Buildings are responsible for almost half of the UK’s carbon emissions, half of its water consumption, around a third of its landfill waste and a quarter of all raw materials used in the economy. This means that the UK’s sustainable development targets cannot be met without a fundamental change to the way in which buildings are designed, constructed and operated. National targets for greenhouse gas emission reductions and the drive for buildings that are ‘low carbon’ in operation present a huge challenge to the construction industry – a challenge which the steel construction sector is playing a major part in overcoming.
|An introduction to the sustainability credentials of steel
with contributions from:
Sustainable construction – legislation and drivers
Sustainable construction is an important subset of sustainable development because of its contribution to the UK economy and the significant environmental and social impacts that buildings and other structures play in all our lives. Our quality of life, comfort and security, health and wellbeing and productivity are all linked to our built environment.
In partnership with industry, Government published a Strategy for sustainable construction in 2008. The Strategy set out a series of overarching targets with specific actions and deliverables. With around 30% of the construction industry’s output being for the public sector, Government wants to set the example for other construction clients, particularly by procuring more sustainable public buildings.
Since the recession of 2008-09, a priority of UK Government has been to support the economic recovery of the construction industry. Part of this strategy has been to reduce the regulatory burden on the industry which has included reducing sustainability targets and drivers. Current Government strategy for construction, which includes some high level sustainability objectives, is set out in the Construction 2025 strategy which was published in 2013.
Below are listed some of the main legislative and other drivers driving more sustainable construction in the UK.
As required under the EU Energy Performance of Buildings Directive, Energy Performance Certificates (EPCs) and Display Energy Certificates (DECs) are required for commercial buildings. All dwellings are also required to have EPCs.
EPCs, which set out the energy efficiency grade of a building, are required when a commercial building over 50m2 is built, sold or rented.
DECs are required annually for public buildings and those occupied by public authorities, which have a total useful area greater than 1000m2 and provide a public service to a large number of people and are therefore frequently visited by those people. The DEC shows the actual energy usage of a building.
EPCs and DECs are intended to create greater awareness and stimulate demand for more energy efficient buildings.
Planning also plays an important role in delivering holistic sustainable development. Most planning legislation and guidance is relatively ‘high-level’ and does not generally impact upon the detailed design and construction of buildings. Two exceptions to this are Supplementary Planning Guidance and the Merton Rule.
Supplementary Planning Guidance (SPG) and Supplementary Planning Documents (SPDs) provides greater detail on the delivery of local development plans. Many local planning authorities have SPG/SPDs relating to the design and construction of sustainable buildings. This guidance can vary dramatically from authority to authority and includes information relating to operational and renewable energy and materials selection criteria, etc. SPG and SPDs are considered in the determination of planning applications.
First adopted by the London Borough of Merton, the (so called) Merton Rule requires all new developments to use renewable energy onsite to reduce annual carbon dioxide (CO2) emissions in the built environment. The policy applies to all residential developments of 10 or more units and all new non residential developments above a threshold of 1,000 m2. It is required to incorporate renewable energy production equipment to provide at least 10% of predicted energy requirements. Some authorities have gone further requiring 20%.
It is estimated that more than 50% of Local Authorities currently have in place a Merton Rule type requirement and Government has stated that it expects all local planning authorities to adopt a Merton type requirement in their development plans.
BREEAM (BRE Environmental Assessment Method) is the leading and most widely used environmental assessment method for buildings. It has become the de facto measure of the environmental performance of UK buildings. Although currently voluntary, many publically funded/procured buildings are required to have a minimum BREEAM rating. Many commercial building clients also recognise the benefits of procuring sustainable buildings and are increasingly using BREEAM to deliver sustainable buildings.
The construction and demolition sectors generate more waste in the United Kingdom than any other. They are also the largest producers of hazardous waste. Waste legislation and drivers impacting the construction and demolition practice include:
European Union legislation is also impacting UK construction. Measures particularly influencing construction practice include the Landfill and Waste framework Directives; the Directive on the energy performance of buildings; the Construction Products Regulation and CEN Harmonisation standards which include CEN TC350 standards on the assessment of the sustainability of construction works and the proposed Energy Efficiency Directive. Many of these are implemented in the UK by the national regulations described above. There is also the EU Circular Economy Package which was launched in 2015. This includes revised legislative proposals on waste, and measures to stimulate Europe's transition towards a circular economy which aims to boost global competitiveness, foster sustainable economic growth and generate new jobs.
In 2007, the UK Government set out an ambitious plan for all new homes to be ‘zero carbon’ from 2016 and for all new non-domestic buildings to be ‘zero carbon’ from 2019, with the public sector leading the way from 2018. The direction of travel was clear and, via Part L of the Building Regulations, a roadmap of likely targets was in place to provide guidance and certainty to the construction industry to enable it to develop solutions to meet future low and zero carbon targets. However, in July 2015, that plan was revised and, as part of the Housing & Planning Bill, which received Royal Assent in 2016, the policy was scrapped. More details can be found here.
Steel and sustainable construction
Its superior strength-to-weight ratio means a little steel goes a long way, giving architects complete flexibility to innovate and create new and exciting buildings that are a pleasure to live and work in. Low and zero carbon buildings and buildings with high BREEAM ratings are readily achievable using steel construction. The example shown is the low energy Devonshire Building at Newcastle University, which achieved a BREEAM ‘Excellent’ rating.
Manufactured from the most abundant element on earth, iron, steel can be recycled or reused endlessly without detriment to its properties. This unique characteristic gives all steel a high value at all stages of its life cycle. The recovery infrastructure for steel recycling is highly developed and highly efficient, and has been in place for decades. Current recovery rates from demolition sites in the UK are 99% for structural steelwork and 96% (on average) for all steel construction products – figures that far exceed those for any other construction material.
Steel is manufactured by two production routes (BOS and EAF), which together comprise a single global system of supply to meet world demand. Both production routes include a significant recycled content, the average of which is 60% for structural steel used in the UK (WRAP).
