Why is shading required in buildings?
When the weather is hot outside you want it to be cooler inside your home. If sunlight happens to enter your house, all its heat gets absorbed by the structure of the building, trapping the heat and making the house uncomfortable.That’s the reason why, through the ages in all parts of the world, people living in warm and hot climates protect themselves from the sun – like carrying an umbrella. It’s as common sense as that. Shading is absolutely essential in hot and warm climates.
What are your views on the current use of shading practices in India?
People are forgetting to shade the openings of buildings or even create shaded spaces outside the building. This is entirely the fault of the current culture of architectural design. The building is seen as an object, which is to be composed, etc. and not something that is designed in response to the climate or how the sun moves around it. This is just forgotten. This gets worse when some people start saying that to have an external shade on an opening is inviting trouble because pigeons will sit on projections and that it’s difficult to maintain. Well, I would say this is a design problem. Whatever you design ought to be maintainable and take care of problems such as birds, etc. Nevertheless you must have shading. If you retreat from the design problem, it does not mean that you have solved it. And if you fall back on the promises of the glass industry saying that you don’t have to do any shading and only darkening the glass can solve the problem, then let me tell you then the glass man is totally misinforming you.The darkened glass is picking up heat and converting the glass into a high temperature surface. It cuts down the light but not the heat transmission. And if you then ask him ‘Look we want to stop the heat transmission, so what’s to be done’, then he tells that ‘We will do a double glazing, put a low-e coating on the inside and the glass used is spectrally selective so that only the visible light comes in and the rest of the light is reflected. But it will cost you three times as much, but then that is the latest technology after all.’ As we can’t afford the latest technology, we settle for the worst of it because we want to look modern. So this is where the problem lies. I’m afraid that people have forgotten how to shade the building and they are trying to convince themselves that they are alright. This is drastically wrong.
Does the shading differ for different typology of buildings?
That’s a very good question. If you look at the problem of ‘designing a shading system’ a little more scientifically, it’s got to do with how you do get the daylight that you want, without getting the sun directly. Or, when you are getting excessive diffused lighting/radiation from outside, how you can filter it. So there is a contradiction here: you want the light to come in but you want it spread nicely in your space. And at the same time you don’t want to let in any more light than what is necessary, and also not let in any heat. Now it depends on what you are lighting up. If it is your home, then the illumination inside your home in all the rooms is not a critical requirement. If you need to do some work by the daylight, you can go closer to the window. But in an office space or an industrial space, where every part needs to have good light so that you can occupy any part of it and work there in good light, it becomes different. So depending on the type of building, how you let the light in and how you shade from excess light is a different design problem. So for residential buildings, it will be one type of solution; for commercial buildings, it will tend to be a different type of solution; and for industrial buildings, yet an another kind of solution. That’s one aspect of the differentiation for the typology of building. There is another important thing. The sun moves on a particular trajectory across the sky depending on where you are located on the globe and it shifts its trajectory during different times and seasons of the year. Hence the shading has to respond to where the sun primarily travels along. It also has to respond to the sky/horizon, especially in the hot-humid climate when the horizon is extremely bright and you get a lot of radiation. What it means is that you have to design the shade for the way your building is oriented. As the sun moves or as its intensity changes, depending on the seasons or the time of day, you end up responding to it with something variable. A kind of universal solution is a variable or movable shading system that is outside the opening or window. If you can design that then you can take care of any orientation, any time of the day, at any location
What are the different kinds of shading that can be installed in buildings? According to you, what is a better option, static shading or movable shading?
From the point of view of being able to respond to the variations in the sky and position of the sun outside or the variation in how the radiation reaches the window – that is, whether one is in a dense urban environment or out in the open – something that is movable is the right option. But, generally, something that is movable will be a more complicated device as it has to be adjusted, whether manually or automatically, and will tend to be a bit more expensive. And when you make something movable, it is more difficult to make it robust.So my general recommendation is to see what you can achieve with a fixed shading first and then add the variable component as required. So you might get a happy balance between the two things. Theoretically, a movable/adjustable device is the universal solution. But, practically, a combination may be better because of cost, durability, maintenance, and many other issues.. For example, if you have a chajja on a west-facing window, it will protect you till about 2.00–2:30 in the afternoon. And when the sun goes down and if you don’t have a building or tree opposite, the heat will start coming in. So may be you can hang a chik under the chajja and tie it down after 2.00 p.m. This chik will be cheap and will last you 3–4 years, after which you can change it. So here is a low-cost response to the idea of a combination of fixed shading – to do quite a bit of the work – and variable shading to shade the remaining part. So the options that are available are very broad. It depends on the ingenuity of the people designing.
