Green housing in urban India is no walk in the park

In a quest to produce modern homes quickly, developers building mass housing complexes find it challenging to also keep green factors in mind. In the first of a two-part series, CarbonCopy explores what these challenges are and how they are being tackled, if at all

India is home to more than a billion people. A growing population and rising urbanisation requires housing solutions that are not only affordable, but also use resources juduciously, have a lower carbon footprint and cater to the needs of residents all the same. 

In 2021, 63,000 housing units were sold in Mumbai alone and the other metropolitan areas of India recorded a significant increase in housing sales as well.

But how many of these houses are green and sustainable? Moreover, how many buyers are asking such questions while looking for a house to buy?

As per the UN’s Global Status Report for Buildings and Constructions 2021, the construction sector was responsible for about 37% of carbon emissions globally. This calls for a growing need to build sustainably. 

Green building in India

There are two agencies in India that certify buildings as green. These are Green Rating for Integrated Habitat Assessment (GRIHA) and Indian Green Building Council (IGBC). IGBC had set a target to achieve 10 billion sqft (100 crore sqft) of green building by this year. Till 2019, 7 billion sqft of it had been achieved with 1.4 million green homes covering 1.9 billion sqft. 

Has the demand for sustainable homes increased overtime? “Those who value sustainability have always opted for such homes. Overall, the idea of building green is more prevalent among developers who build projects like villas. Now the ones making apartments are taking this up too,” said Nilanjan Bhowal, Principal Architect at Design Consortium, a Delhi-based architectural firm.

Luxury housing projects like villas always have bigger budgets and larger share of land, so it becomes easier to incorporate sustainable elements. The challenge is building mass housing complexes while keeping green factors in mind. “When you are building a multi-story residential building, the budget and timeline become the major drivers. With a tight timeline, it is designed in such a way that the execution is quick,” remarks Aquin Noel, a Chennai-based architect. 

“The sustainability of a building depends largely on three factors: the construction palette, the building’s response to local climate, and the form of the building,” said Pankaj Joshi, conservation architect and principal director Urban Centre Mumbai. What kind of materials are being used? Has the building been designed as per the local climate? Is it a high-rise building or a low one? 

In a quest to produce modern homes quickly, many integral aspects of traditional architecture design are now looked over. Earlier, the designs ensured a passive way of responding to the climate. For instance, using filters like jaalis in Rajasthan to battle the hot and dry weather or building verandas and courtyards in Mumbai and parts of Konkan to modulate the monsoons was common. “Buildings which are being built now are not being governed by their response to climate. What you are building in Delhi would be the same thing you’d build in Chennai, or you’d build in Mumbai or Bengaluru. Now there’s an active response to climatic conditions by using air conditioners, coolers, dehumidifiers etc. which requires more energy,” added Joshi.

Therefore, the procedure of building green differs from a typical construction. To begin with, the design for a sustainable house differs to include aspects that reduce energy demand and decarbonise the power supply.

“Thickness of walls, for instance, has to be considered. Typically, 6-inch walls are designed but for such homes, walls have to be insulated, especially the ones facing south-east direction as exposure to heat is maximum there,” said Sandeep Sonigra, designated partner at the Pune-based developing firm Orange County Group, which specialises in building green and has received GRIHA 5 star rating and IGBC platinum rating for their projects. 

Insulating walls and roofs decreases the trapping of heat and saves energy required for cooling. Incorporating dual plumbing to ensure that drinking water is not used for flushing can be incorporated here. Apart from decreasing the need for energy usage, access to clean energy is an important aspect of a green home. Back in 2007, Sonigra started his firm with the idea of providing homes with green electricity generated on-site. In his projects, every apartment comes with free of cost electricity generated by solar panels, a metre that notifies in case a household is exceeding the certain limit of the free electricity provided. In that case, the residents pay for the difference.

Along with that, a solar water heating system, with a capacity to heat and store 125 litres of water for each household, is built and connected to each apartment.  

The choice of construction material 

“Over the last hundred years or so, the construction palette has shrunk. Use of mixed materials like stone, mud, bricks, timber, copper, iron, lime and jaggery, that have a long life  has stopped, age old practices have been lost. We have more or less restricted ourselves to only two materials: cement/concrete and steel structures,” added Joshi. 

Largely still these two components that Joshi mentions dominate the construction palette, but some pockets are observing a return to roots.  “The material specification is also changing gradually. There was a time when people wanted only Italian marble. Now people have come back to more sustainable, local materials like Kota stone or Jaisalmer stone, etc. Indian materials rather than imported with lesser embodied energy are used,” informed Bhowal. 

Choosing safe, environmentally friendly, local materials helps in minimisation of environmental impact from building activity. In his work,  Bhowal has swapped typical bricks for walls with sand lime blocks and fly ash bricks, which are much more energy efficient and have a low carbon footprint. 

To cut out the use of cement, Sonigrah also uses lime mixture for bricks and plaster instead. While using lime gets 20% costlier, it has a longer life cycle, is cooler compared to cement, which results in lower cooling requirements. So, in the long term, lime proves to be more cost effective. Producing limestone is also known to sequester atmospheric carbon. 

The parameters to define if a material is sustainable or not need to be revised. “The parameters are not robust enough. Certain parameters are well defined, say the strength needed for a material to be able to qualify as a construction material. But what is the metric to say that material has to perform this much in terms of thermal comfort? What environmental criteria are you using when you choose a material and promote it?” added Sugeet Grover, programme manager, Sustainable Buildings and Habitat Programme, Centre for Science and Environment. 

Building Material Technology Promotion Council (BMTPC) releases such compendiums for construction technology and materials. In a welcome move, now they have started promoting local materials to build houses with better environmental performances. 

Taller buildings, towering problems

High-rise buildings may be an icon of progress, modernity, and luxury, but they are not a sustainable housing solution. Tall buildings are energy intensive because of the constant up and down movement that happens while using lifts.

There’s one thing to understand before we may think that taller buildings are good because they are able to provide more space—FSI i.e. Floor Space Index. It is the maximum permitted construction on a piece of land. So, for instance, if a land area of 100 square metres is available and FSI is 3, then construction upto 300 square metres is legally allowed. Now, it is the choice of the constructor to build 3 floors of 100 square metres each or 30 floors of 10 square metres. The form of the building—high or low—does not define the density of the building. Therefore, low-rise, high density settlements are cost effective and energy efficient ways of building. 

Another issue is the  technology that is now being used widely in big cities to construct big housing complexes —mivan technology. Conventionally, concrete columns take the load of the structure while walls are made of bricks. In mivan technology, a formwork is made which is then filled with concrete mixture to build walls, where walls take the load of the structure. It is like pouring a cake batter in a vertical baking tray, where each wall is a baking tray. 

Although much quicker, this technology replaces brick and uses significantly more concrete. Apart from the fact that these walls have a higher carbon footprint, these are also thinner and have weaker insulating properties. Are the consumers aware of such technicalities? “Once I saw that it was being sold as an ‘RCC construction’ based building. But does the consumer understand? Do they understand that walls made using this technology are much less thermally efficient and will demand more energy consumption?” added Grover. 

Even while building high rises, using new and more efficient technologies can also significantly contribute towards saving energy. A regular lift will always use the same amount of energy, regardless of the weight inside it. A torque based lift, however, functions differently. Depending on the weight inside the lift, the energy consumption used for the lift to function also varies. The minimum energy, equivalent to the load inside the lift, will do the job, saving a chunk of energy (about 66% less as per Sonigra) which otherwise would have been used by a regular lift. 

NEXT:  Part II – Retrofitting a boon, but greenwashing a bane for sustainable urban housing