Energy consumption and carbon dioxide emissions from European steelmaking have been reduced by 50% and 60% respectively over the past 40 years and work is underway to reduce this further via the ULCOS project.
By-products from iron and steel-making, including sludges, slags and dust, are beneficially used by the construction industry in a range of products including roadstone, lightweight aggregate and as cementitious material used as a substitute for Portland cement. Tata Steel and British Steel, the major steel producers in the UK, recycle or reuse over 90% of their process residues.
All steel components are manufactured in the controlled environment of a fabrication factory, where consistent structural elements with assured quality can be created to meet the specific requirements of each project. In this environment, steel parts can be easily standardised, tested and certified. Any waste material produced during the fabrication phase, e.g. off-cuts, swarfe, can be recycled and used again in the steelmaking process.
Off-site manufacture is more efficient, faster, leaner and safer than site construction. It also yields high quality products with fewer defects that require less ‘snagging’ on site, leading to savings in both time and money.
Being factory based, steel production and fabrication requires skilled, settled workers. There is little need or desire for an itinerant workforce, and as such it provides stable employment. Compared to working on-site, the fabrication factory is a far safer environment for workers; and productivity and quality are not subject to the elements to the same degree as site-based construction.
The steel supply chain
The United Kingdom is the world’s leader in steel construction both commercially, technically, and in terms of quality. From humble beginnings over 200 years ago, the industry has gone from strength to strength achieving a current global turnover of £3,000 million and providing employment for over 100,000 people.
The industry has made dramatic improvements in technology, productivity and efficiency, helping it to maintain strong exports of steelwork and related products and services. In the UK market, 95% and 70% of all single-storey industrial buildings and multi-storey non-residential construction respectively (by floor area) are framed in steel.
The steel construction industry operates through an efficient integrated supply chain. There is an extensive choice of steelwork contractors available to specifiers and buyers in terms of size, expertise and capabilities, thus ensuring a competitive tender list.
The British Constructional Steelwork Association (BCSA) is the national organisation for the steelwork contractors in the UK and Ireland. Its Member companies undertake the design, fabrication and erection of steelwork for all forms of construction in building and civil engineering. BCSA operates a number a number of schemes to ensure the competency and quality of its members and the products and services they supply. These include the BCSA membership assessment requirements, the Register of Qualified Steelwork Contractors for Bridgeworks (RQSC), the Steel Construction Certification Scheme (SCCS), CE Marking, and the Steel Construction Sustainability Charter (SCSC).
Structural steelwork is an engineered product utilising the most modern CAD/CAM products, ensuring a good and accurate fit. 3D and virtual reality models can greatly assist the professional staff in the quality and planning of the product design. BCSA members promote an early involvement in the design process to clearly define the design criteria and give the most cost and speed efficient quality designs over the whole life of the structure.
Industry surveys consistently demonstrate that steel is the safest construction material. Components are fabricated offsite in a safe, controlled factory environment. From here they are delivered to site and erected by a small number of skilled personnel. There is minimal requirement for on-site cutting or adjustment, and no need for the time-consuming and potentially hazardous shuttering and handling operations associated with other construction materials.
Speed of construction
The speed of steel construction has made it the framing material of choice for the UK construction sector. A shorter construction programme reduces disruption and disturbance around the site. Steel is relatively clean and quiet to erect, and requires few site deliveries. Speed of construction delivers an economic benefit too, which is fundamental to sustainable development. The shorter on-site period reduces the cost of preliminaries, reduces the period of financing and delivers buildings that are operational faster – providing a quicker return on investment from rent or sale.
Steel can be reused and recycled repeatedly without ever losing its qualities as a building material. This unique characteristic gives all steel a high economic value at all stages of its life cycle which, unlike some other construction materials, ensures that it is routinely recovered and reused. Consequently, the recovery infrastructure for steel recycling is highly developed, highly efficient, and has been in place for decades. Current recovery rates from demolition sites in the UK are 99% for structural steelwork and 96% for all steel construction products – figures that far exceed those for any other construction material.
Because steel frames are essentially a kit of parts, it is posible that they may be dismantled and reused. Bolted connections allow components to be removed in prime condition and easily reused either individually or en masse as entire structures. It means that steel components have the potential to be perpetually reused in a continuous loop, and never sent to landfill.
A ProLogis two-storey warehouse and office building at Heathrow is shown which was designed to be easily erected and potentially dismantled. Approximately 80% of the portal frame structure is re-usable, 95% of the floor beams and 100% of the galvanized steel components. Click here for more details.
Entire steel structures can be fully dismantled and reconstructed in a different location in a matter of months, without creating any dust and dirt, and very little noise. Constructing a building from a demounted structure is one of the most sustainable ways of creating a ‘new’ building, benefiting the local community and leaving behind no environmental legacy. An example of such a project is 9 Cambridge Avenue, a warehouse which was dismantled and re-built elsewhere on Slough Trading Estate to make way for the new Leigh Road bridge. This is an excellent example of steel contributing to the circular economy.
Significant waste can occur at the end of a building’s life when it has to be demolished and its materials scrapped. Steel-framed buildings are easily adaptable if the configuration of the building needs to change. The ability of steel to span large distances means that steel buildings contain large open-plan spaces which are easily reconfigured with lightweight partition walls. The steel frame itself can be easily adapted, with parts added or taken away, and its light weight means that extra floors can often be added without overloading existing foundations.
Steel structures are commonly used to renovate buildings for example behind retained facades. In this way the historic value, character and resources of the façade are retained and the building structure can be reconfigured to create open, flexible internal space that meets modern client requirements and maximises net lettable floor area.
Kinnaird House was constructed in the early 1920s using Portland stone held in place by an integral steel frame. The client's main criterion for the redevelopment was that the existing character of the building should be maintained while maximising the net lettable floor area.
This was achieved using a shallow floor system, tied to the original steel stanchions, and lightweight concrete on steel decking. The consequential reduction in load carried by the foundations enabled an additional floor to be inserted into the old banking hall area and an extra floor to be added for plant at roof level. The shallow floor construction also allowed an unhindered services zone across each floor plate. The redevelopment of Kinnaird House achieved an excellent BREEAM rating.
