bennetts associates marble arch house afe … · sustainability assessment issue | 14 october 2011...

Marble Arch House (216271-00) Sustainability Assessment Issue | 14 October 2011 |

Ove Arup & Partners Ltd 13 Fitzroy Street London W1T 4BQ United Kingdom vww.arup.com

This document takes into account the particular instructions and requirement of our client. It is not intended for and should not be relied upon by any third party and no responsibility is undertaken to any third party.

Bennetts Associates Marble Arch House AFE sketchbook - Sustainability Assessment Job number 216271-00 Issue | 14 October 2011


Job title Marble Arch House

Job number 216271-00

Document title Sustainability Assessment

Document verification

Revision Date Prepared by Checked by Approved by

Issue 14/10/11 Andrea Charlson Kristian Steele Simon Webster

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Contents Introduction

Façade Types

Embodied Carbon

Embodied Carbon - Transport

Embodied Carbon - Benchmarking

Recycled Content

Responsible Sourcing


Introduction The objective of this study is to support the delivery of façade sustainability objectives on the Mable Arch House development in line with British Land’s Sustainability Brief for Developments and supporting project goals such as BREEAM certification. This includes investigating the materials embodied carbon, façade recycled content, and responsible sourcing of the façade materials. This sketchbook contains a summary of this work.


Façade Types In this study the four principle façade types being used on the building have been examined. Details of these four systems are described below. Cladding Type 1/1A (Edgware Road Elevation)

Panelised glazed window system with double glazed units.

Precast concrete spandrel units with insulation bonded to the rear face.

Precast concrete vertical units with insulation bonded to the rear face to the cill and head of the glazing.

Cantilevered maintenance walkway.

Pressed metal louvre screen to the maintenance walkway.

Cladding Type 2 (Seymour Street Elevation)


Projecting precast concrete spandrel units with insulation bonded to the rear face.

Projecting precast concrete vertical units with insulation bonded to the rear face.

Pressed metal cladding to the cill and head of the glazing.

Pressed metal louvre cladding.

Cladding Type 3 (Seymour Street Elevation)


Projecting precast concrete balcony units with insulation bonded to the rear face.

Projecting precast concrete vertical ‘fin’ units with insulation bonded to the rear face.


Cladding Type 4A (All Elevations) 14% RC by kg



Precast concrete vertical units with insulation bonded to the rear face.


Figure 1: Cladding type 1 Figure 2: Cladding type 2

Figure 3: Cladding type 3 Figure 4: Cladding type 4A


Embodied Carbon It can be argued that climate change represents the defining environmental agenda of our time. It follows that the most widely studied materials issue is embodied CO2 , commonly referred to as ‘embodied carbon’. This is defined as the CO2 associated with the extraction, production and pending study scope, the use and disposal of a unit of material. The key impact of CO2 emissions is to cause global warming / climate change. Other gases besides CO2 can also produce this effect, however these tend to be less significant and for simplicity have not been included in this study. The embodied carbon of the façade has been calculated using a life cycle assessment approach. Life cycle assessment (LCA) is an environmental analysis and accounting method for assessing the environmental impacts of a product, system or service over its lifetime (or defined study period). It is a systematic and quantitative approach, in which the value chain of the product or service being assessed is mapped from cradle to grave (i.e. incorporating process steps from extraction of resources, transport/logistics, manufacture and assembly, energy supply, use of the product or service and end of life), as illustrated in Figure 5. LCA provides the opportunity to report on a range of potential environmental impacts, however for this study the focus has been towards just climate change and therefore embodied carbon. The scope of an LCA can be adjusted to match the goals of the study. The scope of this assessment is defined as ‘cradle to factor gate’ covering the materials used for the façade of Marble Arch House. The aim of this study is to provide an embodied carbon factor for incorporation into the façade specification. In order to carry out the life cycle assessment of the building, material flow models were created for the various façade types. Embodied carbon data from the Inventory of Carbon & Energy published by Bath University (1) was used. (1) Hammond, G., Jones, C., Embodied Carbon The Inventory of

