Benefits of off site manufacture

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Leo Caldwell
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Case Study Benefits of off site manufacture Jocelyn Park, Somerset Jocelyn Park is a housing development owned and managed by South Somerset Homes Housing Association.

1 Case Study Benefits of off site manufacture Jocelyn Park, Somerset Jocelyn Park is a housing development owned and managed by South Somerset Homes Housing Association. There are 64 homes on site designed by Calford Seadon, reaching EcoHomes very good, and intended for rent and shared equity sale. Advanced Panel System (APS) manufactured the timber frame. The construction of 37 dwellings using the APS semi closed panel timber frame system was monitored for 13 weeks between December 2008 and March A site measurement analyst recorded and analysed site skip content twice daily, as well as operative s site activity every hour using CaliBRE and SMARTAudit tools. This case study provides a comprehensive comparison between the APS semi closed panel timber frame system used in Jocelyn Park and a brick and block system used on SmartLIFE project also fully assessed using BRE monitoring tools. Both sites were EcoHomes very good, which is broadly equivalent of Code for Sustainable Homes 3. Start on site - February 2008 Completion - July 2009 Aims of the research To assess the use of Advanced Panel System (APS) in construction of homes against traditional brick and block method in relation to: waste (site and factory); resource required on site; site efficiency and productivity (value added time); environmental impact analysis and end of life assessment; cost Direct and Indirect; installation time health and safety. Completed house Results of this research show The APS system has a very similar cost to traditional brick and block (see page 7). Volume of waste reduced by 27.3% during construction using APS semi-closed panel timber frame system. 27% less labour required for house construction using APS. APS reduces non added value time compared to traditional build There were no reported Health and Safety incidents for operatives working on the off site manufactured products. The Green Guide rating of environmental impact is the same for APS and traditional construction. The APS semi closed panel timber frame system used here is not the most advanced APS product but still demonstrates significant waste savings. If their close panel system was used further reductions could be made.

2 Case study: Off Site Manufacture Somerset Homes

Panelised timber frame system. The Advanced Hybrid Panel.

Panel includes first fix carpentry, insulation and

Benefits Reduced off cuts and site waste.

Factory quality control and improved waste management.

of the product APS house construction process Erect

2 2 Case study: Off Site Manufacture Somerset Homes Features of the Advanced Panel System Introducing APS Panelised timber frame system. The Advanced Hybrid Panel. Timber Frame Wall was used. Brick facing. Panel includes first fix carpentry, insulation and vapour control layer. Benefits Reduced off cuts and site waste. Reduced defects. Factory quality control and improved waste management. Good levels of thermal efficiency and air tightness ((5.4m 3 /(h.m 2 ) on APS site). APS construction process Substructure Technical details of the product APS house construction process Erect timber frame Substructure Erect scaffolding Erect timber frame Internal wall studwork Internal wall studwork Internals External skin (brickwork) Internals House complete External skin (brickwork) House complete

Off Site Manufacture Jocelyn Park, Somerset 3 APS research results performance breakdown (man hours on site) Resource comparison (man hours/100m 2 floor built area) Total average man hours to

3 Off Site Manufacture Jocelyn Park, Somerset 3 APS research results performance breakdown (man hours on site) Resource comparison (man hours/100m 2 floor built area) Total average man hours to contruct 100m 2 floor area: APS Brick and block hours APS Jocelyn Park Brick and block The APS semi closed timber frame system requires an average 27% fewer man hours during construction than the brick and block example. This is because most of the superstructure construction for APS is prefabricated. This includes the internal leaf and battens for dry lining and internal walls. Construction duration for APS from foundation to handover was 12 weeks. For the traditional build monitored for this project the programme was 31 weeks. Substructure Superstructure Internals Predictably substructure and internal work require much the same resources for APS as for traditional build. These parts of the process have not been altered by using the APS product and depend more upon building design. Monitoring at Jocelyn Park has highlighted the benefits of using off site construction e.g. short construction duration to achieve weather tightness quickly, and flexibility of delivery of materials from factory to site. In this case the factory was relatively close (65 miles) to the site and good communication between site and factory managers resulted in just in time delivery and subsequent maximisation of operatives time on site. Prefabricated panels that have been erected. It only takes 3 days to achieve a weather tight plot, in contrast to several weeks for traditional build, making APS less dependent on weather conditions. On site performance and efficiency, APS compared with traditional The proportion of non added value time on APS is 9%, which is lower than the average proportion of 12.5% recorded on numerous sites by BRE using CaliBRE. This highlights that the APS system has been used efficiently on Jocelyn Park. On the SmartLIFE site using the brick and block system, the efficiency was affected by design changes requiring remedial work. Added value time is spent on activities that directly add value to the construction being undertaken (e.g. laying a brick). support time is spent on activities which directly support added value activities (e.g. supervision time), statutory time is time expended by operatives that support legislation or regulations (e.g. break time). non added value time is time expended which adds no value to the project (e.g. remedial work, or time wasted because of a late delivery). Construction productivity comparison for APS and Brick and Block APS Brick and Block Added value Non added value Added value support Added value Non added value Added value support Statutory Statutory 70% 9% 10% 11% 72% 12% 5% 11%

4 Case study: Off Site Manufacture Somerset Homes Overall waste comparison Waste breakdown m 3 per 100m 2 of build The APS transfers a significant proportion of the operation from site to the factory

When the masonry home was studied only site waste was measured. Even so, the amount of waste generated is 27% lower using the APS system.