Shallow floor system behind the retained facade
Attributes of sustainable buildings
The complexity of sustainable construction and buildings requires the designer to consider a diverse range of design issues. These can include regulatory compliance, for example Part L of the Building Regulations, national and local planning policy, or specific client requirements, for example achievement of a certain BREEAM rating.
Below are listed the fundamentals of sustainable building design that are currently most commonly considered in UK construction projects. This is by no means a comprehensive list and no priority or importance should be inferred from the listings.
Key design issues to consider in relation to the location of the building include:
- Proximity to the public transport network and local amenities
- The opportunity to redevelop brown field sites
- Opportunities to reuse any existing buildings on the site
- Maximising recycling of existing materials on site, for example by using the ICE’s Demolition Protocol
- Site the building and use landscaping to develop a favourable micro climate
- Site the building to enhance the ecological value and biodiversity of the site
- Strike a balance between tempering the wind and using it to promote natural ventilation and/or as a source of renewable energy.
Often overlooked, the aesthetic appeal of buildings should also be considered. Buildings provide our homes, places of work and leisure and therefore how they look and how they make us feel is important in a social context. Contemporary buildings stimulate and inspire their users.
Buildings with aesthetic appeal are likely to be cherished meaning that they more likely to be longer lived and hence be more sustainable. Buildings that are contemporary, inspiring AND flexible/adaptable to future change are particularly sustainable.
Tools such as the Design Quality Indicators (DQIs) can be used to help ensure good design.
Low impact materials
Buildings consume large amounts of varied materials and therefore it is incumbent upon the designer to use and specify low impact materials. Issues to consider include:
- Specify responsibly sourced materials
- Consider the whole life environmental impacts of construction materials using tools such as life cycle assessment and the Green Guide to Specification
- Assess buildings holistically, for example by taking account of the structural efficiency of materials and their recyclability and the impact of the superstructure on the substructure, etc.
- Specify materials with a high recycling potential
- Minimise the use of primary aggregates
- Consider whether Modern Methods or Off site construction offer advantages in terms of speed, waste, etc.
- Specify inert and low emissions finishes
- Where possible use prefabricated and standardised components to minimise waste and enable subsequent reuse.
Flexibility and adaptability
The pace of change in all walks of life has never been greater. Changing work patterns, new technologies, changing demographics and new legislation are all putting new and different demands on buildings.
Difficulty in adapting buildings to change often leads to their premature redundancy and subsequent demolition. Even before redundancy, failure or inability to adapt and upgrade buildings can compromise occupant comfort and, in commercial buildings, reduce their productivity.
In times of rapid change, sustainable buildings are buildings that are able to accommodate changes in use and importantly, changes to the heating, cooling, lighting services and IT systems used within them. Sustainable buildings should be flexible to change of use and adaptable to future needs and requirements be they regulatory or market driven.
The useful life of buildings can be extended through the adaptation and reconfiguration of internal space and walls, structural extension and upgrading of the external envelope, etc. In these ways the life cycle costs and environmental impacts are reduced as more value is obtained form the same resources.
To become more sustainable, it is important that buildings can accommodate changing business requirements. By doing so, buildings will last longer and greater value will be extracted from the resources (materials) invested in the buildings, which is a key feature of the circular economy.
There are three principal areas in which buildings can be made more flexible and/or adaptable:
- Structural extension (vertically or horizontally)
- Internal flexibility
- Flexible building services.
In a resource-constrained world the cost and value of the materials and components used to construct buildings is rising. The traditional end-of-life scenario for buildings was demolition and landfill; however, more attention is now paid to the use of materials that can be reclaimed and recycled when buildings reach the end of their useful life. The characteristics of construction materials vary dramatically in terms of their ability to be recycled. Materials such as metals are truly recyclable, i.e. they can easily be recycled into new products of the same quality and function. Many other construction materials are difficult or uneconomic to recycled and can only be ‘downcycled’ into products of a lower quality or function. A common construction example is concrete which is commonly crushed and reused as fill or hardcore. Although this is beneficial in that landfill is avoided, it does not replace the need for new resources to make new concrete. These issues are important in the long-term sustainability assessment of construction products.
Demountability and reuseability
Designers should also pay attention to how their buildings can be disassembled at end-of-life so that the opportunities to reclaim and recycle materials are optimised. So-called ‘design for deconstruction’ can help facilitate greater recycling and reuse of building components.
While this is a relatively new challenge for designers, it is obvious that some construction materials and systems are inherently more demountable and reusable than others. Steel's attributes in terms of recycling and reuse make a significant contribution to the circular economy.
Minimising on-site and local impacts
Inevitably, construction projects impact on local communities. Efforts should be made to reduce and mitigate adverse social and environmental impacts for example by:
- Adopting Site Waste Management plans
- Using the Considerate Constructors scheme
- Monitoring and minimising on site construction impacts including waste, transport, CO2 emissions, productivity, etc.
- Minimising local impacts from construction activities such as traffic congestion, noise and dust.
In addition to specific measures, the choice of construction technology can help minimise local impacts. For example, fast technologies or those based on off-site production can reduce overall construction programmes thereby minimising the duration over which neighbours to building sites are affected.
Operational energy efficiency
The operational energy efficiency (and associated carbon emissions) of buildings has been the focus of most sustainable building design and innovation over recent years. Key design issues include:
- Orientate and space buildings to take advantage of solar gain, natural lighting and any appropriate low and zero carbon technologies
- Incorporate the appropriate amount of thermal mass within the building, ensure that it is exposed and compatible with the ventilation and cooling strategy
- Use glazing, rooflights, etc. to allow solar gain and natural day-lighting
- Provide solar shading to prevent overheating and glare
- Insulate the building well to reduce fabric heat losses
- Incorporate a suitable degree of airtightness
- Consider the integration of appropriate low and zero carbon technologies within or near to the building
- HVAC systems should be selected to match the building’s response and the likely pattern of occupancy
- Use natural or mixed-mode ventilation wherever possible
- Design buildings and services that have the capacity to meet predicted future climate change scenarios
- Provide good controls, sub metering and operating instructions for the building users
- Undertake seasonal commissioning of the building
- Provide appropriate and controllable ventilation to ensure good indoor air quality.
