Global warming and climate change are rising issues during the last couple of decades. Buildings including commercial and residential ones are major contributors to energy consumption. Energy consumption in buildings significantly increases on a yearly basis due to the increased human comfort needs and services . Multiple factors affect the energy consumption used for cooling buildings such as wall structure, window to wall ratio, and building orientation in addition to weather condition

 

A Zero Energy Building (ZEB), also known as a Net Zero Energy (NZE) building, is a building with net zero energy consumption, meaning the total amount of energy used by the building on an annual basis is equal to the amount of renewable energy created on the site or in other definitions by renewable energy sources offsite, using technology such as heat pumps, high efficiency windows and insulation, and solar panels. The concept of a Net Zero Energy Building (NZEB), one which produces as much energy as it uses over the course of a year, recently has been evolving from research to reality. A Net Zero Energy Emissions building either uses no energy which results in emissions or offsets the emissions by exporting emissions-free energy (typically from on-site renewable energy systems).  

The development of zero-energy buildings is encouraged by the desire to have less of an impact on the environment, and by tax breaks and savings on energy costs that make zero-energy buildings financially viable. Many people in developing countries (and elsewhere) already live in zero-energy buildings out of necessity, including huts, tents, and caves exposed to temperature extremes and without access to electricity. The notion of a “zero-energy building” in a modern sense has been discussed since the 1970s, prompted by the petroleum shocks of the decade and subsequent concerns about the consequences of fossil fuel dependency.
The development of modern zero-energy buildings became possible largely through the progress made in new energy and construction technologies and techniques. These include highly insulating spray-foam insulation, high-efficiency solar panels, high-efficiency heat pumps and highly insulating, low emissivity, triple and quadruple-glazed windows. Most zero-energy buildings use the electrical grid for energy storage but some are independent of the grid and some include energy storage onsite. The buildings are called "energy-plus buildings" or in some cases "low energy houses".
Climate change is a scientific fact, and so we, too, must change our thinking and our practices in order to protect people and the planet. A number of organizations are leading the charge in championing Net Zero Energy construction in an effort to bring it into standard practice.

International initiatives
Typical code-compliant buildings consume 40% of the total fossil fuel energy in the US and European Union and are significant contributors of greenhouse gases. To combat such high energy usage, more and more buildings are starting to implement the carbon neutrality principle, which is viewed as a means to reduce carbon emissions and reduce dependence on fossil fuels. Although zero-energy buildings remain limited, even in developed countries, they are gaining importance and popularity. The Energy Performance of Buildings Directive requires that EU countries had to ensure that all new buildings were nearly zero-energy by the end of 2020 while all new public buildings had to be nearly zero-energy after 31 December 2018.  

The Commission’s proposal to revise the directive (December 2021) makes a step forward from current NZEB to zero-emission building (ZEB), aligning the energy performance requirement for new buildings to the longer-term climate neutrality goal and “energy efficiency first principle”.The ZEB requirement should apply as of 1 January 2030 to all new buildings, and as of 1 January 2027 to all new buildings occupied or owned by public authorities. Ensuring buildings are not only designed to NZEB, but actually perform to NZEB standards would require post-construction reporting and analysis and a framework for oversight and enforcement. It would require measurement of actual energy use. However, today’s codes and standards are based on proxies for energy with no requirement to actually quantify the end result.