The use of APS system reduces insulation waste because cavity wall insulation is installed in the factory where off cuts are reused.

panel system, some of which could be returned to the factory. m 3 Overall waste breakdown for brick and block (site waste) 0 1 2 3 4 5 6 Concrete 5.03 Ceramic 4.

4 4 Case study: Off Site Manufacture Somerset Homes Overall waste comparison Waste breakdown m 3 per 100m 2 of build The APS transfers a significant proportion of the operation from site to the factory which reduces site waste. For this reason, as well as looking at site waste only, the waste generated in the factory for APS has also been included in this analysis. When the masonry home was studied only site waste was measured. Even so, the amount of waste generated is 27% lower using the APS system. The concrete waste has been reduced significantly by using manufactured timber inner leaf, replacing concrete blocks. The use of APS system reduces insulation waste because cavity wall insulation is installed in the factory where off cuts are reused. Although waste is reduced, site monitoring highlighted an opportunity for further reduction related to the large quantity of timber and packaging waste produced from the semi closed timber frame panel system, some of which could be returned to the factory. m 3 Overall waste breakdown for brick and block (site waste) Concrete 5.03 Ceramic 4.05 Packaging Timber Plaster Insulation Cement Electrical equipment Plastics Inert Metals Total m 3 per 100m 2 The proportion of waste for APS produced at the factory is 15%, and on site it is 85%. m 3 Overall waste breakdown for APS (sum of site and factory waste) APS Site Waste m 3 per 100m 2 of build Cement 0.11 Ceramics 1.30 Concrete 0.26 Inert 0.12 Insulation 0.41 Metals 0.17 Packaging 3.45 Plaster 1.66 Plastics 0.94 Timber 4.89 Total Concrete 0.26 Ceramic 1.30 Packaging Timber Plaster 1.66 Insulation 0.43 Cement 0.11 Electrical equipment 0 Plastics 0.94 Inert 0.12 Metals 0.17 Miscellaneous Total m 3 per 100m 2 Site waste Brick and block offcuts Packaging waste Plasterboard off cuts Timber waste

Off Site Manufacture Jocelyn Park, Somerset 5 Cause of waste (m 3 per 100m 2 ) This table compares the cause of waste.

Cause of waste Brick and Block APS Design changes 1.32 0.63 Off cuts 12.21 9.72 Miscellaneous 1.82 0.09 Packaging 3.87 5.33 Site Clearance 2.41 APS factory waste At the factory a total of 2.

Timber forms 62% of the factory waste from APS with packaging at 22%. Below is a description of the stages of production and the origin of waste streams.

stages: 1) Cutting timber to make up frames. Timber makes the panel. The studs tend to be the same length but horizontal plates vary.

5 Off Site Manufacture Jocelyn Park, Somerset 5 Cause of waste (m 3 per 100m 2 ) This table compares the cause of waste. The detailed waste monitoring process identifies why the waste is produced and therefore how it can be reduced. This confirms the high proportion of packaging waste produced using the APS system. Cause of waste Brick and Block APS Design changes Off cuts Miscellaneous Packaging Site Clearance 2.41 APS factory waste At the factory a total of 2.43m 3 per 100m 2 finished home s floor area of waste is generated. The graph shows waste generated at the APS factory, separated into product streams. Timber forms 62% of the factory waste from APS with packaging at 22%. Below is a description of the stages of production and the origin of waste streams. Factory waste Plastics packaging 22% Other 7% Packaging 8% Insulation 1% Timber 62% Throughout the APS construction process a lot of timber is cut to size, with waste occurring at the following stages: 1) Cutting timber to make up frames. Timber makes the panel. The studs tend to be the same length but horizontal plates vary. For this reason there are quite a few untreated timber off cuts produced at this stage. 2) Automated milling out of building openings. This is the largest producer of waste timber as currently whole sheets are attached to each side of the frame and the openings are then cut out, leaving regular sized pieces of Orientated Strand Board (OSB). 3) Insulation. There is very little waste of the actual insulation material itself, but packaging is disposed of. 4) Shrink wrapping. Finished frames are shrink wrapped to protect them during transportation. As frames are different shapes there are always off cuts. 5) Structural I-Joists. There are off cuts of I-joists created from making the floor cassettes.

