SUSTAINABLE EVAPORATIVE COOLING AS A BUILDING’S SECOND SKIN
Architect Monish Siripurapu, Founder and Director at Ant Studio, Delhi decodes and demystifies the basics of evaporative cooling. We bring you an excerpt from his conversation with Architect Anjali Mangalgiri.
Anjali Mangalgiri is the founder and principal architect at Grounded, an award-winning architecture and development firm that she founded in 2010.
After graduating with a Bachelor of Architecture degree from the
School of Planning and Architecture (SPA), New Delhi in 2002, Anjali moved to the USA to do a Master in City Planning from the prestigious Massachusetts Institute of Technology (MIT). In 2005, she joined New York based architecture firm HOK, before returning to university to complete a Masters in Real Estate Development at Columbia University in 2008.
This column is a deep dive into all things Sustainable Architecture. Over the coming months, through a series of articles, A+D along with Grounded Architecture will share knowledge and start conversations to demystify technical concepts and practices that promote sustainability in architecture. This column is a follow up to an IGTV series on Grounded’s Instagram, where architect Anjali Mangalgiri discusses with experts the various sustainable architecture techniques, their pros and cons of use, as well as specific challenges in implementation.
Anjali Mangalgiri: Monish, you are an architect, an engineer and an artist all in one, and we are here today to talk about your famous invention, the CoolAnt. The concept behind CoolAnt is to use evaporative cooling to cool air in the interiors of our buildings without using electricity. So in the spirit of demystifying technical concepts in sustainable architecture, tell us what is evaporative cooling?
Monish Siripurapu: Evaporative cooling is nothing but achieving a cooling effect through the evaporation of water. The water takes the heat of the object it touches and the latent heat from the air around it to evaporate naturally, and as a result, it cools the surroundings. The most common example around us is our very own mitti ka matka. And of course, all desert coolers usually work using evaporative cooling.
There are other historic examples, like in
Iran specifically there are ‘Muscatis’, also called ‘Mashrabiyas’, which are essentially windows with
a balcony jutting out from the building facade, much like the Rajasthani jharokhas. These were built entirely using wooden latticework, so the air that entered the building first passed through the latticework or the jaali. And then, inside the building, as a further step, they had earthen pots filled with water. The water in the pots cooled the building and it was also used as drinking water. These were beautiful spaces in the Middle Eastern belt that also functioned as social spaces, where people would gather to drink water or simply come out to sit and watch the street.
AM: How wonderful! I remember my mom used to tell me about her childhood where they would have these chiks, which they would hang outside their windows, and they would actually wet the chik. It was made of the same material that is used to make the pallas for the cooler.
MS: I was actually going to come to that. The history of this detail, if we look at how it started, is quite amazing. The wooden nets or chik mesh used for cooling is derived from an ancient Egyptian system. The Egyptians originally pulled out roots from the river called Reeds, and stacked them to create a cooling divider. This later took on different forms in different regions, right from the chiks in Rajasthan to the Venetian blinds in Europe.
AM: Khas or Vetiver roots were also used, right? Khas has a beautiful fragrance and was often hung up around a space. When they’d wet it, it not only brought a cool breeze into a room but also its own unique scent.
MS: Yes, that is absolutely true. These traditional systems have existed for centuries and have worked pretty well. It definitely depends on the humidity and the region in which they are used, but they are effective systems even in today’s day and age.
AM: Now, let’s talk about your creation—CoolAnt. I have heard how you started off making art installations but that ultimately led to the CoolAnt, a superbly innovative cooling solution where you have taken the traditional technology of evaporative cooling but have updated it for today’s times. Monish, please introduce us to the CoolAnt.
MS: Five years ago, we first started work in a factory. Back then, the idea was to create an art installation that screens the hot air from the DG
The
wooden nets or chik mesh used for cooling is derived from an ancient Egyptian system. The Egyptians originally pulled out roots from the river called reeds, and stacked them to create a cooling divider. This later took on different forms in different regions, right from the chiks in Rajasthan to the Venetian blinds in Europe.
With
a system like the steel mesh,
depending on the sun angle, heat does penetrate at some
points of the day because it is thin and
has lesser depth. CoolAnt also takes the sun’s angle into
account and this increases the depth that ultimately cuts off more heat. This allows the CoolAnt system to work more efficiently compared to the existing systems, which are more two dimensional in terms
of their profiles.
Set machine within that space. The heat around the machine was unbearable, especially in peak summers. Along with that, the air coming out of the machine moved at a speed of nearly 10m/s, enough to push someone who stood in front of the machine. The DG set was impossible to miss as well, it was located bang in between two buildings. To escape this heat wave, people actually used to run from one building to another.
