Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

The Shard

Study about energy efficiency features on "The Shard" by architect Renzo Piano

  • Login to see the comments

The Shard

  1. 1. B u i l d i n g S c i e n c e | 1 THE SHARD
  2. 2. B u i l d i n g S c i e n c e | 2 ABSTRACT Energy efficiency is the first step toward achieving sustainability in buildings and organizations. Energy efficiency helps control rising energy costs, reduce environmental footprints, and increase the value and competitiveness of buildings. Energy efficiency and renewable energy are said to be the twin pillars of sustainable energy policy and are high priorities in the sustainable energy hierarchy. In many countries energy efficiency is also seen to have a national security benefit because it can be used to reduce the level of energy imports from foreign countries and may slow down the rate at which domestic energy resources are depleted. Therefore it becomes necessary, especially to us, architecture students to know about energy efficiency and the various techniques used for it in the buildings present today.
  3. 3. B u i l d i n g S c i e n c e | 3 CONTENTS Title Page no. I. Energy 01 II. The Shard 02 III. Construction 03 IV. Building Technology 07 V. Building Materials 09 VI. Energy Efficiency 15 VII. Active and Passive methods 16 VIII. Renzo piano on energy efficiency of the Shard 18 IX. Bibliography 19
  4. 4. B u i l d i n g S c i e n c e | 4 ENERGY Energy, in building science, is a fuel or resource in building science used to operate machinery, for heating and cooling puposes. The sources of energy are broadly classified into two main groups: Renewable and Non- renewable Renewable Energy Renewable energy is the energy which is generated from natural sources i.e. sun, wind, rain, tides and can be generated again and again as and when required. They are available in plenty and by far most the cleanest sources of energy available on this planet. For eg: energy that we receive from the sun can be used to generate electricity. Similarly, energy from wind, geothermal, biomass from plants, tides can be used to fulfill our daily energy demands Non-Renewable Energy Non-Renewable energy is the energy which is taken from the sources that are available on the earth in limited quantity and will vanish fifty-sixty years from now. Non-renewable sources are not environmental friendly and can have serious affect on our health. They are called non- renewable because they cannot be re-generated within a short span of time. Non-renewable sources exist in the form of fossil fuels, natural gas, oil and coal. Efficient energy use, sometimes simply called energy efficiency, is the goal to reduce the amount of energy required to provide products and services. For energy conservation and efficiency, we can use several methods. They are mainly classified as:  Active energy  Passive energy Energy efficiency has proved to be a cost-effective strategy for building economies without necessarily increasing energy consumption.
  5. 5. B u i l d i n g S c i e n c e | 5 THE SHARD The Shard is a 310 metre high skyscraper located in the London borough of Southwark. It is the tallest building in the UK and western Europe and was designed by world-renowned architect Renzo Piano. The Shard is open to visitors and features 3 restaurants, a hotel and a viewing platform on the top floor. Known for his elegant, light and detail oriented building, Piano’s Shard consists of several glass facets that incline inwards but do not meet at the top. Inspired by the towering church spires and masts of ships that once anchored on the Thames, the Shard’s form was generated by the irregular site plan and open to the sky to allow the building to breath naturally.
  6. 6. B u i l d i n g S c i e n c e | 6 CONSTRUCTION The Shard is a composite structure, with a steel structure through the office floors up to level 40 followed by a post-tensioned concrete frame through the apartment and hotel levels up to 69 topped by the steel-framed and steel-cored “spire”. In all, there are 12,500 tonnes of structural steelwork, 530 of which form the spire. “It’s very important to Renzo Piano as a public space within the Shard,” says Mace senior project manager Adrian Thomson. “It’s a work of architecture rather than just a piece of steelwork.” It was decided very early in the process to find an alternative to lifting the steelwork up individually, especially as there were a lot of relatively small pieces, some only 1.5m long. With winds of more than 100mph at that height, conventional construction would have raised safety, weather and time issues. Instead, a modular system was devised to minimise both safety risks to contractors on site and weather- related delays, as well as ensuring that the quality met the aspirations of the client. The aim was to limit the number of pieces and connections that had to be lifted. This was done by modularising the steel main members horizontally and vertically, based on a 3m module in response to the 3m width of the trailers used to bring the steelwork to site. Flooring panels were fitted to the modules before installation.
