Building information modelling life cycle assessment An introduction to IMPACT

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1 Information Paper Building information modelling life cycle assessment An introduction to IMPACT Daniel Doran This Information Paper is for construction industry professionals who have an interest in assessing embodied impacts and want to know more about IMPACT and automated life cycle assessment (LCA) in building information modelling (BIM). This includes those involved in embodied impact consultancy, BRE Environmental Assessment Method (BREEAM) Assessors and BREEAM Accredited Professionals, environmentally aware designers and construction product manufacturers. It begins by introducing embodied impacts and how they are measured using LCA. This is followed by a review of the key themes and advantages of building-level LCA, integration in BIM and BREEAM. After reading this Information Paper, readers will understand how BRE is approaching building-level LCA, and how it is implemented in BIM through IMPACT. 1 Introduction BRE has played a key role in assessing the environmental impact of construction for over 20 years. In this time, interest in assessing embodied environmental impacts has increased markedly. Construction professionals understand that improvements in resource efficiency are vital in a world of finite resources, and that impacts from buildings extend well beyond the operational energy of heating, cooling and power. Although life cycle assessment (LCA) is recognised as the best way to quantify these impacts, the profusion of standards, methodologies, data sources and tools can be bewildering to non-experts. a wide range of design tools. The first IMPACT Compliant tool by Integrated Environmental Solutions Ltd (IES) was released in For more information on the IMPACT project, see Box 1. Box 1: The IMPACT project The IMPACT project is led by BRE, in partnership with Integrated Environmental Solutions Ltd (IES), WD Rethinking Ltd and AEC3 (UK) Ltd. The project is officially supported by the Construction Products Association, Faithful+Gould, RIBA and NBS. IMPACT received funding from the Technology Strategy Board and was arranged into two phases: Phase 1: Development of the IMPACT method, data and production of the first IMPACT Compliant tool (by IES). Phase 2: Production of a specification of the IMPACT method to facilitate further implementations of IMPACT by other software developers. IMPACT Compliant tools offer both LCA and life cycle costing analysis functionality and are intended for construction industry professionals including architects, specifiers, engineers, quantity surveyors, constructors and specialist environmental consultants. The construction industry has also begun gearing up for the adoption of building information modelling (BIM), where 3D geometry and other types of information are combined into a single, integrated model. The combination of these factors has paved the way for BRE and three other partners to produce IMPACT. IMPACT is not a single software application; it is a method for consistent and robust building level LCA and life cycle costing for incorporation into

2 2 2 Embodied impacts The embodied impact of a building commonly refers to the effects on the environment due to the life cycle of the building other than heating, cooling and power (known operational impacts). This includes the extraction and production of materials, manufacture of construction products, transport, installation, maintenance, demolition and waste (Figure 1). These life cycle stages are defined in detail in BS EN 15978:2011 [1]. There are two broader definitions in common use: cradle-to-gate which covers impacts arising from the production of construction products only, and cradle-tograve covering cradle-to-gate impacts plus all the other life cycle stages listed above. A range of units are used to quantify embodied impacts including embodied carbon, water, ozone and toxicity indicators (for a complete list of BRE indicators, please visit The unit used for embodied carbon may be kilograms of carbon dioxide (Kg CO 2 ) or Kg CO 2 equivalent (kg CO 2 e, note the e suffix) which includes other gases that cause climate change. 2.1 Embodied vs operational impacts Operational impacts are the dominant source of environmental impact over the life cycle of a building. This is particularly true for existing buildings built to a lower thermal performance specification. However, as regulation gradually reduces operational impacts the gap with embodied impacts is narrowing. For some new buildings, we may be at the point of parity. As an illustration, if the overall operational carbon emissions of a building are 50 kg CO 2 /m 2 /yr and embodied carbon is 1000 kg CO 2 /m 2 it would take around two decades for the operational carbon to catch up with the embodied carbon. If plans to decarbonise grid energy supply are successful this time period will increase substantially. Moreover, embodied carbon from the production of construction materials has an immediate effect on the environment, contributing to global warming even before the building is opened. So, with only a short time to avoid dangerous climate change, it is clear that embodied carbon should be taken seriously. IMPACT Compliant tools provide robust embodied impact assessment functionality that can be integrated with operational impact assessment, allowing the balance between the two elements to be understood and the design to be optimised. 