6 6 Case study: Off Site Manufacture Somerset Homes Management of APS waste at factory Product description Glue Lam - laminated timber used for structural details in the main frame. Orientated Strand Board (OSB) Structural, untreated timber I-Joists Insulation Panel shrink wrapping Packaging Plasterboard/gypsum fibre board Waste Destination Off cuts are reused as door and window lintels. Hard to reuse and currently the largest waste product of the factory. On the fully closed panel APS system, gypsum fibre board is fixed at the factory for drylining. This has a structural performance similar to OSB which means that for the more advanced APS products less OSB is used. All off cuts are measured and logged so they can be used as small spacers, or noggins in the making up of some of the frames (1 in every 4 panels is created using a high percentage of off cuts). Combination of untreated timbers and OSB, deemed contaminated. Recycling is hard and dependant on transfer station processing ability (not available at local transfer station). Some off cuts are reused, but the rest go to landfill. Little insulation is wasted because timber frames are designed to allow for exactly ½ of each roll of insulation to fit in-between each stud. Excess plastic is returned to the manufacturer. Used wrapping plastic on site is responsibility of the site management company, sent to landfill in this case. Packaging is segregated and packed into large bags (1m³) that are removed by the recycling company. Collected by British Gypsum and recycled. End of Life pre-demolition audit A pre-demolition audit assesses the quantity of material types produced and their recyclability at the end of life. 100m² floor area of a traditional brick and block house was compared with 100m² floor area of APS construction. The greatest proportion of APS material is concrete (foundation and roofing tiles), followed by ceramics (bricks to clad the building) and then timber (mainly soft timber, oriental strand board (OSB), plywood and MDF). An estimated 91% of this is currently recyclable. The traditional method disposes of no material at the end of the product s life, but the overall quantity of material used is greater compared to APS, which does dispose of 8.05 tonnes per 100m 2 floor area. Although more waste is produced using brick and block, the amount of waste going to landfill is slightly higher for timber frame. This is because of the high quantity of composite timber waste including OSB and glue lam, which is harder to recycle for waste transfer stations than soft untreated timber. End of life destination of materials Recycle Dispose Reclaim te unit 81.2t / 100m t / 100m t / 100m 2 4.4t / 100m 2 APS Brick and Block

7 Off Site Manufacture Jocelyn Park, Somerset 7 Cost The cost of construction using APS is similar to the cost using brick and block. The cost of the material is higher using the APS system, but the labour cost is cheaper due to lower man hour requirements. Cost comparison of the APS versus a brick and block system: Cost comparison ( /m 2 ) Brick and Block averages Timber frame APS closed panel Cost breakdown comparison Preliminaries External works On site labour On site materials Brick and Block ( /m 2 ) On site Labour 234 On site Materials 412 Off site Materials 0 External Works 165 Preliminaries 192 Total 1003 Preliminaries External works Off site materials On site labour On site materials APS Timber Frame ( /m 2 ) On site Labour 166 On site Materials 356 Off site Materials 133 External Works 165 Preliminaries 179 Total 999 True cost of waste ( /100m 2 floor area) True cost of material waste ( /100m 2 floor area) This is based on the cost of the materials, the assumption of 30/m 3 labour cost to collect the waste and put it in the skip and the cost of 150 per 8 yards skip. The cost of material waste (excluding packaging) represents 1.38% of the total construction waste. Material Mineral wool 7.70 Acoustic Batten Mortar Blocks Batten Chipboard Flooring MDF Ply Roofing Tiles Plasterboard Bricks Total

8 8 Case study: Off Site Manufacture Somerset Homes Monitoring Tools Mace and BRE conducted the research and monitoring on this site and put together this case study, and another on a commercial office building in London. Mace and BRE used the established systems of SMARTAudit and CaliBRE to carry out monitoring on site. SmartAudit is a robust and accurate mechanism by which waste can be benchmarked and categorised. The data can be used to highlight opportunities to reduce waste arisings, reuse at source and maximise recovery to extend material life cycles. Two hours a day are spent by the site observer recording the waste information including: skip location; product and product sub-group (e.g. product packaging; sub-group cardboard); cause of waste (identifies which operations are creating the waste, e.g. design, packaging, methods of work, and then the cause, e.g. untrained labour); work package (identifies the part of the build programme the waste has arisen from, e.g. superstructure, and the package, e.g. timber frames); product dimensions (height, width, depth without including void spaces); other relevant notes are recorded; all data is recorded on a hand held computer and then uploaded to a computer. CaliBRE is a measurement tool developed from extensive experience by BRE in the measurement and productivity assessment of various methods of construction. The main task of the CaliBRE toolkit is to use real time performance monitoring to measure on-site efficiency and objectively assess actual construction productivity and performance. The process of monitoring using CaliBRE is similar to SMARTAudit in that the observer records the location they are observing, but instead of monitoring waste the observer is monitoring personnel on site, and waste in terms of non-value added time. Therefore the location, work package and activity being carried out are recorded, along with any cause of non-value added time. Additional information For more information on off site technologies and waste reduction: Envirowise provides free government-supported environmental consultation, advice, and documentation for UK businesses. Buildoffsite is an industry-wide campaigning organisation that promotes greater uptake of off site techniques by UK construction for all markets. WRAP (Waste & Resources Action Programme) helping the construction industry cut costs and increase efficiency through the better use of materials. While steps have been taken to ensure its 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. 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 our Terms & Conditions on our website Waste & Resources Action Programme The Old Academy 21 Horse Fair Banbury, Oxon OX16 0AH Tel: Fax: info@wrap.org.uk Helpline: freephone

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