  7. 7. B u i l d i n g S c i e n c e | 7 The structure was also pre-assembled to enable the team to identify and eliminate any risks and difficulties. “It was a two-stage modularisation — one at the factory, one on site,” says Severfield-Rowen chief operating officer Peter Emerson. “We developed a structure where as many pieces of steel as possible were put together as sub- assemblies determined by transport size. When they got to site, as much of these were bolted together as could be carried by the crane. This significantly reduced the number of lifts we had to make,” says Emerson. Devising the modularisation was a complex task involving the whole design and construction team including Renzo Piano’s London representative, Giles Reid, who visited the test assembly in Yorkshire. “There were several criteria that could potentially conflict — aesthetics, engineering, safety, predictability. We all collaborated on the evolution of the concept into a working model,” says Emerson. Supporting the shard from the ground up The lower part of the Shard — ground to level 40 — consists mainly of public areas, retail and offices. It has been constructed with structural steelwork around a vertical concrete spine and lift core. This was the biggest part of the steel package, involving 15,000 pieces weighing 12,000 tonnes. To maximise floor-to-ceiling heights, fabricated I-beams spanning up to 15m were used to perform a dual function — as well as being structural, they allow the services to pass through. These are 500mm deep with standard holes for the servicing. Each office floor includes three perimeter winter gardens where the steel frame is exposed and detailed as an architectural feature. Steel framing is also used in the lower levels of the hotel from 37-40. Here, edge transfer beams carry loads from perimeter columns at 6m spacing in the offices to 3m spacing in the hotel as the building tapers. At the very top, the columns are just 1.5m apart.
  8. 8. B u i l d i n g S c i e n c e | 8 During the trial assembly, the Shard spire was erected in three sections at Severfield-Reeve’s Dalton plant. Spire construction The spire is constructed from 460 pieces of steel weighing 530 tonnes. It consists of a central core supporting the stairs and an outer structure that forms the main frame. These were structured in a 1.5m grid framework forming 3m-wide panels spanning from the core out to the outer edge. Eight wing wall beams cantilever from the main Shard frame beyond the extent of the floor area. Apart from the box section columns, cladding rails and the wing wall beams that were fabricated sections, most of the rest of the steelwork was in standard sections. The spire includes an enclosed, triple-height viewing gallery on level 69 and an external platform at 72 with a hardwood timber floor to suggest the deck of a ship. Plant and chillers are on 75. The lift extends up to 78 and the same standard of finishes continue to this level. In the viewing levels, the architects were keen to reduce the amount of visible connections. “We’re very conscious that people will be looking up and out through the structure so we added refinement to the steelwork which the public will see,” says Giles Reid, London representative of Renzo Piano Building Workshop. “It was very important to us to push as hard as we could to get a high standard.”
  9. 9. B u i l d i n g S c i e n c e | 9 Making connections Where bolted connections couldn’t be avoided, the architect worked with the steelwork contractor to dress the connections with cover plates. For example, on the connection between the vertical, horizontal and diagonal bracing Severfield-Reeve produced curved plates. Other connections were dressed with filler after erection, and over-coating such as those on the wing walls, which have flush welds or hidden connections. The spire has a steel stair supported by a steel core structure built in three-storey units. The stair extends from floor 67 to 87. It wraps around the central core and is tied to the structure at landings on every third floor. First the stair tower was installed then the landings were hoisted into place. It was installed complete with aluminium treads, handrails and flooring to minimise the number of trades needed after the spire’s installation. The stair core structure alone weighs 100 tonnes and consists of 110 pieces. Trial assembly The stair structure was pre-assembled in Sherburn near Scarborough by Severfield-Rowen’s subsidiary company Atlas Ward Structures — Light Steel Division. The spire main structure was trial erected in three sections at Severfield-Reeve’s Dalton plant in North Yorkshire. “During [trial] assembly we made sure that we put every piece of steel, handrail and mesh into place so that we knew it would fit,” says Severfield-Reeve contracts manager Doug Willis. The very last pieces of steelwork to be installed will be the cantilevered tips. Above level 87 the three highest tips — Shards 1, 6 and 14 — will be lifted, bolted into place and glazed. These are fabricated, vertical trusses joined together to create a 3D frame that holds the glass tip of the shard up. The largest one is a box truss 10.4m long, reaching up some 18.2m above level 87. All spire steel is finished in a high-quality corrosion protection system of three layers topped by a glass flake product for added durability — a specification similar to that used for extreme conditions such as on the Forth Road Bridge. Mace had built in an allowance for temporary works once the spire was installed on the Shard but this wasn’t needed — each piece was within 5mm of what was expected. “From my point of view the spire has taken the incorporation of safety planning, design, production and installation of steelwork to a new and advanced level,” says Mace’s Adrian Thomson.
