MB Green Guide Revised Sept09

8/8/2019 MB Green Guide Revised Sept09

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Concrete and the Green Guide

The use of the Green Guide in the context of sustainable design


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Contents

Concrete and the Green GuideAn overview o The Green GuidePages 4 and 5 set the scene or the Green Guide and how it relatesto the responsible sourcing o construction products and whole li eenvironmental issues.

The Green Guide methodology The guide has been produced to address the principles o elementalLi e Cycle Assessment. How this has been done and how the resultingin ormation can be used by designers is outlined on page 6 .

Achieving the highest ratings with concreteFive design strategies or achieving the best Green Guide ratings areexplored on pages 7, 8 and 9 in this publication. These strategies are:optimising cementitious materials; when to use recycled or secondaryaggregates; optimising mass; use o admixtures; and contacting suppliers

or product speci c in ormation.

The Green Guide as part o a Code or SustainableHomes assessmentSeven steps or considering materials and the guide in the context o the Code or Sustainable Homes (the Code) are outlined on pages 10 to14. These steps demonstrate the importance o iterative, holistic design. This section concludes with an examination o how to score points orresponsible sourcing o products in the Code and other assessment tools.

The Green Guide and element ratings in the contexto sustainable designA designer needs to be able to use the guide in context, as it providesin ormation on just one piece o the sustainability jigsaw. There are other actors which dictate the sustainability o a design;Page 15 helps to put these actors in to the context o the guide.Page 16 explores why it is essential or designers to consider overheatingcontrol, acoustic per ormance, and structural and air tightness requirementsin parallel to using the guide.

The Green Guide as part o a non-domestic assessment

The Green Guide or non-domestic buildings is used in the BREEnvironmental Assessment Method (BREEAM) tool to assess some o thecontribution that materials make to a sustainable design. How to use theguide in this context, and how it is di erent rom its use as part o a codeassessment, is explored on page 17 .

The Green Guide o the uture? The guide is constantly evolving and ve areas likely to be developed arediscussed on page 18 . These include wastage rates, recycled materials,accommodating buildings with a use ul li e greater than 60 years,and new measures or abiotic and biotic resource use.

Introduction 3

The Green Guide in the context of sustainable design 3

An overview of the Green Guide 4

The Green Guide methodology 6

Achieving the highest ratings with concrete 7

The Green Guide as part of a Code for 10

Sustainable Homes assessment

The Green Guide and element ratings in the 15

context o sustainable design

The Green Guide as part of a non-domestic 17

assessment

The Green Guide of the future? 18

References and notes 19

2

Main cover image: courtesy o Tarmac


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Introduction This publication will assist designers to speci y concrete inconjunction with the Green Guide to Speci cation(re erred tothroughout as the Green Guide or the guide). It highlights the guides relevance in the context o whole li e per ormance andsustainable design, SAP, the Code or Sustainable Homes and othersustainability assessment tools, including BREEAM* or high-risedomestic and commercial buildings.

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The guide is not a tick box activityBRE in 2008 [1] suggested that use o the guide should be consideredcare ully, because when it is used simply as a tick box activity, or byspeci ying A or A+ rated elements only, it is less likely to result in themost sustainable long-term building solution.

Concrete products score wellWhere a designer or client has chosen to use concrete products as part

o their design solution they will nd that there are a lot o concreteconstruction elements in the Green Guide. There are some sections o the guide where concrete scores extremely high. For instance, in cavitywalls it is quite easy to score an A or A+ rating or all building types.

Interdependence between operational andembodied impacts The interdependence between operational and embodied impactso construction materials will remain essential to sustainable design,and this requires them to be considered together. Good design willconsider the A+ to E scores in conjunction with other in ormation aboutthe construction element and the overall design, such as air tightness,thermal bridging, thermal mass, overheating requirements, acoustics,and moisture control.

Building Regulations, SAP and thermal massPart L o the Building Regulations is changing to accommodate new

actors, including the thermal mass o a structure and its relationshipto overheating and passive solar gains. Thermal mass is an important

actor in the design o energy e cient low-carbon dwellings therecognised bene ts o thermal mass are currently not accounted

or in the guide.

Responsible sourcing The concrete industry is well placed to demonstrate the highest levelo responsible sourcing per ormance based on e ective managementsystems, local availability o materials and well managed supply chains.Within the Code or Sustainable Homes, responsibly sourced materialsare encouraged and credited, or both basic building elements and

nishing elements.

The Green Guide in the context o sustainable design

Figure 1: The Green Guide in the context o the three pillars o sustainability.

Biotic resources are living resources such as biomass, timber, etc. Their extraction and the associatedenvironmental impacts are not currently assessed in the guide in the same way as the use o non-livingmineral resources are. This is an area or uture development (see page 18).

SOCIAL

ECONOMIC

ENVIRONMENTAL

Quality of building

Cultural values

Indoor amenity

Safety/security

Accessibility

Cost

Risk/sensitivity

Return on Investment

Contribution to GDP

Value

TheGreenGuide Operational

maintenance

Responsiblesourcing

Climate change

Biotic resources

Land use

Resource use

Truly sustainable design solutionswill only be achieved by using the

Green Guide as but a part o aholistic process.