The factory wanted to come up with something to cut off the heat and that’s where we came in. We did our studies on evaporative cooling, and found it to be an effective solution but with one major drawback—it was not the most durable. The systems we studied often required constant replacement of parts or regular maintenance, all of which may not be practical in the factory setting and may not withstand the waves of continuous heat from the DG Set. We needed something more robust.
While doing our research, I found this beautiful Egyptian illustration of a pharaoh sitting, and his subjects fanning the surfaces of pots to keep him cool. So that got me thinking as to how we could reinvent that for the modern time.
We first tried using a brick jaali and poured water on top of that. To our surprise it worked, and that gave us a lot of confidence about the technology. So that was our first prototype—with Kachcha cement and bricks. Then we realised we could make it more aesthetically appealing and with a more refined geometry, much like an art installation. We also realised the heaviness of brick offered more of an obstruction to the air that was passing through, and wanted to build something that was significantly more aerodynamic and offered the least resistance to the air moving through it.
That is when we tried to use earthen pots.
With the DG set, we also had the constraint that air could not bounce back to the machine as it would impair the efficiency of the set. Hence, the idea of making walls in front of the set was ruled out
immediately. So we tried to come up with different profiles that allowed the draft to pass through, settled on the profile of an earthen cone, and then mathematically derived what length the cone had to be for it to be most effective in cutting off the heat.
AM: Does this mean that for each installation of the system, the cone will have to be engineered differently to suit the needs of that case and that particular building?
MS: Ideally yes, but we are trying to optimise it and trying to test the system by pairing different conditions with different forms—not just cones but also other geometries. Since the conditions were extreme in the factory with temperatures going up to 55°C in the summers, we needed an extremely precise solution for that case. For such extreme cases, it is best to engineer custom solutions but for regular cases such as households, we are able to create more standardised systems.
AM: So the basic concept of CoolAnt is that you are creating a web of terracotta cones that is wet, where air can pass through and is cooled as it moves through the web, because the latent heat of the air is used to dry up the cone. And on the other side, as it comes out, it will be cooler.
MS: Yes, absolutely. It is like any other jaali, but operates with the principle of evaporative cooling. We find jaalis made out of stone or wood, which also cool the air inside because of the size of the openings. In this case, we are using the size of the openings along with the advantages of evaporative cooling.
AM: Our conversation earlier led me to bring up this subject with a client where I was telling them about your system. And they told me about a house they’d seen in Goa with a typical Goan terracotta tiled roof, where the owner has installed a pipe with a few holes punctured along the roof. So in the hot summers, he runs water through the pipe, which in turn wets the terracotta tiles, in turn cooling the building.
MS: Wow, that is fantastic, especially because most of the heat gain in a building happens through the roof and the elevations. Depending on the size of the building, the roof may actually be taking in more heat than the sides of the building. In such cases, a system like this on the roof works wonders, and is so simple to implement.
AM: In your innovations with the CoolAnt, you mentioned that you are trying to develop a jaali system that can be configured to fit multiple scales and building sizes. Can you walk us through this evolution process?
MS: When we first began, we were primarily focussed on outdoor cooling solutions because of design constraints and practical concerns such as dealing with water splashback as it dripped down the terracotta web. This led us to explore geometries such as vertical slats that can be plugged onto a building elevation like a second skin, because double skins and envelope cooling can help bring down the energy demands within the building as well.
There are two ways of looking at this. One, as an isolated system where the system can work on its own as a passive design and no air conditioning is involved. The temperature is brought down because of the presence of the second skin, which shields the building and enhances natural ventilation. This usually results in a temperature drop of about 3 to 4°C depending on the location.
The other way is to look at it not as a replacement but as a supplement to an existing system. For a building that already has air conditioners installed, CoolAnt can be installed to bring down the air conditioning load. There is a possibility to reduce the energy loads by as much as 30 percent using this system.
AM: That is amazing! Is this with or without the use of water? How does the effect change?
MS: Without water, there is a variation of 5 to 6 percent. Instead of a 30 percent reduction in energy load, there will be a 24 percent reduction in energy load if the system doesn’t use water. So a
We
also realised the heaviness of brick offered more of an obstruction to the air that was passing through, and wanted to build something that was significantly more aerodynamic and offered the least resistance to the air moving through it. That is when we tried to use earthen pots.
The
system would require a lot less water during the monsoon and
the water would automatically adjust to provide more
water on a hot summer day. I have also noticed that terracotta tends to be hydrophilic, which means that it retains moisture within itself during the monsoon. That also helps bring in
a cool breeze and one does not have to constantly pour water over
the screen.
considerable impact is achieved even without water because you are cutting the heat at the source.
AM: When we are looking at it as a system of second skin, how would it compare with the existing second skin systems such as steel meshes with plants growing over it?
