Studies show that buildings utilise around 40% of the energy produced or generated throughout the world. With increasing demand and depleting energy sources, this fact exposes a big issue in the construction industry. However, the design of net zero energy buildings (NZEB) in many parts of the world is emerging as an effective way of tackling this issue. Continue reading to understand what zero energy buildings are, their types, why they are important and how they are achieved.
What is a Net Zero Energy Building?
A building which generates all the energy required for its operation within its premises itself is called a Net Zero Energy Building (NZEB) or Zero Energy Building (ZEB). Typically, the total energy consumed by a building in a year is compared to the total energy produced by it in the same period, and if the sum of the two values is equal to or nearing zero, the building is said to embody net zero energy. The primary goals of such projects are to reduce the dependence on exhaustible energy resources and lower greenhouse emissions.
Types of Net Zero Energy Buildings
Across the world, definitions vary on what an NZEB really is. Typically, the NZEB definition encompasses the below types:
- Net Zero Site Energy: During the entire project life cycle—including construction, operation and maintenance—the amount of energy utilised is equal to the amount generated within the site.
- Net Zero Energy Costs: In such projects, the amount of money spent on utility bills is less than or equal to the amount of money earned by selling the energy generated within the premises.
- Net Zero Waste and Water: No waste generated in the building is sent to landfills but instead gets recycled, repurposed and/or reused. Water demands are met with the locally available quantities, and waste water is recycled on-site.
- Net Zero Emissions: Also called Zero Emissions Buildings and Zero Carbon Buildings (ZCB), the amount of greenhouse emissions produced by these projects is less than or equal to the amount of emissions they remove from the atmosphere.
Why are Net Zero Buildings Important?
- Sustainability: NZEBs use unlimited and natural resources available locally to meet the building’s energy needs. The reduced carbon footprints resulting from the construction and operation of such buildings encourage sustainable building practices.
- Financial Benefits: Although they have high initial investments, NZEBs save a significant amount of money on utility bills. Any additionally produced energy in buildings can also be sold to the local grid, helping stakeholders in quickly regaining their investments.
- Health Benefits: With high priority being given to maximise natural light and ventilation, along with the use of non-toxic, environmental friendly materials, enhanced mental and physical wellbeing among the building occupants can be observed. Some of the health benefits are increased productivity, reduction in breathing problems and regulated body functions.
- Increased Property Value: Due to the optimised planning, reduced expenditure on utility bills and the high status attached to zero energy homes, they have high property values which only increase with time.
How are Zero Energy Buildings Achieved?
Net-zero energy building design typically involves the following aspects:
Passive Design
Passive design refers to design strategies developed to reduce the reliance of buildings on mechanical ventilation systems for ensuring thermal comfort. Some of the important considerations taken for passive design are:
- Form and Orientation: The sun’s movement patterns across a day and throughout the year, along with seasonal and local wind directions, are studied to ensure that the building’s form and orientation provide optimised thermal conditions indoors.
- Daylighting and Natural Ventilation: Sufficient cross ventilation and natural light required to carry out daily activities are ascertained.
- External Devices: Fenestrations, shading devices, cool roofs, insulation materials and vegetation are some of the elements designed to abide by the principles of climate-responsive architecture.
Renewable Energy Sources
The benefits of using renewable energy are maximised in NZEBs. Zero building energy is mainly achieved by using the following energy sources:
- Solar Photovoltaics: Panels made of semiconductor materials are placed on rooftops and other spaces which receive maximum sunlight to convert the solar rays into usable electrical energy.
- Biomass: Organic kitchen waste is used to generate energy. Apart from the electrical energy produced, this system also minimises the waste sent to landfills.
- Wind Energy: Regions that experience strong winds can install turbines to harness the power of natural breezes.
Apart from these commonly used types, other alternative energy sources such as hydropower and geothermal heat pumps can also be incorporated in a zero energy house.
Energy Efficient Equipment
Electrical appliances that require minimum energy to operate are used, including:
- Lighting: Energy star-rated products like smart lights, LED lights (instead of halogen lights), and circadian lights consume 50-75% less energy than traditional lighting systems.
- HVAC: If any HVAC (Heating, Ventilation and Air Conditioning) systems are used, these typically comply with national and international standards such as ECBC (Energy Conservation Building Code) and ASHRAE (American Society of Heating, Refrigerating, and Air Conditioning Engineers).
- Other Appliances: Other appliances like washing machines, refrigerators and dishwashers are carefully selected on the basis of BEE (Bureau of Energy Efficiency) star ratings.
Often, home automation systems with sensor-based activation technologies are incorporated to reduce the overall energy consumption.
Monitoring Systems
Building automation systems are generally included in Net Zero building projects. These monitor multiple aspects of electrical units—such as daily, seasonal and periodic usage patterns, durations and types—by using technologies like IoT (Internet of Things) and Artificial Intelligence. They provide data on how much electricity needs to be produced on the premises and how much needs to be externally sourced. Such systems also analyse this data and give suggestions on how to improve the operation of different appliances to achieve energy efficiency and minimal wastage. Some of the common equipment that are a part of such systems are smart electrical and water meters.
Recycling Systems
Systems that can recycle water, dry and wet waste and build debris are integral parts of zero energy buildings. These often include rainwater harvesting systems, septic tanks, biomass converters and organic waste pits.
Organisations such as the IGBC and LEED provide green building certifications that verify a building’s net-zero energy status.
The Future of Energy and Buildings
Net Zero Energy Buildings are redefining the meaning of green buildings and leading a revolutionary change. Rather than being considered as an additional expense, buildings across the world need to adopt the zero energy concept as a necessary measure to combat the threats of climate change and diminishing energy resources. This one step towards green and clean energy in buildings can preserve the natural resources that have formed over millions of years and help safeguard the welfare of future generations.
Apoorva H P Achar