Design detailing for materials resource efficiency - … detailing - evidence base... · Design detailing for materials resource ... Voided Biaxial Slab, photo courtesy of Bubbledeck

Evidence base report

Design detailing for materials resource

efficiency

A guide to ten alternative construction design details which offer good materials resource efficiency.

Project code: WAS400-040 ISBN: N/A Research date: November 2008 – May 2009 Date: v1 November 2009 v2 August 2010

WRAP’s vision is a world without waste, where resources are used sustainably. We work with businesses and individuals to help them reap the benefits of reducing waste, develop sustainable products and use resources in an efficient way. Find out more at www.wrap.org.uk

Written by: Ben Stubbs, Faithful+Gould, Euston Tower, 286 Euston Road, London. NW1 3AT

Front cover photography: Voided Biaxial Slab, photo courtesy of Bubbledeck UK. WRAP and Faithful+Gould believe the content of this report to be correct as at the date of writing. However, factors such as prices, levels of recycled content and regulatory requirements are subject to change and users of the report should check with their suppliers to confirm the current situation. In addition, care should be taken in using any of the cost information provided as it is based upon numerous project-specific assumptions (such as scale, location, tender context, etc.). The report does not claim to be exhaustive, nor does it claim to cover all relevant products and specifications available on the market. While steps have been taken to ensure accuracy, WRAP cannot accept responsibility or be held liable to any person for any loss or damage arising out of or in connection with this information being inaccurate, incomplete or misleading. It is the responsibility of the potential user of a material or product to consult with the supplier or manufacturer and ascertain whether a particular product will satisfy their specific requirements. The listing or featuring of a particular product or company does not constitute an endorsement by WRAP and WRAP cannot guarantee the performance of individual products or materials. This material is copyrighted. It may be reproduced free of charge subject to the material being accurate and not used in a misleading context. The source of the material must be identified and the copyright status acknowledged. This material must not be used to endorse or used to suggest WRAP’s endorsement of a commercial product or service. For more detail, please refer to WRAP’s Terms & Conditions on its web site: www.wrap.org.uk

Design detailing for materials resource efficiency 3

Contents 1.0 Introduction ............................................................................................................................. 4

1.1 Background...........................................................................................................................4 1.2 Selection of design details......................................................................................................4 1.3 Assessment criteria................................................................................................................5

2.0 Design details........................................................................................................................... 8 2.1 Exposed ceilings ....................................................................................................................9 2.2 Rotary displacement piles ....................................................................................................12 2.3 Castellated and cellular beams .............................................................................................12 2.4 Post tensioned floor slab ......................................................................................................12 2.5 Voided biaxial slab...............................................................................................................12 2.6 Flexible plumbing systems....................................................................................................12 2.7 Aerated concrete blocks with thin joint mortar.......................................................................12 2.8 Polished concrete floor.........................................................................................................12 2.9 Low waste door jamb ..........................................................................................................12 2.10 Tile detailing .......................................................................................................................12

Version Version Issue date Brief description 1 Nov 2009 Original issue 2 Aug 2010 Section 2.2 amended

Acknowledgements For Atkins Sean Lockie (Surveyor) Jon Casey (Sustainability) Dorte Jorgensen (Engineer) Julian Sutherland (Engineer) Martin Pease (Architect)

Mike Sillett (Architect) Ian Marlowe (Environment) Tom Gent (Architect) Chris Nunn (Environment) Steve Watson (Quantity Surveyor)

Expert Panel Elaine Toogood, Concrete Centre Steve Millward, CPA/Jewson Anthony Harker, EIC Lucy Hall, ISG Robin Fleming, ISG Paul Cockaday, Laing O’Rourke Lee Alexander, Crest Nicholson

Neil Paterson, BRE Dave Marsh, WRAP Sean Rath, Carillion Ben Mackinnon, Jacobs Jolanda Putri, Willmot Dixon/Re-thinking Richard Biggs, CIC

Product Manufacturers/Specialist Contractors Armstrong Ceilings Bachy Soletanche (Geotechnical Specialists) Bubbledeck, UK (Voided Biaxial Slab) Ecoflor (Polished Concrete Floors) Hep2O (Flexible Plumbing) Knauf (Plasterboard) May Gurney (Piling Contractor) ASD Westok (Castellated/Cellular Beams)


1.0 Introduction 1.1 Background Achieving the construction sector commitment target of halving construction waste to landfill by 2012 will require construction designers to identify and act upon opportunities to improve materials resource efficiency (reduced use of materials and waste creation) through planning and design of projects. Work undertaken by WRAP (Waste & Resources Action Programme), Envirowise, AMEC and the BRE has shown that reducing waste being created has a far greater positive impact on reducing waste to landfill compared with improving on-site management of waste. It has also been shown that reducing waste is far more cost-effective. The principles of Good and Best practice Site Waste Management Plans (SWMP) promote that the best opportunities to improve materials resource efficiency occur by working at the earliest stages possible in the construction process. Clearly, working with design teams to implement this through the design process is a critical link in achieving the target. Decisions made throughout the evolution of a design can have a major impact on the levels of materials used and waste which arises during the physical construction, and future demolition, of a project. High-level decisions (for example, the layout or form of a building) and more detailed-level decisions (for example, those that relate to the design of specific elements of a building) can be equally influential. Often these decisions are made based on considerations such as site constraints, client requirements for improved performance or finish, or compliance with Building Regulations, but rarely include improving materials resource efficiency. WRAP is therefore working with designers to build their knowledge and experience of materials resource efficiency, and provide the tools and resources they need to implement it. Two key resource guides have been published by WRAP: Designing out Waste: a design team guide for buildings1. Designing out Waste: a design team guide for civil engineering2. A further resource is a series of data sheets of design details which can provide improved materials resource efficiency compared to standard design details commonly used in UK construction projects. The purpose of these data sheets is to support design teams (architects, consultants, engineers) to consider and implement opportunities for improving materials resource efficiency through the design process. This document provides information on the development of ten data sheets. It presents the basis of the research and the assumptions and underlying data used. The ten data sheets are available from www.wrap.org.uk/construction and are: Exposed ceiling; Rotary displacement piles; Castellated and cellular beams; Post-tensioned floor slab; Voided biaxial slab; Flexible plumbing systems; Aerated concrete blocks with thin joint mortar; Polished concrete floor; Low waste door jamb; and Tile detailing. 1.2 Selection of design details The identification of appropriate design details was carried out in consultation with a panel of experts drawn from various disciplines across the industry; this included architects, designers, technical consultants, engineers, specialist contractors, suppliers and manufacturers. The aim of this process was to ensure that individual details could make a significant contribution to materials resource efficiency through reduced materials use and/or reduced waste creation. A list of consultees is provided in the acknowledgments section of this document. The development of specific design detail sheets builds on previous research by WRAP on design detailing for resource efficiency which resulted in a long list of potential details (Appendix 1). This list was assessed by the expert panel and a resulting short list was then further refined in consultation with individual experts to ensure that the selected options have the potential to deliver measurable benefits.

1 Available for download from www.wrap.org.uk/construction

2 Available for download from www.wrap.org.uk/construction from January 2010.


Analysis of wastage rate data from WRAP’s NetWaste tool3 was also carried out to identify elements and items which generate the most waste (by percentage); this list was further modified taking into account how items could be influenced by design interventions. The table of wastage rates identified during this exercise is included in Appendix 2. Final selection was based on the following key criteria: Potential availability of design information and data; Potential for practical application (e.g. in terms of cost, availability, acceptability etc); Potential for designer influence; Prospects for resource efficiency savings – particularly with regard to waste; and Successful application on a range of completed projects (details which are theoretical or in the early stages of

development were excluded).

1.3 Assessment criteria All of the design details were assessed according to a set list of seven criteria identified during the consultation process. These criteria were selected based on the following: Potential for reduced materials use / waste creation. This is the key objective of the design detail sheets; Relevance to designers and the design process; Construction programme implications (i.e. time, cost, constructability, replicability); and Carbon reduction potential. The construction industry as a whole has a major responsibility in meeting

challenging government targets for carbon reduction, as outlined in the Climate Change Act. Where relevant, benefits have been quantified based on reliable, auditable data; however, this is subject to the limitations of data availability and variations in the options available for each design detail. In addition, appropriate measures are not available for all criteria (e.g. constructability, replicability). Quoted benefits should therefore be treated as a guide only; actual benefits are likely to vary on a project-by-project basis.

In addition to these core criteria, a set of additional criteria were identified which may also have implications for the efficiency of some of the design details throughout their life cycle. Where relevant, information on these criteria is given below but is not included as separate categories on the design sheets. The quantification of benefits under different assessment criteria for the design details involved the collection of data from a wide variety of sources. This included product manufacturers and suppliers, cost consultants, academic literature and construction professionals. All sources are referenced in the footnotes of relevant sections. CORE CRITERIA 1.3.1 Reduced materials use and waste creation The main objective of promoting the design details is to bring about improved materials resource efficiency through reduced materials use and/or reduced waste creation. For each of the ten options, potential savings have been calculated. Implications for further efficiencies throughout a building’s structure are also noted where relevant. The units of measurement for materials resource efficiency vary between different design details according to: a) the most appropriate format to describe savings that can be achieved; and b) data availability. For most details the metrics are volume, area or mass; however, length is also used in the case of piping for plumbing. Whilst absolute numbers based on real examples have been provided where possible, reductions are actually best described in percentage terms for most of the details because a range of sizes or configurations are available. The main potential materials resource efficiency benefits also vary between different details. For some, the main benefit is materials savings; for others it is reduced waste. Data is for whichever is most appropriate, or both metrics where possible.

3 WRAP NetWaste Tool [www.wrap.org.uk/nwtool]


Sources of information in materials resource efficiency include manufacturers specifications, quantity surveyors, architects and structural engineers. 1.3.2 Cost implications A full list of cost comparisons for all design details is provided in Appendix 3. An assessment of potential cost savings which could be achieved by specifying each of the design details was provided by Faithful+Gould and based on specific examples. It should be noted that cost savings were not a prerequisite for inclusion of a design detail; in fact some options may cost more to procure and install than standard options. However, the cost of individual design details should be viewed in whole life terms; any extra costs may be offset by efficiencies which they can facilitate elsewhere in the programme, or due to maintenance or operational savings. 1.3.3 Time implications The potential for any time savings which can be achieved by using each design detail have been assessed and quantified where possible. However, precise savings will depend on the type of project, it’s location and the working practices of individual contractors. Where time savings can be achieved, this has clear implications for overall programme efficiency and may also result in cost savings. 1.3.4 Carbon reduction The construction industry is under increasing pressure to make deep cuts in the carbon emissions (as well as other greenhouse gases) for which it is responsible. For each design detail potential reductions in embodied and/or operational carbon have been assessed and quantified as far as possible. Unless otherwise stated, all embodied carbon calculations were based on data contained within Bath University’s ‘Inventory of Carbon and Energy (ICE)’4. This is currently the most widely recognised source of such data covering a wide range of construction materials. Where carbon factors are unavailable for specific materials, calculations are based on the nearest equivalent. 1.3.5 Recycling implications Designers may have the opportunity to specify recycled content as an option for materials used in individual design details. It is also important to consider the recyclability of specified materials once a building is decommissioned. This section includes information on whether or not recycled content can be specified as well as end of life recycling options. 1.3.6 Constructability Issues which may influence the constructability of individual element, both positive and negative, have been noted. It is particularly important for designers to be aware of any special considerations which should be taken into account during the construction programme. Examples include any extra skills or tools which may be required for installation compared to the standard option. 1.3.7 Replicability The potential to replicate design details across a number of different types of project is important. Where individual details are limited to certain types of project, this has been noted.