What options does the Indian market offer for shading solutions? Or is the Indian market prepared to offer adequate shading solutions?
Are there external shading products in the market? NO, there are none. The only kind of products that are available today is a perforated or cut screen in various materials. These are fixed and they are light filtering screens. These are available. But external movable/variable shading systems that are clever in the sense that they modulate light and bring it in the way that you want and also cut out the sun the way you want are not available.
What should be done to make the market more friendly for buyers to buy such shading systems?
It’s the chicken and egg story. I live in a house and I am troubled by the heat and the sun so I draw the curtains and still the air conditioner does not work properly. Nobody has come to tell me that ‘I can do something else for you. I can put a shade on the outside, which you can adjust from time to time and suddenly the air conditioning works better.’ There hasn’t been any demonstration of external shading systems as to how they improve the condition of a poorly oriented or designed building. The first thing that needs to be done is to develop a retrofit model for existing residential buildings. It needs to be something that can be installed on your 4–5 storey building while standing inside the house. It should be robust and reasonably economical. If somebody comes up with that product and people see its benefit, it will catch on just like the plastic bucket. It’s just a question of the development of a product, its demonstration, and then its marketing. It’s bound to happen. Once that happens, the principle of external shading will be understood by the consumer. And once the principle gets understood by the consumer, then the consumer begins to demand. That’s the next thing to happen. At the moment, we tell ourselves that we need to draw curtains if there is excessive sunshine coming inside the building and that’s all we think needs to be done. We haven’t understood that heat comes in nevertheless. So the principle of external shading needs to be communicated clearly, through some popular means – whether by using a popular actor or other means. Once that is understood, and you have this alternative product on the shelf, then the market will simply pick up. That’s for the residential sector. In Australia, I saw sliding screens on the rails of balconies in a block of flats. It is common place there and people use them conveniently. It’s become the expected norm. In Greece, 8–10 storey residential buildings have balconies surrounding the rooms and every balcony has an awning. People bring down the awning during day-time and lift it at night. This is standard as people know that external shading works. Here we have not understood that.
Can you give examples of how you have incorporated shading in your buildings?
We have incorporated shading in nearly all of our projects and we have tried different strategies. The first strategy we tried was to have a window that has two layers of glass, where the inner side of the glass opens inside and the outer side of the glass opens outside and between the two glass layers we have put venetian blinds. So what it did was it became an insulating window with a break for the sun falling directly and reflecting much light and heat outside. This was a pragmatic solution of a sandwiched venetian blindbetween two sheets of a glazed window. This is in the Transport Corporation of India Ltd (TCI) headquarters in Gurgaon. It works very well but the owners have to be reminded to adjust it seasonally to get its benefit. This is for an office building. For residential buildings, typically what we are now doing is to give a fixed shading device outside the window and then building a frame attached to that fixed shade where you can attach a movable/adjustable shade like a venetian blind, roll-up chik, louvers, etc. Basically giving the user the option to attach it later. May be this way there will be different types of such options that will become available in the market, once people start seeing that it can be done. For other office and institutional buildings, we have usually used fixed shading systems and not used movable shading. Here the principle that we have followed is that the shading system should be very light-weight, should be minimally attached to the building, and it should be perforated. Its geometry should be such that it intercepts the sun during certain seasons and certain times of the day, but as it picks up the heat it loses it to the surrounding air quickly and doesn’t transfer it to the building structure. That is the heat transfer building science behind designing a shading system: the shading system will pick up the sun’s heat. You don’t want that heat to be transmitted into the building, you want to lose that heat quickly to the outside. That imposes a technical discipline. In the last project that we did, we have a combination of a fixed shading and a movable screen, which has to be moved only twice a year. When we want a bit more of the sun to come in, like in the winter months, we turn it one way. And in the summer months, we turn it the other way and cut out the late afternoon and early morning sun. So part of it is movable and it has to be adjusted manually; it has to be adjusted 3–4 times a year.