  10. 10. B u i l d i n g S c i e n c e | 10 BUILDING TECHNOLOGY "The Shard's different spaces all have different energy demand profiles which experience peaks at different times of the day," he says. "This creates the ideal scenario for the installation of Combined Heat & Power plant. CHP involves the local generation of heat and electricity—like a small-scale power plant within the building—which can achieve efficiency savings over the use of grid-supplied electricity due to the reduced transmission losses. The more the CHP operates, the greater the savings, and so a mixed-use building with a more constant heat load is the ideal application." In fact, the emissions reduction offered by a CHP (or cogeneration) system doesn't come solely by reducing the energy losses through energy transmission. In a traditional power station, heat is a by-product which is lost to the surrounding environment via cooling towers, the power station generally being too remote to put it to any sort of use. Often burning biofuels such as woodchip or sawdust, a CHP unit generates electricity in or near the building it serves. By virtue of that proximity, that heat by-product can be put to use, eliminating much of the need to generate heat by other means. While still carbon dioxide-emitting, a well-implemented CHP system puts much more of the fuel's energy output to work. TRANSPARENT FLUSH FACADE Great pains have been taken by Renzo Piano Building Workshop to make the Shard’s facade as transparent and flush as possible, while also ensuring it is thermally efficient. Transparency is increased by specifying low-iron laminated glass. “The glass just disappears, and all you see is the skeleton of the building,” says project architect William Matthews. A colourless solar-control coating of Ipasol made by Interpane has been applied “to make the building look wonderfully glassy”. In addition a colourless low-emissivity coating has been added to reduce the reflection of infra- red radiation back into the building. The main solar control comes from the roller blinds that are woven in glass-fibre by Hexcel to reduce solar radiation by 95% while still leaving the curtain wall semi-transparent. The total solar radiation passing through the facade – the G value – amounts to only 0.12%. To achieve the immaculately flush finish, the external glass panes oversail the polyester coated aluminium glazing beads and butt up against each other.
  11. 11. B u i l d i n g S c i e n c e | 11 Scheldebouw is propping the glass on timber blocks for 48 hours while the silicon that bonds it to the glazing beads sets. This, Matthews claims, eliminates the very slight dishing effect that can mar curtain walls of double glazing units. WINTER GARDENS For the occupants of this immense air-conditioned tower, access to fresh air is offered through two or three winter gardens on each floor. These are located at the “fractures” between the tower’s inclined shards. The winter gardens are enclosed behind conventional vertical curtain walls that step back every sixth floor. The curtain wall is made up of the same sealed double-glazed units as the inner leaf of the inclined shards but without the rainscreen outer leaf and roller blinds. In fact, one of these glazing units in each winter garden is a conventional top-hung opening window. ince the winter gardens are more exposed to the external environment, they are separated from the main habitable floor space by single-glazed partitions. The floor plan shows a typical office level. The winter gardens are located in three corners and feature opening windows. BUILDING MATERIALS Award-winning Italian architect Renzo Piano designed The Shard to be a ‘vertical city’. It used:  11,000 glass panels on the outside, which is equal to eight football pitches.  54,000 m3 of concrete, which is equivalent to 22 Olympic swimming pools  The total piles supporting the building would measure 13.7km if laid end to end.  Inside The Shard there are 44 lifts and 306 flights of stairs.  95% of the contruction materials are recycled.  20% of all the steelwork is from recycled sources.
