1. Introduction

Globally, built environment-homes, offices, institutions, recreational and industrial facilities form over 40 per cent of the carbon dioxide emissions. Most of these emissions come from the combustion of fossil fuels to provide heating, cooling, energy and lighting to power electrical appliances. The increasing human activities on earth such asconstruction processes, manufacture of building materials and products, increased emissions from transportation generated from urban sprawl and power generators peculiar to many third world nations contribute a significant amount of greenhouse gas emissions and consequently affecting climate. These multifaceted human activities on are increasing and many of which are environmentally unfriendly.

Man’s activities within the built environment causes ripple effects of deforestation, desertification, loss of biodiversity, global warming, ozone layer depletion and climate change. According to Goldstein & Neuman[1] in the past 50 years, humans have consumed more resources than in all previous history. Around 90% of them are the non-renewable materials. Among the raw materials consumed in Nigeria, the construction materials (related to buildings), dominate the industry. Perhaps coincidentally, architecture in the tropical regions share common problems, of which perhaps the most easily identified, is the tropical conditions of climate and natural environment[2]. Our built forms are essentially enclosures erected to protect us from the inclement external weather, enabling some activities to take place. This is particularly crucial in the tropical climatic zone.

It is therefore vital that pragmatic measures be harnessed to curtail climate change challenges within the built environment in hot and humid regions of Nigeria. One of such measures is the application of innovative building materials and modern technology in built forms, which is the focus of this paper.

2. Literature Review

2.1. Meaning and History of Climate Change

The global climate is warming. Climatic zones are shifting; glaciers are stirring-up while the sea level is rising. These are not hypothetical issues or scientific fictions, these changes and other episodes are factual, attesting to scriptural predictions that by the word of God the heavens were of old ...and the elements shall melt with fervent heat[3]. Climate is defined as the average weather or the regular variation in weather of a particular region over a given period of time that is not less than 10 years. Long term alteration in global weather patterns, especially increases in temperature and stormy activity, regarded as a potential consequence of greenhouse effect is referred to as climate change. The atmosphere serves as a shield for life and the built environment, protecting us from ultraviolet rays, other harmful objects in orbits that infiltrate into the atmosphere from space. Global warming or climate change is measurable increases in the average temperature of earth’s atmosphere, oceans, and landmasses. It is a scientific consensus that the earth is currently facing a period of rapid warming brought on by rising levels of heat-trapping gases, known as greenhouse gases, in the atmosphere[4]. The fact that heat-trapping gases have been accumulating in the atmosphere is well established. Since the mid-19^th century, the quantum of atmospheric carbon dioxide increased by about 25 percent. Recent investigations unveil that the atmospheric burden of greenhouse gases other than carbon dioxide, such as methane, nitrous oxide (N₂O) and chlorofluorocarbons (CFC’s) is also growing at alarming rate[5].

Historically, an interglacial period began about 10,000 years ago, when the last ice age came to an end. Prior to that ice age, an interglacial period occurred about 125,000 years ago. During interglacial periods, greenhouse gases such as carbon dioxide and methane naturally increase in the atmosphere from increased plant and animal life. But since 1750 greenhouse gases have increased dramatically to levels not seen in hundreds of thousands of years, due to the rapid growth of the human population combined with developments in technology and agriculture. Humanactivities now are a powerful factor influencing earth’s dynamic climate. However, there is now undeniable evidence that global temperatures are increasing, based on direct temperature measurements and observations of other impacts such as melting glaciers and polar ice, rising sea level, and changes in the lifecycles of plants and animals. In fact, there is overwhelming evidence that greenhouse gas emissions from human activities are the main cause of the warming. Greenhouse gases retain the radiant energy (heat) provided to earth by the sun in a process known as the greenhouse effect. Greenhouse gases occur naturally, and without them the planet would be too cold to sustain life as we know it. Since the beginning of the Industrial Revolution in the mid-1700s, human activities have added more and more of these gases into the atmosphere. For example, levels of carbon dioxide, a powerful greenhouse gas, have risen by 35 percent since 1750, largely from the burning of fossil fuels such as coal, oil, and natural gas. With more greenhouse gases in the mix, the atmosphere acts like a thickening blanket and traps more heat[4].

