DAV ANALYSIS
COMMERZBANK TOWER FRANKFURT, GERMANY
Yasha I Laleh I Jessica image source : www.fosterandpartners.com
OUTLINE • INTRODUCTION
• • • • •
MOTIVATION LOCATION BUILDING FACTS CONSTRUCTION TIMELINE SPIN & BUZZ
• STAKEHOLDERS • FEATURES • DAV ANALYSIS
• DOUBLE SKIN FAÇADE • VIERENDEEL FRAME SYSTEM • CONCLUSION
• REFERENCES Image source: www.commerzbank.de
COMMERZBANK TOWER, DAV ANALYSIS
MOTIVATION • • • • • •
Focus on user health and indoor environment conditions quality Sustainable design - World’s first ecological office tower Bringing Nature to indoor spaces - sky gardens Renowned Architect - Foster and partners Renowned structural engineers – Arup and partners Frankfurt's landmark - Tallest skyscraper in Germany (300m)
“An ambitious structural and aesthetic vision with a quest for natural ecological solutions and the wellbeing of the individual” - Norman Foster
Source: www.fosterandpartners.com
COMMERZBANK TOWER, DAV ANALYSIS
LOCATION
COMMERZBANK TOWER, DAV ANALYSIS
• Frankfurt, Germany Business district Historical district
• Located in the heart of the business district in Frankfurt
Images source: www.fosterandpartners.com , www.google.com/maps
BUILDING FACTS
COMMERZBANK TOWER, DAV ANALYSIS
INFORMATION
SOURCE
TYPE
Office skyscraper
Foster & Partners
CONSTRUCTION PHASE
1994-1997
Lambot et al.
DESIGN PHASE
1991-1993
Lambot et al.
GROSS AREA
85,503m2
Commerzbank
WORKPLACES
2400
Foster & Partners
HEIGHT
259m(excluding antenna) 300m(with antenna)
Commerzbank
LEVELS
53
Foster &Partners
COST
$300m
Arend et al.
GROSS VOLUME
538,000m3
Commerzbank
STRUCTURE
Steel structure with Vierendeel frame system
Commerzbank
Image source: www.fosterandpartners.com
DEVELOPMENT OF DESIGN 1960-1980’s Early 1980’s 1989
Feb 1991
Feb-Mar 1991
Mar 27-Jun 3
COMMERZBANK TOWER, DAV ANALYSIS
-Commerzbank occupies 30 building and looks to consolidate -local government restricts development of new skyscrapers (due to public outcry) -Public dislike of skyscrapers relaxes -Site becomes available for construction of new Commerzbank headquarters but only if meets government demands -Structure must benefit Frankfurt public -Address environmental concerns -Include international companies in biding process -12 design companies invited to bid (9 Germany, 2 USA, 1 Britain) with a June 3rd deadline Foster Design -pinwheel/projecting wings allow all office to be naturally lit, but large surface area of façade makes design too expensive -center atrium provide natural lighting to internal space -triangular plan prevent building from directly facing old Commerzbank Tower -Sky gardens on south side and contain elevators structural load concerns -Sky garden on all sides distribute structural load and move elevators/utilities to corners, column free space
Source: Davies & Lambot, 1997
CONSTRUCTION TIMELINE 1989 Site Selection
1991
April: Piling completed June: main foundation completed Aug: steel frame reached level 7 Oct: steel frame reached level 29 Dec: First cladding panels arrived Steel frame reached level 41
Source: Lambot et al.
