It is an inevitable fact that the amount of greenhouse gases present in the atmosphere (carbon dioxide, water vapour, nitrous oxide, and methane), which trap heat and light coming from the sun, has been rising. Considering that these greenhouse gases are good absorbers of heat radiating from the Earth’s surface, the increase in their amount in the atmosphere causes them to start acting like a blanket over the surface. This change transforms into uncontrolled increase in Earth’s temperature, leading to global climate change.
Even though the debate on the effects of greenhouse gases on the global surface temperature is still ongoing, the existence of man-made climate change is regarded as one of the most critical threats to human survival by many scientific bodies. The uncertainty in the predictions made for the future climate is due to our imperfect knowledge regarding science of climate change and the future scale of human activities that are stated as its cause. However one aspect that is certain is that the temperature at the surface of the earth, measured for the last 150 years by various thermometers placed around the world, has been rising.
The temperature rise has not only brought drought to many countries around the world, but also caused increases in sea level, leading to floods and other natural disasters. Humans are thought to influence the global climate system, mainly by amplifying the Earth’s natural greenhouse effect via increased utilisation of the world’s resources through human activities in the areas of residential, transport, and industry. According to the Intergovernmental Panel on Climate Change, there is 90% certainty that the burning of fossil fuels and other human activities are driving climate change.
While climate change and its consequences are blamed on various human activities, the biggest contributor to climate change is the increase in greenhouse effect produced by CO2, which is emitted as a result of fossil fuel burning for the purposes of obtaining energy. The main sources of CO2 emissions from fossil fuel combustion are indicated as public electricity and heat production, energy industries, manufacturing and construction, and transport.
Certain measures in terms of adaptation are needed to preserve food and water resources, ecosystem and biodiversity, human settlements and health, which are essential for human survival. The socio-economic development paths in the areas of economic growth, technology, population, and governance need to be employed to facilitate the necessary change.
Sustainable design works towards eliminating the negative impacts on the environment and enhancing the quality of our lifestyles. This is achieved through revising our approaches towards protecting Earth’s available resources while employing energy-efficiency measures in all areas of our lives. The main objectives of sustainability are listed as reducing our consumption rates, minimizing waste, and creating healthy and productive environments.
Awareness towards environmental issues leads towards the development of eco-friendly approaches in many areas, including construction. In addition to the choices made during the design and construction of a building (e.g. green building materials, eco-friendly design schemes), the maintenance of a building also requires special attention in terms of cutting down the overall carbon footprint. An environmentally friendly building minimizes its negative effetcs on the surrounding environement. The conceptual design of such a building should ideally embrace eco-friendly, sustainable and recycled materials; and allow for a reduction in energy consumption during the entire life cycle of the structure as well as during its construction.
The design and planning of eco-friendly houses can be studied in terms of insulation; renewable energy used for heating and cooling purposes, as well as running the appliances around the house; heating and cooling; lighting; energy efficient appliances; green roofs; and recycling. Additionally, flexibility in design, embodied energies of construction materials, and methods for minimizing construction waste need to be looked into. Many academic institutions are currently investigating these factors affecting the sustainability of eco-houses individually and assessing the scale of their influence on the overall design of an eco-house.
Renewable energy sources such as wind turbines and solar panels are preferred for obtaining the required energy sources to run the appliances around an eco-friendly house. Wind turbines varying in size and capacity can be chosen depending on the desired output and are either connected to the roof or supported on their a separate post. The energy is obtained as a result of wind blowing on to the blades of a wind turbine, which in turn rotates the shaft. The turbine is connected to a generator whose main function is to convert the energy acquired from the rotating shaft into electrical energy. On the other hand, photovoltaic (PV) solar panels, an installation of interconnected assembly of photovoltaic cells, use sunlight to produce electricity. Both of these methods (e.g. wind turbines and solar panels) are not only functional but also present completely environmentally-friendly options by eliminating the dependence on fossil fuel energy generation.
In addition to employing renewable energies to provide lighting and run electrical equipment and power appliances, solar thermal collectors are utilized to provide hot water that can later be used for heating or washing. This technology involves an insulated box with built in pipes that are located where sunlight hits the collector. The water running in the pipes warm up with the help of solar energy and is then circulated via natural convection and passed to a storage tank located above the collector. When combined together, these renewable approaches reduce the gas and electricity requirements of the household to a great extent.
Although most of the energy produced in an eco-house is from renewable sources, it is still vital to ensure that all the appliances used within the house are energy efficient during their operating time. Electrical goods such as washing machines, dishwasher, refrigerators, boilers, and televisions are required to come with an energy efficient label by the Eco-design Directive (2005/32/EC) and Labelling Directive (92/75/EC) regulated by the EU. These labels indicate the efficiency of an appliance on a rate ranging from “A” to “G”, where “A” is the most efficient.
Another aspect of green living is the use of heat pumps to provide heating or cooling. A ground-source heat pump is placed underground where the temperature varies between 8˚C and 13˚C, and can produce up to five times the amount of heat energy for every unit of electrical energy needed to power it. Alternatively, air-source heat pumps are used to adjust the temperature inside the house to a desired degree.
Considered as a replacement for radiators in most cases, underfloor heating systems are another energy efficient method of providing targeted warmth in certain locations around the house (especially in bathrooms and kitchens) due to their low temperature requirement. Due to the fact that the system is placed on an extensive area, the warmth is distributed more effectively, therefore reducing the amount of energy needed and subsequently the cost, making this technology more favourable than radiators. Because they do not make any noise during their operation and are placed underneath the floor and therefore do not take up any indoor space, underfloor heating systems present many advantages to their users.