Many of these issues are complex and strongly interrelated and consequently, require expertise including detailed dynamic thermal modelling, to optimise design solutions. Guidance on many issues is provided in the Target Zero design guides.
Robustness and longevity
It is a fundamental of good design that buildings and structures should be safe and robust and that measures to enhance their environmental performance should not compromise this fundamental requirement. Robust buildings are not only safe buildings but should also be durable, last a long time and therefore be inherently sustainable.
It is important that the robustness requirements or classes for different building types are established and that there are proven means of achieving the required robustness.
Maintenance requirements for some types of building can be high both in terms of cost and environmental impact.
Low maintenance is important in reducing operational costs and can be facilitated by; use of robust forms of construction, efficient, durable protection, and easily maintained servicing and façade systems.
Regulatory requirements have, to date, focused on the reduction of operational carbon emissions from buildings, mainly via Part L of the Building Regulations. However, as the operational efficiency of new buildings is improved, the relative significance of the embodied impacts of construction materials and processes increases. In recognition of this, attention is now being paid to the quantification and reduction of the embodied carbon impacts of buildings and construction products.
The term ‘embodied carbon’ refers to the lifecycle greenhouse gas emissions (expressed as carbon dioxide equivalents – CO2e), that occur during the manufacture and transport of construction materials and components, as well as the construction process itself and end-of-life aspects of the building including demolition, reuse and recycling. CO2e is a measure that describes, for a given mixture and amount of greenhouse gases, the amount of CO2 that would have the same global warming potential (GWP), when measured over a specified timescale (generally, 100 years).
Embodied carbon assessment
Quantification of the embodied impacts of buildings is more complex than for operational carbon impacts. This is mainly due to different scoping and methodology assumptions, concerning the life cycle stages to be included within the scope of the assessment.
In very simple terms, embodied carbon assessments involve the multiplication of quantities of construction products and materials (generally on a weight basis) with embodied carbon coefficients or carbon emission factors. Quantities are generally derived from a ‘take off’ from construction drawings or directly from Bills of Quantities.
Obtaining a comprehensive and compatible set of embodied carbon coefficients can however be far more difficult. Coefficients are dependent upon a number of factors and assumptions that can significantly influence the final results.
There are several standards that set out how to undertake embodied carbon assessments. These include the ISO 14040 series, standards developed under CEN TC 350, specifically BS EN 15804, PAS 2050, etc.
Life cycle assessment (LCA)
The most widely used and highly regarded tool for quantifying the environmental impacts of construction is life cycle assessment (LCA). Despite being conceptually quite straightforward, LCA can be very complex with many important, often material-specific, assumptions than can significantly influence the outcome. LCA is the tool that is used to develop Environmental Product Declarations (EPD) which are increasingly used to describe the environmental impacts of construction products.
LCA involves the collection and evaluation of quantitative data on the inputs and outputs of material, energy and waste flows associated with a product over its entire life cycle so that its overall environmental impacts can be determined.
An LCA essentially comprises three steps:
- Compiling an inventory of relevant energy and material inputs, e.g. iron ore, and environmental releases, e.g. CO2
- Evaluating the potential impacts associated with identified inputs and releases, e.g. the global warming potential of various greenhouse gases
- Interpreting the results to help make a more informed decision.
An important first step in any LCA is to define the goal and scope of the study clearly. The goal and scope of the study will help define key details of the study including:
- The functional unit of the product to be assessed, e.g. 1 tonne of structural steel or 1 m2 of external wall, etc.
- The system boundaries
- Any assumptions and limitations
- The allocation methods used to partition or share the environmental load of a process when several products or functions share the same process
- The impact categories chosen.
In the context of building and construction LCA, the standards recently developed by CEN TC 350 will be very influential in defining how the environmental impacts of construction products and buildings are assessed and will ensure that they are done on a fair and consistent basis throughout the EU.
In the UK, the leading environmental assessment methodology for construction materials and products is BRE’s Environmental Profiles. BRE’s methodology is founded on LCA principles and is used to derive the Green Guide to Specification ratings that are used in BREEAM to asses the embodied environmental impact of construction products.
LCA system boundaries
The system boundaries of an LCA study determine which unit processes are included in the scope of the study. Different systems boundaries that can be considered and should be defined include:
- Geographical area, e.g. UK, EU, World, etc.
- Time horizon, i.e. when the data were collected
- Boundaries between the specific system studied and related technical systems, for example, production of capital goods to manufacture a product
- Boundaries between the technological system and nature, i.e. which life cycle stages are included within the system boundary. Common examples include ‘cradle-to-gate’ and ‘cradle-to-cradle’ system boundaries.
It is important when undertaking LCA and embodied carbon assessments that the system boundaries are clearly defined and, when comparative assessments are undertaken, the data used are consistent in terms of the scope and boundaries defined above. This is a common failing of many comparative LCA and embodied carbon studies.
Accounting for end-of-life and recycling
In the context of buildings, because of the significant waste and environmental impact caused when buildings are demolished, it is recognised that a thorough LCA (or embodied carbon) study should consider the full life cycle of buildings including the end-of-life impacts of demolition and the reuse and recycling of demolition materials.
For many construction products, there is a lack of data on the impacts after they have left the factory gate. Consequently many LCA and embodied carbon studies are currently limited to ‘cradle-to-gate’ studies which exclude all subsequent impacts including transport to site, construction activity (and waste) on site, maintenance and end-of-life impacts including demolition and the benefits of recycling and reuse. This can be very significant since, as shown, the end-of-life outcomes of construction materials can be very different. These important differences are not accounted for in ‘cradle-to-gate’ studies.