They are also gaps in types of energy uses that are included in energy calculations, leaving some uses unaddressed. To reach the goal of net-zero energy buildings, these methods must change. Modelling capabilities must improve, and actual outcomes must be measured.
The Paris Agreement, adopted in December 2015 under the United Nations Framework Convention on Climate Change (UNFCC), is a commitment to accelerate and intensify the actions and investments needed for a sustainable low carbon future, to limit global average temperature rise to well below 2°C above pre-industrial levels, and to pursue efforts to limit the increase to 1.5°C.
International Living Futures Institute (ILFI) is a nonprofit working to build an ecologically-minded, restorative world for all people. Using principles of social and environmental justice, ILFI seeks to counter climate change by pushing for an urban environment free of fossil fuels. ILFI runs the Living Building Challenge, which is the world’s most rigorous green building standard.
The World Green Building Council, and the Green Building Councils participating in the Advancing Net Zero project (project steering committee), are dedicated to supporting market transformation towards 100% net zero carbon buildings by 2050.
There are several metrics that define the performance of buildings such as the net-zero site energy building, net-zero source energy buildings, net-zero energy cost building, and net-zero energy emission building.
Site Energy refers to the energy consumed and generated at a site (e.g. a building), regardless of where or how that energy originated. In a net zero site energy building, for every unit of energy the building consumes over a year, it must generate a unit of energy.
The net-zero source energy building is the building that produces as much energy on an annual basis as it uses as compared to the energy content at the source.
Net Zero Energy Cost is perhaps the simplest metric to use: it means that the building has an energy utility bill of $0 over the course of a year. The net-zero energy cost building is the building that uses energy efficiency and renewable energy strategies as part of the business model
A Net Zero Energy Emissions building either uses no energy which results in emissions or offsets the emissions by exporting emissions-free energy (typically from on-site renewable energy systems).

To achieve net zero energy buildings, optimization of building energy efficiency typically considers the following:
 (1) lighting,
 (2) the walls and roof,
 (3) glazing,
 (4) heating,
 (5) ventilation,
 (6) air conditioning, 
 (7) renewables 
 (8) soft costs, and
 (9) the building usage and behaviours of the occupants.

Each of the above variables work together to ultimately reach the goal of net zero energy.

ZEBs need to produce their own energy on site to meet their electricity and heating or cooling needs. Various microgeneration technologies may be used to provide heat and electricity to the building, including the following:

•    Solar (solar hot water, photovoltaics [PV]).
•    Wind (wind turbines).
•    Biomass (heaters and stoves, boilers, and community heating schemes).
•    Combined heat and power (CHP) and micro-CHP for use with natural gas, biomass, sewerage gas, and other biogases.
•    Community heating (including utilizing waste heat from large-scale power generation).
•    Heat pumps (air source [ASHP] and ground source [GSHP] and geothermal heating systems).
•    Water (small-scale hydropower).
•    Other (including fuel cells using hydrogen generated from any of the above renewable sources).

Examples of zero energy buildings
There are various examples of zero energy buildings around the world, some have been newly constructed, and others have been achieved through retrofitting existing buildings. As the transition from energy intensive to energy efficient gathers pace, buildings across the world are proving that high performance can be combined with renewable energy generation. Let’s take a look at a few.

The Unisphere, Maryland, U.S.A
Spread across an area of 135,000 square feet, The Unisphere stands in the middle of the city in downtown silver spring as a sterling example of technologies embodied, making it a fully sustainable, net-zero energy construction. Completed in 2018, the clients (United Therapeutics) expected nothing less than the world’s largest office building that works on the concept of zero-energy.

 

 

The Unisphere amalgamates automation like Solar Photovoltaic systems, Geothermal wells, high-performance electromagnetic envelope, earth coupled heating-cooling system, a thermal pool, etc., helping the building function with a no carbon footprint. The building sells more power than it buys with the help of 3,000 solar panels that surplus energy from the 1000’s of systems during the day, and sells minimum power back from the grid to the building in the evenings.

Indira Paryavaran Bhawan, New Delhi, India
Opened in 2014, this building was the first ever zero net energy multi-storeyed building in India. The engineers reduced energy demand by providing adequate natural lighting, shading and landscaping to lessen ambient temperatures, as well as producing 100% of its energy requirements via an on-site installed solar panel – located on its rooftop. When compared to conventional buildings, it has reduced electricity consumption by 40%, and water consumption by 55%.

National Renewable Energy Laboratory, Colorado, U.S.A

With the aim of a clean energy future, the National Renewable Energy Laboratory campus nestles in the foothills of Rocky Mountain, Golden Colorado, U.S.A. The entire campus is a living precedent of sustainability, and the people at NREL are transforming energy through augmentation, research, commercialization, and dissemination of renewable and energy-efficient advancements.