Carbon and Energy (ICE), January 2011

Figure 5: Representation of a Life Cycle Assessment for a building


Embodied Carbon To gain an appreciation of which elements were having the most impact on the embodied carbon of the façade, the façade build ups were each broken into a series of defined elemental categories including: Glazing This was only used for the transparent areas of the façade. Framing This included all transoms and mullions. Opaque areas This included the external finish, insulation and support structure. Shading This was used for elements which protruded from the building and the louvers. The charts to the left show the overall embodied carbon figure for each façade type and its breakdown into elemental components. An average embodied carbon factor for the whole façade was found by using this information and factoring up by the areas of each type across the building. From this information it was found that as an average, the embodied carbon of the whole façade is 267 kgCO2/m2. This value has been incorporated into the façade specification.

Cladding Type 1 = 339 kgCO2/m2 Cladding Type 2 = 256 kgCO2/m2

Cladding Type 3 = 202 kgCO2/m2 Cladding Type 4 = 163 kgCO2/m2

12%

13%

22%

53%

Glazing

Framing

Opaque Areas

Shading

16%

18%

14%

52%

Glazing

Framing

Opaque Areas

Shading

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9%

55%

Glazing

Framing

Opaque Areas

Shading

25%

29%

46%

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Glazing

Framing

Opaque Areas

Shading

Figure 6: Breakdown of embodied carbon for the various façade types being used on the project


Embodied Carbon Figure 8 shows the comparison between the four key façade types being used on the building. From this graph it is apparent that there is a large variability in the embodied carbon of the different façade systems. Part of this range is due to the shading devices which are required on some elevations, but not on others. The total embodied carbon of the systems has been split into those elements which are on the face of the building (its envelope), and the shading devices. The splits shown in Figure 8 illustrate how much impact the shading elements have on the overall embodied carbon of the façade system. This is most apparent in cladding type 1, in which these elements account for over half of the total embodied carbon of the whole system. While the additional impacts due to the shading devices may seem high, it is important to note the significant role that they play in controlling the temperatures and comfort within the building. Without these shading devices either a much darker tint of glass would be required, which would result in more lighting being required, or the cooling loads on the plant would be higher, again resulting in increased energy loads. This highlights the importance of considering the whole life cycle of design decisions. It can also be seen that if you ignore the shading devices from the model, there is much lower variation in carbon performance across the façade types. The remaining variations across the systems are due to the different design strategies they take across the building. The significant impact that the framing has on the embodied carbon of the systems also becomes apparent. This can be seen as cladding type 3 has a much lower embodied carbon than the other 3 systems and the significant difference between them is down to the amount of aluminium framing.

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Type 1 (Edgware Road)

Type 2 (Seymour Street)

Type 3 (Seymour Street)

Type 4A (All elevations)

Shading DevicesBuilding Envelope

Figure 8: Comparison of embodied carbon for the various façade types being used on the project

Embodied Car-bon (kgCO2/m2)

401 - 500

301 - 400

201 - 300

101 - 200

1 - 100

Figure 7: Visualisation of the differences in embodied carbon for the various façade types being used on the project

The embodied carbon impact of the shading elements on Marble Arch House are significant. But set against this, they also play an important role in the buildings in-use energy strategy. A fuller study of the carbon benefit these elements provide in operation, as set against the increased carbon they are responsible for at construction, with a life cycle carbon payback determined would provide definitive confirmation of their benefits/impacts.


