Designing a low energy home
Residential energy consumption takes up about 25% share of the total energy consumption in India, a majority of which is drawn from faraway power plants. India is working to achieve its COP 26 goal of becoming a net zero nation by 2070 with a target of increasing its share of renewable energy capacity to 175 GW by 2022. It is seldom recognised that utility scale projects to generate renewable energy are unsustainable because they involve destruction of biodiverse landscapes. In an attempt to solve one problem, the world is marching into another, one where land, livelihood and biodiversity is disappearing at a maddening pace.
An alternative to this arrangement is to build a sustainable home, essentially a decentralised unit that is capable of producing energy, managing its own waste and meeting its water needs without depending on the centralised system. Sustainable homes may be designed using vernacular techniques, that is using locally available materials and construction techniques best adapted to the climate of the place while providing livelihood to local workers and artisans. Such an approach drastically reduces the resource and energy consumption in both construction and operation phases.
Traditional architecture is a treasure trove of wisdom well suited to the context of the region, both climatically and culturally. One such example is the central courtyard house in the hot and dry climatic zones. Courtyards supported a myriad of functions ranging from a place for families to gather, gossip, rest, cook, play and more. It also acts as a light well in the central portion of the house that shelters all the surrounding rooms from severe heat, keeping them well ventilated and cool. As the courtyard is exposed to the sun, the air in the court heats up and rises, drawing cooler air through the house. In a colder climate such as Ladakh, houses are built with thick mud walls and roofs that act as insulators. The walls absorb and store the heat from the sun during the day and release it to the room interiors at night, thus providing necessary warmth for the cold nights. Windows are kept minimal to avoid heat exchange.
Maintaining thermal comfort and daylighting are two processes that consume a significant share of energy in any residence. A good architectural building design can reduce the energy needs for these two primary functions using passive design technology. For example, some techniques to reduce air conditioning in a hot and humid climate could include stack ventilation, cross ventilation, use of shading devices on windows, evaporative cooling like fountains and water screens. A building designed to be well lit throughout the day can employ methods such as appropriate window orientation, glare protection, use of skylights etc. Outdoor lights can also be powered using solar energy captured during the course of the day. It is prudent to use the minimum required outdoor lighting, focussed on the task area and not the sky so as to avoid adding to the high levels of light pollution in the cities. The third largest consumer of electrical energy in residences is attributed to electrical appliances. Water heaters can be powered by solar energy, as is the case with many urban households. A smaller single door refrigerator consumes about half the energy of a double door refrigerator. At every stage, one can make a conscious decision of their family requirements.
After reducing the energy needs drastically by various design measures, one may employ renewable sources to meet the energy needs of the house. An essential approach to sustainability is energy demand reduction before moving on energy efficiency and clean energy sources. A net zero home is one that consumes no net energy from the electricity grid over the course of the year. In essence, a net-zero home will produce as much electricity on-site as it will consume over the course of one year. Net zero homes provide both environmental and economic benefits to residents, while reducing dependency and reliance on the electricity grid.
At residential scale, rooftop solar plants can be used to power the house. Rooftop solar plants save transmission losses by 12 to 15 percent. Typically, 1 Kilo Watt power rooftop solar plant requires about 10 sq.m area , and the energy produced depends on the season and number of sunlit hours, which in turn is determined by the geographical location. The Solar power generated can be used either for self consumption in the premises or can be fed into the grid and be adjusted in the electricity bill through a process called net metering. The Ministry of new and renewable energy MNRE had introduced the Grid connected solar rooftop programme as part of which it provides financial assistance to households in installing solar on rooftops connected to the electricity grid. The subsidy to be given by the Government of India is 40 per cent for roof top of upto 3 KW capacity and 20 per cent beyond that upto 10 KW, and will be credited to the account of the householder. The procedure was found to be cumbersome and riddled with delays. Recently in 2022, the MNRE has issued a notification simplifying the procedure of the rooftop solar programme. Yet, in reality, only around 0.4% of independent urban homes have installed rooftop solar. The major deterrents have been consumer inhibition and low awareness about the technical, financial, and operational aspects of installations.
However, it is necessary to be aware that even a system such as rooftop solar comes with its own set of cons. For example the creation of photovoltaic cells itself is not a green or clean process. The most important aspect of a sustainable house or infrastructure is to create one that consumes less energy in both its production and operation. As human civilization settles down comfortably into a lifestyle of energy and product consumption, we lead ourselves to believe that we can become green by just shifting the source of energy generation, unwilling to fathom that unnecessary product and process creation is the underlying issue. Energy reduction and lifestyle changes can pave the way for true sustainability.
Janani S is an architect with a professional experience in sustainable building technology and works as Assistant Coordinator, Inclusive Urbanisms at Environment Support Group
First Published in : CFA