3 Measuring the embodied impacts using LCA LCA is the discipline concerned with measuring and assessing embodied environmental impacts. International and European standards provide general rules for carrying out LCA. Different industrial sectors and LCA organisations then develop more detailed rules and interpretations known as an LCA methodology, or product category rules (PCRs). Datasets are selected and combined in accordance with the methodology in order to estimate the impact of the system under assessment, eg a construction product. The methodology defines the environmental impact issues considered, and how they are quantified and communicated as indicators. An LCA of a whole building (building-level LCA) typically involves combining existing LCA data and quantities for each of the materials/products in the building. Depending on the data source used, the embodied impact results for a building can vary considerably. To maintain a high level of consistency, it is advisable to use LCA data from a single source or use a buildinglevel LCA tool, like an IMPACT Compliant tool, that contains verified and consistent LCA data. 3.1 Environmental issues and indicators Environmental issues considered in an LCA tend to focus on those that are most relevant to the system (eg product or building) studied and of the greatest concern to society, such as climate change. In an LCA study each issue is characterised using a unit, such as a kg CO 2 equivalent for climate change, to provide a quantified estimate of the impacts associated with the system that is being assessed. To gain a holistic view of the environmental impact it is necessary to use several indicators covering other issues like water scarcity, toxicity, ozone and resource use. Difficulties are likely to arise, particularly for non-lca professionals, when trying to assess performance by comparing several diverse indicators at once as they all use different units and vary in terms of importance. To provide a solution, BRE provides an additional summary indicator called BRE Ecopoints that combine all the 13 issues into one score. For more information on the issues, indicators and Ecopoints used by BRE please visit Reducing embodied impacts The embodied impact of different construction materials varies considerably. If material A, for example, has half the embodied carbon of material B then, all other things being equal, material A would represent a significant saving of carbon overall. Unfortunately, it is rarely that simple. Resource extraction Processing and manufacturing Construction Maintenance Demolition disposal/recycling Figure 1: Basic cradle-to-grave life cycle of a building

3 3 Material B may be inherently stronger than material A, so less is required to achieve the same function. Or material A might be a sheet material that requires an additional substrate C for structural integrity. Alternatively, material A might have a long service life, while material B needs to be completely replaced half way through the life of the building. When all materials are used in a building, the relationships between them, varying quantities, different service lives, and other factors are taken into account, assessing embodied impacts can be a complex and time-consuming task. To make the process of manual LCA manageable for construction professionals, The Green Guide to Specification [2] has been widely used for many years (eg in BREEAM and the Code for Sustainable Homes). As a manual, element-level LCA method it is simple to use but, as a result, has drawbacks that may be overcome using a building-level LCA approach, such as an IMPACT Compliant tool. 4 Building-level LCA LCA in construction commonly assesses construction products or building elements (eg external walls, roof, floor finish) in isolation. Building-level LCA assesses complete buildings (with or without associated landscaping). This is achieved by measuring and adding together all of the building s constituent product/ material life cycle stage impacts. For reporting, impact results may be broken down, for example, per product/material or by building element (eg substructure, external walls, windows, floors, roofs, doors). Building-level LCA allows substructure and primary structural frame designs (specific to the site and building) to be included in embodied impact assessments. In addition, the designer is able to optimise the relationship of embodied and operational (energy) impacts. For example, finding the best combination of high- and low-mass constructions, where the high-thermalmass material has a relatively high embodied impact but improves operational performance. Building-level LCA means that information about the materials in the building can be specified at the product-level. This would result in an overwhelming number of calculations if it were to be undertaken manually, but the use of BIM streamlines the process. Product-level specification (Figure 2) also means that building-specific details are free for the user to edit. These might include layer thickness, density, service life (how long before replacement is needed) and transport distance. Although changes at this level (eg the rate per m 2 ) may seem small, their effect at the building level can be significant. Building-level LCA provides greater accuracy by allowing users to model as-designed quantities. impact overall (Figure 3). This approach is readily integrated with architectural design process where detail builds up as the project progresses. Early embodied impact reductions can be achieved at the concept stage, followed by later reductions as detailed technical decisions are made. In addition, project-specific geographic differences, like weather exposure which affects durability, can be taken into account. 4.1 Comparing embodied impact performance To assess the performance of a building in terms of low embodied impacts, results can be compared with the results of alternative designs, existing buildings or a reference benchmark. This comparison may be based on one indicator, several or a combined indicator such as Ecopoints. Comparisons will be most meaningful where the building designs compared are functionally equivalent. This could be achieved where each design option meets a detailed brief set by the client/developer. Alternatively, functionally equivalent comparisons can be made to similar existing buildings or a reference benchmark of the same use class (eg office, school, hospital), as is common in cost control. 