Achieving Global Climate Goals through the Implementation of Net-Zero Energy Buildings
Global warming and climate change are rising issues during the last couple of decades. The current on-going COP26 summit has been catching global attention and awareness towards those issues. The rise of the world's temperature has been affecting our lives in many aspects and becoming a more serious threat to all species for the future decades. Earth creatures have started facing new challenges of survival because of climate change. Many of our planet’s ecosystems are at risk of extinction if global temperature continues to rise at an uncontrollable rate.
The COP26 summit's main goal is to reach global net zero by the mid century. Countries are being asked to come forward with ambitious 2030 emission reductions targets to achieve the climate goal. The climate goal is to limit the temperature rise below 2° and ideally to an average of 1.5° above pre-industrial levels. It requires the world to cut 30 gigatonnes greenhouse gas emissions annually by 2030. To achieve the climate goals, every sector needs to work hand in hand. The United Nation Environment Programme (UNEP) has identified six sectors with the potential to reduce emissions to keep the world below the 1.5 degree C mark. One of the sectors mentioned by the UNEP is buildings and cities; which have potential to reduce emissions by 5.9 GT.
Building sector is the largest contributor to global greenhouse gases emissions. Buildings use about 40% of global energy, 25% of global water, 40% of global resources, and they emit approximately 1/3 of GHG emissions (Source: UNEP). Yet, buildings also offer the greatest potential for achieving significant GHG emission reductions. Applying energy efficiency investments in buildings would reduce wasted energy usage, GHG, and the demand for non-renewable energy resources. Investing in sustainable building would not only help reduce carbon emissions but would also reduce building’s operational cost, improves comfort, and enhances property value.
Why Net Zero Energy Buildings?
When we talk about sustainable or green building, we don’t only refer to the construction stage or when the building is ready to operate. The carbon footprint of a building covers all of the building life-cycle, including the embodied energy from the building’s material. We already know that the building sector is the largest contributor of global carbon emissions and we have to start making efforts and commit to decarbonize. This is why we have to start to consider building net zero energy buildings. The combination of design, building techniques, and technologies that go into a zero energy building all result in a building that produces net zero carbon emissions.
According to the US Department of Energy (DoE), a zero-energy building is defined as the building that produces enough renewable energy to meet its own annual energy consumption requirements. Net zero energy buildings combine energy efficiency and renewable energy generation to consume only as much energy as it creates. The building has to produce its energy on its own footprint through renewable resources.
Sustainable building is important for the preservation and sustainability of our earth as well as the health of our future generations. The key purpose behind the sustainable building concept is to utilize natural resources in construction as well as other resources in optimal ways. A building that is designed to be more sustainable has the potential to reduce the human impact on the environment.
Case Study: NUS School of Design and Environment (SDE4)
NUS School of Design and Environment or SDE4 is the first new-build net-zero energy building in Singapore and it is designed as a 8,500-square-metre, six-storey, multi-disciplinary space by Serie + Multiply Architects with Surbana Jurong. The building is designed to be climate responsive, energy efficient and environmentally friendly, and only consume as much energy as it creates. The concept of this building really emphasises human-centric design within a sustainable natural and built environment. The contemporary architecture design demonstrates a deep understanding of the tropical climate of Singapore, deploying appropriate effective and efficient passive, active as well as hybrid environmental design responses.
The green features of the building include solar roof installations, a hybrid cooling system, innovative ventilation systems, as well as architectural structures that provide much-needed shade in Singapore’s tropical climate. SDE4 adopts an innovative hybrid cooling system that supplies rooms with 100% fresh pre-cooled air, which combines minimum air conditioning (set at higher temperature and humidity) and a number of ceiling fans that circulate the cool air to generate a breezy, comfortable indoor temperature. The solar photovoltaic system has more than 1200 solar panels installed and could generate up to 500 MWh of energy a year and potentially save up to $180.000 in electricity costs.
The conceptualization and construction of the SDE4 involved collaborative partnership between many experts including NUS SDE’s resident experts, external consultants, builders, and developers. The multidisciplinary collaboration that has been done in this project resulted in better and more sustainable outcomes.
How to Achieve Net-Zero Energy Building (NZEB)
There are two main approaches to attain net zero building: reduce building’s energy consumption and create strategies to produce energy. This could be done by applying a passive and active design approach. Here are some passive and active design strategies on how to achieve net-zero energy building:
Integrated Design Process
Integrated design process is defined as an interdisciplinary design approach with the emphasis on collaboration. All the stakeholders involved in the project met during the design of the plans and specifications to develop optimum solutions for each discipline. This is a comprehensive process that concentrates as much on design, construction and operation as on the occupancy of the building. The aim of having an integrated design process is to design energy-efficient buildings. The approach of active participation by all project stakeholders leads to the consensual search for optimum, innovative, sustainable solutions, considering the building’s entire life cycle.
Adaptive Thermal Comfort
Adaptive thermal comfort could be achieved through passive heating and cooling strategies. Optimum building orientation, shades, and overhangs could minimize HVAC loads and reduce direct sun rays. We could also reduce air conditioning and heater demand by optimizing natural ventilation, planting greeneries around the building, using reflective surfaces and Low-E coatings, and increasing r-value in roof construction.