4 Bath University (2006) Inventory of Carbon and Energy (ICE)


ADDITIONAL CRITERIA 1.3.8 Impact on structure Some of the design details may have an impact on the overall structure of the building; for example, this may include changes in weight, stresses, dimensions or layout. Such impacts, whether positive or negative, are noted in this section. 1.3.9 Procurement issues Most of the design details and related skills are widely available within the UK. Where there are any issues regarding the availability of specific options, these are identified. 1.3.10 Off site construction Design details which involve offsite construction techniques, or options for offsite construction, together with the potential benefits that this may bring, have been noted. 1.3.11 Salvaged components The use of carefully sourced, salvaged components has clear advantages for improving materials resource efficiency and reducing waste to landfill. Although no such opportunities were identified for the current set of design details, this category could be an important consideration for future design details. 1.3.12 Longevity The expected design life of each of the design details is important in the consideration of life cycle materials resource efficiency. Long term materials savings and reductions in waste to landfill may be no better than for standard options if replacement intervals are much shorter or intensive maintenance is required. 1.3.13 Packaging Packaging waste can be a major contributor to landfill waste; the construction industry is responsible for major quantities of such waste. Where relevant, the likely extent of packaging waste has been assessed. 1.3.14 Standardisation For many design details standardisation of sizes, installation or appearance is crucial to ensure adoption across a range of building types and projects. Where relevant, the availability of standard options is noted; however, by their nature, several of the details are bespoke for individual projects (e.g. beams, floor slabs) 1.3.15 Dimensional coordination Any specific issues concerning the dimensional coordination of each design detail with other products or materials, or as part of building elements, are noted in this section. 1.3.16 Repairability The ability to perform simple, cost effective repairs is essential for the long term viability of some design details. This section assesses the opportunities for such repairs and any implications repair work may have on aesthetics or structural integrity. 1.3.17 Deconstructability The reuse of products and materials, without changing their form, is the most efficient waste management option. Where it is possible to remove products or materials from buildings for reuse with minimal or no further processing, this has been noted. However, some elements will always be difficult to reuse; for example, this may be due to their bespoke nature, materials used, size or position within a building’s structure. 1.3.18 Additional information Many of the ten design details covered in this document offer further sustainability benefits in addition to those covered by the headings above; improved thermal performance is one example which applies to a number of design details. Where these benefits are of note, they have been included under ‘Additional information’. This section also includes any further important considerations or information for designers who are considering specifying each of the options.


2.0 Design details This section presents each of the selected design details, together with a detailed breakdown of the data collected to demonstrate their benefits, both in terms of materials resource efficiency and other criteria described above. For each design detail the following information is provided: NBS reference Description, including how it differs from standard practice Type of projects it is relevant to Design stage of implementation Relevant standards5 Quantification of benefits in terms of resource efficiency (as outlined above) Quantification of other relevant benefits Further useful information Design details are presented in order of stated design stage.

5 We have listed the main reference codes for each standard; it should be noted that some standards include a number of versions (e.g. BS EN 12201, Plastic piping systems for water supply, includes separate versions for pipes, fittings, valves, fitness for purpose etc.)


2.1 Exposed ceilings Subject Exposed concrete ceilings NBS reference E05 (In situ concrete construction); E10 (Mixing/ casting/ curing in situ

concrete); E20 (Formwork for in situ concrete); E30 (Reinforcement for in situ concrete)

Type of projects All building types Design stage of implementation

RIBA Stage B (Design Brief)

Relevant standards EN 206-1, Concrete. Specification, performance, production and conformity BS 8500, Complementary British Standard to EN 206-1 EN 13369, Common rules for precast concrete products

2.1.1 Standard option Modern commercial buildings generally use suspended ceiling tiles to provide a uniform and ‘desirable’ ceiling finish. This typically involves the use of ceiling tiles which are held in place by a grid of metal channels suspended on wires from the slab/beams above (Fig. 2.1.1). However, the installation of such systems can result in high levels of materials use and wastage. Traditional mineral fibre tiles, for example, can be easily damaged, offcuts are discarded and there are no opportunities for reuse. In addition, service life is often limited.

Fig. 2.1.1 Suspended ceiling tiles


2.1.2 Resource efficient design detail Leaving the underside of the concrete slab exposed can provide a high-quality, durable ceiling alternative, either left bare of finished with a wide variety of textures or colours. It can also provide benefits in materials resource efficiency. Exposure of the slab represents good passive design, allowing efficient exploitation of the thermal mass of the building; it can reduce the need for mechanical heating and cooling. Where completely exposed concrete isn’t an option, ‘canopy systems’ (clusters of ceiling tiles) can result in substantially less materials use and waste compared to wall-to-wall coverage. It is also possible to specify recycled content.

Fig. 2.1.2 Exposed concrete ceiling


2.1.3 Assessment criteria

Criteria Potential benefits Quantification of benefits Materials saved and/or Reduced waste to landfill

Omission of a secondary ceiling layer results in materials savings.

Exposed ceilings avoid offcuts or damaged ceiling tiles.

A typical suspended ceiling system requires materials amounting to around 5.75kg/m2 (including tiles, hangers, cross tees etc).6 This equates to 37m3 of materials for a 1000m2 building7 (around half of this is the tiles themselves) 7.5% of materials used in suspended ceilings is wasted.8

Cost implications

Although a small additional cost may be required to achieve the desired concrete finish, particularly for bespoke/coloured options, this may be easily offset by the avoidance of suspended ceiling systems.

Minimum net savings of £18/m2 can be expected.9

Time implications

Omission of suspended ceilings can result in major labour savings.

Labour requirements are approx. 1.5hours/m2.10

Carbon reduction

Major carbon reductions are achievable by reducing the use of secondary finishes.

The exposed thermal mass can help minimise CO2 emissions resulting from operational heating and cooling requirements.

Reduced volume/weight of materials can result in reduced transport emissions.

The omission of 1000m2 of mineral tiles represents an embodied saving of 10.4 tonnes CO2e.11 (including aluminium suspension system)

Recycling implications

Consider specifying concrete with recycled content.

Construct-ability

Extra care is required in specification and installation of exposed concrete.

Quality control is essential to minimise variations in concrete appearance.

Protection during site works is necessary to avoid damage.

Replicability Suitable for many types of buildings, although may affect other considerations such as aesthetics, acoustics and M&E service routes.

Natural variations in concrete mean that the finish will vary slightly between projects (and even between pours on the same project).

Criteria Further considerations Impact on structure Provision of M&E services must be planned early; there will be fewer opportunities for

hiding cables etc. Procurement issues None Off-site construction/ modularisation

The soffits of pre-cast floor slabs may be left exposed, but may require extra finishing work.

Salvaged components N/A

Longevity High level of durability compared to ‘softer’ finishes such as ceiling tiles or plasterwork. Minimal maintenance requirements.

The building will be well adapted to climate change so will have an extended service life without the need for extensive modifications.

Packaging N/A

Standardisation N/A

Dimensional coordination N/A Repairability Repairs or adaptations to large monolithic areas are difficult to conceal and could result

in permanent change in apperance.

Deconstructability Poor - as with most large areas of concrete structure.

6 WRAP Case Study Data (Southwark School - currently unpublished) 7 Ibid 8 Ibid. 9 Atkins Data. Armstrong Dune Suspended ceiling @ £30/m2; also includes additional cost of fair-faced formwork to soffit plus two coats of emulsion paint (optional) @ £12/m2. 10 Faithful+Gould Cost Consultancy 11 WRAP Case Study Data (Southwark School - currently unpublished)


2.1.4 Additional information Canopy systems generally use fewer materials than standard suspended ceilings and may

represent a good alternative where exposed concrete is impractical. They can be arranged to avoid the need to cut tiles and to cover specific parts of the ceiling area only. Mineral and steel ceiling tiles are recyclable and can be specified with high levels of recycled content.

Room acoustics can be controlled through diffusion or absorption by special surface finishes, canopy systems, or other room finishes (e.g. carpets).

The thermal mass of exposed ceilings can be used effectively as part of a passive design to help reduce mechanical heating and cooling requirements.

It is important to establish a design strategy for M&E service distributing at an early stage.

Concrete is not the only option for exposed ceilings; in situ steel shuttering or timber can also be left exposed.

2.1.5 Embodied carbon calculation

Table 2.1.5 Embodied carbon of suspended ceiling system12

Product Quantity materials

Quantity of waste Material

CO2 equivalents

13 Embodied

CO2 Waste

CO2

(tonnes) (tonnes) kgCO2e/kg (tonnes/1000m2)

Dune Max Board, 600x600x18 4.62 0.35

Mineral Fibre Tile 0.2414 1.11 0.08

Prelude 24 Main runner 0.22 0.02 Aluminium 8.53 1.86 0.14 Prelude 24 XL Cross tee 0.45 0.03 Aluminium 8.53 3.85 0.29 Prelude 24 XL Cross tee unslotted 0.21 0.02 Aluminium 8.53 1.76 0.13 Wire Hangers 0.04 0.00 Steel Wire 2.83 0.11 0.01 Painted shadowline 20x20x20x20mm 0.20 0.01 Aluminium 8.53 1.67 0.13

Design Totals 10.36 0.78

12 Based on Armstrong Dune Max Ceiling Tiles. WRAP Case Study Data (Southwark School - currently unpublished) 13 Bath University (2006) Inventory of Carbon and Energy (ICE) 14 Assumed equivalent of plasterboard.


2.2 Rotary displacement piles Subject Rotary displacement piles (RDPs) Reference number NBS D30 (Piling) Type of projects covered

All foundation applications where bearing piles are required for either buildings or structures.

Design stage of implementation

RIBA Stage C (Concept Design)

Relevant standards EN 206-1, Concrete. Specification, performance, production and conformity BS 8500, Complementary British Standard to EN 206-1 BS 8004, Code of practice for foundations ISO 11886, Building construction machinery and equipment. Pile driving and extracting equipment. Eurocode 7, Geotechnical Design

Revisions to the data were provided by Roger Bullivant Ltd in July 2010. The previous text is indicated with a strikethrough, and new/updated text in red. The data sheet has been updated and reissued accordingly. 2.2.1 Standard option Some piling systems are responsible for both intensive materials use and the creation of significant waste. Structural support is related to the depth and number of piles whilst drilling can result in the extraction of significant amounts of spoil, which is often transported off site for disposal. Materials use is determined by the depth of the piles required

to provide the necessary support for a building. Typically this involves the use of concrete with steel reinforcement.

Waste is produced by the extraction of significant amounts of

soil for most piling solutions; the resulting spoil often has to be disposed offsite which can create particular problems and expense where soil has been contaminated. It can also cause storage problems onsite.

2.2.2 Resource efficient design detail Rotary displacement piles can provide a viable, resource efficient, low waste solution for some ground conditions (particularly granular soils and weathered chalk). They can result in a reduction in overall foundation costs by reducing pile lengths, reducing and materials used, minimising spoil arisings. Rotary displacement involves the use of a ‘boring’ tool (auger) which penetrates the ground and displaces soils. Concrete is pumped under pressure into the hollow shaft as the auger is reversed out; reinforcement can then be added. The resulting concrete ‘threads’ facilitate load transfer from pile core to soil due to increased overall diameter and surface area of the pile. Rotary displacement also improves soil strength due to compaction and increased soil density around the pile. It results in minimal spoil which is particularly advantageous on contaminated sites.

Roger Bullivant Ltd advised that this length should be amended to 11000, and that the diameter should be ~25% larger than the CFA pile



Criteria Potential benefits Quantification of benefits Materials saved15 and/or Reduced waste to landfill

Threaded nature of the pile provides a large surface area and overall diameter and can enable short pile lengths reducing concrete volume.

Ground is displaced rather than removed so minimal spoil is created, reducing overall site waste and, potentially, waste to landfill. (Materials savings vary widely depending on ground conditions and building specification)

Up to 30% increased load bearing capacity, depending on ground conditions, can enable shortening of pile.16 Up to 40% reduced length. Up to 58% concrete saving can be achieved.17 Corresponding reduced concrete volume, by up to 32%

Cost implications

Possible reduction in overall foundation costs by reducing pile lengths and diameter of core depending on depth of founding stratum.

Omission of costs related to treatment and disposal of contaminated soils.

Low earthwork costs as soil disposal costs are minimised. Reduced transportation costs to low materials use and

waste creation.

Up to 32% (Average Approx £400) cost saving per pile18.

Time implications

Installation system is rapid resulting in benefits to contracting programme; concreting is carried out using mobile concrete pumps.

Minimal spoil means low quantities of spoil to be removed from site.

Low disturbance of contaminated soils limits clean-up operations.

No spoil heaps to interfere with simultaneous works.

Carbon reductions

Reduced pile volume results in embodied carbon reductions – this will vary according to ground conditions and building type/size.

Low materials required and spoil removed from site means reduced transport emissions.

Embodied carbon reduction of up to 58% 32% for concrete use. (740kgCO2e based on an equivalent 18m CFA pile). Steel reinforcement remains the same.


Consider specifying concrete with recycled content.

Construct-ability

Low vibration and noise allows construction closer to existing buildings and structures.

Spoil is minimised, reducing on-site storage and transportation requirements.

Replicability Tests have demonstrated that rotary displacement piles can provide the same level of performance as continuous flight auger (CFA) options with a much reduced depth.19

Replicability depends on ground conditions and building types; each project must be assessed separately. Different ground conditions produce varying benefits.