* According to BRE, BREEAM Buildings can be used to assess the environmental per ormanceo any type o new or existing building. Standard versions exist or common building types(courts, healthcare, industrial, multi-residential, prisons, o ces, retail, education, communities andinternational or developments, regions or countries) and less common building types can beassessed against tailored criteria under the Bespoke BREEAM version

This publication explains whereconcrete solutions score the best Green Guide ratings, and how toimprove the ratings o concrete products within an overall design.


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The Green Guide is a tool or assessing some o the embodied impactso construction elements as part o an overall environmental orsustainability assessment or a project or development. For someprojects, use o the Green Guide is e ectively mandatory due to clientrequirements or as a component part o a Code or Sustainable Homesor BREEAM assessment. For example, a minimum code level 3 ratingunder the Code or Sustainable Homes has been required or all publicsector new homes (those being built using Homes and CommunitiesAgency unds or English Partnerships land) since April 2007.

The revised Green Guide Online www.thegreenguide.org.uk waso cially launched in June 2008. This version o the guide implementsthe new 2007 methodology, covers a larger range o elements thanpreviously, and allows or updates to be made to ratings as manu acturersimprove the environmental credentials o their products. (The originalGreen Guide to Speci cationwas published in 1996).

The new Green Guide to Speci cationcombines and replaces both theGreen Guide to Speci cationand Green Guide to Housing. It has beenexpanded to cover di erent building types:

O ces Educational Healthcare

Retail Domestic Industrial

BRE has advised that the Domestic section o the new Green Guide isonly appropriate or low-rise domestic developments (i.e. not high-rise developments). A pragmatic solution is to re er to the Commercialsection o the Green Guide when working on a multi-storey project, as thespeci cations are more appropriate to the building design. This principlehas been used success ully [by the relevant agencies] on major schemes.

The calculations underpinning the Green Guide start by estimating theenvironmental impact per tonne o each di erent construction material.Materials are then combined to orm components and these componentscombined to orm elements. The elements covered in the guide are:

External walls Internal walls and partitions Roo s Ground foors Upper foors Windows Insulation Landscaping Floor nishes

The relationship between materials, components and elements isshown in Table 1 below.

An overview o The Green Guide

Assessmentstage

Life cycle stage Units Can environmental data becompared at this stage?

Are all issues covered atthis stage of analysis?

Materials Cradle-to-gate (extraction o rawmaterials to production actory gate)

Per tonne No, concrete, steel and timber have

very di erent properties and a tonneo each can be used to producedi erent outcomes

No

Components Cradle-to-site (as above plus deliveryto site and installation)

Per square metreinstalled element

No, as this does not constitute anentity comparable with others until itis installed as part o a building element.For instance a screed is a component,part o a whole foor element

No

Elements Cradle-to-site plus maintenance andend-o -li e (as above plus maintenanceo element and impacts associatedwith end-o -li e processes anddisposal)

Per square metreo element over60 year studyperiod

Yes, the guide allows this No, as at this level there is no accounto the relationship between buildingper ormance and building elements.Note that the analysis does not includeoperational impacts

Whole li ebuilding

Cradle-to-grave (raw materialextraction, product production,on-site installation, the use phase,demolition and end-o -li e impacts)

Per square metreo building overli e o building

Possibly, as part o a complete li e cyclestudy with the Green Guide eaturingas one part

Yes, subject to method andassumptions

Table 1: The relationship between materials, components and elements


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The Green Guide methodologyAs part o a ull sustainability audit, the Green Guide can play a use ulrole in estimating some embodied environmental impacts. AsFigure 1 (on page 3) shows, other issues need to be consideredin conjunction with the guide to assess the social, economic andenvironmental impacts associated with the use o a building.

The 13 environmental issues assessed in the guide are:1. Climate change2. Ozone layer depletion3. Human toxicity4. Fresh water aquatic ecotoxicity5. Terrestrial ecotoxicity6. Photochemical oxidation7. Acidi cation8. Eutrophication9. Fossil uel depletion10. Solid waste11. Radioactivity12. Minerals extraction13. Water extraction

A rating is ormed by banding the weighted score o 13 di erentenvironmental issues or an element into one o six bands (A+ to E). Thisis done by dividing the range o scores given to all the elements withineach building element group into six equal parts. There ore, the ratings

within the Health Upper Floors and Domestic Upper Floors sectionso the guide do not relate to comparable levels o environmental

per ormance and will be di erent depending on the elements that arerepresentative o commonly used UK speci cations within those buildingelement groups.

When considering the ratings within each building element group, aspeci cation receives an A+ rating i it represents the least environmentalimpact in the group, and an element gets an E i it is amongst thespeci cations that have the highest environmental impact o those inits group.

The scores against each environmental issue assessed in the guide areweighted and combined to orm a single score. The use o weightingin this way is greatly debated. A single score simpli es the analysis oran end user. However, the individual importance o the 13 di erentenvironmental issues is lost, and the weighting itsel is subjective.

Generic data, sourced rom a variety o commercial databases, tradeassociations and manu acturers, has been used as a basis or the ratings.Also, data has been gathered or environmental issues that are simple tomeasure; economic or social sustainability actors are not included.