1992
3 June: Deadline for Design Competition 9 Germany-2 USA-1 Britain Foster and Partners Declared the Winner Sep: Detailed design progressed
1995
COMMERZBANK TOWER, DAV ANALYSIS
1996 Jan: Steel frame reached level 51 March: Steel frame completed Installation of building services started Atrium and exterior facade cladding reached level 27 Dec: The 40 m long antenna lifted into position
Sep: Cost simulation, review of complete strategy
1997 March: installation of interior fixtures, garden trees delivered 24 July: Officially opened.
1993 Sub-contractors hired
1994 Aug: Construction started with foundation construction
SPIN & BUZZ
COMMERZBANK TOWER, DAV ANALYSIS
BOOKS: Sir Norman Foster and Partners : Commerzbank, Frankfurt am Main, Fischer, V. 1997, Berlin
Commerzbank Frankfurt : prototype of an ecological high-rise, modell eines ökologischen Hochhauses Davies. C, Lambot. I 1997, UK
AWARDS: • • • •
Green Building Award of the City of Frankfurt – Commerzbank RIBA Architecture Award - Commerzbank Headquarters, Frankfurt Bund Deutscher Architekten - Martin-Elsaesser-Plakette Award - Commerzbank Headquarters, Frankfurt British Construction Industry Awards, International Award to Commerzbank Headquarters
OTHER MEDIA: • • • •
Appears in the Euro Contemporary tile set in SimCity 4 (Deluxe or with Rush Hour) A 3D puzzle of Commerzbank tower Made To Scale Collection released by Wrebbit Featured as a default background for the Motorola RAZR cell phone Featured in the Covert Affairs episode: Levitate Me
Source: www.fosterandpartners.com / library.cmu.edu
STAKEHOLDERS
COMMERZBANK TOWER, DAV ANALYSIS
CATEGORY
FAME
FORTUNE
FUNCTION
SUSTAINABILITY
Client - Commerzbank
X
X
X
X
ArchitectFoster & Partners
X
X
X
X
Structural EngineerArup & Partners
X
X
-
-
Media
X
-
-
X
City of Frankfurt
X
-
X
X
Authorities
X
-
X
X
Contractor
X
X
-
-
Faรงade fabricators(Josef Gartner and Co.)
X
X
-
X
Users
-
-
X
X
FEATURES • Form and Shape • Sky gardens
• Double skin façade (DAV analysis) • Steel Structure (DAV analysis)
COMMERZBANK TOWER, DAV ANALYSIS
FEATURES • Form and shape •
Hollow triangular floor plan with curved corners (Manipulates wind moment, Unique triangular shape)
•
Full height atrium(Allows in natural light, Allows visibility into sky garden)
•
Non-tapering form
•
Total floor area – 85,503 m2 (1,613 m2 per floor)
•
Height, 300 m
Images source: www.fosterandpartners.com , Arend et al.
COMMERZBANK TOWER, DAV ANALYSIS
FEATURES
COMMERZBANK TOWER, DAV ANALYSIS
• Sky gardens •
9 Naturally ventilated sky gardens
•
3 ecologies (Asian, N. American, Meditterrian)
•
Evenly distributed day light (high glazed external walls, reflective ceiling)
•
4 stories tall, situated between two eightstory tall stacks of offices
•
Communal space
•
Provides natural ventilation, passive heating/cooling, outside view and daylight for workplaces
Spiraling sky gardens
DOUBLE SKIN FAÇADE- Description
COMMERZBANK TOWER, DAV ANALYSIS
• Design • Exterior skin- disjointed sections of fixed glass 1.4m x 2.25m sheets of 8mm toughness glass with 20cm gap (Poirazis, 2004) • Interior skin- double-glazed operable windows 3,100 motorized interior windows- controlled by user or monitoring system (MIT, 2000) • Function • Use passive heating, cooling and ventilation • Reduce energy consumption • Create Transparency • Acoustical Reduction
Façade engineer – Gartner and Co.
Image Source: (Volker, 2013)
DOUBLE SKIN FAÇADE- Description
Passive Source: Gartner and Co., Arend et al
COMMERZBANK TOWER, DAV ANALYSIS
Active
DOUBLE SKIN FAÇADE-DAV Analysis
COMMERZBANK TOWER, DAV ANALYSIS
COSTS & RISKS Stakeholder
Qualitative
Envelope engineer – Josef Gartner and Co.
