1. Introduction

The accelerated pace of urbanisation and industrialisation in recent decades has challenges, such as pollution, resource scarcity and climate change. In response, the construction industry is giving more attention to green building design to mitigate the environmental impacts associated with urban development. The three key aspects of green building design, energy efficiency, sustainable materials, and eco-city planning work in a complementary approach to create a sustainable and resilient urban life. Energy efficiency is one of the most important aspects of green building design solutions. It reduces energy use and operational costs by up to 50 per cent, depending on the design features. These include the use of energy recovery systems and advanced solar technologies, which help extract heat as well as light. Such building designs contribute to lower greenhouse gas emissions and align with global efforts to tackle climate change. Sustainable materials are also a crucial aspect of green building design. They are selected based on their environmental performance, including low embodied energy and carbon sequestration; they reduce a building’s carbon footprint by 30-40 per cent. Lifecycle assessments are increasingly used to evaluate materials and their environmental performance from ‘cradle to the grave’. Eco-city planning expands green building design principles to the urban scale, integrating sustainable practices into the urban environment [1]. This includes the extensive use of green spaces; pedestrian-friendly infrastructure; and public transportation systems, which reduce car use and air pollution. Eco-city planning is also resilient and adaptive, and aims to create urban areas that mitigate the impacts of climate change.

2. Energy Efficiency in Green Building Design

Energy efficiency, although it is not the only environmental goal, lies at the core of green building design because reducing energy consumption is both a technical and economic objective and an environmental goal. A recent study demonstrated that energy-efficient buildings can reduce energy use by 50 per cent compared to conventional buildings. Energy efficiency is achieved by incorporating advanced technologies, smart systems and optimised building envelopes. The DOE found that energy-efficient buildings could save 25-30 per cent on energy costs, translating into savings worth billions of dollars. Furthermore, the global market for energy-efficient buildings is expected to grow from $245 billion in 2021 to $418 billion by 2027 due to regulatory constraints and the awareness of adverse environmental impacts [2].

2.1. Advanced Building Technologies

Higher efficiency building technologies also play a crucial role in improving the energy efficiency of buildings. For example, energy recovery in HVAC can provide energy savings up to 60 per cent in commercial buildings. LED lighting has already disrupted the lighting industry, with LEDs consuming 75 per cent less energy and lasting 25 times longer than incandescent bulbs. In one example of a commercial office building, by installing smart thermostats, the electricity bill is reduced by 15 per cent, which equals to $15,000 in savings annually [3]. Building automation systems that control lighting, heating, cooling and ventilation systems with information from real-time sensors have been reported to have a potential energy conservation between 20-30 per cent.

2.2. Passive Solar Design

Passive solar design consumption of energy by between 37% to 40% by optimizing the use of natural sunlight for heating and lighting purposes. In their research, focused on residential buildings in Spain, the author found that the use of south-facing windows, complemented by shading devices, was responsible of reducing the need of artificial heating by 20-25% during the winter months. Employing thermal mass (eg concrete or brick walls) to store up to 50% of solar heat during the day and release it at night was another strategy able to minimize the use of other sources of heating by a further 15-20%. These passive design strategies were responsible of reducing the consumption of energy but also carbon emissions, which is precisely the leading global objective in terms of climate sustainability [4]. Table 1 summarises the impact of the different strategies concerning passive solar design in terms of heating demand, storage of solar heat, energy and carbon emissions.

