2. B u i l d i n g S c i e n c e | 2
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. B u i l d i n g S c i e n c e | 3
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. B u i l d i n g S c i e n c e | 4
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 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 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:
Energy efficiency has proved to be a cost-effective strategy for building economies without
necessarily increasing energy consumption.
5. B u i l d i n g S c i e n c e | 5
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.
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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
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
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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
“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
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.
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During the trial assembly, the Shard spire was erected in three sections at Severfield-Reeve’s
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
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
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.”
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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.
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.
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"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
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.
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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.
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.
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.
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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
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
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. 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
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. 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.
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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
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
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
A plot ratio of 32.1% ensuring land is used efficiently
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. 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.
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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
- RENZO PIANO
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