MS: With a system like the steel mesh, depending on the sun angle, heat does penetrate at some points of the day because it is thin and has lesser depth. CoolAnt also takes the sun’s angle into account and this increases the depth that ultimately cuts off more heat. This allows the CoolAnt system to work more efficiently compared to the existing systems, which are more two dimensional in terms of their profiles.
Also, terracotta by default has a higher heat absorption rate and lower reflectivity compared to steel or any other metal. This allows it to perform better with a lower carbon footprint. Slate and sandstone are also good alternatives to terracotta because of their porosity.
AM: That is very interesting. So while choosing stone cladding for a building, if we choose a stone that is more porous, it can increase the thermal comfort within the building?
MS: Yes, it depends on the application. A perforated jaali as opposed to a solid cladding will definitely perform really well.
AM: When you’re building the terracotta web, what is the frame? Isn’t that made of steel?
MS: Yes, but it is very minimal and we try to reduce it as much as possible using our details. For example, we do an interlocking detail where stone is used. There is the need for a metal framework for support for sure, but its exposure can be limited and the quantities can be reduced.
AM: I would be very interested in learning about the difference in metrics when using plants as a second screen compared to terracotta pipes. That would be a really interesting comparison and give CoolAnt an edge.
MS: Yes, we’re actually trying to integrate plants into the system because it brings together aesthetics with thermal comfort.
AM: I also actually think the system with plants would require a lot more maintenance and in contrast the CoolAnt system requires next to no maintenance. And in both cases, drip irrigation is used as a common element.
MS: Yes, we’re working on ways to control the amount of water used, depending on the humidity changes in different seasons by automating the drip irrigation system. For example, the system would require a lot less water during the monsoon and the water would automatically adjust to provide more water on a hot summer day. I have also noticed that terracotta tends to be hydrophilic, which means that it retains moisture within itself during the monsoon. That also helps bring in a cool breeze and one does not have to constantly pour water over the screen. We have also had questions about dampness in the house. That’s the reason it is proposed as a double skin so that it is segregated and there is no way the moisture can come in.
AM: Rainwater harvesting seems like a great way to use the collected rainwater to wet the CoolAnt skin throughout the year. There is no new water consumption and it could work as a circular system. We would love to see more information about this skin system because this is something that we should consider as a country with hot climates in almost every region. Air conditioners should not be the only things we rely on and this could be an excellent alternative. Air conditioners also increase the urban heat island effect and are responsible for the release of harmful refrigerants, and as you said, this makes for a viable middle ground. It allows you to have air conditioning but reduces the load of air conditioning. Have you ever considered using this system for the roof?
MS: We have one project in the pipeline where it will be used as a shading device instead of a cooling device. This can be done with cane or wood slats and doesn’t have to necessarily use terracotta.
AM: Monish, I also want to talk about how you as an architect, instead of focussing on building, have chosen to build this innovative technique. You have found a way to connect different dots together to make something unique and special. And from there, you figured out a way to show your work and build its credibility. Architects often feel that talking about their work is cheap and not cool. So please, tell us the story of how you went about pitching CoolAnt to different people and publications?
Ms: I finished the factory solution two days before leaving for my PG Diploma. I did not get to see it in action for nearly a year and realised it was still working after all that time. At this point, I also wanted to build my own practice but had no work or clients. This is when it struck me that unless I show my work and talk to people about it, I was not going to find any new work that I wanted to do. That is when I started approaching different publications and showing the installation in different places. Finally after three months, one of the architecture magazine responded showing interest in publishing the project. And that really helped.
I don’t think there is anything wrong in speaking about your work. Worst case scenario is that it is published and no one sees it. But the best case scenario is that the right kind of people, aligned to your values and goals, see it and reach out to you. Whether it is a publication, or a website, or even platforms like Instagram, the visibility helps start a conversation with the right audience.
AM: What is the additional cost of building the second skin?
MS: Right now it is between INR 700-1,000 per sq ft, and this is because the parts of the system are still handmade. With increase in scale, we will certainly be able to optimise more as manufacturing will be streamlined and costs will significantly reduce.
AM: Finally, can a terracotta jaali replace your system of custom made terracotta pipes? Will it have the same benefits?
MS: Yeah, the biggest difference is that we are trying to optimise it based on individual sun angle and airflow of that specific site. The terracotta jaali also cuts off heat, but our slightly more custom solution results in better metrics, more heat cut off, and better performance in the long run.
Another factor is that there are two kinds of terracotta jaalis—porous and non-porous, depending on the glazing used to coat it. While the advantage of using a glazing is that it improves the finished aesthetic of the material because it looks more uniform and stainproof, it also means that its heat absorption abilities are reduced. A more porous material is definitely more effective in cooling the building.
The
biggest difference is that we are trying to optimise it based on individual sun angle and airflow of that specific site. The terracotta
jaali also cuts off heat, but our slightly more custom solution results in better metrics, more heat cut off, and better performance in the long run.