To calculate the environmental impacts of steel manufacturing, the World Steel Association adopts the ‘closed loop recycling’ method of lifecycle assessment, which is the preferred approach under the ISO 14040 series of environmental standards. This approach considers all new steel to be part of single global system of supply and demand and credits can be taken now for future recycling. As an alternative, bauforumstahl, the independent steel promotional organisation in Germany has published an EPD based on data collected from the biggest hot rolled steel sections and plates manufacturers in Europe. This 'European EPD' includes the most up to date embodied carbon data currently available for these products and is based on the Module D approach from BS EN 15804. Both methods give more or less the same overall result.
Embodied carbon comparisons
Increasingly, clients and their professional advisers include embodied carbon comparisons as part of their overall building design decision making. It is important that any comparisons are made on a fair and consistent basis, for example, comparing embodied carbon on a unit weight or volume basis can prove misleading. It is important therefore that construction products and systems are compared on a functionally equivalent basis, e.g. 1m2 of external wall construction to satisfy the current Building Regulations and provide a U-value of 0.25 W/m2K.
In fact, it is preferable to compare whole buildings since some choices can have a significant knock-on effect; this aspect can be missed if comparisons are made on just an elemental basis. For example, a light superstructure can mean far fewer foundations are required.
The Target Zero programme included one of the most recent and comprehensive embodied carbon studies. Focussing on the structural frame, the studies compared the embodied carbon impact of five real commercial buildings. Key conclusions from these studies include:
- Based on the buildings studied, operational carbon emissions are not significantly affected by structural form
- For low-rise buildings, the overall embodied carbon impact is dominated by the foundations, ground floor slab and external works
- For medium to high-rise buildings, the embodied carbon impact is dominated by the frame and upper floors
- Based on the buildings studied, optimised structural steel solutions yielded the lowest cost and lowest embodied carbon compared to the alternative structural options considered.
Steel embodied carbon and LCA data
In 1996, worldsteel launched its worldwide life cycle inventory (LCI) study for steel products. This was the first time that such an international study of a specific material had been carried out. The study is regularly repeated and updated and is in accordance with the BS EN ISO 14040 series of environmental standards and, more recently, to CEN TC350 standards. The closed-loop recycling method from BS EN ISO 14044 is used to account for the benefits of steel recycling.
The worldsteel LCA data have been used in many LCAs; around 200 requests for data are made each year from LCA practitioners and academics around the world. LCAs are used for benchmarking performance, improving products, addressing legislative requirements and assessing competition between materials. Requests for worldsteel LCA data can be made by filling in the online questionnaire to describe how the data are to be used. The request is then discussed with the worldsteel LCA Manager.
In addition to the worldsteel data, in 2014, bauforumstahl, the independent steel promotional organisation in Germany published an EPD based on data collected from the biggest hot rolled steel sections and plates manufacturers in Europe. This 'European EPD' includes the most up to date embodied carbon data currently available for these products and is based on the Module D approach from BS EN 15804.
This EPD has fed into a comprehensive new database of information on end of life LCA and embodied carbon data for construction materials. The following information is extracted from that.
|Sections and plate||Hot finished/formed Tubes||Steel deck|
Note that these embodied carbon values are aggregate values, i.e. the aggregate of Modules A, C and D.
In the drive to reduce national greenhouse gas emissions, significant steps have been taken over recent years to reduce the carbon emissions associated with the use of buildings, principally, in England and Wales, via Part L of the UK Building Regulations.
Operational carbon is the term used to describe the emissions of greenhouse gases during the operational phase of a building. In the context of Part L however, only CO2 (rather than CO2e) emissions are currently accounted for. Emissions arise from energy consuming activities including heating, cooling, ventilation and lighting of the building, so called ‘regulated’ emissions, and other, currently ‘unregulated’ emissions, including appliance use and small power plug loads such as IT. These appliances are not currently regulated because building designers generally have no control over their specification and use and they are likely to be changed every few years.
Operational carbon targets
In 2007, UK Government announced its ambitious plan for all new homes to be ‘zero carbon’ from 2016; for all new non-domestic buildings, the target date was 2019, with the public sector leading the way from 2018. Although precise definitions were not published, Government confirmed that the ‘zero carbon’ target would only relate to regulated emissions.
Approved Document L is the mechanism by which operational carbon emissions are regulated in buildings in England and Wales and has a key role to play in defining suitable intermediate steps on the trajectory towards zero carbon buildings.
UK Government supports a hierarchical approach to meeting a zero carbon standard for buildings, as shown in the figure.
The approach prioritises, in turn:
- Energy efficiency measures - to ensure that buildings are constructed to very high standards of fabric energy efficiency and use efficient heating, cooling, ventilation and lighting systems.
- Carbon compliance on or near site. This is the minimum level of carbon abatement required using energy efficiency measures plus on-site Low and Zero Carbon Technologies (LZC) and/or directly connected heat or coolth.
- Allowable Solutions – a range of additional beneficial measures to offset ‘residual emissions’, for example exporting low carbon or renewable heat to neighbouring developments or investing in community heating.
The 2010 revision to Approved Document L required an average 25% reduction in regulated carbon emissions over the 2006 requirements for non-domestic buildings. The 2013 revision represented a 9% aggregate uplift (compared to the 2010 requirements), significantly lower than the 20% improvement initially proposed; mainly in response to Government’s deregulatory and growth agendas. Although the aggregate improvement for new non-domestic buildings was 9%, this varied, by building type, between 3% for small warehouses to 13% for a shallow plan office.
In July 2015, the UK Government announced that, as part of its Productivity Plan, the zero carbon buildings policy was to be dropped to reduce regulation on house builders. In particular, government stated that it ‘does not intend to proceed with the zero carbon Allowable Solutions carbon offsetting scheme, or the proposed 2016 increase in on-site energy efficiency standards.’ This effectively meant that the 2016 zero carbon homes target were to be dropped, as were the 2019 target for non-domestic zero carbon buildings. It also meant that there were to be no further changes to Part L in 2016. This was confirmed when the Housing and Planning Bill received royal assent in May 2016.