Insulation, applied both for cavity walls and lofts, is one of the most important aspects of eco-friendly houses in terms of preserving the heat indoors, trimming down the amount of energy needed for heating, and thereby reducing the overall carbon footprint of the building. To prevent the heat transfer from indoors to outdoors, insulation, providing a layer with air pockets designed for trapping heat within, is applied around the building. Insulation blankets (e.g. quilts) or blown insulation are used for lofts. Considering that a third of all the heat lost in an un-insulated home is through the walls, another area of the house that requires special attention in terms of insulation is cavity walls. Insulation in this area requires the filling of the cavity with insulating material for the purposes of keeping the heat inside the house from escaping.
In the planning of an eco-house, maximizing the amount of natural lighting reflected inside the building plays a significant role in creating astonishingly lit spaces while saving energy. Every effort needs to be shown to reduce the dependence on artificial lighting, which not only requires energy to run but also produces heat during its operation time and is therefore inefficient. Utilizing natural daylight as the main source of lighting in an interior space has many benefits, ranging from reduced lighting costs to improving the moods of inhabitants of the house and therefore enhancing their productivity and the overall pleasure of living in an eco-friendly house.
Factors including climate, geographical region, building orientation, luminance levels, contrast ratios, window-to-wall ratios, ceiling-to-skylight area percentages, and reduction in glare are considered by the designer for an effective arrangement of lighting options. While the locations of open areas (e.g. windows and skylights) need to be placed strategically around the house, the amount of window area varying between 25 and 40 percent is considered to be competent for obtaining daylight efficiently.
Gardening forms an important part of eco-house design since it facilitates organic growth and eliminates the need for having food travel many miles until it reaches its customers, thereby minimising the carbon footprint. In order to reduce the impact of over consumption of food on the environment, local production of fresh products should be encouraged. To increase the size of the area designated for greenery within the design, the roof of the house can be designed as a green roof. This technology enhances the biodiversity and reduces the amount of surface run-off water, as well as providing a good sound insulation and acting as a protection for the waterproofing membranes beneath the roof.
Being one of the most significant measures that can be taken for a greener world, recycling is widely promoted within and outside the house. Most materials including paper, glass, and aluminium can be recycled on an extensive basis. The importance of this process can be easily observed by considering the fact that it only takes 5% of the energy used to create an aluminium can to recycle it and bring it back into use.
Eco-design is regarded as a concept which allows for flexibility in design and maintenance. For this reason, the interior area of an eco-friendly house should be designed in a way which can be altered without difficulty in the future according to the inhabitant’s changing needs. To provide this flexibility, care must be shown to maximise freedom around the house by providing large areas of unconstrained space within the interior of the house.
Considering the fact that choices of materials and design principles have a significant impact on the energy required to construct a building, the embodied energies of the feasibility options need to be properly evaluated. Designing on a regular grid will not only introduce simplicity to the project but will also reduce manufacturing effort. The future flexibility of the building should also be considered in the design to ensure no part of the construction is wasted or demolished after the implementation of the future phases.
Proposing the right construction materials that would impose the smallest adverse effect on the environment plays a critical role during the design of a project. This requires a sensible approach in choosing, reusing and recycling materials during design, and construction. In addition to these phases, the maintenance period of a building should be thoroughly planned, ensuring that resource requirements, which is the main interest in terms of deciding on the right construction materials to be used for a project, are minimized. Since it has a much lower embodied energy per unit mass than most of the other construction materials, timber can be used as the primary construction material for a project involving the design and construction of an eco-house.
The sustainability of other construction materials, such as concrete can be further enhanced by incorporating recycled aggregates (e.g. crushed concrete recycled from nearby demolition sites) in concrete mixes, and using supplementary cementitious materials like fly ash and latently cementitious materials like ground granulated blastfurnace slag (ggbs), which are waste products from power generation industries and smelting, respectively.
Reinforced concrete involves the use of steel which has a higher embodied energy per unit mass than concrete, but it has a much greater strength to weight ratio. Being a lightweight construction material, steel uses less energy to be transported and can therefore result in smaller and lighter foundations with lower embodied energies. Since it also has a good recycling potential, much of the steel can be reclaimed as reused with minimum energy input at the end of the building’s life. In the case of reinforced concrete, the reinforcement quantities (kg steel/m3 concrete) should compare favourably with benchmarking standards for an efficient design.
Finally, the impact of the structure on the surrounding areas has to be minimized. Depending on the location of the building, the construction process must be planned with utmost care to minimize disrubtion to the surrounding areas. Waste generated during construction must be kept at a minimum level through means of reusing and recycling as much as possible. In addition to material pollution, noise pollution should also be reduced by employing the essential technologies in order to protect the welfare of the sourrounding citizens. Once the necessary permits are obtained to commence the construction period, the access to site and plan deliveries should be clearly stated.
It should be very obvious to everyone that wondering whether we can possibly live without being dependent on fossil fuels for our survival is not even an option any more since we all have to learn to adjust to a new way of living in which we will have to make low or zero-carbon choices due to the cost and environmental implications of doing so otherwise. Considering that a significant proportion of emissions are caused by the housing sector, buildings play an important role in achieving a greener approach that can have a huge impact on future generations’ lifestyles.