What is Net-Zero Energy Building (NZEB)?

As per the National Renewable Energy Laboratory (NREL) in the United States of America, Net-Zero Energy Buildings (NZEB) is a "building that offsets all of its energy use from renewable energy resources available within the footprint". 

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NZEB can be interpreted as buildings that utilize renewable energy to satisfy building energy needs. It is a building that produces as much energy as its uses over the course of a year. 

Statistical studies show that buildings are the primary energy consumers in the U.S. This fact emphasizes the importance of targeting building energy use as a key to decreasing the nation's energy consumption.

A Net Zero Energy Building combines ideal building design to minimize energy requirements and renewable energy systems to meet reduced energy needs.

Different Metrics of  Net Zero Energy Buildings (NZEB)

There are several metrics that define the performance of buildings. They are:

1. Net Zero Site Energy: This is the energy consumed and generated at site (building). It does not consider where and how the energy is originated. A net zero site energy building, must generate unit of energy for every unit of energy the building consumes.
2. Net Zero Source Energy: It is the primary energy needed to extract and deliver energy to a site, including energy lost or wasted in the process of generation, transmission, and distribution. A net zero source energy building produce as much energy on an annual basis as it uses as compared to the energy content at the source.
3. Net Zero Energy Costs: It is the simplest metric, where the building has an energy utility bill of $0 over the course of a year. This means, that all the energy required for the building is taken from the on-site renewable generation.
4. Net Zero Energy Emissions: A net-zero energy emission building does not use energy that results in emissions i.e. it uses emissions-free energy.

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Energy Efficiency of Net Zero Energy Buildings (NZEB)

The fundamental design criterion and the highest priority of NZEB projects is to minimize the energy use through efficient building design. The criteria of energy efficiency is the most cost-effective strategy that gives highest return on investment and maximize energy efficiency plans.

Some of the energy efficiency measures includes techniques and methods to reduce the demand-side loads like:

1. High-performance envelopes
2. Daylighting
3. Air barrier systems
4. Passive solar heating
5. Natural ventilation
6. Water conservation
7. Sun control and shading devices

Some of the efficient equipment and systems that can be used to reduce the building loads are:

1. Energy efficient lighting
2. High-performance HVAC
3. Geothermal heat pumps
4. Electric lighting controls

Some of the energy conservation devices are:

1. Fuel cells
2. Combined heat and power systems
3. Microturbines

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