In response to the cancellation of the scheme a successful amendment was tabled at the Report stage of the Housing and Planning Bill 2105-16 in the House of Lords. This would require the Government to put in place regulations for a carbon compliance standard for new homes by 2018. The amendment was removed in the House of Commons and replaced by a commitment to a review the energy performance requirements under Building Regulations.
Operational carbon assessment
The operational carbon emissions of UK buildings are assessed using thermal modelling software. Various commercial dynamic thermal simulation models are available but the most common tools, which are used for demonstrating compliance with Part L, are SAP (Standard Assessment Procedure) for dwellings and SBEM (Simplified Building Energy Model) for non-domestic buildings.
SBEM is based on the National Calculation Method (NCM) which is a requirement under the EPBD (Energy Performance of Buildings Directive). The NCM sets out the methodology for calculating the annual operational energy use (and associated carbon emissions) for a proposed building and comparing it with the energy use of a comparable 'notional' building. Both calculations make use of standard sets of data for different activity areas and call on common databases of construction and service elements. A similar process is used to produce an 'asset rating' (which is required for an EPC) in accordance with the EPBD. The NCM therefore comprises the underlying method plus the standard data sets.
For compliance with Part L, the modelled Building CO2 Emissions Rate (BER) must be less that the Target Emission Rate (TER) which is based on a 2013 ‘notional, building. The BER and TER are calculated using a monthly quasi-steady state energy balance methodology (SBEM).
Embodied versus operational carbon
Although the relative significance of the embodied carbon impact of buildings is increasing as the operational energy efficiency of buildings is improved, designers can still make a far greater impact by addressing operational carbon reduction.
The ratio of embodied and operational carbon for a new office building over a 60 year lifetime is shown. The figure shows the ratio based on a office building meeting the 2010 Part L requirements and the ratio based on the same building meeting a 50% reduction in regulated emissions, i.e. the likely reduction from carbon compliance required to achieve the 2019 zero carbon target (based on the most recent government research). The remaining 50% will have to come from either additional carbon compliance or allowable solutions. This will still leave the unregulated emissions, which are a sizable proportion of the total.
Although these figures are indicative only, since operational carbon performance will change over time as the UK energy mix is changed, it does show that that even in 2019, operational carbon remains the more significant impact over the lifetime of a typical building.
Part L 2010 compliant (60 years)
Breakdown of energy use in buildings
To design more energy efficient buildings, it is important to understand the breakdown of energy use in buildings.
The pie-chart shows the breakdown of carbon emissions by energy demand in a Part L (2006 compliant) typical, large city centre office building and reveals that unregulated demands including applicances, IT, etc. make the biggest contribution to the total. Of the regulated energy demands, lighting and fans and pumps are the greatest contributors. This breakdown can help to identify where the biggest savings can be made most cost effectively. For example for this office building, analysis showed that the energy efficiency with the greatest predicted impact are those related to space cooling and fan and lighting efficiencies.
Energy efficiency measures
Energy efficiency measures include improved thermal insulation levels and airtightness, improved lighting, improved glazing and solar control measures and improved HVAC efficiencies, etc. They can often represent the most cost effective means to reducing operational carbon emissions.
However, as operational carbon reduction targets become more onerous, the whole life cost effectives of many energy efficiency measures becomes less attractive than other measures, such as low and zero carbon technologies and allowable solutions.
The Target Zero design guides give guidance on the cost effectiveness of different energy efficiency measures for a range of new building types.
Low and zero carbon (LZC) technologies are broadly defined as technologies which meet building energy demands with either no carbon emissions, or with carbon emissions significantly lower than those of conventional methods. Generic LZC technologies include wind turbines, solar (hot water and pv), ground and air source heat pumps, combined heat and power (CHP) and combined cooling, heat and power (CCHP).
The cost effectiveness of introducing LZC technologies into buildings is highly dependent upon the cost of the technology and any relevant subsidies, such as the Feed-in tariffs and the Renewal Heat Incentive; both of which are subject to change.
It is important that the effectiveness of LZC technologies, in terms of both cost and carbon reduction, is assessed in conjunction with appropriate energy efficiency measures so that an optimum, compatible package of measures is defined. The Target Zero design guides give guidance on the cost effectiveness of different LZC technologies for new buildings.
Optimum solutions for low and zero carbon design
The Target Zero programme assessed the operational carbon reductions achievable using individual energy efficiency measures and LZC technologies and ranked these in terms of their whole-life cost effectiveness. Target Zero also identified the most cost effective packages of compatible energy efficiency and LZC measures which could achieve what were, at teh time teh work was done, likely future Part L Carbon Compliance targets.
The Target Zero design guides provide summaries of the most cost effective packages of energy efficiency and LZC technology packages to achieve what were regarded as possible future likely operational carbon reduction targets. By way of example, the results for a typical secondary school are shown.
Main article: Thermal mass
Thermal mass, more appropriately called Fabric Energy Storage, is the ability of the fabric of a building to absorb heat. Effectively utilised, it can reduce cooling loads and, in some cases, remove the requirement to provide air conditioning entirely in some buildings. There is a common misconception that buildings must be heavyweight to achieve an optimum level of thermal mass. This myth has probably arisen because large buildings such as churches are always cool, even in the hottest summer. However, the main reasons that churches stay cool is because they have very few windows, which reduces solar gain, and have low internal heat gains.
In modern buildings, the greatest accessible mass is found in the upper floor slabs. Independent research has shown that in a UK climate, the optimum thickness of concrete floor slab for providing thermal mass is 75 - 100mm. This thickness of concrete floor slab is routinely available in almost all steel-framed buildings, which are also generally the lightest form of construction.
The extra weight associated with heavy, concrete frames is not required to improve thermal mass and is surplus to requirements. In fact, the extra mass of heavyweight concrete components may actually increase the energy required to heat and cool the building.
The Wessex Water HQ in Bath in which coffered concrete floor units on a steel frame have been used to provide an efficient naturally ventilated, low energy building is shown.
