CPD: Embodied impact assessments
• An explanation of Life Cycle Assessment and Life Cycle Cost
• The relative weightings of embodied and life cycle carbon
• How these are reflected in BREEAM and LEED
M&S’s new store in Cheshire scores highly for its sustainability credentials
Evaluating embodied environmental impact alongside operational cost and performance at design stage is now within the reach of more project teams, thanks to a BRE research project and new software tools. Niall Gibson, business development manager at IES, reports.
Both Life Cycle Cost (LCC) and Life Cycle Assessment (LCA) are becoming increasingly mainstream as large corporates and retail giants begin to mandate certain standards in their building requirements as part of all-encompassing corporate social responsibility (CSR) initiatives. The evolution of LEED and BREEAM credits in these arenas is also serving to further promote their importance, plus manufacturers are starting to use them to differentiate products.
LCA is a term used to describe the assessment of the embodied (or life cycle) environmental impacts of materials and products used in a building. LCC is concerned with the overall monetary cost of ownership of a building across operation, maintenance and demolition. They are linked very closely to the CO2 emissions (CO2e) of a building.
Construction accounts for 35% of annual global material consumption and therefore embodied CO2e from industry related to construction amounts to 13% of total global CO2e. While, for CO2e associated with buildings in operation, the global impact is even more significant, 32% (see Figure 1).
Figure 1: Breakdown of construction and non-construction emissions
Integrating LCC and LCA
As buildings and other structures have long design lives it is often the case that a significant proportion of the overall impact and cost associated with their materials and products will come from operation, maintenance and demolition. Typically, the majority of carbon emissions associated with a building is due to the consumption of fuel/energy for heating, cooling and power during operation. Similarly, water consumption and the maintenance and replacement of the building fabric have a considerable effect overall. However, as improvements in operational performance are achieved, the relative importance of embodied impacts increases (see Figure 2).
Figure 2 (left): Embodied carbon versus operational carbon, annualised. Figure 3: Embodied carbon versus operational carbon, year on year
Figure 2 shows embodied and operational emissions normalised to a per year figure. Figure 3 compares operational and embodied carbon for a building completed in 2013 on an annualised basis, with the embodied carbon investment present from Day One plotted against every year. Embodied carbon increases over time, stepping up every 10 years as the building undergoes periodic refurbishment. In the early years, operational carbon emissions are fairly insignificant in comparison, but the cumulative total increases year on year, reaching the level of embodied carbon investment put into the building at construction two thirds of the way through its expected lifetime.
In addition, increasing thermal performance to improve operational efficiency, for instance specifying thicker insulation or triple glazing, can lead to increased embodied impacts. And as these specification changes are largely “up-front”, the mitigation window is also greatly reduced.
It is also worth looking at how, over the life of a building, the life cycle CO2 emissions relates to operational CO2 emissions. The split between embodied and operational emissions is important. Figure 3 is an example of a typical office building where, as operational impact builds up to match the embodied impact at approximately two-thirds of the building’s expected life, and of course as operational CO2e reduces, if embodied levels do not follow then the embodied carbon becomes the greater concern over time.
This demonstrates why LEED and BREEAM are focusing more on driving down embodied impacts and making energy credits (associated with operational energy efficiency such as EAc1 for LEED and ENE1 for BREEAM) as proportionally less dominant than before. It also demonstrates the importance of choosing the correct study period. Sustainable buildings need to last but we also need to be realistic – buildings in some sectors have relatively short lives. Major refurbishments being undertaken every 30-40 years is a big issue, as the consequences of ripping out and replacing materials more often than not wipes out operational energy savings.
While a great deal of industry focus has been on operational energy use, due to rising energy fuel costs, there is also a growing focus on quantifying the overall impact of the whole building. Not simply in its operational stage but from the very beginning: what is the impact from attaining the minerals, the manufacturing process, etc as well as the impact at the end of the building’s life? Without this knowledge how can designers truly understand, in full, if one option is better than another? When selecting products and materials, the impact of the water, energy and raw materials used should be assessed across all of the products’ life cycle stages to understand their impact on the air, soil and water through emissions.
The cost of operating and maintaining a building builds up over time and can easily exceed 200% of the construction costs. Typical value costs are shown in Figure 4.