Embodied Carbon: Benchmarking It is currently quite difficult to compare these results with other façades as there is little or no published comparable data. However there is some embodied carbon data for façades published in the BRE Green Guide to Specification (2). The Green Guide specification carbon factors, for those most applicable to the façade types studied in this project, are summarised in Table 1. The Green Guide looks at the opaque and glazed areas separately. Table 3 shows an estimation of the equivalent green guide rating for the cladding types in the project and how the calculated values compare. It can be seen from this table that the calculated values are lower than those estimated from the Green Guide data. Although these results from the Green Guide are our best current authoritative comparison source, it should be noted that these ratings are for specific construction build-ups with pre-defined performance criteria corresponding to 2006 building regulations, and therefore should be used merely as a guide for the performance, and not as specific targets. In addition they include maintenance and replacement over a 60 year design life as well as the end of life impacts, which may explain why our calculated values are lower. Some additional benchmarks from previous projects are summarised in Table 2. From this table it can be seen that the values calculated for Marble Arch House (excluding shading devices) are within the range found on other projects. Although the factors for Leadenhall and Broadgate buildings appear on the lower side compared to this project, it is difficult to explore the relationship further without further clarity on the calculations methods in those projects.

Specification Embodied Carbon (kgCO2/m2)

Reconstructed stone faced precast concrete cladding

panel, insulation, light steel studwork, plasterboard, paint

230

Extruded aluminium stick type curtain wall: 1 transom per floor, laminated sealed

glass unit, glue bonded insu-lation, medium dense con-

crete solid blockwork, plas-terboard on dabs, paint

200

Windows - Aluminium cur-tain walling system

170

Specification Estimated Green Guide Embodied Carbon

(kgCO2/m2)

Cladding types 1, 2 & 4A (75% glazing, 25% opaque,

structural strong back) 178

Cladding type 3 (75% glazing, 25% opaque, structural precast concrete

unit)

185

Calculated (MAH) Embodied Carbon

(kgCO2/m2)

123 - 163 (excluding shading)

91 (excluding shading)

Specification Embodied Carbon (kgCO2/m2)

Leadenhall Building 88

Fully glazed curtain wall system (Arup)

153

2 transom curtain walling system (Arup)

227

5 Broadgate Building 58

Table 1: Façade embodied carbon benchmarks from the Green Guide to Specification

Table 2: Façade embodied carbon benchmarks from previous projects

Table 3: Comparison of façade embodied carbon results for Marble Arch House (MAH) against benchmark estimates calculated/adapted from Green Guide equiva-lent specifications and their embodied carbon factors


Embodied Carbon: Transport Although the embodied carbon of transport has not been included in the carbon value used in the specification, it has been investigated independently, specifically for the precast concrete elements. When assessing the embodied carbon of precast concrete, the climate change impacts come from two main sources, the extracting and processing of the raw materials into concrete, and their subsequent transportation. The embodied carbon associated with the material extraction and processing of concrete is dependant on its composition. The assumptions made for this study are recorded in Table 4. The sources of the embodied carbon factors for materials were taken from the Bath ICE database (1). At this tender stage there are a variety of possibilities for the sourcing of the precast concrete elements, therefore the carbon associated with the transportation of the precast concrete elements will vary, based on both the distance travelled and the mode of transportation. Likely transportation scenarios were considered for each source, as shown in the figures and the carbon impacts associated with these scenarios were calculated. The carbon impacts associated with the transportation were taken from DEFRA (3) figures, from which average values for HGVs, rail and container ships were used. Results are presented on the following page. (3) DECC & DEFRA, 2011 Guidelines to DEFRA & DECC’s

GHG Conversion Factors for Company Reporting, July 2011

Material Quantity (kg/m3)

Embodied carbon per kg

(kgCO2/kg)

Embodied carbon per m3

(kgCO2/m3)

Portland Cement 249 0.970 242

GGBS 106 0.052 5.512

Coarse Aggregate 1227 0.004 4.91

Fine Aggregate 818 0.004 3.3

Concrete mix (total)

2400 0.107 255.7

Additional impact due to precast processing

0.027

Precast concrete (total)

