Net zero energy or zero energy building is a building with net zero energy consumption during its operation & maintenance on annual basis. Thus in a net zero energy building, total amount of energy consumed by the building on an annual basis is equal to the amount of renewable energy generated in the building either onsite or offsite. When such amount of renewable energy is generated at site, the building is known as onsite net zero energy building otherwise offsite net zero energy building. When generated energy is more than consumed, it is called energy plus or positive energy building. The objective of net zero or net zero plus buildings is to contribute in saving environment and contribute less in generating greenhouse gases during its operation while objective of green buildings is to construct eco-friendly energy efficient and water efficient building having comfortable hygienic indoor air quality. Therefore, ideally a building should be net zero energy green building conforming to sustainable development, environment friendly and for wellbeing of occupants.
Features of a Net Zero and Green Building:
I. Features of Net Zero Buildings
- Building envelope and its orientation to minimize energy consumption and HVAC loads.
- Energy efficiency measures by adoption energy conservation through energy efficient fans, lights, ACs, electric pumps, and other electric equipment.
- Energy generation through renewable energy resources like solar, wind, bio mass etc.
- Regeneration of electric power through nonconventional sources like regenerative lifts, floor friction measures.
- Providing energy efficient gadgets and equipment requiring electric power.
- Bringing down the HVAC load by circulation of cool water in the cooling system for example through geothermal system.
- Providing sun reflective building materials, paints and coatings during summer and sun absorbing during winter.
- Providing energy insulation in the outer walls/ surface and roof.
- Energy efficient design of the building.
- Constructing smart homes avoiding wastage of energy.
- Reduction of carbon footprint
II. Features of Green Buildings
- Energy efficient
- Water efficient
- Comfortable and hygienic indoor air quality
- Green and sustainable building materials
- Waste minimization
- Structural efficiency
- Durability and safety
- Preservation of natural materials
- Reduction of air, water and noise pollution
- Welfare of construction employees at site and reduction of adverse health impact during its occupancy
- Innovations in adoption of eco-friendlymeasures
Cost of Net Zero Energy Building:
Green buildings are reported to be costly compared to conventional buildings by 2 to 18% and payback period is reported to be varying from 3 to 7 years. Since life of a permanent RCC framed building is considered to be 75 years, in long run it always becomes economic. Vyas and Jha (2018) have reported that average increase in initial cost of green building is 3.10% for three-star rating and 9.37% for five-star green building. A five star rated building can be considered equivalent to platinum rated building. Further, they have reported that discounted payback period for green buildings is 2.04 to 7.56 years for three-star and 2.37 to 9.14 years for five-star rated projects. Thus, discounted payback period and additional cost in case of green buildings depend upon the green rating though it is obvious.
India’s Commitment:
India has promised to cut its emissions to net zero by 2070. Hon’ble Prime Minister Narendra Modi made the pledge and first time India has set a net zero target, at the Glasgow summit. Net zero, or becoming carbon neutral, means not adding to the amount of greenhouse gases in the atmosphere. India has large network of thermal power plants as such it has to switch over to carbon neutral power generation resources. Therefore, it is likely that hydro power plants will also be in the ambit of net zero mission of carbon free emissions including renewable resources like wind, solar, tidal and bio mass power generation. Net zero carbon emissions can be achieved through onsite or offsite green power generation.