Table 1: Passive Solar Design Impact Data

2.3. Renewable Energy Integration

Integrating renewable energy, especially solar photovoltaic (PV) systems, is essential for reaching net-zero energy in buildings. Responding to the call for 100 CEBCs, based on simulations and case studies involving several buildings, we found that a PV system, with proper orientation and site selection, can satisfy 20-30 per cent of the energy usage on a yearly basis, depending on the geographic location and building design. Another detailed study in California focused on household electricity consumption in residential buildings with solar installations. Whenever the sun was shining, the building saved money on grid-sourced electricity, compared with a situation when solar wasn’t available. Researchers monitored how much electricity these buildings earned in credit from the grid by using their own solar electricity for a period of one year. The results were clear: buildings with solar installations reduced their reliance on grid electricity by 25-30 per cent. They thus saved between $1,500-$2,000 per year, per household. To get these numbers, the researchers first compared the household’s electricity bills before the installation and after [5]. The careful analysis also had to eliminate seasonal changes in energy use: for example, households tend to use more heating or cooling during the winter or summer. Additional energy that is generated but not immediately used can be stored, for example with use of a lithium-ion battery. Preliminary insights into energy storage were provided by a pilot project in Germany, where the electricity that was drawn from the grid and that which was sent back to the grid from buildings with PV panels and battery storage was measured, over time. PV panels with battery storage reduced grid electricity use by 85 per cent compared with just PV panels. This reduction shows that renewable energy systems can significantly reduce demand for non-renewable energy, especially when energy that is generated during high solar flux is stored and used later when needed (for example, at night or when there is little solar input) [6].

3. Sustainable Materials in Green Building Design

Sustainable materials are essential to reduce environmental footprints for the whole lifecycle of buildings. Sustainable materials are chosen for their low environmental footprints, as well as durability and potential for recycling or reuse. These attributes are crucial to realising sustainable construction for any building. Evidence of the success of sustainable materials’ effectiveness derives from quantitative analyses from lifecycle assessments (LCA) and comparisons of sustainable materials and conventional materials. LCAs track the environmental footprint from extraction of materials through to disposal; by way of this analysis, researchers can quantify the reduction of carbon footprints. Examples of studies demonstrate that the use of these materials such as recycled steel and reclaimed wood reduces a building’s carbon footprint by 30-40 per cent as compared to more conventional materials. This is mainly attributed to lower embodied energy and fewer emissions during production and transportation. Furthermore, market analysis reveals that the global market for sustainable building materials is projected to reach $570 billion by 2028; upon analysing current market trends, adoption rates and projected growth at a compound annual growth rate (CAGR) of 11.4 per cent from 2021 to 2028, these market research firms have established these projections [7]. Of significance is that sustainable materials aid in environmental conservation and also offer economic benefits as shown by numerous case studies and cost-benefit analyses for buildings using green materials, which result in reduced long-term costs associated with maintenance and replacement of materials.

3.1. Lifecycle Assessment of Materials

A Lifecycle Assessment (LCA) of building materials is an essential tool for determining the environmental impact of a material. LCA studies reveal that recycled steel uses 60% less energy to produce than virgin steel and reduces greenhouse gas emissions by 58% (‘Closing the Metals Loop’, Pacific Institute, 2008). Other studies show that the use of cross-laminated timber (CLT) in construction can also have a positive effect on the environment, sequestering 1.1 tons of CO2 per cubic metre of wood (‘An Environmental Assessment of Cross-Laminated Timber in Construction’, 2013). Therefore, choosing materials that have a low embodied energy will have a significant impact on reducing your building's overall footprint by 10-20% [8]. Table 2 below shows the comparison between various materials, their lifecycle assessments and their environmental impacts.

Table 2: Lifecycle Assessment of Materials Data

3.2. Recycled and Reclaimed Materials

Avoiding the need to mine and manufacture new materials can reduce the environmental footprint of construction by 15-20 per cent. For example, a case study of a residential building in the United States where it was possible to use reclaimed wood for exterior cladding found that the material reduced the demand for virgin timber by 35 per cent and therefore saved about 15 tons of CO2 over the building’s lifetime [9]. Similarly, it was found that the use of recycled concrete for road construction reduced material costs by 20-30 per cent and the carbon footprint by 25 per cent. In other words, these materials help to make buildings more sustainable while also helping to reduce costs and avoid new extraction.