The Green Guide methodology is an example o element Li e CycleAssessment (LCA). Speci c assumptions on assessment conditions havehad to be made as part o the process. More in ormation can be oundin the BRE methodology document available on the Green Guide website:

www.thegreenguide.org.uk . Generic guidance on LCA can be ound byreferring to the ISO 14040 series of standards.

Figure 3: How the Green Guide is ormulated

Elements

The quantity o material incorporated inbuilding elements (per m 2 and over a

generic 60 year study period) is calculatedrom speci cation design details. Anyreplacement over the 60 year period

is included.

Calculation

The quantity o the materials withinan element is combined with the

environmental impact data o each acrossthe 13 categories ( rom their extraction,manu acture, transport and end-o -li e).

13 environmentalissue categories

Climate changeFossil uel depletionSolid waste etc.

Environmentalimpact

The result is a measure o the environmental impact

o the element acrosseach o the 13 categories.

Weighting

These impacts aremultiplied by

environmentalweightings oreach category.

Single score

The weighted scoresin each category are

summed to orma single score oreach element.

Banding

The scores or all elements within eachbuilding element group are divided into A+to E rating bands (building element groups

include, domestic roo s and commercial andindustrial upper foors).

6


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Developing a sustainable design involves maximising the points scoredin all the other parts o the sustainability assessment whilst optimisingthe score in the Materials section [2].

Where a designer or client has chosen to use concrete products as parto their design solution they will nd that there are many concreteconstruction elements in the Green Guide, many o which score wellagainst the rating system o A+ to E. There are also sections o the guidewhere concrete scores extremely highly. For instance, in cavity walls orall building types it is quite easy to score an A or A+ rating. There area number o design strategies that can be considered when selectingconcrete elements, each o which can infuence the overall rating

positively. Examples o these strategies are:

Optimising cementitious materials. Use o recycled or secondary aggregates. Optimising mass. Use o admixtures. Contacting suppliers or product speci c in ormation.

Optimising cementitious materials The use o ground granulated blast urnace slag (GGBS), fy ash or limestone

nes as part o a actory-made cement or in concrete can make products

with a signi cantly reduced environmental impact. GGBS and fy ash areby-products o other industrial processes (the blast urnaces used to makeiron and coal red power stations). The urther processing required to makeGGBS, fy ash and limestone nes suitable or use as cementitious materialsis signi cantly less than the energy required to make CEMI cement, and theiruse will reduce the environmental pro le o concrete. Data on the carbon

ootprint o various cements and concretes is available romwww.sustainableconcrete.org.uk .

The use o GGBS and fy ash can have a number o positive infuenceson concrete per ormance, including improved workability and increasedlong-term durability o concrete when subjected to aggressive

environments. Their use is very common in the manu acture o productssuch as blocks where the slightly longer setting times associated withusing GGBS or fy ash are o less importance. The use o GGBS or fy ashcan reduce embodied CO 2 levels. With increasing levels o GGBS andfy ash, the development o early strength can be slower or concretemixes designed or similar 28 day strengths. These e ects may be morepronounced in cooler weather. Where striking times are critical, theper ormance o these mixes should be con rmed as suitable or theseapplications. Eighteen per cent o all the cementitious materials used inthe UK are GGBS or fy ash [3].

Achieving the highest ratings with concrete

1 Coleman Street has proved the feasibility of using 100% secondary coarse aggregatein a large scale project. Courtesy of Arup.

Green Guide ratings within theCode or Sustainable Homesand BREEAM O ce contribute4.5 per cent and 6.25 per cent respectively o the total pointsavailable in those schemes.


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Use o recycled or secondary aggregatesA large number o the elements in the guide contain recycled aggregate,used in a sub-base and/or as a replacement or virgin aggregate inconcrete. Speci ying recycled aggregates rather than virgin aggregateswill always improve the elemental score but only sometimes by a

su cient amount to improve an elements rating in the guide.

For example, within the ground foor details o the Domestic section: The chipboard (P5) decking on timber joists with insulation, over

100mm 50 per cent GGBS oversite concrete element scores an A.

The chipboard (P5) decking on timber joists with insulation, over100mm 50 per cent GGBS oversite concrete (100 per cent RCA) scoresan A+. 100 per cent RCA implies that 100 per cent o the aggregate inthe concrete is Recycled Concrete Aggregate.

There are other elements in the guide where the speci cation o recycledaggregates does not change the rating.

Whether the use o recycled aggregates improves an elements rating inthe guide does not refect all the sustainability impacts o sourcing thematerial. The calculation happens without consideration o the transportdistances involved in the use o the materials and it is up to the speci erto consider this (as a sustainability issue) as it is not captured by theGreen Guide.

Designers should already be aware that nearly 100 per cent o harddemolition waste is used [4] and there ore speci cation o recycledaggregates does not decrease virgin aggregate extraction. Speci cationonly changes the location in which recycled aggregates are used.

The research summarised in Table 2 suggests that designers should onlyconsider the use o recycled aggregates when travel distances o thematerial, by road to site, are less than 10 miles.

Speci cation o virgin aggregates will in many cases include up to 20 percent recycled content, as allowed under BS 8500. The recycled contentwill be at the discretion o the ready-mix supplier based on availabilityand cost (with aggregates levy and land ll tax in-built in any costcomparison).