Criteria Further considerations

Impact on structure No impact on overall structure.

Procurement issues Check availability of boring machinery Off-site construction/ modularisation

N/A

Salvaged components N/A Longevity 60+ years.

Packaging N/A

Standardisation Uses standard machinery. Depth of pile can be varied according to requirements.

Dimensional coordination N/A

Repairability N/A Deconstructability Poor. Piles are difficult to extract and concrete could be contaminated.

15 Based on CFA Pile of 18m x 450mm and RDP of 7.5m X 450mm 16 Concrete Centre [Correspondence] 17 Faithful+Gould Cost Consulting. Based on rotary bored piles instead of CFA piles. CFA pile; 450mm diameter; 18m deep vs. Rotary displacement pile; 450mm diameter; 7½m deep. (Raw data: May Gurney, Piling Contractor) 18 Ibid. 19 Bachy Soletanche ‘Rotary Displacement Piling: Screwsol. BAe Broughton Fire Station’. (http://www.bacsol.co.uk/downloads/case_studies/Rotary%20Displacement%20Piling/A404%20-%20BAe%20Broughton%20Fire%20Station.pdf)


2.2.4 Additional information Whilst a variety of piling solutions are available, the exact choice will depend on geological/ground

conditions and the nature of the structure to be supported. Rotary piles are best suited to granular soils and weathered chalk. They are not suitable for

stiffer clay soils.


Table 2.2.5 Comparison of embodied carbon in concrete20: CFA and rotary displacement piles (volume of steel reinforcement is the same for both options) Continuous flight auger Rotary displacement pile

Dimensions (m) 0.45 x 18 0.45 x 7.5

Volume (m3) 2.86 1.19 Embodied carbon21 (kgCO2e/kg) 0.211 0.211 Mass (kg) (concrete density @ 2100kg/m3)

6006 2499

Embodied carbon (kgCO2e/kg) 1267 527 Embodied carbon saving per pile (kgCO2e)

n/a 740

% embodied carbon saving (concrete only)

n/a 58%

20 Dimensions provided by Atkins Cost Consulting 21 ICE/Bath University Data. Assumed high strength concrete @ 0.211kgCO2/kg (steel reinforcement not included)


2.3 Castellated and cellular beams

Subject Castellated (Cellular) Beams NBS reference G10 (Structural Steel Framing) Type of projects Particularly suited to long spans (e.g. car parks, hospitals, stadia,

schools, bridges etc…) Design stage of implementation

RIBA Stage C/D (Concept Design/ Design Development)

Relevant standards BS 5950, Structural use of steelwork in building (BS 5400 for bridges) Eurocode 3, Design of steel structures BS EN 1993, Design of steel structures (UK annex to Eurocode 3)

2.3.1 Standard option Standard I-beams have an ‘I’ or ‘H‘-shaped cross section with a solid web (vertical section) (Fig 2.3.1). Usually made of structural steel, British and European standards refer to them as Universal Beams (UBs). I-beams provide effective structural support. However, since the strength of the beam is more closely related to its depth rather than the volume of steel, they often have a strength far exceeding the engineering requirement and so in many applications other resource efficient solutions may be suitable.

Figure 2.3.1 Standard I-beam

2.3.2 Resource efficient design detail Castellated and cellular beams can achieve the same strength as solid I-beams of the same depth with significantly less steel use; they are therefore both strong and comparatively light weight. Castellated beams are created by forming ‘web openings’ in a standard universal beam section. This involves cutting along the length of the section in a ‘wave form’ and welding the two pieces together to form a deeper section with hexagonal openings (Fig 2.3.2a). Precision cutting techniques with laser technology can alternatively produce circular or oval openings, the position of which can be more easily planned. These are cellular beams (Fig 2.3.2b). Castellated and cellular beams also offer designers a number of opportunities for bespoke sizes and sections; for example, this includes varying the depth of the beam or creating tapered sections. Castellated beams are particularly suited to long span applications with light to moderate loadings such as roofs.


Figure 2.3.2a Castellated beam

Figure 2.3.2b Cellular beam




Openings in the web allow for a significant reduction in overall steel use compared to standard I-beams.

Castellating results in a beam which is 40-60% deeper than its parent section.

Since services can pass directly through the beams, it may not be necessary to include voids between beam and ceilings (i.e. ceilings can be attached directly to the beams rather than suspended)

For cellular beams, the cutting process results in approx 1% waste; however, this can be easily recycled.

The light weight of the beams allows further materials savings in the supporting structure (e.g. columns, supporting walls, foundations etc)

Castellating typically results in a 25% reduction in steel weight for the web (flanges unaffected).22 Weight savings of over 50% have been achieved in the web.23 Up to 15% reduction in materials use for M&E has been reported.24 A castellated beam is up to 2.5 times stronger than its parent section.25

Cost implications

Cost savings will be directly related to the amount of steel saved – this varies between individual beams.

For some castellated beams, costs of production may be close to those of standard beams due to extra work involved in cutting and welding.

Cost savings for cellular beams are also reduced due to more complex manufacture.

The relatively light weight of castellated beams may allow transportation and on-site cost savings.

Further savings are possible due to lighter supporting structure.

Integrating services into the beam can may result in M&E cost savings.

Average savings of £38/metre (around 10%) for castellated steel beams26.

Time implications

Long spans and light weight allow omission of some supporting structure leading to quicker construction.

Light weight and manoeuvrability may allow some time savings on site, although this is unlikely to be significant.

Time savings will depend on exact nature of overall structure.

Carbon reduction

Reductions in steel use whilst achieving the same structural strength result in significant embodied carbon reductions.

Reduced volume/weight of materials can reduce transport emissions.

Steel embodied carbon savings of 41 kg CO2e/metre can be expected 27.


Steel is 100% recyclable. Most steel produced in the UK contains recycled content;

levels can be specified. Manufacturing waste is recycled.

Construct-ability

The light weight of castellated beams means that they can be easier to assemble than solid I-beams.

Bolted sections are easy to disassemble. Some M&E services can pass through openings in the beam.

Replicability Castellated beams are proven across a range of buildings and are produced using standard procedures in factory conditions.

Beams are usually bespoke for individual projects – laser precision cutting ensures efficient manufacturing process.

Particularly suitable for longer spans such as stadia, car parks and bridges.


Impact on structure Weight of structure is reduced significantly due to 25% lighter beams.

Procurement issues Castellated and cellular beams are widely available and produced by specialist manufacturers.

Off-site construction/ modularisation

Castellated beams are produced offsite under factory conditions.

Longevity 60+ years

Packaging N/A

22 ASD Westok Ltd [Telephone Interview] 23 Ibid. 24 Ibid. 25 Ibid. 26 Faithful+Gould Cost Consultancy. Based on castellated steel beams instead of BS4 steel beams. 305 x 305mm UC x 240kg/m ~ beam for 7.5m span. 27 ICE Bath Data: Based on steel carbon factor of 1.82kg CO2/kg; see section 2.1.5 for assumed weights. Includes steel manufacture only; does not include cutting and welding.


Criteria Further considerations Standardisation Castellated and cellular beams are usually bespoke for individual jobs. However, they

are produced on a standardised ‘production line’ under factory conditions. Dimensional coordination Bespoke items.

Repairability Beams can be reinforced in situ to provide extra strength, if necessary, by the addition of additional steel plates or by closing web openings.

Deconstructability As with standard universal beams, bolted sections can be easily dismantled for reuse. Emerging good practice is to stamp the load rating onto the beam to enable easier

future reuse.

2.3.4 Additional information This is an established approach – the use of castellated beams became particularly important

during the years following the Second World War when steel was scarce.

Additional reinforcement can be added to stress points, if required, by either omitting or plating web openings.

Emerging good practice is to stamp the load rating onto the beam to enable easier future reuse. Castellating can be used to produce both straight and tapered beams.

2.3.5 Embodied carbon calculation Table 2.3.5 Solid I-beam vs castellated beam (305mm x 305mm) Solid I-beam Castellated Beam Embodied carbon of steel 1.82kgCO2e/kg 1.82kgCO2e/kg Steel Mass (kg/m) (Flanges+Web) 240kg 218kg Embodied Carbon (kgCO2/m)28 437 396

Embodied carbon reduction = 41kgCO2e/m

28 ICE Bath Data: Based on steel carbon factor of 1.82kg CO2/kg. Includes steel manufacture only; does not include cutting and welding.


2.4 Post tensioned floor slab Subject Post-tensioned concrete NBS reference E05 (In situ concrete construction); E10 (Mixing/ casting/ curing in situ

concrete); E20 (Formwork for in situ concrete); E30 (Reinforcement for in situ concrete)

Type of projects covered

All types of structures; especially commercial (particularly high-rise), car parks, bridges (i.e. where long spans are required).


RIBA Stage C/D (Concept Design/Design Development)

Relevant standards BS 8110, Structural use of concrete Eurocode 2, Design of concrete structures

2.4.1 Standard option The strength of ordinary reinforced concrete slabs is dependent on the thickness of the slab and the degree of reinforcement included – this must be carefully calculated to overcome concrete’s low tensile strength. Slabs can be either prefabricated or poured in situ; prefabricated units are manufactured in factories to the required shape/dimension and transported to site, whilst in situ slabs are poured onsite using temporary or permanent formwork. The resulting concrete slab is solid concrete with steel reinforcing mesh encased within.

Fig. 2.4.1 Typical solid concrete floor slab.


2.4.2 Resource efficient design detail Post tensioning enhances concrete’s load carrying capacity by using high tensile steel cables or rods to apply compressive forces to the concrete after it has set. All tendon forces are transmitted to the slab (no stresses are applied to the formwork). Post-tensioned slabs have been widely and successfully used in the USA and Australia for several decades and are now becoming increasingly popular in the UK. They are significantly thinner than ordinary reinforced slabs, minimising the weight of a building as well as reducing its overall height (it may be possible to incorporate an extra storey on a ten storey building). Materials resource efficiency is achieved not only by reducing materials in the slab itself, but also in columns, walls and foundations which have less weight to support. Enhanced strength means that it also possible to achieve greater spans between columns or walls.

Fig. 2.4.2 Post-tensioned floor slab.




Reduced slab thickness, light weight and long spans can allow fewer columns and thinner foundations. Deep downstands can be eliminated.

Minimum floor thickness can reduce the overall height of the building and cladding requirements.

Consider leaving a polished concrete floor, to avoid requirement for additional floor coverings.

Insitu concrete can be ordered in specific quantities. Regular building shapes minimise cutting of plywood sheets for formwork.

Slab thickness typically reduced by 75mm29. 2.2m3 waste to landfill savings per 1000m2.30 Overall storey height can be up to 300mm lower than some other structural solutions.31

Cost implications

Post-tensioned floors are a frequently used solution as an economic choice of floor slab.

Light weight allows efficiencies, not only in the floor slab itself but also throughout the building structure (i.e. frame, columns, cladding, foundations etc)

Post tensioned slabs generally become economic at spans greater than 6m.32 35% (£67/m2) saving compared to solid slab.33 Overall potential construction cost savings of ~£13K/1000m2.34

Time implications

Reduction of both reinforcement installation and concrete pour can speed up programme.

Large area pours reduce the total number of pours and increase construction speed.

Prefabrication of tendons reduces fixing time and early stressing enables formwork to be stripped quickly.

The thin slab may reduce curing times.

Carbon reductions

Reduction in slab thickness will reduce level of embodied CO2. Further embodied carbon reductions in supporting structure. Minimising screed (i.e. powerfloating) will also reduce

embodied CO2. Reduced volume/weight of materials can reduce transport

emissions.

Embodied carbon reduction of 82 tonnes CO2e/1000m2 for concrete.35


Consider specifying concrete with recycled content. Concrete is 100% recyclable; post-tensioning has no

implications for recyclability. Formwork can be reused a number of times and proprietary

systems returned to suppliers for reconditioning.

Construct-ability

Construction techniques are well established and understood. Design methods can accommodate irregular grids; tendons

can be deflected to suit the building’s geometry. Clear, flat soffits enable flexibility and economy in service

layout. Slab can be poured onsite, or precast units can be produced.

Replicability Formwork systems provide a high level of control and replicability.


Impact on structure Light structure and low floor-to-floor heights.

Procurement issues There are a number of specialists who can install post tensioned slabs. It is recommended that suppliers are CARES approved36


Tendons can be prefabricated to allow faster construction.

Longevity 60+ year design life

Standardisation Standard installation procedures, although specialists should be used. Dimensional coordination Dimensions are flexible.

