Given the drastic climate change and its cascading effect, UNFCCC’s Paris Agreement requires all countries to take climate action, to keep global warming well below 2°C by drastically reducing greenhouse gas emissions.
Construction and operation of a building accounts for nearly 36% of the total global energy used, of which 39% of energy expended is related to CO2 emissions. In order to reduce these emissions, governments across the world are developing ways and means to minimise these, including standards for zero or near zero emission buildings. In fact C40 has pledged “to enact regulations and/or plan policy to ensure new buildings operate at net zero carbon by 2030 and all buildings by 2050.”
While we would have heard the terms ‘Net zero energy’ and ‘Net zero carbon’ used in this context, and often interchangeably; they are very distinct in nature. Here we take a closer look at these two; and what sets them apart.
Net Zero Energy Buildings- These buildings have zero net energy consumption with emphasis on the word ‘net’. Such buildings create on-site renewable energy that is equal to the energy used by the building annually. These buildings use non-renewable energy sources and produce greenhouse gases. In short, they offset the harm done by producing an equal amount of renewable energy or by buying carbon credits.
An example that would explain it better; The Indira Paryavaran Bhavan is India’s first net Zero Energy building. Constructed with the help of energy efficient materials like such as fly ash bricks, recyclable materials, outer wall insulation by rock wool, high reflective terrace tiles, it also has a rooftop solar power system. Apart from that doorframes and shutters built using renewable bamboo jute composite material, UPVC windows with hermetically sealed double glass, calcium silicate ceiling tiles, grass paver blocks for roads and pavements are used. It also has low-discharge water fixtures, sewage treatment plant, geothermal cooling for HVAC system, rainwater harvesting and curing compounds. Natural daylight accounts for 75% of its energy consumption and 40% of other savings are through chilled beam systems deployed for air conditioning.
While this method is popular the world over, with significant improvements and changes, the World Green Building Council is advocating another term “net zero carbon buildings”.
Net Zero Carbon Buildings- The World Green Council, in its Global Action Summit in 2018, asserted the need for net zero carbon buildings. They called upon the world to join hands to implement and reverse damage associated with climate change. According to the definition “net zero carbon buildings” are highly energy efficient and fully powered from on-site and off-site renewable energy sources”. This means, that such buildings do not consume non-renewable energy or produce greenhouse gases. Renewable energy resources like wind turbines, hydropower generators or solar panels provide energy to such buildings.
Constructing new buildings in adherence to the new policy is the easy part, retrofitting existing buildings is the bigger task, and even harder to accomplish. But, the goal remains the same - to reduce carbon by increasing the share of renewable energy.