine the strengths of both biophilic and passive cooling principles. Integrating vegetation into courtyards, shading windows with trees or green screens, maximizing natural ventilation, and designing with appropriate materials can simultaneously reduce indoor heat loads and improve occupant connection with nature. Evidence from international studies suggests that these strategies are not only thermally effective but also socially and psychologically beneficial. However, there is limited localized research assessing how such interventions perform in the specific socio-cultural and climatic context of Adamawa State.

This study therefore investigates the combined application of biophilic and passive cooling design strategies to improve thermal comfort in low-rise residential buildings in hot and dry regions of Adamawa State. By documenting existing building conditions, evaluating feasible design interventions, and assessing both quantitative thermal performance and occupants’ perceptions, the study seeks to generate evidence-based recommendations. Ultimately, this research aims to contribute to the design of affordable, sustainable, and climate-responsive housing solutions that address the realities of heat stress while enhancing the well-being of households in Adamawa State and similar hot-dry regions.

1.2 Statement of the Problem

Residents of Adamawa State are increasingly confronted with thermal discomfort as a result of building designs that do not respond to the peculiarities of the hot-dry climate. High solar radiation, low relative humidity, and significant diurnal temperature ranges make it imperative for buildings to be designed with climate sensitivity. Unfortunately, many low-rise residential structures in the state are built with modern lightweight materials and layouts that absorb and transmit excessive heat into living spaces. As a result, occupants often endure extreme indoor temperatures that compromise health, productivity, and overall quality of life.

One of the key deficiencies in these houses is the lack of passive cooling features, such as cross-ventilation, shading devices, thermal massing, or orientation considerations. Without these strategies, indoor spaces tend to overheat during the day and fail to cool adequately at night, despite the large diurnal temperature variations common in hot-dry climates. Poor indoor air circulation further exacerbates the problem, resulting in stagnant and uncomfortable living environments. This design inadequacy creates a mismatch between the built environment and the climatic conditions it is meant to serve.

Consequently, residents increasingly resort to mechanical cooling systems such as ceiling fans, evaporative coolers, and air conditioners. While these devices provide short-term relief, they contribute to high household energy costs and are often unsustainable due to erratic power supply in the region. Many families cannot afford the consistent operation of air-conditioning systems, and those who do face rising energy bills. At the macro level, the widespread use of mechanical cooling increases greenhouse gas emissions, further aggravating the challenges of climate change and environmental degradation.

Although international research has shown the effectiveness of biophilic design and passive cooling strategies in improving thermal comfort, there is a dearth of localized studies in Adamawa State. Most existing studies focus on temperate or humid tropical climates, with little emphasis on hot-dry regions in northern Nigeria. This lack of contextual evidence limits the ability of architects, builders, and policymakers to confidently adopt or promote these strategies within the state. For example, while vegetation and courtyard systems have proven effective in other hot-dry contexts, their feasibility in Adamawa’s socio-cultural and economic environment has not been adequately tested.

Another critical issue is the absence of guidelines or building codes that prioritize climate-responsive residential design in the region. Current construction practices are largely driven by cost, aesthetics, and speed of development, with minimal consideration of thermal performance. This policy gap allows unsustainable housing models to proliferate, trapping households in cycles of thermal discomfort and energy poverty. Without empirical data and tested models, government agencies and professional bodies lack the necessary framework to develop practical regulations or incentives for sustainable residential construction in Adamawa State.

Therefore, the central problem this study addresses is the lack of empirical, context-specific knowledge and design frameworks on how biophilic and passive cooling strategies can be effectively applied in low-rise residential buildings in hot-dry climates of Adamawa State. Bridging this gap is crucial not only for improving thermal comfort and reducing energy dependence but also for promoting sustainable housing practices that are affordable, environmentally friendly, and culturally acceptable.

1.3 Purpose of the Study

The purpose of this study is to evaluate the effectiveness of biophilic and passive cooling design strategies for enhancing thermal comfort in low-rise residential buildings in hot and dry regions of Adamawa State, Nigeria. The specific objectives are:

1. To identify the prevailing thermal comfort challenges in low-rise residential buildings in Adamawa State.
2. To examine the biophilic design elements and passive cooling strategies most suitable for residential buildings in hot and dry climates.
3. To evaluate the extent to which biophilic and passive cooling strategies reduce indoor temperatures and improve thermal comfort.
4. To assess occupants’ perceptions and acceptance of biophilic and passive cooling interventions in low-rise residential buildings.

