Monthly Archives: May 2014
When a wound does not get cured despite varied treatments, what do the doctors do? They study the symptoms deeply, get a basic understanding of the wound and try finding out the root causes. If this diagnosis works out well, they are sure to counter the disease at the starting point itself. All our best intentions and actions will fail if we fail to reach the source of problem.
This analogy applies to sustainable development equally well. Increasing number of studies from around the world are suggesting that globalisation is among the root causes for unsustainable development. This theory is yet to be fully proven and can be questioned putting the blame on the impulses of many developing nations towards matching the developed world and aspirations of millions of people to live the way rich nations live, which together can result in energy consumption and materialistic desires. However, the global market cannot be totally exempted from the blame, without which the nationalistic and individualistic urges cannot be met.
The modes by which unsustainable ideas get fuelled by the global economy are both subtle and strong.
Helena Norberg-Hodge comically points that oranges from 10,000 km away are costing less than oranges from 1,00 km away. No logical theory that we are aware of from historical times can explain this. Of course, we can thank increased production technology, instant communication, paper-less transfer of international currencies, insured global movement of goods and all such reasons that make the above statement true. However, the point is not about proving her observation, but about realising at what cost to nature we are achieving it all.
From an economics perspective, the construction materials we buy may cost less, but from an ecological perspective, making the product in one place and marketing it in another causes havoc to nature. It demands elaborate logistics for packing, transporting, marketing team, C & F agencies, insurance, internet connections, managerial staff, software and hardware for online records.
The embodied energy of the product at the destination cannot even be calculated by our present methods. Even if we manage to get the energy figures, most possibly it would be ridiculously high compared to local materials.
Building with products from far away Indian locations or from abroad may appear beneficial from cost, but would be disastrous from the climate perspective.
Globalisation also has cultural impacts, mostly on the negative side, as such localisation can ensure cultural continuity. The multinational market showcases investment to boost local economy or job creation, but it also siphons off local income back home and discourages local skills, draining the nation of its resources. As such, localisation is necessary to preserve nature, culture and economy.
It is time we critically look at localisation, understand why it is necessary for a sustainable future and then dovetail all our alternative ideas within this frame, so that energy consumption may reduce, wastage may get minimised and we get to live with lowered carbon footprint in the future.
The human mind never ceases to think and explore, even when we know that all the innovations may not be beneficial, for the simple reason that one valid ideation among a hundred failed ones is still worth the effort. On a comparative note, the building industry does not indulge in continuous and steady research; hence a whole lot of established concepts continue to be employed. As such, occasionally when a great new idea springs up, we should not lose out on the opportunity to explore it or even employ it.
The last century has seen innovative roofing ideas such as hyperbolic structures, catenary curved vaults, tensile membranes, domes without formwork, prefabricated shelters, geodesic domes, ferro-cement roof panels, space frames, and pre-engineered structures. Mostly known to architects and engineers, these high-ended ideas demand a thorough knowledge of roof behaviour, technological expertise to manufacture the components and skilled labour force to execute them at site. However, these conditions do not mean they should be excluded from routine public buildings and normal house constructions.
Funicular shells also belong to this set of alternative solutions. Many architects have used this idea extensively in their projects. Shell roofs are most economical in short spans of 1.5 to 3 metres, so the roof area is divided into grids of judicious spans, preferably square, even though rectangular shapes are also workable. These grids are formed by RCC beams, virtually creating a framework of side supports with the central part to be filled by the shell roof. The central filler part is a two-way curved shallow dome-like profile generated by the required geometry. Upon the form work, bricks are laid in a chosen pattern, which becomes a self-supporting system, held by the beams in the edge, with minimal steel and concrete.
In case of large halls, the main columns can be in the designed spacing, but the space in between needs to be subdivided by cross beams to take the shells, while in areas like bedrooms, each room can get one roof. The edges of this shell roof shall be thick to balance the thrust effect of the roof weight, becoming thinner as it reaches the top centre. The upper part of the shell can be filled with brick bats or lean mortar to get the level floor finish as required. The weight of the flooring material pushes the shell down, stiffening it in the process and making it stable.
Achieving perfect geometry is very important to ensure arch action within the curved shell, transferring the loads to the side supports. Considering the detailed calculations required for roof form, making fibre glass formworks in smaller parts becomes even more economical than individual formworks, besides the possibility of them in different combinations to get roof forms.
Once these basics are followed, a wide variety of patterns can be worked out for the roof. What initially appears as complex, emerges as a do-able idea.
How is the Taj Mahal roofed? It is a question that need not be asked because all of us know it is roofed by a dome. The commoners may not know of the technical details about the bulbous shape atop, but the technical experts can analyse its form and behaviour from different perspectives. Domes have dominated the historic skyline for centuries and continue to have a prominent role even today.
However, most buildings that we build today cannot take a dome for reasons like upper floors are ruled out, they effect the possible terrace, the rise of the dome may create unwanted interior volume, expert skills are required to do a stable dome or that they are possible mainly on circular plans. Does anyone wish to have a dome shape, without any of the above limitations? The answer lies in shell roofs.
Technically, shell roofs are not the same as the domes, but share a few common factors like arch action for transferring the building loads. Among the viewers, of course, they evoke similar feelings as domes due to the curved form. The shell roofs can be in thin concrete or masonry, curved in form, spanning short distances. Unlike the domes, they are not hemispherical in form and do not rise high, as such enable useable floors above them.
