Technology is playing a big role in reducing the carbon footprint of homes and offices
If you believe that transport, manufacturing and energy generation are the biggest sources of carbon emissions, think again. Buildings and construction together account for 36 per cent of global final energy use and 39 per cent of energy-related carbon dioxide emissions, according to the International Energy Agency's Global Status Report 2017 prepared for the Global Alliance for Buildings and Construction.
While rising awareness about climate change and its impact on lives and livelihoods is encouraging more and more people and companies to build sustainable, net zero energy and zero carbon buildings, the trend, say experts, is not catching on fast enough to make a meaningful difference. According to the World Economic Forum, less than 1 per cent new buildings are constructed as zero carbon today, though a number of cities, companies and real estate organisations have committed to having a 100 per cent zero carbon portfolio by 2030. "The concept of net zero carbon (buildings) is at a very nascent stage but certainly gaining importance at the corporate level. Housing projects may take some time to chase net zero carbon status," says S. Karthikeyan, Principal Counsellor, CII Indian Green Building Council. The reason is simple - building a zero carbon home is not an easy task.
There are no guidelines for designing a zero carbon home in India. However, the India Green Building Council (IGBC) published a pilot version of the "Net Zero Energy" rating system in November 2018 which can act as a guide while designing a zero carbon home. "Carbon is different from energy. Carbon covers the bigger picture, including materials with which the building is constructed," says Sunita Purushottam, Head of Sustainability at Mahindra Lifespace Developers Ltd.
At present, companies are focusing on net zero carbon status for mostly commercial projects. The main reason is that companies need scale considering the resources needed to build and run a zero carbon building. "Some of the major challenges are awareness about what net zero carbon means and availability of supporting service providers, low carbon products, materials and technologies, apart from use of renewable energy (onsite/offsite), which plays a significant role in achieving net zero carbon status," says S. Karthikeyan. Experts say government policies - such as high tariffs on cheaper imported solar modules - are also discouraging optimum use of renewable energy in buildings. Regulations, too, vary across states.
Moreover, a zero carbon home does not merely mean an energy-efficient building with neutral or negative emissions. The process starts from the planning stage itself and covers the choice of site (so that there is enough sunlight and wind to generate renewable energy) and construction material to use of renewable energy, apart from efficient waste and water management.
Real estate companies say the success of their efforts also depends on how the building is operated by tenants over which they have no control - particularly emissions associated with downstream leased assets.
How to Design a Zero Carbon Home
Site/orientation: As the house will use electricity generated by renewable sources, choose a location that gets ample light, heat and air. Architects can help you use the cool breeze and sun's heat to ensure passive heating and cooling.
Construction: There is a belief in a number of western countries that walls should have good insulation. This does not hold true for most parts of India. Instead of walls, ensure apt insulation for top floor roof by using thermally optimised bricks. According to IGBC, the exterior wall should be built using six-inch fly ash bricks, with plaster on both sides. In addition to fly ash bricks, green cement (manufactured using a carbon-negative process) and heat reflective paints should be considered. Besides, green cover should be added wherever possible. Use rapidly renewable materials such as bamboo, eucalyptus, bagasse and certified wood for furniture and other fixtures.
Clean Energy, Energy-Efficient Appliances: Renewable electricity should power everything. The thumb rule is that the house should be able to produce as much electricity, or even more, than it consumes. The best option is to install rooftop solar panels. If there is shortage of space for that, the home should be connected to a renewable power grid.
Other sources of renewable on-site energy such as biogas digesters and small wind systems may also be explored. In addition, large glass windows can make sure that the home gets ample daylight, eliminating the need for switching on lights during the day. Energy consumption can also be reduced by installing BEE-certified appliances and using LED low power consuming light fittings. Sensor-based lighting solutions reduce the use of electricity by turning off lights if there is nobody in the room.
Recycle & Reuse Water Waste: An on-site water treatment system and separate plumbing lines for reuse of treated wastewater for flushing and other requirements can ensure optimum use of water. Even rainwater should be harvested. The treated water can be used for landscaping or car washing.
Waste Management: Households generate a large amount of waste. Segregation at source can prevent it from being sent to landfills. Separate bins should be installed in every dwelling unit to collect dry waste (paper, plastics, metals, glass, etc.,) and wet waste (organic). While wet waste should be turned into compost and used in the garden, dry waste should be sent for recycling.
EV, Charging Point: Emissions from vehicles contribute significantly to carbon emissions. Use of an electric vehicle (EV) can eliminate this.
Upgrading Existing Home
An existing home can be remodelled and made zero carbon but with a lot more effort and money than is required to build a new one. "For retrofitting old or existing buildings, consider structural options with lighter framework that can save 40 per cent on embodied carbon, especially for foundations," says Suraksha Acharya, Founder, Principal Architect, Midori Architects. One can also go for equipment upgrades, improved building insulation and, where possible, on-site renewable energy installations.