0.134

Table 4: Embodied carbon of precast concrete

Figure 9: Transport from Lincolnshire

Figure 10: Transport from Dublin Figure 11: Transport from Brussels


Embodied Carbon: Transport Figure 13 shows the total embodied carbon of the precast concrete elements including the impacts due to extraction and transportation. It can be seen that the transport contributes approximately 30-40% of the total embodied carbon of the precast concrete. The embodied carbon of the transport form Lincolnshire and Brussels is approximately equal, despite use of different transport modes. If the elements were to be transported from Dublin this would increase the total embodied carbon due to the greater overland distance that would need to be covered. It should be remembered that embodied carbon is only one aspect of sustainability. There are other social & economic benefits that can be attributed to using more local supply chains.

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Figure 12: Embodied Carbon for various freight transport modes per tonne km

Figure 13: Total embodied carbon for various sources of precast concrete

The carbon associated with the transport of the concrete elements of the façade is significant at 30-40% of total supply chain impacts.


Recycled Content In order to support the recycled content target for the project the potential recycled content of the various façade types was calculated. Table 5 summarises the assumed recycled contents for the key materials in the façades. Table 6 shows the total potential recycled content (by mass) for the four main façade types in the project. Based on these figures, our calculations covering façade types 1-4, show an average of 13% recycled content for the whole façade, by mass. To the left we provide a listing of the key façade systems and the recycled content levels of each component that can be assumed. Models for each of these have been developed to establish the headline figure above of 13% recycled content (mass) for the whole building façade. Whilst these recycled content figures have been used to inform the recycled content targets for the project, it has been decided not to include these figures as targets in the specification. Here we have set out what has and has not been included in the specification concerning recycled content: We have advised not to specify recycled content for any of

the metals used as this will not encourage more recycling that currently takes place by the industry.

We have advised not to specify an absolute recycled content

for the precast concrete. The approach we have applied is to specify a percentage cement replacement for the precast, which implicitly will also ensure a precast solution with recycled content outcome.

The rebar in the precast can be assumed 100% recycled and

this has not been accounted for in the calculations shown. We have advised to specify a 60% recycled content for the

insulation, which is a best case scenario for insulation options considered as per BREEAM targets.

Material % RC by mass Aluminium extrusion 33

Aluminium sheet 0

Steel sections 39

Steel reinforcement 99

Glass 0

Insulation 60

Precast concrete 6.6

Table 5: Assumed recycled contents of façade materials

Façade Type Total Area (m2) % RC by mass

Cladding Type 1/1A 1454 20%

Cladding Type 2 280 8%

Cladding Type 3 198 6%

Cladding Type 4A 841 14%

Table 6: Calculated recycled contents of various façade types

Cladding Type 4A (All Elevations) 14% RC by kg

Panelised glazed window system with double glazed units. (Al DGU 0%

RC)


(Insulation RC 60%, Concrete = 6.6% RC due to pfa or ggbs use (i.e.

based on 30% cement replacement), rebar = 100% RC)

Precast concrete vertical units with insulation bonded to the rear face.

(Insulation RC 60%, Concrete = 6.6% RC due to pfa or ggbs use (i.e.


Pressed metal cladding to the cill and head of the glazing. (Al 0%RC)

Cladding Type 1/1A (Edgware Road Elevation) 20% RC by kg Panelised glazed window system with double glazed units. (Al DGU 0%RC)


(Insulation RC 60%, Concrete = 6.6% RC due to pfa or ggbs use (i.e. based

on 30% cement replacement), rebar = 100% RC)

Precast concrete vertical units with insulation bonded to the rear face

(Insulation RC 60%, Concrete = 6.6% RC due to pfa or ggbs use (i.e. based

on 30% cement replacement), rebar = 100% RC)


Cantilevered maintenance walkway. (This will be as steel T section but

would we would advise against specifying RC content in steel as not useful;

however a 39% value has been applied in the calculation)

Pressed metal louvre screen to the maintenance walkway. (Al 0%RC)

Cladding Type 2 (Seymour Street Elevation) 8% RC by kg


RC)

Projecting precast concrete spandrel units with insulation bonded to the

rear face. (Insulation RC 60% discussion, Concrete = 6.6% RC due to pfa

or ggbs use (i.e. based on 30% cement replacement), rebar = 100% RC)

Projecting precact concrete vertical units with insulation bonded to the rear

face. (Insulation RC 60%, Concrete = 6.6% RC due to pfa or ggbs use (i.e.