2.2. Evidences of Climate Change and its Impacts on the Built Environment

It is a ready known fact that the global climate has changed significantly in the last one century ago. The Intergovernmental Panel on Climate Change IPCC is an international group of scientists that evaluates scientific and technical information related to climate change and global warming (an increase in Earth’s surface temperature). The IPCC identified human activity as the primary cause for global warming. Human activities have produced inadvertent effects on weather and climate. Accordingly, addition of gases such as carbon dioxide and methane to the atmosphere has increased the greenhouse effect and contributed to global warming by raising the mean temperature of the Earth by about 0.5℃ (about 0.9℉) since the beginning of the 20th century. More recently, (CFCs), which are used as refrigerants and in aerosol propellants, have been released into the atmosphere, reducing the amount of ozone worldwide and causing a thinning of the ozone layer. The impending consequences of these changes are vast. Global warming may cause sea level to rise, and the incidence of skin cancer may increase as a result of the reduction of ozone[6]. Besides, man’s aspirations of living close and accessible to coastal and beach areas are potentially threatened by climate change. Impacts of climate change are likely to cause conflicts for society, such as where people want to live and where they can live safely. This could negatively impact our ability to continue to develop built environments to support some of our lifestyle aspirations. There is a need to start responding to the impacts of Climate Change within our built environments – however these are not insurmountable. This is required at both the individual building level and also for our neighbourhoods and communities in the way that they are structured/ serviced allowing for greater resilience to sudden shocks. For example, in an effort to prevent such consequences, production of chlorofluorocarbons has been curtailed and many measures have been suggested to control emission of greenhouse gases, including the development of more efficient engines and the use of alternative energy sources such as solar energy and wind energy.

2.3. Building Materials and Sustainable Built Environment

Sustainability in planning and architecture has become a factor in building as economic-ecological capital can no longer be ignored in the calculation of building cost to the society[7]. The environment must no longer be ignored, but the society is required to reinvest in ecology through renewable technologies to make good depredation resulting from adverse environmental impact of buildings and structures. Adedeji[7] opined that achieving sustainable development and construction by developing economies require two pragmatic approaches: it is first necessary to create a capable and viable local construction sector; second, it is necessary to ensure that the sector is able to respond to the demands that sustainable development places on its activities. This can only be possible if all the different stakeholders cooperate in the implementation of a clear strategy that involves specific supportive actions by all role players and the development of a set of enablers[8]. To create an enabling environment for sustainable construction, it is necessary that institutions such as the different levels of government, development agencies, academic and research institutions, professional associations and non-governmental organisations adopt sustainable development and its principles as a seminal aspect of their operations and develop their own capacity to support sustainable construction and use the associated technology. Also, the intelligent adaptation of local materials initiative, offers several advantages such as design flexibility, cost effectiveness, light-weight, eco-friendly and sustainable.

3. Methods

Data for the study was carried out through case studies, observations and photographic prints. Selected cities were purposively chosen as study areas due to the prominence of modern and local building materials used in these cities. The cities are Akure, Lagos, Abuja in Nigeria. Buildings raging from residential to institutional and commercial that exhibited the use of modern materials in enhancing thermal comfort under the changing climatic challenges were carefully observed and analysed below. These buildings demonstrated the application of modern building materials in adaptation of buildings to climate change scenario in their environment as presented under the findings and discussion section. These solutions include:

4. Findings and Discussion of Results

4.1. Use of Earth Walls and Local Material

Examples of earth wall materials are solid interlocking laterite blocks (Hydraform blocks), adobe blocks, laterite bricks earth wall construction (local soil types need to be tested to see if suitable) and straw bale construction. Earth masonry (Hydraform blocks) were extensively used in some residential estates and public buildings in many cities in Nigeria including Abuja, Lagos, Akure and others to improve thermal comfort in buildings. Moreover, owing to laterite composition of the material, it is environmentally friendly as blocks are produced under high compression from subsoil, without the need for the fuel-wood used to burn bricks. The material is characterised with excellent thermal capacity (the ability to absorb and hold heat) characterises the blocks. Hydraform blocks are three times as efficient as concrete and almost twice as efficient as fired clay bricks in terms of the thermal insulation they offer[10][11]. Attractive, face brick finishes (in a variety of natural colours derived from the soil found at individual sites) is also possible with the use of the material. The interior walls may or may not be plastered, painted or sealed.

Cases of earth walls are found in Urban Shelters estates in Abuja, Electronic Testing Hall, Federal University of Technology, Akure; Obasanjo Estates in Ado-Ekiti,- constructed solid interlocking laterite blocks. Brick facings can be used to finish walls as shown in Figures 1 and 2.

Figure 1. School of Earth and Mineral Sciences, Federal University of Technology, Akure. Use of Brick facing as Wall Finishing

These earth materials are eco-friendly and not do not require frequent renovations as compared to painted walls. In addition, walls, column and beams can be finished with mosaic tiles, which are more durable and enduring materials with high attractive finish rather than using paints that are easily liable to fading as shown in Figure 1.