More in ormation on how to speci y concretes that incorporate recycledaggregates is available in Concrete Structures 7 seewww.concretecentre.com/publications .

Asphalt planings used as recycled aggregate.

To ensure a sustainabledesign only speci y recycled aggregates i they can be locally sourced.


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Use o admixturesAround 90 per cent o concrete in the UK includes some orm o admixture. Admixtures are specially ormulated products which areadded in small amounts to concrete, mortar or grout during the mixingprocess in order to modi y the concrete properties in the plastic and/orhardened state.

Admixtures can bring environmental bene ts, reducing water demandand thus cement content and overall embodied CO 2. Water reductionscan range rom 10 per cent to over 30 per cent. Admixtures are mainlyorganic chemicals and have inherently high embodied CO 2 content,depending on admixture type. However, the quantity o admixtureadded to concrete is small, rarely more than 0.3 per cent o concreteweight, and more typically, less than hal this quantity.

Information on the use of admixtures can be received from the Cement Admixtures Association www.admixtures.org.uk or the concrete supplier.

Material Returndelivery

distanceto andfrom siteby road

(km)

Cradle-to-gate

(kg CO 2/tonne)

Transportkg/ tonne

[11]

Total kg/tonne

+/- % CO 2

Virgin aggregate [6, 12] 58.5 6.6 2.7 9.3 0.0%

Recycled C&D aggregate [7](used on-site) 0 7.9 0.0 7.9 -15%

Recycled C&D aggregate [7] 10 7.9 0.5 8.4 -10%

Recycled C&D aggregate [7] 20 7.9 0.9 8.8 -5%

Recycled C&D aggregate [7] 40 7.9 1.8 9.7 5%

Recycled C&D aggregate [7] 100 7.9 4.5 12.4 34%

Recycled C&D aggregate [7](100 miles delivery distanceby road)

322 7.9 14.6 22.5 143%

Recycled C&D aggregate [7](200 miles delivery distanceby road)

644 7.9 29.3 37.2 301%

Optimising massEnvironmental impacts in the Green Guide are linked to the weight o the materials. According to the guide methodology, the mass o theconcrete construction elements can account or around 50 per cent o their overall environmental impact [8]. There ore, where there is potentialto design out the mass whilst maintaining structural per ormance, thiscan have a signi cant positive impact on the rating. For example, areview o Green Guide ratings shows:

1. The use o a hollowcore foor slab to deliver the same structuralper ormance as a solid slab will reduce the mass o the elementand will get a better rating.

2. Pre-stressing, as opposed to ordinary rein orcing, can also reducethe mass, and thus improve the rating.

3. Environmental per ormance with foors can be improved bypower-foating the concrete foor, avoiding the need or ascreeded nish, thus reducing mass.

The environmental bene t o minimising mass is counter intuitive whenthere is an opportunity to use it to improve the passive per ormanceo a building. The thermal mass available in heavyweight construction

is typically a key eature o passive design, and can help reduce thedemand or cooling in summer and heating in the autumn, winter andspring. Over the li e o a building, the energy saving this provides issigni cant, and can outweigh the lower embodied impacts resulting

rom decreased mass.

The thermal mass benefts o usingconcrete need to be balanced with

the benefts o weight optimisationrewarded in the Green Guide.

There is increasing interest in the use o recycled aggregates,

with some clients speci ying a minimum percentage o recycledmaterials in projects.

The current version o the guide gives a large reward or the useo recycled aggregates. The size o this reward is disproportionateto the environmental impact as the guide does not account oraggregates being plenti ul in the UK [5] and that virtually all therecycled aggregates in the waste stream are already being re-used[4]. It does not consider transportation in comparison to sourcingother orms o aggregates. The guide also does not consider theadditional cementitious content that may be required in a concretemade with recycled aggregates to ensure the same strength.

As Table 2 shows in terms o carbon dioxide emissions, incentivisingpeople to use recycled aggregates as the most sustainable option,without considering the transport o the materials, is not the bestoption. Generally, when transported by road, the use o recycledaggregates is only a lower carbon option when used within 10miles (or 15 km) o their source.

Table 2: Implications of transporting recycled aggregates


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The Code takes a holistic approach to sustainability and includes othersocial and environmental issues beyond those covered by the GreenGuide. Code assessments (by licensed assessors) are carried out at twostages: rstly the design stage and a urther assessment or veri cationbeing required at the post construction stage. The ollowing seven stepsshow how to use the Green Guide as part o a code assessment duringthe design stage.

Seven steps to using the Green GuideStep 1: Ensure that you have the latest version o the Code or

Sustainable Homes Technical Guidance rom the Communitiesand Local Government website.

Step 2: Work with a code assessor; a national register o assessors iskept up to date on the Green Book Live website.

Step 3: Recognise that the Green Guide contributes 4.5 per cent o the overall score iterative, holistic and sustainable designwill be required, accounting or all nine categories in the Code.

Step 4: Re er to Mat 1: in the materials category EnvironmentalImpact of Materials.

Step 5: Convert the credits scored to points.

Step 6: Consider bespoke ratings where relevant or speci c productsor construction elements.

Step 7: Consider construction elements in relation to Mat 2:Responsible Sourcing o Materials Basic Building Elements.