  12. 12. B u i l d i n g S c i e n c e | 12 The Shard is a hybrid structure: concrete in the basement, steel to level 40, concrete again to level 69 and finally a steel ‘spire’ at the top © WSP SHARD CONCEPT The Shard is an unusual mixture of concrete and steel, a tiered wedding cake of a building with a concrete basement, structural steel from ground to level 40, concrete from levels 41 to 69, and steel again from there to the top at level 95. The whole structure is given stability by a massive concrete core that is placed in the middle of the building. This design solution was driven by the intended use of The Shard, but its side effects have been to improve the dynamics of the building, save money and add lettable space – seeControlling the sway. The lower floors of the structure will be offices, with spans of up to 15 m from perimeter to core. Structural steel columns and beams were the optimal solution for these floors, with plenty of space between the deep beams for the extensive services required. In the upper part of the building, the use changes to hotel and residential accommodation, where fewer ceiling-mounted services are required and where acoustic separation of the floors becomes much more important. The tapering of the building here means that the maximum span at this height is down to 9 m. Concrete columns and post-tensioned concrete flat slabs were the best solution on these floors. And then by reducing the storey height in this section
  13. 13. B u i l d i n g S c i e n c e | 13 from 3.75 m to 3.1 m it was possible to include two extra floors – an important consideration since the overall height was limited by the Civil Aviation Authority. EXCAVATING WHILE BUILDING With the perimeter wall built and the ground floor slab cast, concrete piles were sunk to support the building, the largest piles being underneath the core and extended down as far as 53 m. Massive steel plunge columns were then embedded in the top of the piles, rising up to above B2 level. The building (and particularly, the core) could then start to rise upwards, supported on the plunge columns, while excavation of the basement proceeded underneath. With excavation complete, the B3 basement slab, the bottom of the building, was ready to be cast. Here, the engineers worked hard to design the slab to be as thin as possible, both to save unnecessary excavation and to avoid the complications of deepening the secant pile walls. The result was a remarkably thin slab by comparison with similar sized buildings elsewhere in the world. Nevertheless, at 3 m thick under the core with four layers of reinforcement in each direction, this was a massive slab, requiring the UK’s largest ever continuous concrete pour: three concrete pumps placed 700 truckloads over 36 hours, a total of 5,500 m3. The concrete used ground-granulated blast furnace slag – a byproduct of steelmaking – as a substitute for 70% of the Portland cement. The slag has a much lower carbon footprint, eliminating 700 tonnes of CO2emissions in the base slab alone while at the same time giving off less heat as it cures. Even so, the temperature of the base slab reached more than 60°C during curing. With the base slab in place, the missing section of the core walls between the bottom of the core and the B3 slab could be cast. By the time that the core was at last resting on its final foundations, the building above had risen 23 storeys. 3D modelling showing how on certain levels of The Shard the perimeter columns kink and the floor plates have to resist lateral forces © WSP
  14. 14. B u i l d i n g S c i e n c e | 14 BUILDING UPWARDS Slip-forming the core – pouring the concrete almost continuously while sliding the formwork continuously up the building – has now become a conventional technique; in The Shard’s case this was done at the rate of 3 m a day. For the tricky task of steering the slip-form to achieve an accuracy of ±25 mm in the position of the core, the contractors tried both GPS and more conventional laser guidance. To most people’s surprise, the GPS produced more consistent results. Buildings usually have some form of symmetry or regularity which can aid design and construction. By contrast, The Shard is an irregular pyramid with highly complex geometry, governed largely by the irregular shape of the site. The tower has 18 facets – a combination of large planes of glass and narrow re- entrant ‘fractures’ in between – together with a 19-storey extension, or ‘backpack’, attached to the eastern side. And because The Shard tapers as it rises, every floor plate is different. This presented plenty of design challenges requiring rigorous analysis and extensive use of 3D modelling. Up to level 40, the structure has steel columns and steel beams supporting composite steel floors consisting of steel plate with a 130 mm layer of concrete on top. From level 41, concrete columns support post-tensioned concrete floors just 200 mm thick. With fewer ceiling-mounted services needed in the hotel and residential sections, the storey height could be lowered with most of the services confined to the edge of the floor plate. The top section, the spire, reverts to steel with composite steel floors – see Preassembling the spire. The tapering of the building creates a series of challenges for the design of the perimeter columns, both to ensure effective transfer of loads and to avoid unsightly detailing. By and large, these perimeter columns slope with the face of the building, but in places they ‘kink’ towards the vertical, creating horizontal forces that have to be transferred back to the central core through the floors. The perimeter columns are designed so that their weight, size and spacing reduce with the height of the building, adding to the effect of an increasingly delicate structure tapering into the sky: spacing varies from 6 m at the base to 3 m in the hotel section to 1.5 m in the spire. Where the changes occur, transfer structures are needed and these have been ‘hidden’ in the façade. To avoid deep beams round the perimeter, loads were transferred using three-storey deep vierendeel trusses (frames with fixed joints that are capable of transferring and resisting bending pressures).