Figure 4: Lifetime costs over 60 years
The graph above shows the 60-year life cycle costs of a building completed in 2013 with a capital cost of approximately £6.5m. Each vertical bar shows the cumulative capital and operational costs up that point: ie £6.5m plus the running total cost of maintenance, refurbishment, cleaning and operating the building. By Year 60, the full cost of operating the building has reached approximately £27.5m at present values.
Bringing cost analysis to the earliest feasible stages within a design project means the project team can receive detailed cost data from the cost consultant or quantity surveyor as the design goes through the latter design stages to construction. Up-to-date cost data can be fed into the BIM model, so that each design team member can rapidly account for the cost impact of their design decisions.
Clients are increasingly asking for this reasoning, or business case, when it comes to design decisions: why should we do this? What will this cost me? What will it save me long term? By bringing LCC and LCA analysis together designers can evaluate how suitable a product or material is in respect of its thermal, environmental and cost impact.
This enables the designers to perform sensitivity analysis, a process which assesses several criteria at once to understand which materials and products will make the biggest impact in the areas of interest on that particular project throughout all stages of the design process, and most importantly at the concept and scheme design stages where the ability to make the largest savings is the greatest.
Advances in legislation
There is a convergence and finalising of standards around LCA and LCC within the EU, BS and ISO standard organisations.
The latest version of BREEAM includes LCA and LCC credits: these are the MAT 01 Life Cycle Impacts materials calculator tool and the MAN 05 Life Cycle Cost and Service Life Planning management section.
Indeed, the BRE was involved in a collaborative Technology Strategy Board Funded project to develop new methodology for LCA and LCC assessment.
Termed IMPACT (see below), there is now extra innovation credits available within MAT01 for using IMPACT-compliant tools in the BREEAM 2011 revision (version 3) which was updated in February this year.
Giving BIM more IMPACT
IMPACT – the Integrated Material Profile and Costing Tool – was a three-year project funded by the Technology Strategy Board to create a database of specification information that can be used for Life Cycle Assessment and Life Cycle Costing within project design software. The IMPACT study was undertaken by BRE, software company IES, Willmott Dixon and AEC3, with additional advice from RIBA, NBS, Faithful & Gould and the Construction Products Association.
The IMPACT methodology was developed with integration into BREEAM in mind, while IMPACT data has been designed to “plug in” to a range of software applications used by the industry. Barrier-free sharing of electronic information within the BIM environment was a core aim, achieved via IFC (Industry Foundation Class) interoperability standards.
The first IMPACT-compliant software tools have been produced by IES, integrating directly with the IES Virtual Environment BIM analysis suite. The tools use a new building-level methodology and data for both generic and certified products/materials, developed by BRE and Willmott Dixon. A library of customisable cost templates is available for different building types. Users must subscribe to the regularly updated datasets, but the IES software tools are available free.
In most projects, calculating cost and environmental impacts is a specialist role, and is likely to remain so. However, as we increasingly work in BIM-enabled integrated design teams, IMPACT-compliant software tools will be able to quantify the impact of different design options before the specialists arrive.
IMPACT methodology - LCC
IMPACT is aligned with latest BSI and RICS industry guidance on life cycle costing, and provides early indicative estimates as well as more detailed estimates at the latter stages of design. It also enables shorter periods of assessment than the entire life cycle. Those using the tool can set the life cycle period within a range of 0-80 years. 60 years would be the industry typical analysis period. The ability to report life cycle costs over the different phases of the life cycle is available within the tool, as required by the European Committee for Standardization CEN/TC 350 for integrated assessment of economic sustainability.
IMPACT Methodology - LCA
IMPACT follows the BRE methodology, where each material and product that make up the whole building is calculated, culminating in various outputs, including an Ecopoint score. Designers can quickly understand the environmental impact of each of their design choices and how that impacts relative to the building.
The BRE Ecopoint is made up of 13 environmental issues (see table), each normalised and with its own weighting. Each environmental issue is measured using its own unit, for example BRE measures mineral extraction using tonnes of mineral extracted and climate change in mass of carbon dioxide equivalent. By comparing each environmental impact to a norm, each impact can be measured on the same scale. BRE has taken as the norm the impacts of a typical UK citizen, calculated by dividing the impacts of the UK by its population.
Environmental impacts in one category can be caused by many different emission substances (inventory flows), and one substance can contribute to several impact categories. The step of characterisation assesses all the different substances contributing to an impact category relative to one another to give an overall measure of the level of environmental damage in that category.