-design must withstand high finds and high moisture -potential for building to act differently than modeled -condensation obstruct view of nature
Architect- Foster
Client
-potential for façade to be used less than predicted value of 60% of year
User
-variation in indoor environment due -potential for glare -teach workers double façade system installation -glass was delivered on a as-needed basis (potential for construction delays)
Contractor
Quantitative
Sources (Hartkopf, 2013)
-4 surfaces of glass to clean as opposed to 2 for conventional façade (increase cleaning cost) -operable windows increase maintenance costs -Cost of cooling system -$15 million dollars to do research on facades for high wind and moisture environment
-more time intensive than single facade
(Hartkopf, 2013)
DOUBLE SKIN FAÇADE-DAV Analysis
COMMERZBANK TOWER, DAV ANALYSIS
BENEFITS Stakeholder
Qualitative
Quantitative
Façade engineer – Josef Gartner and Co.
-made way for future double facades in Germany
-$15 million dollars to do research on facades for high wind and moisture environment
(Hartkopf, 2013)
Architect- Foster
-emphasizes idea of ecological tower -utilizes sustainability -adds transparency -reduces energy consumption for ventilation, heating and cooling
-NPV = $30.4 million -annual energy savings = $484,000 -Natural ventilation 80% of year (originally estimated to be 60%)
(Foster & Partners) (Gartner & Co.)
Client
User
-user control work space -environment conducive to working (natural light, natural ventilation, access to nature) -visibility/ transparency
Sources
(Poirazis, 2004)
DOUBLE SKIN FAÇADE- NPV Calculations Floor to floor height = 3.75m Surface Area of façade = (24+34+36 office wings)(3.75m)(34m) =11,730m2 Material & Construction = (Cost per m2)(Double skin area) = ($915.83/m2 )( 11,730m2 ) = $10,742,742 in 2003$ Research Investment = $15 million in 1994$ Operating Costs = ( 7 €/m2 )* ($1/(1.0919 €))(11,730m2 ) = $75,200 per year in 2003$ Cleaning Costs =( 3.9 €/m2 )* ($1/1.0919 €)(11,730m2 ) = $41,900 per year in 2003$ NPV = $30.4 million
COMMERZBANK TOWER, DAV ANALYSIS
Source (Davies & Lambot, 1997) (Davies & Lambot, 1997) (Poirazis, 2004)
(Volker, 2013) (Poirazis, 2004)
(Poirazis, 2004)
DOUBLE SKIN FAÇADE- Savings Calculations Commerzbank uses passive heating, cooling and heating for 80% of year
COMMERZBANK TOWER, DAV ANALYSIS
Source (Foster & Partners) (EIA, 2003)
Electricity Consumption for Conventional Office Building = 15.5 kWh/ft2 Area of floor area = 920,314 ft2 Ventilation = 5% of total electricity Space Heating & Cooling = 48% of total electricity Energy Savings = (80%)[(53%)(15.5 kWh/ft2)(920,314ft2) = $464,000 per year
(See below) (EIA, 2003) (EIA, 2003) (EIA, 2003)
**Potential for additional savings to due user health and productivity benefits** Source: “Commerzbank Head Office.” https://www.commerzbank.com/media/konzern_1/konzerninfo/hochhaus_1/commerzbank-tower-facts.pdf
DOUBLE SKIN FAร ADE- BENCHMARKING
COMMERZBANK TOWER, DAV ANALYSIS
Type of Faรงade
Investment Cost [$/m2]
Running Cost [$/m2]
Standard faรงade
$405-$675
$3.38-$4.73
Double skin standard
$811-$1082