29 Ibid. 30 Concrete Centre [Correspondence] 31 Stevenson, A. M. Post-Tensioned Concrete Floors in Multi-Storey Buildings. British Cement Association. 32 Minson, A Post-tensioned suspended floors gain favour. Concrete Centre [Available at: http://www.concretecentre.org/main.asp?page=1089] 33 Faithful+Gould Cost Consultancy. Post tensioned concrete slab instead of insitu reinforced concrete slab. 34 WRAP Case Study (Colchester Magistrates Court - currently unpublished) – Comparison between ribbed solid concrete slab and post-tensioned slab. Includes cladding savings due to thinner slab consequent floor heights. 35 Ibid. 36 www.post-tensioning.co.uk


Criteria Further considerations Repairability Care must be taken not to disturb or damage tendons. Deconstructability Post-tensioned floors are easier to separate out steel and concrete

Avoid contamination of material during deconstruction. Bonded post tensioned slabs (most commonly used in this country) require no special

consideration compared to demolition of standard insitu slabs. Recycling the demolished concrete is marginally easier due to the reduction in embedded reinforcement.

Unbonded post tensioned slabs require specific sequencing for demolition 2.4.4 Additional information Post-tensioned flat slabs are economic up to 12m.

Exposing the soffit improves the benefits of thermal mass. This can help regulate temperatures and will assist in reducing M&E requirements.

Active thermal mass systems can be designed to pump air at low velocity or water through slabs to activate more of the mass.

Reducing slab thickness may affect sound insulation. Take care to avoid the need for increased ceiling structure to compensate, particularly in residential properties.


Table 2.4.5 Potential embodied carbon savings using post-tensioned slabs Savings achieved using post-tensioning

Concrete Steel

Reduction of slab thickness 75mm37 Volume of material saved 0.075m3/m2

75m3/1000m2

Mass of materials saved 157kg/m2 157tonnes/1000m2

20kg/m2.38 20tonnes/1000m2

Embodied carbon reduction39 25.6kgCO2e/m2 25.6tonnesCO2e/1000m2

56.6kgCO2e/m2. 56.6tonnesCO2e/1000m2

Total embodied carbon reduction = 82kgCO2e/1000m2

37 Concrete Centre [Correspondence] 38 Stevenson, A. M. Post-Tensioned Concrete Floors in Multi-Storey Buildings. British Cement Association. Steel weight can be reduced by up to 50% (Comparison is with 410mm solid concrete slab incorporating 42kg steel/m2). 39 Bath University (2006), Inventory of Carbon and Energy (ICE) (Concrete = 0.163kgCO2e/kg; Steel wire = 2.83kgCO2e/kg)


2.5 Voided biaxial slab Subject Voided biaxial slabs (VBS) (e.g. Bubbledeck, Cobiaxdeck) NBS reference NBS Ref: E05 (In situ concrete construction); E10 (Mixing/ casting/

curing in situ concrete); E20 (Formwork for in situ concrete); E30 (Reinforcement for in situ concrete)

Type of Projects Covered

Can be used to replace solid reinforced slab for most building types.


RIBA Stage C/D (Concept Design/Design Development)

Relevant standards BS 8110, Structural use of concrete Eurocode 2, Design of concrete structures

2.5.1 Standard option Standard solid concrete floor slabs can be either prefabricated or poured in situ; prefabricated units are manufactured in factories to the required shape/dimension and transported to site, whilst in situ slabs are poured onsite using temporary or permanent formwork. The resulting concrete slab is solid concrete with steel reinforcing mesh encased within. Not all of the concrete slab contributes to its structural strength - the middle of the slab is ‘non-working’ dead load. But, the specification of supporting foundations, columns and walls must all take into account the total weight of the solid slab.

Fig. 2.5.1 Standard solid concrete floor slab.


2.5.2 Resource efficient design detail Voided biaxial slabs (VBS) provide a resource efficient design for concrete slabs by incorporating voids which significantly reduce overall materials use (Fig 2.5.2). Several VBS technologies have been introduced during the last decades, primarily to reduce the weight of buildings, and designs now have comparable strength to solid concrete slabs. Typical systems use hollow plastic spheres placed in a precise modular grid; these can be fixed in place using only reinforcement mesh. Solid concrete above and below the voids ensures greater strength at the points of highest stress. Semi pre-cast systems offer faster, straightforward construction. VBS systems offer excellent freedom in architectural design, by allowing a variety of building shapes, large spans and few supporting points. As a result they allow the construction of flexible and easily changeable buildings. The light, strong slabs can also allow materials savings throughout the building structure, including in supporting beams, columns and foundations.

Fig. 2.5.2 Voided biaxial slab




Voids in the slab reduce concrete use and therefore give weight savings.

Biaxial design also allows weight savings in steel reinforcement.

Light slab and large spans allow further materials savings, and therefore good resource efficiency throughout the structure – supporting beams, columns, foundations, walls etc.

The use of formwork is avoided for semi-precast systems.

Up to 35% lighter than solid slab of the same thickness40 30% concrete saving in the slab41 – up to 50% saving has been reported.42 1kg of plastic replaces 100kg of concrete43 Up to 40% fewer columns44 20% less concrete in frame and structure45

Cost implications

Modest cost savings or slight increase in cost for the slab itself. However, this is offset when the frame and substructure are included; a light slab and large spans allow materials cost savings for other structural elements (beams, columns, foundations etc).

Reduced weight can result in lower transport costs. Less powerful lifting equipment is required. Potential reduction of downstand beams and load

bearing walls contributes to cost reductions.

Manufacturer estimates suggest 5-15% cost savings for the building carcass46. Savings of £8/m2 for 450mm VBS instead of 900mm solid slab47. This equates to 4%.

Time implications

Semi-precast systems incorporate permanent formwork with factory production and finish which simplifies finishing work on site.

The potential to eliminate downstand beams and some load bearing walls allows fast construction times. Subsequent installation of services is also fast.

Some fully finished VBS elements can be used for certain applications (e.g. balconies; staircases)

Low concrete volume can allow for short drying/curing times.

Time savings of up to 40% have been achieved (semi-precast systems)48

Carbon reductions

Embodied carbon emissions are reduced in correspondence with low concrete use.

Enables simple placement of installations like ducts and heating/cooling systems directly in the slab; thermal heating/cooling slabs can substantially reduce energy consumption.

The thermal mass of the slab can be exploited through passive or active means to reduce heating or cooling for buildings in operation.


Potential embodied carbon reductions of around 90kgCO2e/m2 are achievable, based on 340mm VBS.49 (See table 2.5.5)


Consider specifying concrete with recycled content. Recycled HDPE spheres are used in some systems. Specifying VBS systems has no negative impact on the

recyclability of the slab.50

Constructability Problems associated with reduced resistance to shear, local punching and fire in older VBS systems have been reduced. However, it may be necessary to omit voids near columns and walls where the shear stress is high.

The reduced weight of the slab can allow long spans between columns, or alternatively reduced deck thickness for equivalent span.

Subsequent installation of services can be simplified due to flat soffits with no obstructing beams. It is

Up to 50% increase in span between columns can be achieved

40 Bubbledeck (http://www.bubbledeck.co.uk/) and Cobiax (http://www.cobiax.ch/html/english/cobiax_big5/big5_benefits.html) 41 WRAP – Waste Minimisation Design Review (University of Bristol – currently unpublished) 42 Bubbledeck (http://www.bubbledeck.co.uk/) 43 Ibid. 44 http://www.cobiax.ch/html/english/cobiax_big5/big5_benefits.html 45 WRAP – Waste Minimisation Design Review (University of Bristol – currently unpublished) 46 http://www.bubbledeck.co.uk/ 47 Faithful+Gould cost consultancy 48 http://www.cobiax.ch/downloads/english/press/New_Concrete_06_06.pdf 49 See table 2.5.5. Data supplied by Bubbledeck ‘Bubbledeck-v-Solid Slab Comparisons’ (February 2009) 50 Bubbledeck (http://www.bubbledeck.co.uk/)


Criteria Potential benefits Quantification of benefits possible to use precast soffits onto which the slab can be poured.

The size of the reinforced elements (before concrete is added) can be bespoke to suit specific projects.

Different versions of VBS systems are available according to the degree of prefabrication.

Replicability Can be used in the construction of most building types.

Can be treated as a normal flat slab supported on columns in the UK. Conforms to ISO standards.

Examples include offices, apartments, hotels, schools, car parks, hospitals and factories.


Impact on structure Buildings can be designed to be flexible, with future changes in layout achievable.

Procurement issues Widely available throughout the UK Off-site construction/ modularisation

Included above

Salvaged components N/A Longevity 60+ years replacement interval51 Packaging N/A Standardisation Cage modules (reinforcement and voids) and semi precast units come in a range of

standard sizes. Repairability Same as solid reinforced slab.

Deconstructability Throughout a structure’s lifetime, the envelope and all internal work can be removed, and the original frame refitted for a new purpose. Internal reconfiguration is possible.

2.5.4 Additional information Use of the some VBS systems can help to achieve credits under LEED (Leadership in Energy and

Environmental Design). The effect of post-tension cables in VBS systems can be enhanced, allowing spans of up to 50

times the deck thickness. Semi-precast VBS systems do not require formwork and offer a flat, smooth soffit finish which can

be left exposed. Prominent buildings which have made use of VBS technology include Le Coie, Jersey; Millennium

Tower, Rotterdam; Sogn Arena, Oslo; and Tesco in Orpington, UK. Risk during construction is reduced due to low weight and fewer crane lifts.


Table 2.5.5 Embodied carbon of VBS vs. equivalent solid slab52 VBS (340mm) Solid Slab (410mm)53 Steel Weight (/m2) 18kg 42kg Concrete Weight (/m2) 574kg 914kg HDPE Weight (/m2) 3.7kg N/A Steel Embodied Carbon (kg CO2/m2)54 31 72 Concrete Embodied Carbon (kg CO2/m2) 94 149 HDPE Embodied Carbon (kg CO2/m2) 5 0 Total Embodied Carbon (kg CO2/m2) 130 221 Embodied carbon reduction (slab only) using VBS = 91kgCO2/m2 (approx 41%)

51 BRE ‘Green Guide to Specification’ (http://www.thegreenguide.org.uk/) 52 Data supplied by Bubbledeck ‘Bubbledeck-v-Solid Slab Comparisons’ (February 2009) 53 Solid slab must be thicker for the same span. 54 Embodied carbon factors based on ICE/Bath Data. Steel Bar = 1.72kgCO2/kg ; Concrete Slab = 0.163kgCO2/kg; Recycled HDPE = 1.44kgCO2/kg (assumed 20% less than virgin HDPE figure)


2.6 Flexible plumbing systems Subject Flexible Plumbing Systems NBS reference NBS S90 (Hot and cold water supply systems) Type of projects covered

All buildings incorporating water services.


RIBA Stage D (Design Development)

Relevant standards BS EN 12201, Plastic piping systems for water supply. Polyethylene Pipes. BS 7291, Thermoplastics pipes and associated fittings for hot and cold water for domestic purposes and heating installations in buildings. BS ISO 4427, Plastic piping systems. Polyethylene pipes and fittings for water supply.

2.6.1 Standard option Plumbing in buildings has traditionally relied on the use of rigid copper piping. Although copper is proven, reliable and safe for potable water supply, piping can often involve complex layouts using many components for bends and branches. Installation, maintenance and repairs can be labour intensive, requiring the services of a trained plumber and specialist tools.

Fig. 2.6.1 Standard copper piping and joints


2.6.2 Resource efficient design detail Flexible, plastic plumbing systems have developed rapidly over recent years, and now offer levels of performance at least comparable with copper pipe. Plastic solutions are available for both hot and cold water applications as well as above and below ground drainage. Flexible pipes are supplied on long rolls, creating less waste than rigid lengths by reducing the number of offcuts. Fewer joints and fittings are required and most systems enable these to be easily demountable and reusable.

Fig. 2.6.2 Flexible plastic piping




Supplied in lengths of up to 100m, means few offcuts are created when pipes are cut to length. Number of fittings required is also low.

Fittings can be reusable. Good insulating properties reduces the need for additional

lagging.

Approx 75% lower weight than copper piping.55

Cost implications

Materials costs savings. Significant installation and maintenance cost savings. Little price fluctuation.

16% cost savings compared to copper pipe. (average £4/metre of pipe run.56)

Time implications

Simple installation and maintenance – many have push-fit joints.

Major time savings from few joints/bends. Soldering of joints is not required.