BREEAM (Building Research Establishment’s Environmental Assessment Method) is the world’s leading and most widely used environmental assessment method for buildings. In the UK it has become the de facto measure or standard for the environmental performance of non-domestic buildings. BREEAM is updated on a regular basis to keep pace with best practice and related regulations, notably the Part L requirements for operational energy efficiency. The current version is BREEAM 2014, which consolidates all previous BREEAM non-domestic schemes into one comprehensive technical manual.
BREEAM is a performance based assessment method and certification scheme for new buildings. A separate, similar scheme is available for refurbishing existing buildings. Buildings assessed under BREEAM are awarded credits according to their performance within a range of eight environmental categories: management, energy use, health and well being, pollution, transport, land use, ecology, materials and water. Credits are either mandatory, i.e. must be achieved for compliance, or voluntary. In addition, there are innovation credits which encourage exemplar performance or which recognise a building that innovates in the field of sustainable performance.
Credits achieved are weighted according to environmental category and then summed to produce a single overall score on a scale of Unclassified, Pass, Good, Very Good, Excellent and Outstanding.
Building projects are assessed by registered assessors and reviewed by a third party (BRE Global) before being awarded a certificate. Since 2008 it has been compulsory to undertake a ‘Post Construction Review’ to confirm that the ‘as built’ information correlates with the design information. The BREEAM rating benchmark levels enable a client or other stakeholder to compare an individual building’s performance with other BREEAM rated buildings and the typical sustainability performance of new non-domestic buildings in the UK. In this respect each BREEAM rating level broadly represents performance equivalent to:
- Outstanding: Less than top 1% of UK new non-domestic buildings (innovator)
- Excellent: Top 10% of UK new non-domestic buildings (best practice)
- Very Good: Top 25% of UK new non-domestic buildings (advanced good practice)
- Good: Top 50% of UK new non-domestic buildings (intermediate good practice)
- Pass: Top 75% of UK new non-domestic buildings (standard good practice).
Although voluntary, a number of Government departments and other public bodies either require or encourage the use of BREEAM. These include the Welsh Assembly Government, the Northern Ireland Executive, UK health authorities and the Department for Education. Many private sector clients and developers also use BREEAM to deliver sustainable buildings.
Optimum routes to BREEAM targets
For the first time, the Target Zero project has investigated the most cost effective routes to achieving BREEAM (2008) ‘Very Good’, ‘Excellent’ and ‘Outstanding’ ratings for a range of non-domestic buildings. The results demonstrate the significant influence of location and good design and construction practice on the cost of achieving high BREEAM ratings. The table gives the percentage capital cost uplift to achieve the highest BREEAM (2008) ratings for the Target Zero case study buildings.
|Building type||% capital cost uplift to achieve BREEAM|
The Target Zero design guides provide detailed breakdowns of the most cost effective routes for each building.
Material assessment within BREEAM
Under BREEAM, the life cycle environmental impacts of construction materials and products are assessed (under Mat 01) using the Green Guide to Specification ratings which are derived using the BRE Environmental Profiles LCA methodology. The Green Guide to Specification ranks building elements on a scale from A+ to E.
Building element ratings are aggregated to give a whole building score for which a maximum of six Mat 01 credits are available. Reflecting the growing importance associated with material impacts, the Materials weighting in BREEAM 2014 has increased to 13.5%.
The superstructure is not specifically included either within the Mat 01 scope of assessment or within the Green Guide. According to the Building Research Establishment (BRE), this is because it is not possible to provide either representative functional units for these elements or comparable specifications. Upper floors however are included within BREEAM and the Green Guide and the table gives the Green Guide ratings for upper floor systems commonly used in commercial and industrial buildings.
|Specification||Green Guide rating|
|Power floated in-situ reinforced concrete floor slab||C|
|Power floated post-tensioned in-situ reinforced concrete floor slab||A|
|Power floated in-situ reinforced concrete slab on ‘deep’ profiled metal decking||A+|
|Power floated in-situ reinforced concrete slab on ‘shallow’ profiled metal decking||A+|
Sustainable procurement and responsible sourcing
There is growing demand within the construction industry to demonstrate that buildings are sustainably procured and that their constituent materials and componenets are responsibly sourced.
Sustainable procurement is procurement that aims to deliver real long term value. It involves understanding and assessing the effect of goods and services on the environment, the communities affected by its supply chain and the economy and then taking steps to reduce any negative effects and promote benefits wherever feasible.
It is about using purchasing power to benefit the environment, society and the economy. This means including sustainable considerations alongside the traditional criteria of purchase price, quality and service and making purchasing decisions that achieve best value for money over the lifetime of the goods.
Introduced by the Government’s Sustainable Task Force in 2006, the Flexible Framework is a key sustainable procurement tool. It lists the steps needed at an organisational level to improve procurement practice and covers five themes:
- Policy, strategy and communication
- Procurement process
- Engaging suppliers
- Measurement and results.
More detailed information and advice on sustainable procurement is provided in BS 8903.
Sustainable procurement within the steel sector
Raw materials for steelmaking are responsibly sourced by companies such as Tata Steel and ArcelorMittal, who champion environmentally responsible practices throughout their supply chains. This provides a route for their customers to obtain responsible sourcing credits under the BREEAM family of certification schemes.
The leading UK manufacturers and suppliers of structural steel, British Steel, Tata Steel and ArcelorMittal, have all been certified under the BRE Environmental & Sustainability Standard BES 6001, a responsible sourcing certification for the UK construction market.
For these companies, sustainable procurement is part of a wider corporate responsibility that involves the integration of financial and strategic goals with a commitment to the health, safety and well-being of their employees and communities; a focus on improving environmental performance and providing sustainable products, and conducting all aspects of their business with honesty and integrity.
Responsible sourcing standards
Responsible sourcing of construction products is included within the Government’s 2008 Sustainable Construction Strategy which includes the target to develop Framework Standards to facilitate the development of sector Responsible Sourcing schemes. Since 2008, two standards have been produced BES 6001 and BS EN 8902.