4.2 Establishing reference benchmarks While comparing alternative building designs with each other is an effective way of discovering an optimum solution for a given construction project, using an external reference benchmark offers an opportunity to assess performance relative, for example, to similar buildings in the same country. Assessing performance against a benchmark provides a means for building designers, assessment schemes (like BREEAM) and regulators to 3D CAD/BIM model Material product specification For each object Building-level LCA tools can allow the designer to iterate through different building shapes, elemental constructions and product specifications in order to progressively reduce the Calculations explore changes to optimise... or... results or or Four studs Three studs, more sheathing Final results Figure 2: Illustration of product-level specification within an element Figure 3: The IMPACT process

4 4 rate the design against other similar buildings, award credit and set minimum standards. BRE intends to stimulate the data gathering of real buildings to improve knowledge of embodied impacts in buildings, set robust benchmarks and pave the way for building-level performance assessment. It is further hoped that regulations based on minimum standards will be introduced. BRE expects to achieve this goal through IMPACT (and equivalent tools). Building designers will be invited to submit their IMPACT BIM to BRE to build a sample of data that is large enough to create viable benchmarks representing average embodied performance for different building-use types. Performance assessment of future building designs will then be based on the percentage difference to the benchmark. Aside from the creation of benchmarks, another advantage of a large sample of real building data is that BRE will be able to conduct essential research to identify the products and elements where embodied impacts are most concentrated and offer the greatest opportunity for reductions. This knowledge can be used to provide guidance to building designers to focus their efforts on certain priority elements and product types, thereby reducing the number of design iterations required to achieve an optimal solution. 4.3 Building-level data gathering and IMPACT in BREEAM The adoption of BIM by the construction industry signals readiness for the integration of building-level LCA in design. BRE has responded through the recognition of IMPACT Compliant tools (and equivalent) in BREEAM schemes. Initially, new exemplary credits will be awarded to projects that use an IMPACT Compliant tool (or equivalent) and submit the results to BRE. Information gathered through this initiative is expected to be the primary way that real building data required for benchmarks and performance assessment will be gathered. Further information on the criteria for achieving these credits can be found in BREEAM technical manuals on the BREEAM website ( BRE anticipates that it will take around two years to collect sufficient data for benchmark reference values to be determined. This will vary according to IMPACT user participation, and common building use type categories are likely to be completed sooner. Once statistically robust benchmarks and a scale for rewarding achievements are available, quantified buildinglevel performance assessment based on IMPACT Compliant (or equivalent) tools will be possible in BREEAM. Capital and life cycle costing Deconstruction Embodied impact assessment Thermal analysis Energy use 5 BIM and LCA The advantages of building-level LCA were explored in the previous section. A valid question is Why isn t it more common? The answer is that the time required to measure (take off) the quantities of products and elements manually from architectural drawings, and combine this with LCA information to compute the building s impact, is onerous. BIM software, like IMPACT Compliant tools, automates the process and improves accuracy, so a building-level LCA can be calculated in a fraction of the time and cost. BIM offers opportunities for making the construction industry far more efficient (Figure 4). The advantages BIM offers cannot be ignored and the UK government will require 3D BIM (with all project and asset information, documentation and data being electronic) on its projects by 2016 [3]. Much of the construction information already required in a BIM can, with some additional work, be used for building-level LCA. As such, the time required is significantly reduced and it is anticipated that as BIM use grows building-level LCA will follow. 5.1 IMPACT Compliant BIM IMPACT is not a single BIM software application, it is a specified method designed for software developers to add IMPACT LCA (and life cycle costing) functionality to new or existing BIM applications. The development of the IMPACT method was split into two distinct phases: Phase 1 covered the development of the LCA method, data and the first IMPACT Compliant applications by IES Ltd ( Phase 2 covered the production of the IMPACT Specification to communicate the precise technical detail of the IMPACT method to software developers to enable further implementations of IMPACT Compliant software and, in addition, IFC requirements for LCA interoperability. Specification Water usage Lighting analysis Maintenance Fire design Compliance Construction Figure 4: Uses for building information modelling