1.4 Research Questions

This study is guided by the following research questions:

1. What are the prevailing thermal comfort challenges in low-rise residential buildings in Adamawa State?
2. Which biophilic design elements and passive cooling strategies are most suitable for residential buildings in hot and dry climates?
3. To what extent do biophilic and passive cooling strategies reduce indoor temperatures and improve thermal comfort?
4. How do occupants perceive and accept biophilic and passive cooling interventions?

1.5 Research Hypothesis

The study will test the following hypothesis:

H₀: Biophilic design strategies have no significant effect on thermal comfort in low-rise residential buildings in Adamawa State.

H₁: Biophilic design strategies significantly improve thermal comfort in low-rise residential buildings in Adamawa State.

1.6 Significance of the Study

The study holds great practical value for architects, builders, and homeowners by providing actionable design recommendations tailored to Adamawa State’s hot and dry climate. Many existing residential buildings in the region are constructed without sufficient regard for thermal comfort, often leading to reliance on air conditioners and fans. By demonstrating the effectiveness of biophilic and passive cooling strategies, this research offers practical solutions for integrating natural ventilation, shading, vegetation, and material selection into design. These recommendations will enable stakeholders to create more comfortable living spaces with minimal reliance on energy-intensive mechanical systems.

From a policy perspective, the findings of this study have the potential to influence building regulations and housing development frameworks in Nigeria. Current building codes rarely emphasize climate-responsive and environmentally sustainable strategies. By generating evidence-based insights, this study can guide government agencies, urban planners, and regulatory bodies in formulating policies that encourage or mandate passive design elements in residential projects. Such interventions would not only support sustainable housing development but also align with Nigeria’s broader commitments to environmental protection and climate change mitigation.

Academically, this research contributes to the growing body of literature at the intersection of biophilic design and passive cooling in tropical hot-dry regions. While studies on sustainable architecture have expanded globally, limited empirical research has been conducted in Adamawa State and similar climatic contexts in Nigeria. By addressing this gap, the study will serve as a reference point for scholars and students in architecture, building technology, and environmental design. Furthermore, it encourages future investigations into context-specific design solutions that balance aesthetics, functionality, and sustainability.

The social significance of this study lies in its potential to improve the quality of life for residents of Adamawa State. Prolonged exposure to high indoor temperatures can lead to discomfort, stress, and even health challenges such as dehydration, fatigue, and heat-related illnesses. By promoting biophilic and passive cooling strategies, this research supports healthier indoor environments, especially for vulnerable groups such as children, the elderly, and those with pre-existing health conditions. Additionally, improved thermal comfort enhances productivity and overall well-being among household members.

Another important dimension of this study is its potential to reduce household energy consumption and associated costs. In hot and dry climates, residents often spend a significant portion of their income on electricity bills to power fans and air conditioners. By adopting design solutions that minimize the need for mechanical cooling, households can experience substantial cost savings. This economic benefit not only eases financial burdens on families but also reduces the strain on Nigeria’s already challenged power supply infrastructure.

Finally, the study carries significant environmental implications. Increased dependence on mechanical cooling contributes to greenhouse gas emissions and exacerbates the problem of climate change. By demonstrating alternatives that rely on natural processes for cooling, this research promotes environmentally friendly building practices. Widespread adoption of biophilic and passive cooling strategies could contribute to reducing carbon footprints at both household and community levels. In this way, the study aligns with global calls for sustainable development and the transition toward low-carbon, climate-resilient societies.

1.7 Scope of the Study

The study is limited to low-rise (one to two storey) residential buildings in selected hot and dry climate zones of Adamawa State. It focuses on measurable passive and biophilic interventions such as vegetation, shading, ventilation, thermal mass, and orientation. The study will use surveys, thermal measurements, and simulation to analyze outcomes.

1.8 Limitation of the Study

• Limited time and resources may restrict the number of buildings studied.
• Availability of climatic and building data may constrain analysis.
• Some proposed interventions (e.g., extensive landscaping) may be difficult to implement due to land-use or cost constraints.
• Cultural preferences may influence the acceptance of certain design strategies.

1.9 Definition of Terms

• Biophilic Design: A building design approach that integrates natural elements (plants, daylight, water, and materials) into living spaces to improve human comfort and well-being.
• Passive Cooling: Architectural techniques that reduce heat gains and enhance heat dissipation without mechanical energy input.
• Thermal Comfort: A condition in which an individual expresses satisfaction with the surrounding thermal environment.
• Low-Rise Residential Buildings: Domestic housing structures typically of one or two storeys.
• Hot and Dry Climate: A climate characterized by high temperatures, low humidity, and significant diurnal temperature fluctuations.

Project – Biophilic and Passive Cooling Design Strategies for Thermal Comfort In Low-Rise Residential Buildings in Hot and Dry Climate Regions