Step 1: Ensure that you have the latest version o the Code orSustainable Homes Technical Guidance

The in ormation in this publication is based on Version 2, May2009 o the technical guidance; which can be downloaded romwww.communities.gov.uk/publications/planningandbuilding/codeguide

Step 2: Work with a code assessorA registered code assessor is required to carry out an assessment at theend o the design stage. A code assessor may also be required duringthe design stage. He or she, who may be an in-house expert or anexternal consultant, will:

Validate assumptions and calculations.

Use prescribed tools to make the calculations (some of thecalculations in step 3 are carried out in a particular way using speci cspreadsheet tools).

Provide advice on how to use speci cations to achieve the bestoverall score in the Code.

In an organisation where there is considerable knowledge about theCode it may not be necessary to engage an assessor until the point atwhich a design stage assessment is required.

Some practitioners will o er other design or building related services aswell as assessing against the Code. The BREs Green Book Live website www.greenbooklive.com contains more in ormation and providescontact details or all registered assessors.

The Green Guide as part o a Code

or Sustainable Homes assessment

Nightingale Estate, Hackney. Southern Housing Group project uses tunnel form in-situ concrete construction.


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Health and well being 14%

Water 9%

Responsible sourcingof materials 2.7%

Environmental impactof materials as assessed

in the Green Guide 4.5% Materials 7.2%

Waste 6%

Pollution 3%

Energy and Emissions 36%

Ecology 12%

Management 10%

Surface water run off 2%

)

Step 3: Engage in a process o iterative, holistic andsustainable design

Figure 4 illustrates the importance o the guide in relation to the othercategories in the Code. Materials account or 7.2 per cent o the totalpoints available in the Code.

The total o 7.2 percentage points available or the houses buildingabric refects the current ratio o embodied environmental impacts to

the impact o a total building. Over time, this may change with embodiedimpacts becoming more signi cant due to the UK Governments goal orall new homes and schools to be zero carbon by 2016, all public sectorbuildings by 2018, and potentially all new buildings by 2019.

The interdependence between operational and embodied impacts o construction materials will remain essential to sustainable design and thisrequires them to be considered together. When using the Green Guideconsider the A+ to E scores in conjunction with other in ormation aboutthe construction element and the overall design, such as air tightness,thermal bridging, thermal mass and overheating requirements, acoustics,and moisture control.

In practice this will mean that an iterative design process will likely needto be employed to develop a design that satis es a clients requirementswhilst also meeting the required level o per ormance against the Code.

* Figure derived rom Code or Sustainable Homes, October 2008, Communities and Local Government.

Figure 4: The Code or Sustainable Homes - nine categories*

Consideration o the GreenGuide ratings is but a part o creating truly sustainabledesign solutions.

Recycling operations: crushed demolition waste to be used as secondary aggregate.Courtesy of Tarmac.


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Step 4: Re er to Mat 1 in the materials categoryEnvironmental Impact of Materials

Mat 1 is the speci c section o the Code where credits are scoredaccording to the Green Guide ratings. This section contributes 4.5 percent o the total marks available in the Code (62.5 per cent o the points

available in the Materials category) [9].

There is a mandatory requirement or at least three o the ollowing vemajor elements o the building envelope to achieve a Green Guide ratingo D or above.

Roof External walls Internal walls (including separating walls) Upper and ground oors (including separating oors) Windows

Credits or this section are awarded based on the speci cation o all

ve elements, with credits awarded as set out in the table below. A teradding credits or the ve elements together the nal score in a Mat 1calculation is always rounded down (i.e. 9.75 becomes 9).

Table 3: Calculation o credits or the environmental impact o the vemajor elements o the building envelope in the Code

There ore, in principle: If three of the ve elements are rated as D and the other two as C

then the overall score is 1. The maximum credits achievable for this section is for ve A+ rated

elements, each scoring three points, with a total o 15.

However, the Code Mat 1 calculator tool must be used to carry outan assessment. BRE makes this tool available to registered codeassessors. The tool takes into account issues such as:

Rounding down the nal score as explained above.

Composite designs: where there is more than one speci cation foran element (e.g. more than one type o external wall being used ora dwelling) credits are awarded or that element, based on thearea weighted rating o each speci cation.

The Code technical manual contains guidance or designing multipledwellings contained within a single envelope, or or mixed use

developments. It also states that where there are several identical buildingswith identical building envelopes there is no need to assess thebuildings separately. The technical guidance or the Code also indicates the example evidencerequired by an assessor at the design stage. At the post constructionstage it is also necessary to ensure that the evidence provided at thedesign stage is still valid, and that no changes have occurred duringconstruction. Where changes have occurred, the code assessor is likelyto re-assess the calculations.

Green Guide Rating Credits

A+ Rating 3

A Rating 2

B Rating 1

C Rating 0.5

D Rating 0.25

E Rating 0

Courtesy of: Martin Grant Homes


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Step 5: Convert the credits scored in this Mat 1 sectionto points

Be ore moving on to the next step in the process, the credits accumulated

by the construction elements must be converted to Code points.

A design is assessed against the Code out o a total available points scoreo 100. There are a di erent number o credits available in each o thenine categories and each is judged as carrying a di erent weight in theoverall sustainability assessment.