5 5 This approach has been taken to maximise dissemination, consistency, trust and comparability in environmental impact assessment (and life cycle costing). It also means users can benefit from IMPACT functionality inside their familiar software tools and typical workflows. To enable recognition of IMPACT Compliant software a logo has been developed, see Figure 5. Building-level LCA using BIM offers building designers the advantage of a greater accuracy and precision than existing approaches. Elements that are only properly assessed at the building level, such as substructure, can be included. In addition, better integration with other activities is possible, improving workflow efficiency and facilitating overall optimisation (eg of embodied and operational impacts). The IMPACT Specification allows any software developer with a suitable BIM tool to implement the IMPACT method. This approach has been taken to maximise the adoption of the IMPACT method, which, in turn, will provide the industry with much needed consistency and comparability in building-level LCA. Figure 5: The IMPACT compliance logo 6 Conclusion LCA shows that embodied environmental impacts account for a significant proportion of the impact of a building. As regulation gradually reduces operational impacts, the gap between operational and embodied impacts is narrowing. For some new buildings, we may be at the point of parity. With a profusion of standards, methodologies and data sources LCA can be bewildering to non-experts. To bridge the gap, IMPACT contains verified data and follows the principles of European standards for more detailed reporting, whilst offering simplifying solutions such as BRE s Ecopoint indicator for a straightforward interpretation of the results. IMPACT is incorporated into BREEAM with credits available for projects that use an IMPACT Compliant tool (or equivalent) and submit a compliant BIM. Once enough project data is gathered it will be possible to create statistically-robust benchmarks and a credit award system for rewarding low embodied impact performance. In addition, IMPACT will provide users and BRE with an invaluable insight into the nature of embodied impacts in buildings, leading to guidance for building designers on how best to reduce impacts. 7 References 1. BSI. Sustainability of construction works Assessment of environmental performance of buildings Calculation method. BS EN 15978:2011. London, BSI, Anderson J, Shiers D and Steele K. The Green Guide to Specification. BRE BR 501. Bracknell, IHS BRE Press, 2009, 4th edn. 3. Construction Products Association and NBS. BIM for the terrified: A guide to manufacturers. Construction Products Association and NBS, industry-affairs/display/view/bim-for-the-terrified. For many years, tools like The Green Guide to Specification have been available to the construction industry that facilitate robust yet simple LCA of building elements. However, increasing interest and knowledge of LCA, and the increased uptake of BIM, now makes more sophisticated building-level LCA tools a realistic and powerful proposition. IMPACT is BRE s response.

6 6 Project partners Project support group Acknowledgements Acknowledgements The research and writing for this Information Paper has The been research funded and by BRE writing Trust. for this Information Paper has been funded by BRE Trust. BRE Group (BRE) is a world-leading centre of built environment expertise, research and training, and includes a third-party approvals organisation offering certification of products and services to international markets. BRE, Garston, Watford WD25 9XX Tel: +44 (0) enquiries@bre.co.uk, BRE is owned by BRE Trust, the largest UK charity dedicated specifically to research and education in the built environment. BRE Trust uses the profits made by BRE to fund new research and education programmes that advance knowledge, innovation and communication for public benefit. IHS (NYSE: IHS) is the leading source of information, insight and analytics in critical areas that shape today s business landscape. Businesses and governments in more than 165 countries around the globe rely on the comprehensive content, expert independent analysis and flexible delivery methods of IHS to make high-impact decisions and develop strategies with speed and confidence. IHS is the exclusive publisher of BRE publications. IHS Global Ltd is a private limited company registered in England and Wales (no ). Registered office: Willoughby Road, Bracknell, Berkshire RG12 8FB. All URLs accessed February Any third-party URLs are given for information and reference purposes only and BRE and IHS do not control or warrant the accuracy, relevance, availability, timeliness or completeness of the information contained on any third-party website. Inclusion of any third-party details or website is not intended to reflect their importance, nor is it intended to endorse any views expressed, products or services offered, nor the companies or organisations in question. Any views expressed in this publication are not necessarily those of BRE or IHS. BRE and IHS have made every effort to ensure that the information and guidance presented here were accurate when published, but can take no responsibility for the subsequent use of this information, nor for any errors or omissions it may contain. To the extent permitted by law, BRE and IHS shall not be liable for any loss, damage or expense incurred by reliance on the information or any statement contained herein. Information Papers summarise recent BRE research findings, and give advice on how to apply this information in practice. BRE publications are available from or IHS BRE Press, Willoughby Road, Bracknell, Berkshire RG12 8FB. Tel: +44 (0) , Fax: +44 (0) , brepress@ihs.com. IHS No part of this publication may be reproduced or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, or be stored in any retrieval system of any nature, without prior written permission of IHS. Requests to copy any part of this publication should be made to: The Publisher, IHS BRE Press, Garston, Watford, Herts WD25 9XX. Tel: +44 (0) , brepress@ihs.com., May 2015 ISBN