Programme savings: it may be possible to fit floors before pipes.

Carbon reduction

Embodied carbon reduction of up to 88% compared to copper pipe.

Modern high-performance plastics have a long life-expectancy and are corrosion-free.

Reduced weight of materials can result in reduced transport emissions.

For 15mm Pipe57: HDPE = 0.12kg CO2e/m Copper = 1.07kg CO2e/m SAVING = 0.95kg CO2e/m = 88%


Polybutylene/PVC pipe can be recycled and converted back to granular form ready for re-use in the production of other plastics-based products.

Construct-ability

Long pipe lengths means few joints/fittings may be required. The light weight and flexibility of plastic pipes can result in

easy handling and installation. Safer and fast electrical installation is possible, reducing the

need for earthing. Pipework can be ‘threaded’ through complex routes – flooring

can be installed before pipes. Many flexible pipe fittings can be rotated in situ, even under

pressure. Repairs can be made without emptying pipes. Long runs are possible resulting in few joints (support

spacings may need to be adjusted). Fittings are designed to connect to standard copper pipes

where necessary.

Plastic piping is round ¼ the weight of rigid copper pipe.

Replicability Standard pipe sizes and fittings ensure full replicability between projects.

Criteria Further considerations Impact on structure None

Procurement issues Standard materials. Available throughout the UK. Off-site construction/ modularisation

N/A


Longevity Modern flexible plumbing systems come with long guarantees – typically 50 years or more.

Flexibility means that pipes have good resistance to minor impacts. Flexible pipes are able to cope with ground movement which, together with long pipe

runs and few joints, can result in less leakage. Packaging Generally supplied on rolls of up to 100m. Standardisation Most flexible systems are compatible with conventional pipe materials and jointing

techniques.

55 Based on Hep2O Performance Data: 0.75kg/m for Hep2O; 2.81kg/m for copper (http://content.wavin.com/WAXHW.NSF/pages/PDF_HEP2OTHB_PERFDATAEN/$FILE/THPerformanceData.pdf) 56 Faithful+Gould. Copper pipework with end feed capillary joints (weightings 50%:15mm, 30%:22mm, 20%:20mm) vs. Hep2O pipework with proprietary joints (weightings 50%:15mm, 30%:22mm, 20%:20mm) 57 See table 2.5.5


Criteria Further considerations Dimensional coordination N/A

Repairability Easy to remove and replace sections and fittings, even for non-professionals.

Deconstructability Most flexible plumbing fittings are fully demountable and reusable (e.g. ‘push-fit’ fittings)

2.6.4 Additional information Plastic piping can provide a low contamination risk to potable water. Plastic piping has good insulating properties, reducing thermal loss. Noise and vibration problems (‘knocking’) are virtually eliminated.


Table 2.6.5 Embodied carbon of copper vs. plastic pipe (15mm diameter) Copper Pipe Plastic Pipe Mass (g/m pipe run)58 281 75 Embodied Carbon (kgCO2e/kg)59 3.8 1.6 Embodied Carbon (kgCO2e/m) 1.07 0.12

Total embodied carbon reduction by substituting 15mm copper pipe for 15mm polybutylene (or HDPE) pipe = 88%.

58 Hep2O Performance Data [http://content.wavin.com/WAXHW.NSF/pages/PDF_HEP2OTHB_PERFDATAEN/$FILE/THPerformanceData.pdf] 59 Bath University (2006), Inventory of Carbon and Energy (ICE) (NB: No carbon factor available for polybutylene. Assumed equivalent to HDPE)


2.7 Aerated concrete blocks with thin joint mortar Subject Aerated concrete blocks (aerated autoclaved concrete - AAC) with thin

joint mortar NBS reference NBS F10 (Brick/Block Walling) Type of projects covered

Wide variety of domestic and commercial building types.


RIBA Stage D/E (Design Development/Technical Design)

Relevant standards BS EN 771-4, Specification for masonry units. Autoclaved aerated concrete masonry units. BS 8110, Structural use of concrete Eurocode 2, Design of concrete structures

2.7.1 Standard option Standard concrete building blocks consist of cast concrete which is made up of cement, aggregate and varying levels of sand/gravel depending on the density required. Although it is possible to incorporate recycled content, particularly in lower density blocks, many use high proportions of virgin materials. These types of blocks are usually bonded with sand/cement mortar (proportions depending on required strength), 10 mm thick.

Fig. 2.7.1 Standard Concrete Blocks and Mortar


2.7.2 Resource efficient design detail Aerated autoclaved concrete (AAC) blocks, together with thin joint mortar, represent a fast and efficient construction alternative to standard aggregate blocks with cement mortar; they are strong, durable and time-tested. Modern large format AAC blocks are manufactured to exacting dimensional tolerances and can be easily cut where necessary. Major materials resource efficiency savings come from the light weight of the blocks (around 25% of the weight of conventional concrete on average) and lower mortar requirements. In addition most AAC blocks include recycled content, in the form of pulverised fuel ash (PFA). A high level of design flexibility is possible allowing for a variety of plan forms, awkward sites and bespoke projects. The autoclaving process involves the use of high-temperature, high-pressure steams to ensure strength, rigidity and dimensional stability. It can produce in a matter of hours concrete strengths equal to those obtained in a concrete moist-cured for 28 days at 70° F (21°C). Thin joint mortar is a cement-based product that only requires the addition of water and allows joints of 3mm or less, although thickness can be varied to allow perfect levelling. Applied to the blocks with a serrated applicator, it is quick-setting allowing rapid construction progress. Movement control mesh compensates for the strength of the mortar and distributes any movement stresses that may build up within the blockwork.60

Fig. 2.7.2 AAC Blocks and Thin Joint Mortar.

60 Thin Joint Technology [http://www.thinjoint.com/basic-frame.html?main=basic.html]




High strength/weight ratio results in reduced material use61. Low mortar requirement – also results in low waste. The manufacturing process for aerated concrete blocks is

highly efficient; any waste is minimised and can be easily recycled.

Block off-cuts can be used elsewhere. Good fire resistance, thermal, acoustic and surface properties

can eliminate the need for finishing materials such as insulation and plasterboard.

High quality internal finish may eliminate the need to skim for some applications.

Light weight blocks (for masonry) allow lightweight building structure and foundations.

Up to 80% less mortar materials are used for thin joints (joints are 2-3mm thick)62 For every cubic metre of raw material used, around 5m2 of finished product is produced.63

Cost implications

Any material costs increases are offset by labour and programme savings.

Lightweight materials and the potential reduced materials use can result in lower transport costs.

Lower foundations costs due to lightweight of building.

Modest extra cost of £2/m2 can be expected.64 Value of wasted materials is reduced by 44%.65 Waste disposal costs reduced by 50%66

Time implications

Large, lightweight block sizes allow rapid construction. Thin joint mortar is quick-setting, allowing fast progress. Buildings are watertight quickly using thin joint mortar. For cavity walls, internal works can be initiated before

completion of the external leaf. Consistent wall surfaces helps speed up the work of finishing

trades and provides a suitable base for the application of plasters or renders. Snagging work is potentially reduced.

AAC formats for solid wall construction omit the need for outer leaf altogether.

Construction times equivalent to offsite methods are claimed - a house can be ready for roofing in 5-6 days (4-6 weeks for conventional methods).67

Carbon reduction

Although aerated concrete blocks have higher embodied carbon per kg, this is offset by the light weight of the blocks (/m3) – see table 2.7.5.

Further savings come from low mortar requirements. Low weight of materials can result in reduced transport

emissions. Good thermal efficiency allows potential operational carbon

reductions due to reduced energy requirements.

Thermal efficiency is 10X higher than aggregate concrete.68 The production of standard AAC blocks involves around 21% less embodied CO2e/m3 compared to standard equivalent sized blocks69.


PFA, a by-product from coal fired power stations, is used as an ingredient.

100% of aerated concrete blocks can be recycled or reused at the end of a building’s life.

No implications from use of thin joint mortar.

Aerated concrete contains 85% PFA, a waste product from coal power stations.70

Construct-ability

Modern aerated blocks are manufactured to exacting dimensional tolerances.

Blocks are lightweight and easy to handle. A range of face sizes, thicknesses and strengths are available

to match individual applications. Low mortar requirements mean less onsite storage is required

(i.e. bulk sand and cement) Thin joint technology allows easy laying and levelling of

blocks; simple training can be provided through builders merchants or onsite.

Dimensional accuracy helps to improve construction quality by

Thin joint mortar sets within 20 minutes.71 A typical 100mm block weighs approx 1/3 of the 20kg health and safety guideline.72 70% lighter than standard concrete blocks.

61 Greenspec (http://www.greenspec.co.uk/) gives strengths of 2.8 to 8.4 N/mm2 for AAC Blocks. 62 Tarmac (Durox System) [http://www.tarmac.co.uk/topblock/DuroxSystemproduct.aspx] 63 Aircrete [www.aircrete.co.uk] 64 Faithful+Gould Cost Consultancy. 100mm Thermalite Turboblock wall with 10mm clm 1:2:9 mortar joints vs. 100mm Durox ‘Supabloc’ wall with 3mm joints. 65 WRAP Case Study (Queenshill Court – currently unpublished) – replacement of traditional brick & block internal and external walls with Thermoplan terracotta blocks with an external render finish. 66 Ibid. 67 Tarmac (Durox System) [http://www.tarmac.co.uk/topblock/DuroxSystemproduct.aspx] 68 Ibid 69 See section 2.7.5 70 Aircrete [www.aircrete.co.uk] 71 Ibid 72 Aircrete [www.aircrete.co.uk ]


Criteria Potential benefits Quantification of benefits providing flat and even wall surfaces.

Special shapes and infill pieces can be easily cut and sanded using standard tools.

Replicability Aerated concrete blocks are a mass-market solution and are readily available in the UK.

Can be used for single leaf, external solid wall construction. They are recognised as a ‘Modern Method of Construction’ by

the Housing Corporation.


Impact on structure Entire structure is lightweight for masonry which has implications for the specification of other structural elements (i.e. foundations)

Procurement issues AAC blocks are available from most merchants across the UK.


Recognised as a modern method of construction by the Housing Corporation. Assembly times can rival offsite solutions.


Longevity Aerated concrete blocks have very good durability in use and are virtually unaffected by insect attack, sulphates, frost or water.

60+ years Packaging Usually packaged on reusable wooden pallets and shrink wrapped.

Standardisation High levels of dimensional accuracy from precision factory cutting. AAC blocks come in a variety of sizes including 215mm course height to match standard

blocks. Dimensional coordination Available in a number of standard sizes compatible with standard blocks.

Repairability Masonry construction is inherently simple and easy to repair.

Deconstructability The concrete is 100% recyclable; however, blocks are easily damaged during deconstruction and may be difficult to reuse.

2.7.4 Additional information As well as reducing materials use, thin joint techniques can also improve air tightness, thermal bridging and

sound insulation. Excellent thermal efficiency allows cost-effective solutions to meet current Part L Building Regulations. Can be used in load-bearing walls up to 5 storeys. AAC is a relatively soft material and chipping or denting is possible. However, damaged ends can be trimmed

and thin joint mortar can be used to ‘glue’ broken pieces.


Table 2.7.5 Embodied carbon of AAC blocks compared to standard concrete blocks Celcon standard AAC block Standard concrete block

(medium weight) Embodied Carbon/kg73 0.32kgCO2/kg 0.163kgCO2/kg Density 600kg/m3 74 1500kg/m3 75 Embodied Carbon/m3 192kgCO2/m3 244.5kgCO2/m3 Reduction in embodied carbon using AAC blocks = approx 21%

73 Bath University (2006), Inventory of Carbon & Energy 74 HHCelcon http://www.hhcelcon.co.uk/c/document_library/get_file?folderId=54610&name=DLFE-2802.pdf 75 Concrete Block Association http://www.cba-blocks.org.uk/


2.8 Polished concrete floor Subject Polished concrete cloors NBS reference E05 (In situ concrete construction); E10 (Mixing/casting/curing in situ);

E20 (Formwork for in situ concrete); E41 (Worked finishes to in situ concrete); M10 (Cement based levelling/wearing screeds); M41 (In situ terrazzo)


Schools, supermarkets, hospitals, industrial etc


RIBA Stage D/E (Design Development/Technical Design)

Relevant standards BS 8204, Screeds, bases and in situ floorings EN 206-1, Concrete. Specification, performance, production and conformity. BS 8500, Complementary British Standard to EN 206-1 EN 13369, Precast Concrete

2.8.1 Standard option Traditional hard floor finishes, such as terrazzo or ceramic tiles, laminates, stone, slate, lino and vinyl, can consume large quantities of materials in their manufacture and installation. Cutting shaping and damage can result in significant waste.