Finding the right balance between lighting and ventilation helps maximize daylight while minimizing undesired heat transfer. Low-E coatings are microscopically thin metal or metallic oxide layers added to a glass surface to help keep heat on the same side of the glass from which it originates and it helps to keep the inside of the building cooler for warm climates. Reflective surfaces on walls contribute in reducing cooling load in air-conditioned spaces and improves comfort in non-air-conditioned spaces. Roof construction with higher r-value means that it has greater insulation power; and it would save energy as insulation reduces the amount of energy needed to run the building by keeping the air warm in during the winter and out during summer.
Reduce Water Consumption
Buildings consume a large amount of water. We could reduce building water usage by having a rainwater harvesting system, greywater recycling system, water metering, and using low-flow water fixtures. Rainwater harvesting is a sustainable process that helps in preserving rainwater for different purposes and for the future needs. It is a method to collect and store rainfall for future water use. Rainwater harvesting system also helps in getting rid of drought tendencies as it replenishes the ground water resources.
Greywater recycling is one of a sustainable preserving water system. Greywater recycling is a method of saving water in which wastewater is collected from kitchen sinks, washing machines, and showers, and is then recycled for usage in toilets or for garden irrigation. It could lower water usage as it makes use of recycled water.
Water metering is the practice of measuring water use. Water metering could also save water usage and cost as it is not just only monitoring water usage but could also help identifying the potential water efficiency. Low-flow water fixtures could also reduce building water consumption. Using low-flow water fixtures would decrease water consumption as it is specifically designed to limit water waste by using a lesser amount of water.
Landscaping
Planting greenery around the building has many benefits in environmental, health, ecological, and economic. Plants can act as barriers to reduce heat and air pollution; cooling the air of the surroundings and providing shade. Trees and other plants help cool the environment, making vegetation a simple and effective way to reduce urban heat islands. Trees and vegetation could reduce energy use by directly shade buildings so that the demand for air conditioning is decreased. Trees and vegetation could also improve air quality and lower greenhouse gas emissions by decreasing the production of associated air pollution and store and sequester carbon dioxide.
Efficient Lighting System
Efficient lighting systems can be achieved by optimizing natural lighting and using LED bulbs with lighting sensors in certain areas. Natural daylight optimization means lighting up buildings naturally by bringing sunlight in. Natural lighting mostly relies on glazing and ventilation so it is important to find the right balance between window to wall area. Choosing the right wall paint would also help to maximize natural lighting.
LED is highly energy efficient as it produces more light with less power compared to standard incandescent bulbs. With the same light output, LED bulbs use 85% less electricity compared to conventional lighting. LED bulbs also have a longer life span, thus lower carbon emissions.
Utilizing daylight and occupancy sensors could also help to save energy as it provides automatic on/off switching depending on the needs. Occupancy sensors will switch the lighting on when motion is detected in a room and it will switch off when the room is vacant or no more motion detected. Photoelectric or daylight sensors will activate light only when natural light is insufficient. Having a lighting sensor system would not only reduce energy consumption but would also enhance convenience, security and long term-energy savings.
Lower Carbon Materials
The embodied energy contained in a building's materials is an important aspect of a building’s total carbon emissions. Embodied energy of building materials constitutes the total energy expenditure for manufacture of building materials, including the process of raw material extraction and associated transportation. A material that is locally sourced and is relatively un-processed will have a low level of embodied energy. Choosing low carbon materials plays a big role in reducing the total carbon footprint from the building sector.
On- site Energy Production
Having an on-site energy resource would cover the building's energy consumption by producing it back as much as it spends. Solar photovoltaic systems can replace energy that is often generated from fossil fuels such as coal and natural gas. A photovoltaic (PV) system is composed of one or more solar panels combined with an inverter and other electrical and mechanical hardware that use energy from the Sun to generate electricity. When the sun shines onto a solar panel, energy from the sunlight is absorbed by the PV cells in the panel. This energy creates electrical charges that move in response to an internal electrical field in the cell, causing electricity to flow. Buildings with solar photovoltaic systems can generate electricity on their own with low emissions while also saving electricity costs.
Source:
https://ukcop26.org/wp-content/uploads/2021/07/COP26-Explained.pdf (COP26 Summit)
https://www.unep.org/interactive/six-sector-solution-climate-change/ (UNEP)
https://news.nus.edu.sg/nus-opens-first-net-zero-energy-building/ (NUS SDE)
https://www.sde.nus.edu.sg/arch/facilities/net-zero-energy-building-sde-4/ (NUS SDE)
https://www.intechopen.com/chapters/71982 (NZEB principles and applications)
https://www.strategiaconseil.ca/en/2018/11/19/the-integrated-design-process-principles-and-guidance-to-success/ (integrated design process)
https://www.epa.gov/heatislands/using-trees-and-vegetation-reduce-heat-islands (vegetation)
https://www.energy.gov/eere/solar/how-does-solar-work (solar photovoltaic system)
https://www.buildersmart.in/blogs/ways-to-reduce-water-usage-in-buildings/(water consumption reduction)