Responsible Sourcing is also included within BREEAM 2014. All materials used to construct a building are assessed for the level of certification achieved. Recognised schemes include BES 6001, environmental managements systems (EMS) such as ISO 14001 and FSC (Forest Stewardship Council), etc.
The UK steel construction sector
The UK steel construction sector is leading the way in developing a more sustainable construction industry for the UK. Our commitments range from producing design guidance on creating buildings that meet the Government’s low and zero carbon targets to researching the environmental impact of steel in buildings and developing products and processes to reduce that impact.
Reducing the carbon footprint of buildings is set to remain a top priority for the UK steel construction sector. The UK steel construction sector is committed to:
- Working with Government to meet the objectives of its sustainable construction strategy.
- Providing design guidance and information that allows designers to create buildings which reduce the whole-life costs and environmental burdens associated with buildings.
- Providing design guidance and information that allows designers to create buildings that can achieve the highest BREEAM ratings and which meet Government aspirations for zero-carbon buildings in operation.
- Developing patterns of sustainable procurement consistent with the requirements of emerging standards in this area.
- Continuing to invest in research and development to reduce the carbon footprint of its processes and products.
- Providing industrial companies in the sector with the means of improving the performance of their businesses through sustainable business practices.
- Giving specifiers and procurement agencies the opportunity to identify key supply chain partners that share a commitment to sustainable construction.
BCSA Sustainability charter
In 2005, the British Constructional Steelwork Association (BCSA) became the first representative organisation in the UK to launch a Sustainability Charter. The objective of the Sustainability Charter is to develop steel as a sustainable form of construction in terms of economic viability, social progress and environmental responsibility. BCSA has three levels of status under the Charter, i.e. Member, Silver and Gold, the status achieved depending on the number of points scored following audit. BCSA Member and Associate Member companies that agree to be bound by the charter have to make a formal declaration of their commitment to a set of sustainable principles, and are assessed and monitored against a range of environmental, social and economic criteria. BCSA requires Charter Members to formally declare to operate in sustainable ways that work towards:
- Adding value to clients and stakeholders
- Optimising the eco-efficiency of steel construction life cycle
- Promoting resource and energy efficiency in steel construction through reuse and recycling
- Operating in a safe, healthy and environmentally sound manner
- Promoting respect for people and communities associated with steel construction; having high ethical standards
The Charter has been used to help improve understanding of sustainability among steel construction companies and to help them manage their businesses in more sustainable ways.
BCSA Carbon foot-printing tool
Consistent with the steel sector’s approach measuring, reporting and reducing its carbon footprint through all stages of the construction life cycle, the BCSA has developed a carbon foot-printing tool.
Developed in 2008, the tool enables BCSA member companies to measure both their company and their product carbon footprint on a robust and consistent basis across the sector.
- ^ 1.0 1.1 1.2 1.3 Strategy for Sustainable Construction; Department for Business, Enterprise & Regulatory Reform. First published June 2008
- ^ Construction 2025, HM Government, July 2013
- ^ Calculating and declaring recycled content in construction products. WRAP 2008
- ^ 4.0 4.1 4.2 BS EN 15804:2012 Sustainability of construction works. Environmental product declarations. Core rules for the product category of construction products. BSI
- ^ 5.0 5.1 PAS 2050:2011 Specification for the assessment of the life cycle greenhouse gas emissions of goods and services. BSI
- ^ 6.0 6.1 6.2 6.3 6.4 The Green Guide to Specification, 4th ed., BRE and Oxford Brookes University, 2009.
- ^ Embodied carbon: The inventory of carbon and energy (ICE). BSRIA BG 10/2011, 2011.
- ^ 8.0 8.1 Environmental Product Declaration. Structural Steel: Sections and Plates
- ^ BS EN ISO 14040:2006. Environmental management – Life cycle assessment – Principles and framework. BSI
- ^ BS EN ISO 14044:2006. Environmental management – Life cycle assessment – Requirements and guidelines. BSI
- ^ Zero carbon for new non-domestic buildings; Phase 3 final report. Department for Communities and Local Government, July 2011
- ^ 12.0 12.1 BREEAM UK New Construction, Non-domestic buildings (United Kingdom), Technical Manual, SD5076: 4.1 2014. BRE Global Ltd.
- ^ Methodology for environmental profiles of construction products: product category rules for type III environmental product declaration of construction products. BRE, August 2007.
- ^ BS 8903:2010 Principles and framework for procuring sustainably. Guide. BSI
- ^ 15.0 15.1 15.2 BES 6001: ISSUE 3.0 Framework Standard for the Responsible Sourcing of Construction Products, BRE Environmental & Sustainability Standard, 2014
- ^ BS 8902:2009 Responsible sourcing sector certification schemes for construction products. Specification, BSI.
- ^ The Greenhouse Gas Protocol - A Corporate Accounting and Reporting Standard (Revised Edition), World Business Council for Sustainable Development (WBCSD) and World Resources Institute.
- Carbon footprint tool for buildings
- Steel construction – Embodied carbon
- Steel construction – Thermal mass
- The whole story – from cradle to grave
- Target Zero – Cost effective routes to carbon reduction
Target Zero design guides:
- Guidance on the design and construction of sustainable, low carbon office buildings
- Guidance on the design and construction of sustainable, low carbon warehouse buildings
- Guidance on the design and construction of sustainable, low carbon supermarket buildings
- Guidance on the design and construction of sustainable, low carbon mixed-use buildings
- Guidance on the design and construction of sustainable, low carbon school buildings
- Sustainable construction legislation, regulation and drivers
- Construction and demolition waste
- Recycling and reuse
- Life cycle assessment and embodied carbon
- Operational carbon
- Thermal mass
- Target Zero
- The recycling and reuse survey
- Steel and the circular economy
- British Constructional Steelwork Association
- Tata Steel
- Waste Resources Action Programme (WRAP)
- BRE Global
- Steel Construction Institute
- Ultra Low Carbon Dioxide Steelmaking (ULCOS)