Fig. 2.8.1 Tiled floor construction


2.8.2 Resource efficient design detail Specifying an exposed, polished concrete floor instead of additional, separate layers of flooring has major potential for good materials resource efficiency.

Both new and existing concrete can be ground and polished to a high shine for attractive flooring which needs no coating or waxing. Polished concrete looks like polished stone and is highly durable. It is decorative, practical and economical.

The use of ‘dry shake’ finishes gives the option of different colours and textures and helps ensure a more homogenous surface. It is also possible to use additional ‘toppings’ on existing surfaces to achieve the desired finish.

Fig. 2.8.2 Exposed concrete floor




Omission of further flooring layers clearly has good resource efficiency implications – particularly when an existing concrete surface can be used.

Offcuts associated with tiles, carpeting and linoleum are avoided for poured monolithic surfaces.

Efficiencies can be achieved by co-ordinating volume required with concrete ready-mix load.

Potential major reduction in waste to landfill compared to other surfaces which may need periodic replacement (e.g. carpet, linoleum, laminate).

Potential elimination of materials used for maintenance (polishing/waxing).

Waste associated with floor surface manufacturing is virtually eliminated.

Tiled flooring has an average wastage rate of 8% - much of which often goes to landfill.76 Polished concrete represents a virtually 100% saving in materials use when replacing additional layers.

Cost implications

Potential cost savings compared to other floor finishes (e.g. terrazzo, timber, marble) if concrete is already proposed as the floor structure. Avoid use of screed where possible.

The premium associated with a special colour or finish to the concrete is offset by savings of material and labour cost of fitting separate floor finishes.

Durability ensures long life cycle.

Up to 83% cost saving (typically £39/m2) achievable compared to terrazzo tiles with screed layer.77

Time implications

Significant labour and programme time savings usually achievable compared to hand-laid floors (terrazzo, timber etc).

Grinding and polishing of existing concrete floors is a quick solution to achieve a high quality floor finish.

Carbon reductions

Omission of additional layers of flooring allows notable savings in embodied carbon.

Low maintenance requirements also allow carbon reductions for buildings in operation.

Exposing thermal mass can help reduce operational energy demand for heating and cooling.

Avoidance of transporting additional flooring materials to site can result in reduced transport emissions.

8.4kgCO2/m2 for tiles 15kg CO2/m2 for screed layer Total = 23.4 (See table 2.8.5)


Consider specifying concrete with recycled content. Exposing concrete has no implications for recyclability. Inclusion of recycled glass aggregate can give further

desirable aesthetic effects.

Construct-ability

Exposed concrete floors offer a high quality finish with minimal extra effort. Consider employing specialist installers.

Care is required in specification and installation to achieve acceptable appearance.

Ground supported concrete floors are laid between 100mm and 150mm thick and are reinforced with steel mesh; there is no requirement for initial concrete work on the site. (If there is an existing floor slab, maximum thickness will be 75 – 100mm).

Appropriate protection during site works is essential. Stains during curing are difficult to remove.

Small areas present challenges for installation.

Replicability Quality control and protection on site is essential to minimize variations in concrete appearance. Natural variations will occur between projects.

However, dry shake finishes can be used to provide a consistent finish between pours where required.

Criteria Further considerations Impact on structure Minimal, although weight of floor will be reduced.

Procurement issues Standard materials used, although specialist installer / polishing company is likely to be required.


Offsite manufacturing of concrete flooring slabs is possible. However, some of the waste benefits may be lost unless slabs are manufactured to fit intended location.


76 WRAP – Netwaste Tool 77 Faithful+Gould Cost Consultancy. Polished concrete floor instead of terrazzo tiles. Based on 300 x 300 x 28mm Terrazzo tiles laid in semi-dry screed vs. power float unset concrete & apply surface hardener.


Criteria Further considerations Longevity 60+ year replacement interval

Durability ensures a long life-cycle, even for industrial applications. Minimal maintenance requirements (clean with soap and water). No harmful chemicals

required. Can be buffed to restore shine if necessary. Future flooring layers can be installed on top if requirements for the space change. Repairs or adaptations to large monolithic areas are difficult to conceal. However, it is

possible to use pre-fabricated, smaller slabs. Packaging Materials can be delivered by concrete mixer. Further additives (i.e. dry shake colour)

likely to be packaged in bags. Standardisation Natural variations in concrete mean that it is important to complete a floor in one pour.

The finish may vary between different pours and projects. Dimensional coordination N/A

Repairability It is difficult to conceal repairs to large monolithic surfaces. Any access to services below the slab should be carefully planned and infill trays should

be used. Deconstructability Deconstruction will result in break up of floor surface. Efforts should concentrate on

separating concrete for recycling. 2.8.4 Additional information Underfloor heating works more effectively when additional floor coverings are omitted. This

represents an effective and efficient heating solution, particularly if the thermal mass is used as part of a passive solar design strategy.

It is important to consider the acoustic implications of omitting soft floor finishes. The addition of a resilient layer below the screed can help limit sound impacts in residential properties.

Slip resistance requirements should also be taken into account and the exposed finish adapted appropriately. However, if kept clean and dry a polished concrete floor is no more slippery than regular concrete.

Installation may be affected by weather conditions, for both internal and external applications.


Table 2.8.5 Embodied carbon of terrazzo tiles and separate screed layer Terrazzo tiles (assumed

28mm thick) Screed layer (assumed 70mm thick)

Embodied carbon78 0.118kgCO2/kg 0.102kgCO2/kg Tile weight (300x300x28mm)79 6.4kg n/a Screed density (kg/m3) n/a 2100kg Tile/screed weight/m2 71.1kg 84kg Embodied carbon/m2 8.4kgCO2e/m2 15kgCO2e/m2

Total embodied carbon for terrazzo flooring including screed = 23.4kgCO2e/m2 = 23.4tonnesCO2e/1000m2

78 Bath University (2006) Inventory of Carbon and Energy (ICE) 79 Kengate Terrazzo [http://www.kengate-terrazzo.co.uk/tech-testdata.htm]


2.9 Low waste door jamb Subject Low waste door jamb

NBS reference NBS K10 (Plasterboard dry linings/partitions/ceilings)


Retail, offices, residential, healthcare, schools, hotels etc.


RIBA Stage E (Technical Design)

Relevant standards BS 8212, Code of practice for dry lining and partitioning using gypsum and plasterboard

2.9.1 Standard design detail Plasterboard has one of the highest wastage rates for construction materials. Every year around one million tonnes of waste plasterboard is created from construction, refurbishment and demolition activities, with resulting environmental impacts and waste management costs.80 The construction of door openings can make a major contribution to this waste. Traditional methods for constructing door openings involve positioning a plasterboard sheet half way or fully over the door position and then simply cutting out the required opening (Fig. 2.9.1). This results in large off cuts.

Fig. 2.9.1 Traditional door construction

80 WRAP (2006) Review of plasterboard material flows and barriers to greater use of recycled plasterboard. [http://www.wrap.org.uk/downloads/PBD0004_Plasterboard_material_flows_report1.7f70e4d4.2424.pdf]


2.9.2 Resource efficient design detail More efficient door jamb arrangements can significantly reduce the amount of plasterboard waste generated, by positioning full sheets of plasterboard up against studs at each side of the door opening and using an off cut from elsewhere above the door. Arrangement of studs is the same as for the standard door jambs. Further material efficiencies can be achieved by taping and skimming over joints rather than applying a plaster skim to the entire wall. As an alternative, for lighter doors it may be possible to eliminate the secondary strengthening studs at each side of a door opening to reduce metal use instead of plasterboard. However, this is only possible with standard plasterboard arrangements.

Fig. 2.9.2 Low waste door jamb



Criteria Resource Efficiency Considerations Quantification of benefits Materials saved and/or Reduced waste to landfill

Potentially significant reduction in plasterboard waste. Reduction in total number of plasterboard sheets required

(actual saving will vary from project to project)

27% reduction in plasterboard waste compared to standard door jamb construction detail.81 25% reduction in the number of bins required per floor.82 Potential plasterboard saving of 5.4m2/100m2 wall area83.

Cost implications

Potential cost savings due to reduced number of plasterboard sheets required.

Less waste reduces disposal costs. Reduced materials use can result in lower transport costs.

Typical £8 saving per door opening.84

Time implications

Time savings may not be significant for the construction of the door openings themselves.

Time savings will be realised due to reduced materials handling.

Minimal.

Carbon reduction

Carbon reductions correspond to the reduction in materials used and waste generated.


Embodied carbon reduction of 3.44kgCO2e /standard door opening.85


Remaining plasterboard waste should be carefully segregated; it can be fully recycled into its constituent parts – gypsum and paper – if it is uncontaminated.

Recycled content of 75% or more can be specified.86

Construct-ability

Uses standard plasterboard sheets without affecting final appearance or structural integrity of the jamb.

No additional training or equipment required for installers. Successfully used on a variety of projects.

Replicability Proprietary systems are available which allow full replicability and consistent standards.

Particularly efficient for buildings with many doors at regular intervals (e.g. hotels, student accommodation)


Impact on structure No effect on the final appearance or structural integrity of the door jamb.

Procurement issues None. Proprietary systems are widely available and independent, bespoke versions can be put together by installers.


Factory produced proprietary systems are available.


Longevity Typically 15 year replacement interval

Packaging N/A

Standardisation Uses standard plasterboard sheets.

Dimensional coordination Room dimensions should be coordinated with standard plasterboard sizes where possible.

Repairability Large areas of damaged plasterboard are difficult to repair. Sections may have to be replaced if badly damaged.

Deconstructability Steel studding can potentially be demounted and reused, although care is required in deconstruction. For plasterboard, recycling rather than reuse is likely to be the most practicable option.

81 Knauf [Online] Knauf Drywall Anti-waste initiatives generate big savings. [http://www.knaufdrywall.co.uk/news/page_175.html] 82 Ibid. 83 Ibid. Based on reduction of plasterboard wastage rate from 16% to 12% 84 Faithful+Gould Cost Consulting. Based on plasterboard discarded per door opening (traditional method vs Knauf Eco door jamb method) 85 See section 2.6.5 for calculations. 86 Ecology Action [Online] Green Buildings Materials Guide [http://www.ecoact.org/Programs/Green_Building/green_Materials/gypsum.htm]


2.9.4 Additional information All stability, fire, acoustic and door-leaf weight requirements must be considered in conjunction

with the manufacturer.

The biggest source of plasterboard waste is the offcuts resulting from dimensional specifications which do not correspond with sheet sizes. Wherever possible, design to standard sheet sizes.

Chipping plasterboard waste saves storage space and reduces the overall volume of waste to be managed.

For projects with larger plasterboard requirements (i.e. >10,000m2), it may be cost effective to specify bespoke sheet sizes. However, accurate estimates of quantities will be necessary to maximise waste reduction potential.

As an alternative to this plasterboard detail, for lighter doors it may be possible to eliminate the secondary strengthening studs at each side of a door opening to reduce metal use instead of plasterboard. However, this is only possible with standard plasterboard arrangements.


Table 2.9.5 Embodied carbon reduction from use of low waste door jamb. Embodied carbon calculation Embodied carbon of plasterboard 0.24 kgCO2e/kg87 Plasterboard density 652kg/m3 Plasterboard mass (12.5mm sheet) 8.15kg/m288

Offcut mass for standard door (assumed dimensions of 2064mm x 852mm, including jamb)

14.33kg

Embodied Carbon of offcuts of standard door size 3.44kgCO2e

87 Bath University (2006) Inventory of Carbon and Energy (ICE) 88 Knauf Drywall. Based on Knauf standard wallboard.


2.10 Tile detailing Subject Tile detailing NBS reference NBS M40 (Stone/ Concrete/ Quarry/ Ceramic tiling; Mosaic/ Plastered/

Rendered coatings) Type of projects covered

All types of occupied buildings.


RIBA Stage E (Technical Design)

Relevant standards BS 5385, Wall and floor tiling. 2.10.1 Standard option Wall and floor tiles can be responsible for significant amounts of construction waste at the fit-out stage: typically between 8 and 10%89 is wasted. However, when using larger sized tiles this rate can be significantly higher due to the increased offcuts produced and higher damage rates, particularly when working around smaller details or in awkward spaces (Fig 2.10.1). Whilst some offcuts can be reused, in practice most end up as waste. The recent trend towards the use of larger tiles, particularly for wall finishes, can therefore have a potentially increased impact on the resource efficiency of a project unless carefully planned.