Table 4 below eatures in the Technical Guidance or the Code ( Version2, May 2009) and gives the approximate weighted value o each credit inthe materials category as 0.3. There ore, a score o 15 credits in the Mat 1section is equal to 0.3 * 15 = 4.5 points, a score o 10 credits is equal to0.3 * 10 = 3 points.

Table 4: Total credits available, weighting actors and points

Step 6: Consider using or obtaining bespoke ratings whererelevant or speci c products or construction elements There are two situations when it is relevant to use bespoke ratings

or construction elements:

1. When a manu acturer has its own product specifc rating

Generic ratings are reported or the speci cations that eature in theGreen Guide Online and the Green Guide publication. These genericratings refect average data collected rom a number o companiesand product manu acturing sites.

Product speci c pro les published by BRE are available i they have beencommissioned by the manu acturer. The product speci c ratings refectthe manu acturing environment and methods o an individual company,and o er a wider range o possible ratings to the designer.

Individual manufacturers will provide information on products with speci c ratings scoring more highly than the generic ratings.By requesting a copy o the suppliers BRE certi cate, it will givein ormation that the code assessor would use in an assessment.

When a speci c company product with a product speci c rating isspeci ed it may be necessary to use the BRE mixing desk. The mixingdesk is an Excel spreadsheet available to code assessors that allows parto a generic construction element (e.g. a standard block used in a squaremetre o wall) to be substituted with a speci c product and how thissubstitution would change the score available or that building element.

2. In the case o specifcations that have no matchingrating in the Green Guide

In the case of a design speci cation that has no matching rating in the Green Guide or no company or product speci c rating thereare alternatives:

The appointed code assessor may be able to nd a similarspeci cation. For instance, i there is a similar speci cation in theguide or which there is a rating, then that can be used instead.

If in doubt, or if no similar speci cation is available, the assessor can contact the BRE Materials team who will advise which

rating should be used.

29 36.4% 1.26

6 9.0% 1.50

24 7.2% 0.30

4 2.2% 0.55

7 6.4% 0.91

4 2.8% 0.70

12 14.0% 1.17

9 10.0% 1.11

9 12.0% 1.33

- 100.0% -

Categories of environmental impact

Total credits ineach category

Weightingfactor

(% pointscontribution)

Approximateweighted

value of eachcredit

Category 1Energy and CO 2 Emissions

Category 2Water

Category 3Materials

Category 4

Sur ace Water Run-o Category 5

Waste

Category 6Pollution

Category 7Health and Wellbeing

Category 8Management

Category 9Ecology

Total

There are a range of blocks available that provide A+ ratings.


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For a designer to be able to use the guide appropriately it is important tolook at the guide in context, as it provides in ormation on just one pieceo the sustainability jigsaw.

As part o a ull sustainability audit the guide can be used to estimatesome embodied environmental impacts, whilst other tools need tobe used to assess the social, human, economic and the environmentalimpacts associated with the operation o the building.

For instance, the common actor that decides i construction elementsare considered as equivalent in the guide is their U-value per ormance.U-value per ormance is only one signi cant measure when consideringsustainable design. Part L o the Building Regulations is changing toaccommodate other actors, including the thermal mass o a structureand its relationship to overheating and passive solar gains. Thermalmass is an important actor in the design o energy e cient low-carbondwellings the recognised bene ts o thermal mass are currently notcaptured in the guide.

The Green Guide and element ratings in the

context o sustainable design The bene t o thermal massOver the li etime o a home, the energy used to heat, light and coolit (operational impacts) are greater than the embodied impact o the manu acture o the materials used to build it.

27% o the UKs carbon emissions come rom operational impactsfrom homes. It is essential that they are taken in to account whenevaluating the per ormance o construction materials.

Independent research carried out by Arup Research &Development takes account o expert predictions or climatechange and demonstrates that the thermal mass in masonryhomes reduces the need or energy intensive air conditioning [10].

The research also highlights the additional savings that can beachieved through using thermal mass to capture solar gains,thereby reducing the consumption o winter heating uel. TheCO2 savings associated with heavyweight construction can o set

the slightly higher level o embodied CO 2 in as little as 11 years andultimately lead to the lowest whole li e CO 2 emissions.

This e ect is even more pronounced in commercial properties.

For urther reading on thermal mass see Thermal mass or housingbrochure and other related publications atwww.concretecentre.com/publications

140

120

100

80

60

40

20

02000 2010 2020 2030 2040 2050 2060

Years

C O

2 E m i s s i o n s

( t o n n e s )

Additional embodied CO 2 o set in 11 years

Lightweight house

Mediumweight house

Figure 5: Cumulative CO2 emissions (air-conditioned type)

St. Matthews keyworker estate, Brixton.Courtesy of Benedict Luxmoore/arcaid.co.uk

Great Bow Yard, Somerset features a sunspace as part of a passivesolar design that utilises the thermal mass of concrete. Courtesy of Building for Life/Design for Homes. Photography: Richard Mullane.


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Overheating and the guide Thermal mass is crucial to the thermal performance of buildings. It helps toprevent overheating as well as storing heat.