  15. 15. B u i l d i n g S c i e n c e | 15 Mace, the construction company building The Shard, aimed for continuous improvement in safety through the project. Risks were highlighted on design drawings and details were amended so that these areas were safer to construct. The edge beam in the steel levels, for example, was fabricated with floor decking, edge trim, façade brackets and edge protection already in place so that less work was needed at height in this hazardous area. An ‘empty pockets’ policy was introduced to reduce the risk of falling objects. Throughout the build there were no major incidents, but the minor incidents were investigated thoroughly in order to learn lessons and prevent recurrence. The ‘shards’ are triple-glazed, with a naturally ventilated cavity between the external glazing and the double-glazed units on the inside. Solar gain is reduced by blinds within the cavity, which are driven down automatically when necessary by the building maintenance system. The outside windows are cleaned via building maintenance units at levels 29, 75 and 87 – nine in all. These units have multi-jointed arms that can reach around the building and lower cradles to all parts of the façade. Construction of The Shard hit its first target of ‘visual completion’ in time for the London Olympics, and now fit-out is continuing, including completion of the tower’s 44 lifts, some double-decked and some stacked over each other to serve just part of the tower. The three- storey-high viewing gallery on levels 69 to 71 will open next February, followed soon after by the five-star, 200-plus bedroom Shangri-La hotel. Then all that is needed are tenants to occupy the offices, and owners to be found for the spectacular apartments at the top of The Shard. CONTROLLING THE SWAY All tall buildings move in the wind, and gusts of 100 mph have been recorded near the top of The Shard. What the occupiers will notice is not the movement itself – in The Shard’s case, up to around 300-400 mm at the top – but the horizontal acceleration as the building sways back and forth, and this was particularly important in the hotel and residential section. A limit of just 0.15 m/s2at level 65 was placed on the design, and achieving this required a combination of damping the oscillations (provided, conveniently, by the heavy concrete section between levels 41 to 69) and increasing stiffness. The stiffness was increased by WSP with a ‘hat truss’ at level66. This uses outrigger struts rising diagonally from the perimeter columns to the central core, with the sole purpose of reducing the lateral acceleration. But tightening the bolts on the truss had to be left until near the end of The Shard’s construction. This was because buildings shorten during construction – through foundation settlement, elastic compression of materials and (with concrete) shrinkage and creep. For a building up to around 15 storeys, the effects are negligible but with The Shard they are substantial, and they vary across the building: the perimeter columns have shortened much more than the core. This meant many additional deflection calculations for various stages of construction using ETABS structural analysis software, and considerable extra complications in construction: floors, for
  16. 16. B u i l d i n g S c i e n c e | 16 example, had to be built slightly off the horizontal so that they would settle into the correct position. And only once the building was complete and most of the shortening had taken place could the hat trusses be finally fixed. REACHING NEW HEIGHTS Getting workers and materials up to the top of The Shard during construction, without delaying the high-speed programme and in all kinds of weather, was particularly challenging for the design and construction team, and prompted some unique solutions. Gaining access to the lower floors was relatively straightforward with four tower cranes round the edges of the site doing most of the heavy lifting. When the building reached 162 m, the cranes had come to the limit of their reach and new cranes were called for. First, a tower crane was attached to the rig that rose steadily up the building with the slip form – the moving formwork. This is believed to be the first time the technique of attaching a crane to the slip form has ever been tried outside North Korea, where it failed due to the difficulties of keeping the crane stable. Here, stability was successfully achieved by extending the lower section of the tower crane down into one of the already-cast lift shafts where guide rails kept it vertical. For the top section of the building, the central crane would have been in the way. So a new tower crane was erected outside the building envelope, cantilevering off the concrete core – the first time such a technique had been used outside the US, and at 317 m, the UK’s highest ever crane. This made a dramatic sight on the London skyline, as the tapering building moved further away from the crane as it progressed upwards (see diagram) With the external construction complete, there came the inevitable conundrum: no crane can lower itself to the ground. A ‘recovery crane’ was erected by the cantilevered tower crane, which was then dismantled and lowered by the recovery crane. Then a smaller, spider crane
  17. 17. B u i l d i n g S c i e n c e | 17 was taken up the jump-lift in pieces, assembled, and taken down the same way after lowering the recovery crane in pieces. PREASSEMBLING THE SPIRE At the top of The Shard sits the steel and glass spire. Containing just 530 tonnes of The Shard’s total weight of 12,500 tonnes of structural steel, it is light compared with the remainder of the building, but at 60 m and 23 storeys high, it is a significant building in its own right. In addition, It had to be assembled 300 m up in the air, over the top of the highest point of the concrete core, where winds can reach speeds of 100mph.