Fig. 2.10.1 The use of larger tiles resulting in higher volume of offcuts.

89 WRAP Netwaste Tool.


2.10.2 Resource efficient design detail Careful coordination of the type and size of tiles with the space in which they are to be used can have a major impact on the amount of materials used and waste created. Larger tiles may be appropriate for large, uninterrupted wall areas where minimal detailing is required. However, using smaller or mixed-size tiles, particularly for smaller or less regular spaces, and around furniture and fittings (e.g. basins, toilets etc) can result in a significant reduction of tile wastage (Fig. 2.10.2). Tile sheets can also offer improved workability and even the smallest offcuts can be easily reused.

Fig 2.10.2 Smaller tiles: reduces volume of offcuts.




Exact materials saving will depend on the precise dimensions of chosen tiles, room layout, furniture and fittings, and the level of skill of the installer.

In many cases, moving away from larger sized tiles, or optimising tile sizes, will result in fewer offcuts and therefore reduced overall materials use and waste.

Damaged or broken tiles are usually unavoidable. For smaller tiles this clearly represents a much smaller materials loss.

Wastage can be reduced from 15% to 8% or better by careful selection of tile size to suit the space in which they are being used.

Cost implications

Reduction in tile wastage results in cost savings. Value of wasted material can be cut by 50% (typically £2/m2)90

Time implications

Time implications depend on the precise specification of tile sizes and the space they are used in. Although increasing the overall number of tiles could result in increases in labour time, this may be offset if less cutting is involved.

The use of tile sheets which cover larger areas, and are easier to cut, could result in significant time savings.

Dependant on individual room layout and dimensions.

Carbon reduction

Embodied carbon of waste material may be reduced by half. 58.86kgCO2e/100m2 wall space (see table 2.10.5) Total embodied carbon reduction of 7.5% for tiling.


Fired ceramic waste can be recycled at specialist facilities. This includes grinding down and adding to the standard mix for new tiles.91

For standard sized, plain ceramic wall tiles best practice recycled content rate is 46%. For glass tiles, this can be higher.

Up to 46% recycled content for ceramic tiles.

Construct-ability

Tile sheets allow large surface areas to be covered quickly.

Replicability No restrictions other than aesthetic considerations. A slight variation in the overall size of tiles occurs during

manufacturing. Where possible, sufficient tiles for the area to be covered should be obtained in one consignment to avoid mismatching tiles being rejected on site and wasted.

Exact colours may also vary between batches. Depnding on the effect required, contents of different cartons can be mixed to create a more natural finish and colour blend.


Impact on structure None.

Procurement issues Dependent on source/supplier.


Pre-fabricated bathroom pods may include pre-fitted tiles. Factory processes, standardised pod sizes and increased opportunities to reuse offcuts can help to significantly reduce overall waste.


Longevity 60+ years. Ceramic tiles have extremely long lives and are generally replaced for aesthetic reasons rather than due to wear and tear.

Packaging Tiles are necessarily supplied in protective packaging. This is usually cardboard and can be recycled assuming it is not contaminated.

Standardisation Wall and floor tiles are available in a range of standard sizes

Dimensional coordination Tiles should be carefully selected to match the size of room. For hand made/bespoke tiles, lower tolerances can be accommodated

Repairability Broken tiles must be replaced. Matching may be problematic if spares are not available.

Deconstructability Tiles rarely survive intact when removed from walls or floors. Opportunities for reuse are therefore very limited.

90 Faithful+Gould. Based on 100mm x 100mm tiles instead of 400mm x 400mm. 91 Johnson Tiles [http://www.johnson-ceramics.com]


2.10.4 Additional information Pre-fabricated bathroom pods may include pre-fitted tiles, and this factory production can

significantly reduce tile waste on site.

Ceramic tiles are extremely durable. Consider refreshing rather than replacing on existing buildings.

Broken tiles may be used in mosaics to provide an attractive and distinctive finish.


Table 2.10.5 Embodied carbon savings of reducing tile wastage Embodied carbon calculation Standard tile thickness (mm) 8mm Tile volume 0.008m3/m2 Tile density 1900kg/m3 Tile mass 15.2kg/m2 Embodied carbon 0.43kgCO2e/kg Embodied carbon 6.54kgCO2e/m2 Total embodied carbon of waste (kgCO2e per 100m2 wall space based on 15% wastage rate)

115.1kgCO2e

Total embodied carbon of waste (kgCO2e per 100m2 wall space based on 8% wastage rate)

56.24kgCO2e

Total embodied carbon reduction for waste (kgCO2e per 100m2 wall space) 58.86kgCO2e Total embodied carbon reduction (% per 100m2 wall space) 7.5%


Appendix 1 Long list of potential design details

IDEAS TO REDUCE WASTE IN DESIGN Use similar designs/materials in both projects so waste in one project can be used for the other (lagged programme between the two) Reuse car park as fill Wire cages parking lot as SUDS (A-C) Block work instead of plasterboard (more structural load and foundations) (A-B) Don’t use plasterboard or dry lining in build (internal) Packaging to be reused as part of public art installation e.g. elephant in Rowan House or Kitchen worktops Reuse car park cover for internal floor finish in Colchester (quality constraints) Site strip/enabling works waste to be reused Cavity fill with asphalt Re-melt tarmac and pour into moulds for landscaping and water proofing (B-D) Block work instead of plasterboard (more structural load and foundations) (A-B) Use all waste products as cladding materials Wire cages parking lot as SUDS (A-C) Bricks and rubble for landscaping or put in wire cage for fence and street furniture Custody area block work – use recycled blocks Re-melt tarmac and pour into moulds for landscaping and water proofing (B-D) Funding rules require that at least 70% of the development must be new build. The sports hall is demolished in the early stage of work, and the crushed aggregate will form a working platform. There is plenty of space for on-site storage (e.g. tennis courts). A soft strip pre-demolition phase is planned before full demolition. Timber – segregated on site Bricks - Cement mortar used - no good for reclamation Limited opportunity to re-use from demolition but could be some from PRU (another Phase 2 project with existing buildings)

Demolition material for hard landscaping Sloping site / backfill Use on green roof As sub-base Coordination between other phase 2 builds – for material sharing Rubble for thermal heat stores Recycled aggregate in concrete mix Furniture and equipment - Reuse for charity Recycle through supply survey Timber flooring materials Roof tiles (depending on condition check) - Clay tiles from Seacole (in poor condition) - local reclamation centre required External lighting (flood lights) Structural steel (gets recycled, no plan to use on-site) Reclaimed benches Retention of reclaimed materials for the purposes of education in the new school Re-use (retention) of existing brick boundary wall on Donegal St as a retaining wall, other boundary walls will be demolished. (being considered seriously)

1.

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Improving specifications of materials on site, technical compost


IDEAS TO REDUCE WASTE IN DESIGN Contractor’s internal symbiosis;

Use of existing material from adjacent building sites (Dependent on the level of contamination) Some slate is being excavated and could either used on site for walls, landscaping or drainage. There may be quality issues with this Bubbledeck or similar alternative could be used to reduce the quantity of concrete in floor slabs of first floor Concrete could be specified to contain a recycled content or PFA Sports hall will have a sprung timber floor – could a second hand floor be found? The front of the gym will have to be removed to provide a large window to allow light in – this could be used as fill or sub base Demolition of existing plant room and changing rooms will provide fill or sub base Outbuilding, repair existing; spares. Slate roofs and LS bricks (reuse in haha wall). Car park tarmac – base material Hedges – compost on site Haha being dug out, reuse in landscaping? Children’s playground being moved Interface, take away carpet Reuse old metal safe doors – architectural salvage A tarmac public footpath runs across part of the site. An application to divert this has been submitted and a decision is awaited. The tarmac could be left in place or reused elsewhere on site Carpets in classrooms could be carpet tiles to reduce off-cuts and reduce waste when repairs are required Could a water tank be sourced from one of the existing schools? Could soil be remediated and used on another part of the MoD site? Cost likely to make this unviable

Wall protection could also be moveable – so only protecting the area being worked above There is the opportunity to excavate additional slate for these uses Recycled materials could be specified for landscaping

Concrete paving/ blocks already specified for paths around classrooms as are better than pre-cast in terms of embodied energy – this could be extended down to the sports fields Rotary Piling suggested for foundations to reduce excavation – may cause stability problems with the listed wall Software modelling noted above but with the input and coordination of the subcontractor

Net amount of material required measured accurately by QS Reusable packaging for standard elements to optimise the process Establish project wastage KPIs End of life considerations taken into account during design requiring manufactures and subcontractors input Eliminate basement and associated excavation Off site cladding panels – reuse waste in factory, reduced weight and therefore materials in foundations Prefabricated stairs Prefab stair wells Thermo deck off site pre cast concrete structure Modular design 2.

Off

Sit

e co

nstr

ucti

on/

Use prefabricated timber construction instead of concrete (thermal mass issue)


IDEAS TO REDUCE WASTE IN DESIGN Two sets of stairs in the admin block are already planned to be pre-cast. Could standard moulds be used? The external cladding could be modularised, this could reduce cost and increase speed of construction. Rendering would fit in with local area but there may be a weather issue. Cladding could still be brick Can all toilet blocks be standardised and brought in as pods? Toilets and changing rooms could be brought in as pods? Access would make this nearly impossible. Changing rooms to have OSM components for assembly on site? Concrete will all be cast in-situ as the shapes don’t lend themselves to pre-cast. Beam and block could be considered. External cladding could be cut to size off site External cladding to be cedar or oak, depending on availability. Could be panellised. Glazing sizes could be altered to fit with this

Gym roof lights to be translucent panels that can’t be cut to size so roof tiles will be removed to fit. Tiles are thought to be clay and could be reused BUT won’t be available until the end of the project. May be too late, could be used in access ramps? Gym floor to be replaced – could use a second hand sprung floor

External lifts are already being considered instead of ramps which will require a lot of concrete Piling not strips Steel frame (Kit set – recycle off cuts) Reinforced concrete pad (reused substrate) Cladding, prefer OSM to bricks Masonry would be local LS

Plasterboard, replace with: Fermacell – more expensive, but less wastage. More fit for purpose? Stairs Doors (off the peg) Windows, component / on site assembly OSC, form finding software approach to vinyl flooring Pod/OSC of operating theatres Pre-cast / minimise variants of stairs Floor build ups – void formers to reduce in-situ concrete requirement e.g. BubbleDeck

Two classrooms need to be 10m2 larger than the others, currently these are wider but they could be longer instead. This would make the toilets and two classrooms a standard layout with an additional length which would be easier for off site manufacture of components Building steel framed – driven by contractor - grid at 4.735 centres – not standard – could grid be changed? Floor slabs are planned to be cast in situ – most of them could be pre-cast. Ground floors will all have under-floor heating Pool plant could be bought as a package – access may restrict this Lift Can the 12 classrooms be made identical and be made as pods off site?

Off-site construction and manufacture already an integral part of the method of working. Pre-fabricated services sections for all heating, electrical, ICT, phone, fire alarm, sprinklers systems Modular plant rooms


IDEAS TO REDUCE WASTE IN DESIGN

Modular form work (not PCC) and grid dimensions to minimize in-situ concrete slabs Tea-point stations Bespoke science and DT desks Off-site staircases (x4) Toilet pods Toilet services modules Sports changing rooms – toilets & showering services modules Standardisation of bedroom and bathroom units (Plug-ins) Theatres to be manufactured as modular units Offices for administration to be manufactured as modular units Façade modular panels Panelock Post-tension flat slabs to minimise slab depth, flat soffit, partitions and formwork. Also implications for deconstruction. Piles foundations – rotary system to reduce the amount of spoil to be reduced Modular shuttering for concrete Pre-cut wall elements and delivered with doors and clip into place (A-B) Prefabricated core with M&E openings Pre-cut wall elements and delivered with doors and clip into place (A-B) Create module for walls and windows to reduce cut offs especially in dry walls Consider construction / manufacturing procedures to eliminate/reduce waste Revisit model to schedule plasterboard, insulation Revisit model to check for pipe lengths, clasps Time construction and delivery through 3D model and locate and plan storage for exact quantities Concrete core shuttering and standard modular openings Ensure sizing of services of materials as accurate as possible, less material used (programme issues0 Coordination of stairways Design practices already embody elements of dimensional coordination Structural grid / modular (lesson learnt from Phase 1) Standardised windows Standardised doors Plasterboard - Ordered to size of module Re-use of off-cuts (also already occurring?) Flooring – use of tiles / sheet flooring - Carpet, marmoleum, non-slip, sports floor Rounded edges and non-orthogonal building shapes reduced Positioning of buildings to maximise any opportunities on existing site levels Shuttering system – PERI – non timber with integral safety handrail Car-parking areas reduced from 100 (based on Highbury Grove) to 40 Partition sizes for class room

Building form and layout, especially grouping of individual units and amount of external walling Regular / orthogonal spaces (may already be occurring) Planning of sheet flooring to minimise cuts and coordinate with coving Modification of building form and layout (BB highlighted risk liability problems here) Perimeter fencing (concern that standardised fencing not appropriate because of varied site levels) Dimensional co-ordination - plasterboard Reduce the amount of excavation – screw piles

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Standardisation


IDEAS TO REDUCE WASTE IN DESIGN Design simplification Steel frame could be co-ordinated with OSM cladding panels (1200mm standard).