S treets, which have always been known to be the lifelines of any city, have been rendered lifeless in many cases since the COVID-19 outbreak. These crucial elements of cities, which have always signified public life, are now left as mere pathways, only to be used in dire need to reach a destination. During the lockdown, the streets were deserted due to government mandates. Post lockdown, they remain just somewhat populated, that too only by those who have no other choice but to be out there.
It has indeed been a frightening time amidst this worldwide pandemic. Anxieties about COVID-19 seem to have taken a psychological toll. The unpredictability surrounding the virus has further led to magnifying the situation and spiralling out into devastating apprehension and terror. As lockdowns and restrictions soothe in various cities, many
people find it exceptionally challenging to readapt to “normal” life. As the restrictions ease, mental health experts are noticing a phenomenon as the next emerging mental health crisis—anxiety about life after lockdown.
Dr Steven Taylor, author of the book The Psychology of Pandemic and a professor in the Psychiatry department at the University of British Columbia in Canada, explains this seemingly emerging phenomenon as: “These people [anxious about life after lockdown] aren’t frightened of having panic attacks, they’re frightened of infection.” This emerging phenomenon of post pandemic anxiety imperatively calls for a solution. Will psychotropic medications (for anxiety) be the only way out in the times to come? Maybe not.
In her 2005 work titled ‘Designing urban space for psychological comfort: The Kentish Town Road project’, Ruth Dillon from the Department of Architecture at the Royal College of Art in the
UK, has very clearly stated that “the tendency of urban environments to produce anxiety is well documented in a range of theoretical and historical literature, but there is little current work that considers how public spaces might be designed to alleviate anxiety among their users.” In this context, streetscapes, which describe the natural and built fabric of streets, have also found a rare mention in writings related to international health.
In 2016, Marjia Jannati, a junior at Georgetown University pursuing a BSc in International Health, wrote in a blog post on ‘Sanity and Urbanity’—an Urban Design/Mental Health blog, that exposure to monotonous features in streetscapes have
Streets
and Streetscape Design have been well researched and more than one definition of the ‘Great Street’ has been developed. Most definitions present somewhat overlapping descriptions, very similar to this one by Toole Design Group, a firm founded by Jennifer Toole with a mission to support innovative streets and dynamic communities.
The
perspective of a theoretically extracted and empirically authenticated system for assessing streetscapes for anxiety among its users may offer assurance for future research and theory building that can inform policy and design. Designing anxiety alleviating streetscapes may, in fact, become the new normal.
been associated with sadness, stress and even addictions. These ideas and mentions from past studies about streetscapes with reference to anxiety, and the emerging phenomenon of post pandemic anxiety, seemingly point towards the need of a whole new distinct field and area of practice, to be acknowledged and evolved globally—Anxiety Alleviating Streetscape Design.
Streets and Streetscape Design have been well researched and more than one definition of the ‘Great Street’ has been developed. Most definitions present somewhat overlapping descriptions, very similar to this one by Toole Design Group, a firm founded by Jennifer Toole with a mission to support innovative streets and dynamic communities. It says, “Great streets do more than get you from point
A to B—they encourage you to linger, chat with a neighbour, watch the world go by, or sit and enjoy a good book.” Also, over the years, in the sincere attempt to achieve great streets, cities worldwide have prepared their respective streetscape design guidelines. These guidelines present significant objectives to great streetscape design, as apt for the respective city. The streetscape design guidelines manuals may also present principles to ensure that design directions and guidelines align with the visions for the streets in question.
These principles are usually evolved through inventory and analysis of the area, public engagement and review of previous studies, policies and trends in streetscape design. The evolution of these guidelines in several cases have also engaged learnings from theorists such as Jane Jacobs, an American-Canadian journalist, author and activist who influenced urban studies, sociology and economics.
Many of these streetscape design guidelines, no doubts, remain crucially relevant even in the present day. However, with the unexpected and alarming COVID-19 pandemic, which seems to be causing anxiety in every other individual who needs to interact with any of the city streets, it is indeed time to review these streetscape design guidelines once prepared, and most importantly, add objectives to them in relation with anxiety alleviating streetscape design.
The evolution of a whole new and much needed distinct field of ‘Anxiety Alleviating Streetscape Design’ may require the combined perspective of practicing architects and urban designers with those of behavioural and health scientists and clinicians. Theories with regard to this distinct field may evolve when these experts collaborate in transdisciplinary research that integrates the knowledge base and theoretical approaches of each discipline. An in-depth enquiry into the complex interaction amongst physical features, social processes and individual behaviours in relation with the built environment may be the way forward. The perspective of a theoretically extracted and empirically authenticated system for assessing streetscapes for anxiety among its users may offer assurance for future research and theory building that can inform policy and design. Designing anxiety alleviating streetscapes may, in fact, become the new normal.