  18. 18. B u i l d i n g S c i e n c e | 18 ENERGY EFFICIENCY Mindful of the Shard’s environmental impact and in order to maintain the highest levels of energy efficiency, the building is fitted with a natural gas-fuelled combined heat & power plant. The Shard utilises a GE Jenbacher JMS416GS-NL gas engine and the cogeneration facility was engineered, installed and will be maintained by Clarke Energy. This combined heat and power (CHP) plant will provide both 1.131MW of electricity and 1.199MW of hot water at high efficiency (85.3% total, 41.4% electrical) to the surrounding area. This helps to reduce carbon emissions and contributes to the low-carbon footprint of the building. In parallel this provides significant cost savings versus the separate purchase of electricity and gas from the national grids. The generators are located in the basement of the building and are housed in acoustic enclosures in order to negate the emission of sound from the engines. The gas engines are also characterised by very low levels of NOx emissions (<250mg/Nm3) which is important to achieve the strict air quality requirements in the capital. Of the steel that was used in construction, 20% was recycled, while 95% of the waste produced during construction was recycled as well. Also, sky gardens on each floor promote natural ventilation and improve air quality. The Shard's extensive use of energy-saving materials and techniques contributes to the building using 30% less energy than other high-rises of comparable dimensions. For structural reasons, the emphasis in the design of a tall building is to reduce weight, and so the Shard is a lightweight building in terms of its ability to store heat. Buildings that have heavy concrete walls and slabs [think Empire State Building again] are able to store heat in their structure."  95% of construction materials recycled  20% of all steelwork from recycled sources  Combined heat and power creates efficiencies across the whole site saving 10% CO2 annually  Triple skin intelligent façade minimising the effects of solar gain, whilst allowing maximum use of natural light  Winters gardens providing naturally ventilated workspaces  Mainline rail, tube and bus hub integrated into the development vastly reducing secondary journeys  A plot ratio of 32.1% ensuring land is used efficiently
  19. 19. B u i l d i n g S c i e n c e | 19 ACTIVE AND PASSIVE METHODS  The Shard’s energy efficiency is boosted thanks to triple-glazed glass, with a layer of sun shielding glass sandwiched between the inner and outer sheets.  The blind control system automatically adjusts itself throughout the day, ensuring shade is only used when and where necessary. The panes in the outer layer of glass contain low levels of iron, creating a highly reflective surface that limits heat build-up, and adds a shine to the building. These external panes do not meet, which create constant airflow that naturally regulates the Shard’s internal temperature.  The tower's design features angled glass façade panels which result in a multiformity of changing reflected light patterns.  The building's façade is both double-skinned and ventilated, thus reducing solar gain whilst maximising light intake. In the “fractures” between the shards opening vents provide natural ventilation to winter gardens.  Excess heat generated by the offices is used to heat the hotel and apartments, whilst any superfluous heat is dissipated naturally via a radiator atop the building.  The Shard deals with heat by using "a ventilated inner cavity housing a solar-control blind, and a double-glazed unit on the inside. An intelligent blind control system is used which tracks the position and intensity of the sun to deploy the blinds only when required." Less solar gain means less cooling, which represents an energy savings, but it also saves on riser space. With the climate façade an extra pane is added at the inside. The intermediate shading devices reflects a majority of the incoming solar radiation back through the external glass. The proportion of absorbed solar radiation is converted into "sensible" heat and re-radiated back into the air space between the inner and outer panes. In the summer the heated air in the air space is exhausted to the outside of the building. In the winter situation the cold radiation from the glass surface is reduced, because the inner pane is heated by the heated air stream. Second skin facade or naturally ventilated facade Second skin façades are an effective means of providing protection against solar radiation. The system operates on the principle of using a ventilated second "skin" with an intermediate-shading device. The intermediate shading devices reflects a majority of the incoming solar radiation back through the external glass. A proportion of the absorbed solar radiation is converted into "sensible" heat and re-radiated back into the air space between the inner and outer panes. Ventilation of heat gains in the air space is dependent on the effects of external wind pressures and/or "stack" effect. The "stack" effect works on the principle that the heat absorbed and re-radiated by the blind and glazing rises within the cavity. Cooler air is drawn into the air space to replace the buoyant warmer air, which is ventilated. To effectively ventilate the wall, using wind or stack effects, the depth of