Figure 2. Ikeja Plaza Building, Awolowo way, Ikeja. The use brick facing, recesses and horizontal shading devices in combating climate change challenges

The use of mosaic tiles is becoming more popular in banks and institutional buildings as found in Ondo State liaison office, Abuja and other buildings.

4.2. Use of Composite, Light-Weight and Cladding Materials

The use light-weight materials in walling and ceiling is relevant in Lagos climate scenario where there is the need to quickly dissipate heat gained into the inside environment of buildings from the external environment. Finished steel cladding mass-produced for assemblage is another constructive material in the market that has exhibited potentials for combating excessive heat from climate change imbroglio in the tropics. The typical raw material used for this composite is palm kernel fibre, an agricultural waste obtained from palm produce. The choice of the local product for building is based on the large quantity of Oil palm grown in the country as Nigeria. The World Bank played an important role in the promotion of the oil palm business in

Nigeria. According to a recent World Bank document, Nigeria has been the second largest recipient of World Bank palm oil sector projects, with six projects over the 1975 to 2009 period. Results achieved included the plantation of 42,658 ha of oil palm, as well as road improvement and increased milling capacity[12] .

The components of the composite wall panels are made of lightweight sandwich panels, consisting of 12mm thick layer of expanded polystyrene (EPS) fixed to boards (600 x1200 to 1200 x 2400) mm ranges and 25mm thickness of composite panel shaft at the centre, finished with two 6mm thick plasterboard at the interior(Figures 3). The EPS acts as waterproof material and add aesthetic value to the material to make it socially acceptable. The panels were factory-made. Installation was done with laminated steel profile. The ceiling was of cement reinforced with “koinkon” a material used for a local sponge. This can either be obtained from palm tree of any other plants that has similar property. Materials that were of tensile property were used to reinforce the cement, which is brittle and only good in compression (Figures 3).

The use of walls from composite materials should take the place of monolithic walls commonly used in Nigeria.

Figure 3. Comparison of external composite wall insulated with expanded polystyrene to internal composite wall without insulation

The composite properties of these materials, which can be in layers as used in some advanced countries, reduce the transfer of heat into the interior. Examples of such composite materials are wood composite, fibre composite and agro-waste composite. Such materials could be insulated externally with non-conducting heat materials to reduce heat gained into buildings from excessive direct heat from increased direct sun rays and surrounding environments.

4.3. Use of Specialised Glazing

The amount of solar radiation penetrating into a building through windows and the indoor temperature of buildings can be controlled with the type of glazing used in that building. Before recent innovations in glass, films, and coatings, a typical residential window with one or two layers of glazing allowed roughly 75-85% of the solar energy to enter a building. Internal shading devices such as curtains or blinds could reflect backs some of that energy outside the building. With the use of specialised glazing system, light may be allowed into a building while solar radiation is prevented from the building in order to ensure thermal comfort (Figure 4).

Figure 4. Use of Specialised Glazing in Corporate Affair Commission Building, Abuja

4.4. Additional Methods of Combating Climate Change

To further combat climate change, it was suggested that Nigerian architects need a lot of guidance concerning what building designers must do in the years ahead to ensure that building-related greenhouse gas emissions are appropriately reduced[13]. Raman[14] in his presentation provided the basis for setting specific building emissions targets that designers can start to advocate and, hopefully, implement immediately. Moreover, doubling the life span of the building can reduce the environmental impact by half[1]. This is achievable through renewal and reuse. Goldstein & Neuman,[1] advocates that “renovation creates 30 to 50 percent less green house gases than new construction, produces less construction waste, and utilizes existing resources - buildings” . Other means of combating climate change include developing workplace strategies that merge efficiencies with people-focused design; sharing facilities such as copy centres, kitchens and conference rooms; making meeting areas and large spaces multipurpose; efficiently scheduling to fully utilize facilities; and right sizing for work needs.

5. Conclusions

Climate change will have an impact on the way we use materials to enhance the sustainability of buildings. Since predictions of climate change are based on models which may metamorphose as human behavioural and industrial patterns change, the use of scenarios to establish best case and worst case climate change impacts becomes inevitable. Maximising the contribution of building materials to the design of buildings that will be adaptable to the climate throughout this century nevertheless falls within the realm of scientific analysis, and therefore technological realization.

ACKNOWLEDGEMENTS

SAP Productions wishes to acknowledge all the contributors for developing and maintaining this template.