$5.41-$10.14
Double skin w/ adjustable air inlet and outlet
$947-$1352
$14.74
Double skin with openable exterior sashes
$1082-$1758
N/A
Running Cost includes maintenance and cleaning costs Cleaning- interior faces cleaned once a year, exterior face cleaned twice a year and shading devices (exterior once a year, interior every five years) Source: (Poirazis, 2004), BBRI
DOUBLE SKIN FAÇADE- BENCHMARKING Location
Commerzbank Tower
Arag 2000 Tower
Torre de Cristal
Bligh skyscraper
Frankfurt, Germany
Dusseldorf, Germany
Madrid, Spain
Sydney, Australia
1997
2000
2009
2011
300m (53)
125m (31)
250m (45)
139m (30)
85,500 m2
38,100 m2
77,000 m2
42,700 m2
Foster and partners
RKW, Dusseldorf - Foster and Partners
César Pelli
Architectus Ingenhoven Architects
Completion Year Height (stories) Area
Architect
COMMERZBANK TOWER, DAV ANALYSIS
Facade
Segmented fixed exterior with operable interior windows
Shaft-box system
Ventilated curtain wall with automatic blinds
An inner sealed skin of doubleglazed units and a ventilated outer skin of clear glass
Total cost
$300 mil
$63mil
$ 340 mil
$270 mil
Source: Foster and partners,
DOUBLE SKIN FAÇADE- BENCHMARKING
COMMERZBANK TOWER, DAV ANALYSIS
AESTHETICS
Commerzbank Tower
Arag 2000 Tower
Torre de Cristal
Bligh Skyscraper
Weight
PERFORMANCE
Commerzbank Tower
Arag 2000 Tower
Torre de Cristal
Bligh Skyscraper
Weight
Commerzbank Tower
1
7
2
5
0.54
Commerzbank Tower
1
4
1
1/3
0.19
Arag 2000 Tower
1/7
1
1/5
1/3
0.06
Arag 2000 Tower
1/4
1
4
1/7
0.08
Torre de Cristal
1/2
5
1
4
0.29
Torre de Cristal
1
1/4
1
1/3
0.11
Bligh skyscraper
1/5
3
1/4
1
0.10
Bligh skyscraper
3
7
3
1
0.55
1.84
16
3.45
10.33
5.25
12.25
9
1.81
Commerzbank Tower
Arag 2000 Tower
IMPACT ON OCCUPANTS
Scale Torre de Cristal
Bligh Skyscraper
Weight
1
1/5
1/5
1
0.08
5
1
1/2
6
0.30
Torre de Cristal
5
2
1
7
0.54
Bligh skyscraper
1
1/6
1/7
1
0.07
12
3.37
1.84
15
Source: Akin, 2013
Torre de Cristal
0.94
Commerzbank Tower
0.81
Bligh skyscraper
0.72
Arag 2000 Tower
0.44
one over another
5: Strong or essential Arag 2000 Tower
Score
1: Equal importance 3: Moderate importance of
Commerzbank Tower
Building
importance
7: Very strong or demonstrated importance
9: Extreme importance 2,4,6,8: Intermediate values
Max score of 3
DAV FEATURE ANALYSIS – Vierendeel System
COMMERZBANK TOWER, DAV ANALYSIS
• First skyscraper in Germany to incorporate steel as its main structural component • Standardized 8 story Virendeel truss system • To support weight of steel, three mega columns consisting of h-framed steel columns with diagonal bracings encased in concrete were used on the vertices of the triangular plan.
• Piles Foundation to support steel structure 8 story Virendeel truss
image source - http://www-classes.usc.edu/architecture/structures/Arch513/lectures/08-vierendeel.pdf
DAV FEATURE ANALYSIS – Vierendeel System • Structural Engineer - Arup & Partners
• Contractor - Hochtief AG • Beginning of Installation - June 1995 • Total time taken - 12 months
image source - http://www-classes.usc.edu/architecture/structures/Arch513/lectures/08-vierendeel.pdf
DAV FEATURE ANALYSIS – Vierendeel System QUANTITATIVE FACTS S.No.