However, materials with low density score well in the guide on the wholebecause they use less material and there ore are judged to have lessenvironmental impact. The speci cation o light materials may lead to higherenergy use because o the need or additional cooling or heating. This isbecause thermal mass is a unction o speci c heat capacity and density. To nd out more in ormation Thermal Mass Explained is available onwww.concretecentre.com/publications.

For example, in energy e cient designs or housing, schools and o ces,heavy concrete foors are o ten used to store heat and to preserve coolingin the summer, thereby avoiding air-conditioning (with its high energy andcarbon impact) and occupant discom ort. As a consequence o the guideand its underpinning methodology, the bene ts o thermal mass in domesticbuildings are not recognised. Heavy foors do not achieve the highest ratings,whereas lightweight foors do. There ore designers need to consider

overheating control, acoustic per ormance, and structural and air tightnessrequirements in parallel to using the guide.

The same principles can be applied to external elements, particularly roo s,

where roo s with the same U-values might have very di erent thermal mass. The consequence can be lower internal peak temperatures o up to 4C and areduced need or air conditioning.

High-rise residential developments and the guide The Domestic part o the Green Guide is used mainly or speci ying low-risehousing. If it is used to specify high rise residential projects, there can be someunintended outcomes, because the use o some materials (which attracthigher Green Guide ratings) may not be appropriate or multi storey use, or anumber o reasons, or example due to higher structural loadings.

There ore it has been recommended by BRE that it is more appropriate to usethe Commercial part o the Green Guide or Speci cation when speci yinga multi-storey residential building. This approach should be agreed with theappointed code assessor as early as possible in the design stage.

St. Matthews keyworker estate, Brixton.Courtesy of Benedict Luxmoore/arcaid.co.uk


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The winner o The Concrete CentresSustainability Award 2008,55 Baker Street, London, proved

that long-term robustness and adaptability are key to sustainableconstruction. The Green Guide inits current orm does not deal withbuildings with a li e longer than 60 years, nor does it incorporate there urbishment o existing buildings.

The guide is available online or ve types o non-domestic buildings:

Commercial buildings, such as o ces

Educational

Healthcare

Retail

Industrial

BREEAM ratings can be used to assess the environmental per ormanceo any type o building (new and existing). Standard versions exist orcommon building types (including courts, healthcare, industrial, o cesand education) and less common building types can be assessed againsttailored criteria under the bespoke BREEAM version.

Essentially the areas to be aware o when using the Green Guide aspart o a non-domestic assessment o sustainable construction arevery similar to those associated with the use o the guide in conjunctionwith the Code. The Green Guide or non-domestic buildings is used, ina manner similar to the domestic guide in the Code or SustainableHomes, in the BRE Environmental Assessment Method (BREEAM)system www.breeam.org.

Elements in BREEAM are not examined in quite the same way as inthe Code. BREEAM accounts or the di erent areas o elements, as

opposed to the Code that gives equal weighting to the elements,regardless o whether one is signi cantly bigger than the other. There ore, when working with BREEAM, look or the best GreenGuide ratings or the elements with the largest sur ace area rst;i.e. start with foors, walls and roo s.

The act that the guide is not the answer or all environmental orsustainability questions is even more important in the context o non-domestic buildings because o the increased scope and scale o the development. For example, during the use o a commercial buildingthere are major issues associated with the health and productivity o people at work, as well as energy use and carbon emissions.

Points are available in the assessments or Materials. This section usesthe Green Guide to allocate some o the points available. Points arealso available or the re-use o building acades and existing buildingstructures and or the responsible sourcing o materials. Additional pointsare available or the use o recycled aggregates in the Waste section o BREEAM, on top o the incentive already given in the guide itsel (re er topage 8 or more on when it is green to use recycled aggregates).

When using the guide or non-domestic buildings, designers can use theguidance in the achieving the highest ratings section o this publication(page 7) to use concrete and recycled materials in the most sustainablemanner possible.

The Green Guide as part o a non-domestic

assessment


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BRE advised in late 2008 that, in uture, the guide needs to be usedand developed to consider the relationship between speci cations,their environmental per ormance and the overall environmental orsustainability per ormance o a building over its li e.

The concrete industry ully supports this advice, and sees it as vital tothe development of an e ective system. In the interim, information isavailable to allow designers to make these kinds o calculations anddecisions themselves.

The guide has already gone through a number o iterations. EcoPoint scoresand A+ to E ratings have changed too. More o these changes can be

expected on an ongoing basis.

New standards being developed in Europe, most notablyCEN TC350,Sustainability o construction works, will provide standardisedmethodologies or assessing the sustainability o buildings.

Topics o particular relevance to the concrete industry, arediscussed below.

Wastage ratesCurrently, the calculations behind the guide assume that, on average,7.5 per cent o ready-mixed concrete is wasted. This has been based on

quantity surveyors data and thus includes an allowance or over-ordering. The 7.5 per cent gure suggests that over 1.9 million cubic metres o concrete are wasted each year. Contractors placing concrete on-sitecould not withstand the nancial cost o such a high level o ine ciency,even in a buoyant construction market. The Mineral Products Association(MPA) believes the true gure or wastage on site is approximately 2.5per cent maximum. MPA is in the process o collecting more data onwaste and has made representations to BRE.