3.3. Low-VOC and Locally Sourced Materials

Another exemplary material is low-VOC (volatile organic compounds). Low-VOC paints and finishes have been shown to reduce indoor air pollutant loads by 50-60 per cent, directly leading to healthier occupants and better comfort. The use of low-VOC materials in a Swedish school led to a decrease of 30 per cent in respiratory issues among students. Sourcing materials locally can lead to a 20-25 per cent reduction in emissions related to transportation. An effort in the UK, where 80 per cent of the materials were sourced locally within 50 miles, led to a 22 per cent reduction of the project overall carbon footprint [10].

4. Eco-City Planning and Green Building Design

Eco-city planning is an approach for urban development that integrates green growth and sustainability into the design of cities green buildings integrate into eco-cities through synergistic ways. We found that integration of green buildings in eco-cities can reduce a city’s total carbon emission by 15 to 20 per cent, and improve a city’s energy efficiency by 10 to 15 per cent. A case study of seven eco-cities in China showed that when green building standards spread across the city, a city-wide energy consumption reduced by 25 per cent and a city-wide water usage reduced by 30 per cent. This showed the enormous potential of eco-city planning to generate synergies into an integrated city project with a broader urban sustainability aim.

4.1. Sustainable Urban Design

Sustainable urban design contributes significantly to the implementation of eco-cities. A study in Copenhagen demonstrated that increasing the proportion of green space, pedestrian streets and public transport in the built environment decreased car use by 35%, increased public transport users by 25% and consequently reduced city-wide carbon emission by 20% and resulted in 15% improvement in air quality. Introducing green building certifications such as LEED or BREEAM into urban design projects also enhances the sustainability of buildings. The use of these certifications resulted in 15-20% better energy performances in certified buildings compared with those without [11]. Figure 1 demonstrates how sustainable urban design influences each feature of eco-cities.

Figure 1: Impact of Sustainable Urban Design on Eco-Cities

4.2. Integrated Water and Waste Management

Living systems are the crux of this integrated water and waste management system, which is fundamental to the sustainability of eco-cities. In the rainwater harvesting and grey water recycling systems of one of Singapore’s green building projects, water usage was reduced by 40 per cent, easing the pressure on municipal water systems. The same project also has waste management systems with a 50 per cent recycling rate, diverting large quantities of refuse from landfill. In addition to easing pressure on the environment, these systems contribute positively to the sustainability of the city by conserving resources and reducing waste. Table 3 summarizes the impact of various integrated water and waste management systems, including rainwater harvesting, grey water recycling, and waste management. [12]

Table 3: Integrated Water and Waste Management Data

4.3. Resilience and Adaptation to Climate Change

How well can they adapt to changing climates? These questions are critical in eco-city planning and in the design of green buildings. After a year that brought Europe’s worst flooding in more than 50 years, the study of such buildings in New York City demonstrates that buildings built to withstand extreme weather events took 20 per cent less damage than common buildings during the city’s last hurricane. Incorporating features to deal with stormwater – a major consequence of hurricanes and flooding – reduced flooding by 30 per cent, keeping the buildings dry during these events. These features of green buildings can also protect buildings from the impacts increase the resilience of the city, and its ability to stay resilient in the face of changing climates.

5. Conclusion

The integration of energy efficiency, sustainable materials, and eco-city planning represents a comprehensive approach to green building design that addresses both environmental and economic objectives. The evidence presented in this paper demonstrates that these strategies, when implemented together, can significantly reduce energy consumption, lower carbon emissions, and enhance the overall sustainability of urban environments. The adoption of advanced building technologies, the use of lifecycle assessments in material selection, and the incorporation of resilience measures in urban planning are all essential for creating sustainable cities that can thrive in the face of climate change. As the global demand for sustainable development continues to grow, it is imperative that policymakers, architects, and urban planners embrace this holistic approach to ensure that future urban growth is both sustainable and resilient. This approach not only supports global sustainability goals but also provides a blueprint for the transition to a low-carbon future.