Pressed metal louvre cladding. (Al 33%RC)

Cladding Type 3 (Seymour Street Elevation) 6% RC by kg


RC)

Projecting precast concrete balcony units with insulation bonded to the rear

face. (Insulation RC 60%,, Concrete = 6.6% RC due to pfa or ggbs use (i.e.


Projecting precast concrete vertical ‘fin’ units with insulation bonded to

the rear face. (Insulation RC 60%,, Concrete = 6.6% RC due to pfa or ggbs

use (i.e. based on 30% cement replacement), rebar = 100% RC)



Responsible Sourcing Responsible sourcing of materials (RSM) is an approach of supply chain management, responsible manufacture and product stewardship, and encompasses social, economic and environmental dimensions. In the construction products sector, the aspect is most mature within the timber industry with timber supply schemes like the Forest Stewardship Council (FSC) and the Programme for the Endorsement of Forest Certification schemes (PEFC) leading the way. The reality however is that responsible sourcing should be an objective of all material supply sectors. There are two ‘framework’ standards which define what responsible sourcing means: 1. BS 8902: 2009, Responsible sourcing sector certification

schemes for construction products - Specification (from BSI) 2. BES 6001: 2008, Framework Standard for the Responsible

Sourcing of Construction Products (from BRE) It is possible to get construction products certified to these standards in the UK. It is noteworthy that many green building rating systems like LEED, BREEAM, Green Star and Estidama etc., have credits or criteria that address responsible sourcing. Façade contractors are not currently well placed to respond to responsible sourcing objectives and there are not the same frameworks in place outside the UK. This makes achieving responsible sourcing of façade a challenge and for this reason we have taken a measured approach to specification which calls upon the supply chain to meet certain objectives (environmental management) whilst not making it overly onerous and causing problems with supplier negotiation. The clauses to the left have been included in the specification to encourage the responsible sourcing of materials.

Responsible sourcing of the facade As required by the Schedule of Submissions, documentation shall be produced for the Works by the Sub-contractor following the principles and guidelines of either BES 6001 or BS 8902; or following the princi-ples and guidelines of BS EN ISO 14001 or equivalent. A copy of BES 6001 certificate number, and/or Environmental Management System (EMS) certificate shall be provided to demonstrate how environmental management will be implemented from award of Contract through to Contract Completion. The products shall be sourced from suppliers capable of providing one of the following:

Certificates of responsible sourcing to either standard BES 6001 or BS 8902; or

Certificates of EMS for product manufacture and key supply chain processes. Independently certified EMS schemes include BS EN ISO 14001, or equivalent.

Purchase orders from the supplier including (as appropriate) Chain of custody evidence and/or BES 6001 certificate number, and/or EMS certificate shall be provided to demonstrate how en-vironmental management will be assured from the supply chain.

Responsible sourcing of insulation products

At least 80% of the insulation used in the works shall be respon-sibly sourced to either standard BES 6001 or BS 8902; or must be from a source with a certified Environmental Management System (EMS) for product manufacture and key supply chain processes. Independently certified EMS schemes include BS EN ISO 14001, or equivalent. Purchase orders from the supplier in-cluding (as appropriate) chain of custody evidence and/or BES 6001 certificate number, and/or EMS certificate shall be pro-vided.

Extracts from the façade specification used to achieve project out-comes on responsible sourcing

bennetts associates marble arch house afe … · sustainability assessment issue | 14 october 2011...

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