Description
Quantity
Unit
1
Total amount of steel used
18,800
tons
2
Vierendeel system
9000
tons
3
Horizontal member size (upto 65mm thk)
475 x 1100
m
4
Vertical member size (upto 85mm thk)
475 x 1000
m
5
Total Horizontal member length
5406
m
6
Total Vertical Member lengths
1908
m
7
No. of floors
53
DAV FEATURE ANALYSIS – Vierendeel System COSTS • Total Steel used in Vierendeel System – 8954 tons • Material cost – $ 2375/ ton • Labor - $ 425/ ton • Equipment – $ 140/ ton • Total Cost of steel used for Vierendeel system - $ 31.5 million • NPV - $ (31,500,000 (1+0.0274)2013-2010 = $ 34.16 mil
DAV FEATURE ANALYSIS – Vierendeel System COSTS & RISKS Stake Holder
Qualitative
Client - Commerzbank
• Construction was less time consuming
Structural EngineerArup & Partners
•
• • Contractor
Users
First building in Germany to incorporate structural steel as its main structural component Risk of settlement in neighboring buildings because of clay soil Simpler structure, repetitive details -
•
Risk of settlement in neighboring buildings because of clay soil
Quantitative Weight of the building Is 132,000 tons = Old 32 story commerzbank tower
• Fire proofing @$1000/ton = $ 10 million (Added cost)
-
DAV FEATURE ANALYSIS – Vierendeel System BENEFITS
Stake Holder Client Commerzbank
Qualitative • •
Architect - Foster & Partners
• • •
Structural EngineerArup & Partners
•
Users
• •
•
Quantitative
Source
Tallest skyscraper in Germany Currently 8th tallest in Europe
• Rent Increment
Non Tapering Form Pre Fab Assembly, ease of construction Standardization
• Increase in rentable space on top floors • Allowed for 25% more glazing area than a concrete vierendeel system
Pre Fab Assembly, ease of construction Reduction in weight
• Reduces assembly time due to uniformity by 20%
Lambot et al
Column free spaces Allows spatial reconfiguration
• -Use of steel allows 400sq.m of column free space (compared to concrete) • CS - reduces turnover costs of $4100 per person, based on an average annual salary of $45,000
Arend et al
Foster & Partners
Fitz-Enz, 2000
VIERENDEEL SYSTEM- BENCHMARKING
COMMERZBANK TOWER, DAV ANALYSIS
COMMERZBANK TOWER
SILBERTURM TOWER
JOHN HANCOCK CENTER
HEARST TOWER
Building Type
Office building
Office building
Office building
Office building
Location
Frankfurt, Germany
Frankfurt, Germany
Chicago, USA
New York, USA
Architect
Foster & Partners
ABB Architekten
Skidmore, Owings & Merrill
Foster & Partners
Structural Engineers
Arup & Partners
BGS Ingenieursozietat
Skidmore, Owings & Merrill
The Cantour Seinuk Group
VIERENDEEL SYSTEM- BENCHMARKING
COMMERZBANK TOWER, DAV ANALYSIS
COMMERZBANK TOWER
SILBERTURM TOWER
JOHN HANCOCK CENTER
HEARST TOWER
Type of structure
Steel Vierendeel system
Concrete structure
Tubular system with cross bracing
Diagrid steel frame
Amount of steel used
18,800 tons
-
46,000 tons
10,480 tons
Material cost
$ 45 million ($ 2375/ ton)
-
$ 109 million ($ 2375/ ton)
$ 25 million ($ 2375/ ton)
Height (Stories)
259m (53)
166m (32)
344m (100)
182m (46)
Construction
1994-1997
1972-1978
1965-1969
2003-2006
Cost
$ 300 mil
-
$100 mil
$500 mil
VIERENDEEL SYSTEM- BENCHMARKING AESTHETICS
Commerzba nk Tower
John Hancock Center
Hearst tower
COMMERZBANK TOWER, DAV ANALYSIS
Silberturm
Commerzbank Tower