In India, many well-known institutions like Structural Engineering Research Centre, Auroville or Anangapur Building Centre have explored shell roofs for application towards cost-effective, fast track constructions with an alternative aesthetics. The former ones worked with varied materials including concrete roofs, while the last one worked mainly with natural masonry materials. The building centre worked with what is technically termed as funicular shells based on the catenary curve principle, which suggests the curved shell roof would transfer loads to the edges in an axial or perpendicular manner, creating least of deflection and turning moments.
For a flat roof
Shell roofs normally enable a normal flat roof, create beautiful patterns in ceilings, speed up the work, save much of concrete and reduce steel consumption by more than half. While the funicular roof best suits square profiles, it can be constructed atop rectangular plans also.
Of course, the profile needs to be evolved carefully and the formwork done to the specific curves. For all the advantages of funicular shell roofs, it demands expert advice and masonry skills. Once trained, the team may venture into even complex roofing solutions.
Today, in the urban construction industry, mainly in the large commercial and residential projects, everyone is talking green; claiming green; promoting green; and the future appears to be the place we all can be proud of. The generations to come are all safeguarded, or we tend to think so. Even in the smaller scale projects dealing with houses, resorts and schools, we claim to be designing sustainable buildings, as if, if all the new buildings are built this way, the earth can retain its ecological balance. But should we hype these new green ideas and feel romantic about being eco-friendly?
With the carbon dioxide count crossing the tipping point of 400 parts per million, we have already crossed the limits. Only a blanket ban on construction activities may help us, which we know is impractical to impose across the globe.
As such, every concern and every action towards reducing carbon consumption is definitely welcome and laudable. But to turn our actions into a fashion statement to be talked about in public is a dangerous trend, for we know fashions change rather too fast. Today’s hype can turn into tomorrow’s ignorance. Positioning the efforts towards energy efficient designs on a flimsy trend, hoping to gain increased market share thereby can defeat the purpose in the long run.
Let us realise and honestly admit that what we are talking about are simply the alternatives and not yet about the saviours. We still do not know what approach would and what materials could ensure a zero carbon construction industry. The much hyped net zero energy buildings are not yet our saviours because they still use solar panels coming with high carbon footprint, batteries with disposal problems and as a building may have high embodied energy. Of course they are among the major steps we have taken towards sustainable building, but cannot be the reason to feel complacent and start celebrating.
About a decade ago, where was all this talk about green or the energy leadership? What if in the next decade all this concern vanishes? Of course there have been individuals and institutions doing eco-friendly buildings in the past and they will continue doing so into the future irrespective of the trends, but their impacts will be minuscule in future as the lurking danger of climate change gets even more powerful. We need every human being to be aware of the implications of his/her individual actions.
Any attempt trying to package eco-friendly designs as a romantic idea to talk around the town could be pretence for self-satisfaction or boost the ego by claiming a social position. Building with nature is not a mystic approach only a few consultants and builders are capable of, but it is something that every one can aim for. Only this pragmatic awareness can help in spreading the idea of eco-green and lead us into a safer future.
Among all the building parts, which has captured maximum human attention? Possibly the roof — structurally a challenge to ensure it does not collapse; aesthetically important for it covers the whole building; functionally critical since it has to take on rain, sun or snow; and to top it all, constructing a roof over an empty space below demands high skill.
Accordingly many ideas have evolved across time in every settlement, some of which we have covered in the earlier essays.
People are obsessed not only with how the roof is built, but also with how it is seen, from above as a roof and from under as a ceiling.
Along a sloping site, say in hill station, what we see below are mostly roofs after roofs, in receding stepped fashion, which offer an attractive profile for the whole hill station.
Looking up from the interior of a space, we generally see flat white painted surface, which could appear predictable and dull for many people. As such, there have been experiments with the roof both in terms of materials and technology, to evolve an attractive roof.
One such method is to cast the RCC roof with inverted clay pots or shallow mud bowls set within as filler material. Conceptually it is a method to substitute the replaceable concrete by cheaper clay pots to reduce cost and weight.
As such, there are no structural problems or apprehensions about the performance of the roof. Once cast, the ceiling appears attractive with inverted pots, as if it’s decorative false roofing.
With the centring ready for the roof, the clay pots of chosen diameter are kept face down as per design, at designated spacing and pattern.
A thin layer of mud is spread around the pots to ensure they do not move during the concreting, steel reinforcements tied as per the advice of the structural engineer around and above these pots, electrical conduits are placed around the pots with no fixture overlapping with the pots and then the roof is cast.
The spacing for steel reinforcement needs to be specially designed based on pot size, room spans and such others, hence this idea does require a qualified engineer around.
The mud layer is removed from underneath after concreting, highlighting the pattern of the pots.
While the soffit of the roof shows an attractive pattern of clay pots, the upper surface is flat to take on another floor.
Of course, any pattern can be produced today by false ceiling, but they come at an extra cost, can be justified only at specific locations and are done with cheaper materials like POP (Plaster of Paris) or gypsum.
If we can build naturally and integrally to get a unique roof design, better to chose such right alternative methods over the more common place false ceiling methods.