The building and construction industry in India is posed with several challenges today. Rapid urbanisation coupled with larger disposable income has led to a surge of affordable cooling systems in the market. To put things in perspective, the air conditioning market has been growing faster than other sectors, at CAGR of 18-20 per cent over the last decade. Furthermore, India is projected to overtake the US to become the world’s second-biggest emitter of carbon dioxide from the power sector before 2030. As the nation’s electricity demand skyrockets, carbon dioxide emissions from India’s power sector are expected to rise nearly 80 per cent by 2040 as power use almost triples, driven in part by air conditioning.
While active cooling systems provide controlled comfort conditions, they come with a higher capital investment and operation and maintenance (O&M) costs. Passive systems on the contrary have lower investments both in terms of capital and O&M costs. Passive cooling systems, however, require a nuanced understanding of space planning and climate responsive design strategies which must be integrated within the building from the design inception. In this regard, contextual solutions are essential for optimum comfort and one strategy can often not be made to fit different site conditions and project requirements.
In lieu of exponentially increasing energy demands, passive cooling strategies are critical to drive down energy consumption and carbon emissions in turn. This article illustrates some of the case studies which have implemented various low or no cost space conditioning technologies.
Residential – Smart Ghar (affordable housing), Rajkot – registered for GRIHA AH (affordable housing)
Located in Rajkot and developed under the PMAY (Pradhan Mantri Awas Yojana) by Rajkot municipality, the project demonstrates one of the no or low-cost strategies which can easily be implemented without increasing the capital investment of the project i.e. climate responsive designing.
In modern high-rise residences, the provision for openable windows to allow for cross ventilation in spaces when the ambient temperature is comfortable and often not provided. Inadequate fenestration design without proper shading results in unfavourable conditions such as glare, wind-driven rain or strong wind drafts in the space which in turn prompts users to keep the windows shut or blinds drawn, even if the ambient conditions are favourable.
Vernacular design strategy i.e. use of ventilators has been incorporated in these affordable flats. Focusing on the affordable nature of these flats, the design ensures that the dependency on active cooling systems is reduced to the maximum extent possible. The windows have been provided with top hung ventilators providing an option to the users to operate it during pleasant weather times and with the opening, the wind speed can also be controlled. The top hung window also acts as a protection from rain and prevents its entry inside the building. To create a through passage within the living space the door design also incorporates louvered ventilators for cross ventilation.
In the flat’s design, negative spaces such as toilets and kitchen share the shafts for piping and ventilation. However, to make sure that there is negative pressure in toilets and kitchen which will provide a natural air suction through bedroom and living room windows and facilitate cross ventilation, forced ventilation is being done on the roof in these common shafts. This strategy also makes sure that the foul smell does not go inside the living space of the flats. To reduce heat ingress and further facilitate thermal comfort, the buildings have cavity walls built with AAC blocks.
Climate responsive design philosophy if implemented properly can easily reduce 90-80 per cent space conditioning cost both at the initial installation as well as future operation.
Commercial – Akshay Urja Bhawan office (HAREDA), Panchkula – GRIHA 5-Star rated
Located in Panchkula, Haryana, this government office building has been made to showcase passive and hybrid space conditioning systems. Panchkula with 8-9 months of dry and hot weather and remaining 2-3 months of rains provided a suitable location for a naturally ventilated office design.
Looking at the glass façade, most of people assume that this is an air conditioned building. However, it is one of the buildings which contradicts the belief that glass buildings cannot be sustainable and require air conditioning. The building planning has been done keeping the regularly occupied spaces in north and southern façade. East and west façade window fenestration design is responsive to the direction, making sure that there is no glare and reduced heat.
Further, the south façade has been designed with excess glass and concrete box (solar chimney) making sure that the internal office space is rapidly heated. Solar chimneys located inside the office space have the provision of louvers which facilitate exhaust for the heat generated.
This process makes sure that the office space develops negative pressure. The project has been designed with a courtyard. To further generate positive pressure and initiate the wind flow to cool the office spaces. The project has installed misting system in the courtyard through which small water droplets are sprinkled in the courtyard to cool the air.
As per the wind flow, air from the courtyard starts flowing towards the office space. To facilitate this, flow the corridor walls have designer jalis created near the floor level. The draft created from these jalis and the exhaust created by the louvers in chimney makes sure that the space is thermally comfortable.
These projects demonstrate how innovative solutions can not only provide adequate comfort conditions for the users but also reduce energy demand significantly. The adaptive thermal comfort models reinforce the idea that building users are comfortable in a much wider range of temperature, RH and wind speed conditions, which provides the opportunity for a wide range of building typologies to adopt such strategies. Furthermore, advancements in software to simulate heat exchange and wind flow patterns allows designers to not only iterate strategies but also predict thermal performance in buildings more accurately.
In wake of the multifarious challenges that India faces, it is imperative to make a paradigm shift towards passive and hybrid cooling systems especially in cooling dominated countries like India where ample solar and wind energy can be harnessed for improved thermal comfort and reduced energy consumption.
Senior Program Manager,