John Hancock Center
Hearst tower
Silberturm
Weight
PERFORMANCE
Weight
1
3
5
7
0.60
Commerzbank Tower
1
5
1/3
6
0.23
Commerzbank Tower
John Hancock Center
1/5
1
1/5
3
0.09
John Hancock Center
1/3
1
3
5
0.22
Hearst Tower
3 1/6 4.37
7 1 1.70
0.60 0.06
Hearst Tower
1/5
1/3
1
4
0.11
Silberturm
1/7
1/5
1/4
1
0.06
1.68
4.53
9.25
17
Silberturm
EASE OF CONSTRUCTION
Commerzbank Tower
5 1 1/3 1/7 11.33 1.68 John Hancock Center
Hearst tower
Scale
Silberturm Weight
1
4
4
8
0.62
1/4
Hearst Tower
1/4
1
1
5
0.16
demonstrated importance
Silberturm
1/8
1/5
1/5
1
0.05
9: Extreme importance
1.63
6.20
6.20
19
Source: Akin, 2013
5
0.16
1.45
Hearst Tower
0.87
John Hancock Center
0.45
Silberturm
0.17
importance
John Hancock Center
1
Commerzbank Tower
one over another
5: Strong or essential
1
Score
1: Equal importance 3: Moderate importance of
Commerzbank Tower
Building
7: Very strong or
2,4,6,8: Intermediate values
Max score of 3
IMPACT ANALYSIS
COMMERZBANK TOWER, DAV ANALYSIS
1st order
2nd order
3rd order
(construction phase)
(0-3 years)
(3-10 years)
Client - Commerzbank
--
+
+++
ArchitectFoster & Partners
+
++
+++
Structural EngineerArup & Partners
+
+
++
Media
+
++
0
Frankfurt InhabitantsPublic
---
+
++
Authorities
0
++
+++
Environment
-
+
++
Contractor
++
0
0
Faรงade fabricators(Josef Gartner and Co.)
++
+
0
Users
0
+++
+++
CATEGORY
CONCLUSION
COMMERZBANK TOWER, DAV ANALYSIS
LIMITATIONS & DIFFICULTIES OF OUR STUDY • DAV Analysis of only two features of building • Difficult obtaining information from primary source • Some information found in German, so we were unable to understand • Unable to find revenue generated from restaurant, retail and parking rental specific to Commerzbank Tower • Some assumptions made on costs and quantities by using data from similar buildings/ feature • Time
CONCLUSION
COMMERZBANK TOWER, DAV ANALYSIS
OBSERVATIONS • Double skin facade • Driving force was energy consumption and employees’ quality of life while working •
Vierendeel system • Driving force was a non-obtrusive form capable of supporting a high rise structure and sky gardens
• Additional physical building features (form & shape and sky gardens) are equally important for DAV analysis because of their energy efficiency and user benefits, but they not feasible to do because of the lack of data • Commerzbank Tower served as a catalyst for sustainable development in Frankfurt • Successful execution of design DAV parameters (features and functions) starts with good collaboration and communication between architect and engineers
SOURCES • • • •
• • • •
• • • •
• • • •
COMMERZBANK TOWER, DAV ANALYSIS
Poirazis, Harris. Double Skin Facades for Office Buildings. Department of Energy and Building Design. (2004). pg 77-78 Leaman, Adrian (2001) Productivity Improvement. Buildings in Value, Vol. 3, Ch. 19.Building Use Studies Ltd., 2001. Fjeld, T, B. Veiersted, L. Sandvik, G. Riise, F. Levy (1998) The effect of indoor foliage plants on health an discomfort symptoms among office workers. Indoor & Built Environment, 7, pp. 204-209. Mackey, Jennifer. Evaluating workspaces in European sustainable high rise buildings- assessments, responses and speculations from the inhabitants. University of Florida.