Windows would need to be standardised to co-ordinate with the panel systems of steel and cladding. All could be standardised to 1200mm. It is expected that changing the windows to 1200mm would be cheaper than specifying the panellised cladding to match the windows

Working to a 1200mm frame and panel system could allow ceilings and floors to be co-ordinated If the slope on the pool floor is graded over a shorter distance then there would be less off-cuts of tiles

Ceiling tiles and flooring tiles could be chosen instead of sheet/ rolls to reduce off-cuts Sirtex is specified as insulation – could this be replaced with a panel system? Or replace with recycled materials? Sirtex is very efficient as an insulator and allows very thin walls but does generate a lot of waste and is hard to recycle

Ceiling tiles are specified but have high wastage. An open ceiling with baffles is planned for the sports hall but ceiling tiles in the classrooms would provide the acoustic buffering to keep classroom noise down and prevent excessive noise from rain on the metal roofs. Potential to make a feature of areas of exposed ceiling to prevent the need for cutting ceiling tiles Specification review – e.g. double or single board Specifying recycled content in materials Coordination of planning grids with materials throughout the building Full door height or doors with fanlights versus overboard Rationalisation of partition layouts with suspended ceiling Find an alternative to black tarmac (slate with resin?) Recycled content – recycled slate / demolition in concrete or screed (need for on-site mixing plant)

Smaller plasterboards as easier to handle – need for discussion with specialist subcontractors Unitised cladding systems, manufactured off site Reuse of demolition as fill or landscape Reuse aggregate in concrete from this or other sites in Bristol Modular services – off site assembly into packages Shuttering with regular modules – e.g. 45 degree rotations between beams Volumetric WCs and other areas, e.g. staircases Standard ceiling grids (in labs) resulting in less cuts but a need for a higher level of M&E coordination Engage University – do they have any materials for reuse on site (prefab building on site being dismantled)? Solar re-heating collector Resin on top of concrete or screed in Maths lecture theatres in basement – less waste due to pouring Maths building: Finishes – carpet tiles review – must be Omni-directional Salvage assessments of site Walkways (bridges) – steel prefabricated already Match skirting boards with off-cuts Modular and Volumetric Lab benches plug and play, made off site Client Furniture strategy – consistent & flexible – long term impact Packaging – parallel with consumer purchasing – begin dialogue with suppliers Burning packaging waste on site and use heat – adjacent to hospital – no biomass boiler


IDEAS TO REDUCE WASTE IN DESIGN Chip pallets and plastic for university Site wide strategy to conserve energy Life cycle costing to make mainstream and test decision making Exposed rock gabion walls hard core excavated material Excavated materials used for retaining and landscape features Identify larger contractor storage site – room for waste segregation Rationalise use of building materials De-classify conservation areas – make new buildings more efficient in terms of layout Employ a specialist/’sympathetic’ waste specialist for removing/dealing with waste Contractual documents to specify that contractors supply chain is reviewed at contractor selection Create a financial incentive on the contractor to reduce and recycle waste Talk to suppliers of wall lining systems about reduction of actual material waste opportunities

Method statements from contractors to reduce waste on site and for correct installation of fragile materials Dialogue with plasterboard manufacturer Architects to specify responsibly sourced materials (A-B) Client buy in when it comes to their construction input, e.g. ATOS/SERCO, involve third parties

Architects to specify responsibly sourced materials (A-B) Source materials locally – more likely to recycle and less fuel ‘waste’ in delivery Recyclable fuels – biomass in itself renewable M&E on time Efficient standards and systems already operated Meet environmental standards in Islington procurement code BB have policy on specifying reduced packaging from suppliers BB’s policies on ordering from suppliers - Minimise over ordering Take-back schemes for certain materials, such as plasterboard off-cuts SWMP and monitoring of quantities Good site storage facilities / JIT delivery

Specify increased recycled content (not a direct waste saving but reduces waste sent to landfill) Simplify specification Early supply chain involvement Specification writing, added flexibility in the contract Appropriate procurement and incentives Take-back systems could be specified for plasterboard and ceiling tiles off-cuts Take-back systems could be specified for plasterboard and ceiling tiles off-cuts Precast basements No basements - no excavation so no internal fill Use of natural materials – long term durability so less maintenance and replacement

Steel frame Volumetric systems for offices / labs (pods) Standard University construction type / grid Modular / demountable partition systems Recyclable / Deconstructable partition systems Modular structure, series of facets rather than circle. Only circular part is outer panel cladding. All beams are radial. Cantilevered flat slab. Precast concrete frame rather than in situ pouring

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No ceilings to non-lab areas


IDEAS TO REDUCE WASTE IN DESIGN Management of waste / sign off of waste per package – responsibility at point of tender

Plasterboard strategy – future flexibility – dimension and consistency Rock for façade – Serra Stone – Quintain developed process of developing/manufacturing façade stone on site Bubbledeck – minimise the weight of the structure – reduce slab material use Omni-deck – no shuttering but quality/finish issues Reuse second hand installation – issues with warranty, etc Auditorium – raked timber (built on site) or steel modular systems build off site Explicit part of brief? Client buy-in?

Mechanical handling of plasterboard or protection on board edges at manufacture to minimise damage Find out what waste current products produce when deconstructed Brickwork and mortar to be recyclable (A-B) Reuse car park cover/recycled demolition product Consider reuse potential once design life complete Pre-fabricated elements should be taken away, detailing? Brickwork and mortar to be recyclable (A-B) ‘Best fit’ material selection (not too large selection – stone, etc), broken down and reused at later date Screw fix where possible for better deconstruction

Installation of Wi-Fi systems could reduce cabling required around the school but could have a significant adverse effect on the carbon footprint (very energy intensive in use) and have cost implications for repair and replacement Grasscrete could be used for the car park, fire access area and deliveries areas? Although there is interest in future adaptability of the building and design for deconstruction, the focus during the workshop was on the re-use of materials and components, off-site construction, procurement, and dimensional coordination. Adaptability plans for the extended use of the buildings by the community are already included in the specification. This is being implemented as a zoning system so that certain sections of the school can be zoned off for use. Wired & wireless ICT system – exists as back-up, future/existing use

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Identify any future adaptations or extensions to the school, such as possible final link building, where dismantling to facilitate additions.


Appendix 2 Net Waste Tool wastage rates

Element Sub element Component Wastage rate standard (%)

Walls, Floors and Ceilings - finishes Walls 12.5mm plasterboard, paint finish 22.5 External Walls Outer skin Brickwork 20 External Walls Inner skin Blockwork 20 Walls, Floors and Ceilings - finishes Floors

80/20 wool/nylon carpet, natural fibre underlay 20

Internal Walls Internal walls Fabric-covered framed panelling 15.45 External Walls Insulation All types 15

Roof Roof covering 3 Coat Asphalt roof covering, solar reflective paint 15

Structural concrete Structural concrete Steel reinforcing 15 Substructure Ground slab Concrete Pre Cast, Beam and Block Flooring 14

Floors Concrete pre cast

Pre-cast concrete 50 thick Omniadec plank; concrete topping; 300mm thick overall; reinforcement not exceeding 5% 13

Earthworks Landscape Fill / hard standing / drainage 10

External Walls Outer skin Limestone cladding 10

Internal Walls Internal walls Window boards, MDF, timber panelling, timber stud etc 10

Substructure Foundations user defined Steel reinforcement in foundations 10

Walls, Floors and Ceilings - finishes Walls Panelling, battening etc 10 Walls, Floors and Ceilings - finishes Floors

Hardwood flooring, marble tiled flooring, laminate etc. 10

External Walls Outer skin Tile cladding, blockwork cladding, timber cladding 8.1

Roof Roof covering Tiles/slate 8 Walls, Floors and Ceilings - finishes Walls Ceramic tiles 8 Walls, Floors and Ceilings - finishes Floors Quarry tiles, granite tiles, ceramic, terazzo etc 8 External Walls Outer skin UPVC Shiplap cladding 5.25 External Walls Outer skin Render, plaster etc 5 Internal Walls Internal walls Wallboard, particle board 5 Structural concrete Structural concrete

Bases, footings, pile caps, ground beams, walls, slabs, piers 5

Substructure Foundation Concrete foundations, ground beams, piles etc 5 Walls, Floors and Ceilings - finishes Walls Render, plaster etc 5 Walls, Floors and Ceilings - finishes Floors Carpet tiles/vinyl sheet flooring 5 Walls, Floors and Ceilings - finishes Ceilings Plaster 5


Appendix 3 Cost comparison table Design detail Option Cost

(£) Unit Fair faced concrete slab instead of Armstrong Dune suspended ceiling Armstrong Dune suspended ceiling 30.00 /m2 ceiling Additional cost of fair faced formwork to soffit & 2 coats emulsion paint 12.00 /m2 ceiling

Exposed ceilings

Sub-alternative of canopy suspended ceiling system ~ 25% of ceiling to have canopy (incl ff/painted soffit) 19.00 /m2 ceiling Thin bed block wall instead of traditional block wall with mortar joints 100mm Celcon block wall with 10mm clm 1:2:9 mortar joints 27.86 /m2 wall area

Light weight concrete blocks

100mm Celcon AAC block wall with 3mm Celcon thinjoint mortar 29.42 /m2 wall area PVC pipework instead of copper Copper pipework with end feed capillary joints (weightings 50%:15mm, 30%:22mm, 20%:20mm) 25.00 /m of pipe run

Flexible plumbing

Hep2O pipework with proprietary joints (weightings 50%:15mm, 30%:22mm, 20%:20mm) 21.00 /m of pipe run Adopt Knauf system for creating door openings in plasterboard stud walls instead of traditional "cut-out" method Plasterboard discarded per door opening (traditional method) 8.00 /door opening

Low waste door jamb

Plasterboard discarded per door opening (Knauf method) 0.00 /door opening Castellated steel beams instead of BS4 steel beams 305 x 305mm UC x 240kg/m ~ beam for 7.5m span 414.00 /m of steel beam

Castellated beams

Ditto but castellated web (218g/m) 316.00 /m of steel beam Polished concrete floor instead of terrazzo tiles 300 x 300 x 28mm Terrazzo tiles laid in semi-dry screed 47.00 /m2 floor area

Exposed concrete floor Power float unset concrete & apply surface hardener 8.00 /m2 floor area

Post tensioned concrete slab instead of insitu reinforced concrete slab Post tensioned slab 125.00 /m2 slab

Post-tensioned slab

Traditional reinforced concrete slab 192.00 /m2 slab Rotary bored piles instead of CFA piles CFA pile; 450mm diameter; 18m deep 1,260.00 /pile

Rotary displacement piles Rotary displacement pile; 450mm diameter; 7½m deep 863.00 /pile

340mm Bubble-deck concrete slab instead of 410mm reinforced concrete floor BD340 slab 137.00 /m2 slab

Voided biaxial slab

410mm Solid reinforced concrete floor 181.00 /m2 slab Tile detailing to reduce waste from 15% to 8% by using 100 x 100mm instead of 400 x 400mm ceramic tiles Wastage costs 100mm x 100mm ceramic tiles 2.16 /m2 tiled area

Tile detailing

Wastage costs 400mm x 400mm ceramic tiles 4.05 /m2 tiled area Notes & assumptions All figures include prelims@15% All figures exclude VAT & consultants fees All figures based on prices prevailing at Q2, 2009 Figures prepared by Steve Watson of F+G 01/05/09

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Design detailing for materials resource efficiency - … detailing - evidence base... · Design detailing for materials resource ... Voided Biaxial Slab, photo courtesy of Bubbledeck