  20. 20. B u i l d i n g S c i e n c e | 20 the air space and vent dimensions are considerably greater than an active or interactive wall. This results in a deep and heavy façade. Whilst the system is effective in controlling solar heat gains, the introduction of cold external air into the cavity during winter means that the benefits of an air "buffer" is negated. Triple skin facade with mechanical exhaust or triple climate facade This system combines the principles of the climate facade and the second skin facade. The inner pane is now a screen (third skin). An extra extension on this system is that the rate of ventilation of the outer air space can be controlled by a small energy efficient built in fan powered by solar energy or conventional means. Such a wall is more compact requiring a much smaller overall section depth than a naturally ventilated wall PASSIVE DESIGN SUN-SHADING “What we are building here is a great big greenhouse,” explains William Matthews. “So the problem is how to stay cool inside. The simplest way would be to provide external sunshading. But you can’t do that 200 metres up in the air, where it would flap around in the wind.” Instead sun-shading is provided by motorised roller blinds incorporated within the external envelope. The design team stuck rigorously to this principle over the 10 years that the building took to design and pass through a £4 million public inquiry. But this posed another major problem in technical design that was solved with a U-turn from what Matthews calls an active facade to a passive facade. The active facade initially adopted by the design team involved mechanically ventilating the cavities in the double-glazing units that housed the roller blinds. But the increased energy efficiency brought in by the 2006 revision of Part L of the building regulations meant that low- velocity fans would now be needed to ventilate the cavities. This in turn called for bulky ducts to be housed within the cavities and affect the facade’s transparency. So the team switched to a passive facade in which the roller blinds are protected from wind and rain by single glazing. Thermal insulation is provided by hermetically sealed double-glazed units making up the inner skin of the facade. Each outer cavity housing the roller blind is now 250mm wide, unventilated and requires periodic maintenance by opening the internal double-glazed panel on side hinges. Because of the depth of this cavity, the aluminium window mullion has been split into two connected by narrow spacing bars. Winds at the spire’s pinnacle are less of a problem than turbulence at lower levels caused by the neighbouring Guy’s Hospital tower, claims Matthews. The slight inclination of the facades reduces updraft, while a 4m-wide glass canopy at first floor level shields pedestrians outside.
  21. 21. B u i l d i n g S c i e n c e | 21 RENZO PIANO ON ENERGY EFFICIENCY OF THE SHARD “Architecture is not construction. Architecture is art, but art vastly contaminated by many other things. Contaminated in the best sense of the word – fed, fertilised by many things. But I came to this attitude that architecture is art starting as a builder. As you know we are aiming to save a lot of energy. We are working on different things. One is that because it’s a mixed use, we have extra production of heat from the offices that we can reuse in the residential part. This is un-poetic but it is very intelligent. The other thing is the composition of the glass. We are working with double glass – actually triple glass – with a space in between where we have lamellas – venetian blinds – that cut heat gain from the sun. And when you don’t have sun – which happens in London – you can lift up the lamella. They are inside the glass. Of course the air between the two panes of glass heats up, but then we evacuate it and reuse it. So the composition of the façade is part of the mystery, part of the story. And we are working on a chemical glass with a composition… the blinds are better than tinted glass. You can see them. At night they will disappear. There will be some facets that will probably not even have lamella. It’s like the trunk of a tree, acting differently all the way round, depending on how much sun it gets. The south side will not be the same as the north. We don’t use mirror glass or tinted glass. We use new technology which is more subtle. The language of the building will depend on this. We will use clear glass – low iron glass. It’s also called extra white glass in England. This is very different from regular glass, which is very green. If you use low iron glass you end up with something that really is like a crystal. So depending on the day, the light and the position of the sun, the building will look different. It will not look like a massive glass meteorite - choom! - as many towers do. It’s going to be more vibrant and changing.” - RENZO PIANO
  22. 22. B u i l d i n g S c i e n c e | 22 BIBLIOGRAPHY       