(2010) “CO2 Accounting Energy Use.” http://sustainability2009.commerzbank.com/reports/commerzbank/annual/2009/nb/English/703025/co_sub_2_s ub_-accounting-energy-use.html. Commerzbank AG. (November 30, 2009). Accessed September 2013 Goncalves, J & Bode, K. “The importance of real life data to support environmental claims for tall buildings.” (2011) Fischer, Volker. Sir Norman Foster and Partners : Commerzbank, Frankfurt am Main. Stuttgart : Axel Menges, 1997. Lambot, Ian. Commerzbank Frankfurt: Prototype for an Ecological High-Rise. Boston : Watermark Birkhäuser, 1997. Foster & Partners. "Commerzbank Headquarters." http://www.fosterandpartners.com/projects/commerzbankheadquarters/ Accessed September 2013. Arend, John; Benkert, Mike; deFilippis, Audrey; Tillmaand, Saretta. “Commerzbank Tower.” http://www.mbenkert.com/arend.benkert.defilippis.tillmaand.pdf Accessed September 2013 “Commerzbank Head Office.” https://www.commerzbank.com/media/konzern_1/konzerninfo/hochhaus_1/commerzbank-tower-facts.pdf Accessed September 2013 Arup & Partners. “Commerzbank.” http://www.arup.com/Projects/Commerzbank.aspx (2013/2014). Accessed September 2013 Akin, O. More VBD Analysis Methods(2013): Optimization, Xtreme Design and AHP lecture for Value Based Design course Hartkopf, Volker. “Towards a Sustainable Future: Integrating Environmentally and Economically Future Proof Technologies and Practices” NSF/IUCRC Annual Meeting, Jan 2013 Washington DC EIA. “2003 EIA Commercial Building Energy Consumption Survey (CBECS)” http://www.eia.gov 2003
SOURCES • • • • • • • • • • • • • • • • • • • • • • • • •
COMMERZBANK TOWER, DAV ANALYSIS
http://www.pbs.org/wgbh/buildingbig/wonder/structure/john_hancock.html http://www.aviewoncities.com/buildings/chicago/johnhancockcenter.htm http://www.ritchiewiki.com/wiki/index.php/John_Hancock_Center http://www.hearst.com http://www.archdaily.com/204701/flashback-hearst-tower-foster-and-partners/ http://www.allaboutskyscrapers.com/property/torre-de-cristal http://www.australiandesignreview.com/architecture/17855-1-bligh-street http://cmiserver.mit.edu/natvent/Europe/rwe.htm http://www.rwe.com/web/cms/en/8308/rwe/about-rwe/profile/eco-tower/ http://www.academia.edu/180367/Innovative_Building_Skins_Double_Glass_Wall_Ventilated_Facade http://www.fosterandpartners.com/projects/hearst-tower/ http://www.fosterandpartners.com/projects/arag/ http://en.wikipedia.org/wiki/1_Bligh_Street http://www.flickr.com/photos/64210496@N02/6713563055/lightbox/ http://en.wikipedia.org/wiki/1_Bligh_Street http://en.wikipedia.org/wiki/RWE_Tower http://en.wikipedia.org/wiki/Arag-Tower http://en.wikipedia.org/wiki/Commerzbank_Tower https://www.commerzbank.de/en/hauptnavigation/presse/bilddaten/buildings/buildings_1.html http://www.officingtoday.com/2011/01/affirma-opens-business-center-on-roof-of-madrid/ http://www.emporis.com/building http://pcparch.com/project/torre-de-cristal http://twistarsphotography.com/?p=149 http://www.bdonline.co.uk/news/frankfurt%E2%80%99s-towering-letting/3139045.article http://www.bbri.be/activefacades/new/download/Ventilated%20Double%20Facades%20%20Maintenance%20and%20durability%20aspects%20-%20dfv1%20-%20final.pdf
COMMERZBANK TOWER, DAV ANALYSIS
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