Concrete that is not used on-site and is returned in a ready-mixedconcrete truck is rarely wasted. Where possible, and technically appropriate,it may be re-assigned to a lower grade use. If not, it is used to producerecycled concrete aggregate or the aggregate is recovered. When itis to be used or recycled concrete aggregate, the concrete o ten hassome extra water added, is re-mixed and then discharged into a storagearea. To cover the costs o providing the acilities to recover or recycleconcrete, ready-mixed concrete suppliers charge their customers orreturned concrete i.e. concrete returned to a batching plant rom adelivery site, thereby deterring over ordering and potential wastage.

Assessing the use o mineral resources using abioticresource depletionIn the guide an approach called Total Material Requirement (TMR) is usedto assess mineral resource depletion. Because this is done on a massbasis it has a signi cant e ect on the ratings. The end result is that50 per cent o the score or a tonne o concrete could be attributed tothis measure, depending on the use o recycled aggregates. Thisexplains why products o a lower mass are assessed as more sustainablein the guide.

Whilst the quantity o materials used in a product is a very importantmeasure o sustainability, this measure does not link extraction volumesto the availability o resources. Best practice in li e cycle assessment isto use an approach called Abiotic Resource Depletion (ARD) to assessthe sustainable use o non-living abiotic resources (such as concrete,asphalt and steel). This approach takes into account the relative scarcityor abundance o the materials.

As Friends o the Earth has pointed out, the UK is sel -su cient inthe materials to make concrete or hundreds o thousands o years.Meanwhile, the industry works hard to minimise impacts o extraction.

Including the impacts of biotic resourcesCurrently, only products made rom mineral resources (such as concrete,asphalt and steel) have their extraction assessed, as above, in the guide. The guide would be a more rounded assessment tool i it included theimpacts o extracting and using non-mineral resources too, such asbiomass and timber. This omission has been partly due to a lack o methods or including these impacts in a LCA. However, as the guideis becoming such an important decision-making tool this gap needsto be lled to prevent decisions being made on the sustainability o products with incomplete environmental in ormation.

Public availability o dataMany practices and consultancies are beginning to come to terms with

the di erent environmental categories and would like to make their owndecisions about which o the impacts are more important than others. Todo so they require access to the 13 indicators raw data or each constructionelement. Practices also want this in ormation or each raw material so thatthey can model the results or speci c construction elements not eatured inthe guide. Making this in ormation publicly available is something that manypractices and consultancies want BRE to do.

Practices can also potentially source this in ormation by requesting itrom the relevant trade associations.

The Green Guide o the uture?


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Re erences and notes1 Statement On The Green Guide From BRE Global And The Construction

Products Association, published: 1/12/2008, available atwww.bre.co.uk/newsdetails.jsp?id=524

2 The points available in the other versions o BREEAM vary, as thesections (Materials, Management, Health & Wellbeing, Energy, etc.)in BREEAM have di erent weightings depending on the buildingtype being assessed

3 The Concrete Industry Sustainability Per ormance Report: 1st Report,Concrete Industry Sustainable Construction Forum, 2009.Available romwww.sustainableconcrete.org.uk

4 Survey o Arisings and Use o Alternatives to Primary Aggregates inEngland 2005, Construction and Waste, DCLG, 2007

5 McLaren D, Bullock S, Youse N,Tomorrows World: Britains Share in aSustainable Future, Friends o the Earth, Earthscan, 1999

6 QPA Environmental Pro les Report or QPA Generic Limestone,BRE, 2007

7 QPA Environmental Pro les Report or QPA Generic Recycled C&Dwaste, BRE, 2007

8 The signi cance o this matter is heightened as the guide includes an

assessment o the impact o extracting mineral resources rom theenvironment whilst excluding a measure or the impact o extractingbiotic (living) resources

9 The remaining 37.5 per cent (2.7 per cent o the total available in theCode) are or responsible sourcing o materials criteria discussed inStep 7

10 Embodied and operational carbon dioxide emissions rom housing:a case study on the efects o thermal mass and climate change, Hacker,de Saulles, Minson, Holmes, 2006

11 2008 De ras GHG Conversion Factors Note Values or ar ticulatedlorries >17 tonnes assuming average load o 21.3 tonnes:www.de ra.gov.uk/environment/business/reporting/pd /ghg-c -guidelines-annexes2008.pd

12 Data calculated rom 2008 QPA Sustainable Development Report.

Proo o the excellent durability o concrete comes in the shapeo Marine Crescent, Folkestone,a concrete building that hasstood just a stones throw romthe sea since 1870 and which,

ollowing renovation, looks set to celebrate its 200th birthday.

19

For urther reading and in ormation, there are many publications available online which explore a variety o related topics.

Please visit www.concretecentre.com/publications.


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All advice or in ormation rom MPA -The Concrete Centre is intended only or use in the UK by those who will evaluate the signifcance and limitations o its contents and take

The Concrete CentreRiverside House,

4 Meadows Business Park,Station Approach, Blackwater,Camberley, Surrey GU17 9AB

First published 2009 MPA - The Concrete Centre, 2009

Re : TCC/05/17ISBN: 978-1-904818-79-3

The Concrete Centre is part o theMineral Products Association, the trade

association or the aggregates,asphalt, cement, concrete, lime, mortar

and silica sand industries.

www.mineralproducts.org

www.concretecentre.com

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