Evaluating embodied environmental and operational cost implications on a whole-building basis, both at concept and detailed design stages, is the next generation in integrated assessment. Niall Gibson looks at recent developments in this area.
Both Life Cycle Cost (LCC) and Life Cycle Assessment (LCA) are becoming increasingly more mainstream as large corporates and retail giants begin to mandate certain standards in their building requirements as part of all-encompassing CSR initiatives. The evolution of LEED & BREEAM credits in these arenas is also serving to further promote its importance, plus manufacturers are starting to use it 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. While LCC is concerned with the overall 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 a very significant proportion of annual global material consumption and therefore CO2e:
- 6Gt of Steel ~ 1.8Gt/CO2
- 8Gt of cement ~ 2.8Gt/CO2
However, when you look at construction embodied CO2e compared to operational CO2e the global impact is even more significant; 32% for operational and 13% for embodied.
By incorporating both LCA and LCC analysis into the mix designers can facilitate improvement in design and decision-making through a coordinated approach to low-impact design.
Integrating LCC & 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.
In addition, increased thermal performance to improve operational efficiency can lead to increased embodied impacts, and as they are largely ‘up-front’ the mitigation window is greatly reduced too.
It is also worth looking at how, over the life of a building, the Life cycle CO2e relates to operational CO2e. The split between embodied and operational emissions is important. Below is an example of a typical office building and as you can see the operational impact builds up to match the embodied impact at approx. two-thirds of the building expected life, and of course as operational CO2e reduce, if embodied levels do not follow then the embodied carbon becomes the greater concern over time.
This is quite significant, it demonstrates why LEED & BREEAM are focusing more on driving down embodied impacts and placing energy credits as proportionally less dominant than before. It also demonstrates the importance of choosing the correct study period; 60 years, 40 years etc. 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 it more often than not wipes out operational reductions.
While a great deal of the industry focus is currently on operational energy use, due the rising energy fuel cost, 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 building’s end of life. Without this knowledge how can designers truly understand in full, if one option is better than another?
The cost of operating and maintaining a building builds up over time and can easily exceed 200% of the construction costs. Present value costs typically look like this.
Bringing cost analysis to the earliest feasible stages within a design project can help enable the receipt of detailed cost data from the Cost Consultant or Quantity Surveyor as the design goes through the latter design stages to construction. Current cost data can be fed into the BIM, 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 & LCA together designers can evaluate how suitable a product or material is in respect to its thermal, environmental and cost impact.
This enables the designers to perform sensitivity analysis (the ability to understand which materials and products will make the biggest impact) 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
At the present time one can see a convergence and finalising of standards within the EU and ISO standard organisations.
On the LCA front, CEN/TC 350 “Sustainability of construction works” is responsible for the development of voluntary horizontal standardized methods for the assessment of the sustainability aspects of new and existing construction works and for standards for the environmental product declaration of construction products. In 2004 the Standardisation Mandate M/350 was addressed to CEN for the development of horizontal standardised methods for the assessment of the integrated environmental performance of buildings. The work has been allocated to CEN/TC 350.
On the LCC front, a number of relevant standards exist:
- ISO 15686-1:2011 Buildings and constructed assets — Service life planning — Part 1: General principles and framework
- BS EN 15643-1:2010 Sustainability of construction works. Sustainability assessment of buildings. General framework
- ISO 16739 – Industry Foundation Classes, Release 2x, Platform Specification (IFC2x Platform)
While in the voluntary rating system arena, the proposed LEED V4 includes a new MR4 credit for whole building LCA assessment, and the latest version of BREEAM now includes LCA & LCC credits; MAT01 ‘Life Cycle Impacts’ & MAN 05 ‘Life Cycle Cost and Service Life Planning’.
Indeed the BRE was involved in a collaborative Technology Strategy Board Funded project to develop new methodology for LCA & LCC assessment. Termed IMPACT, 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.
What is IMPACT?
During the collaborative Technology Strategy Board research project both a new methodology and a new suite of tools, which are fully integrated within Integrated Environmental Solutions Ltd (IES) building performance analysis suite the Virtual Environment, were created. The project team members were IES, BRE, Wilmot Dixon Re-Thinking and AEC3 with advisors from RIBA, NBS, Faithful & Gould, and the Construction Products Association.
The IMPACT Compliant tools integrate previously disconnected know-how and data on whole building Capital Cost, Life Cycle Cost and Environmental Impact (Life Cycle Analysis) within the IESVE BIM analysis suite.
The project also resulted in Datasets for Capital Cost, Life Cycle Cost and Environmental Impact assessments, to which designers can subscribe and access through their Virtual Environment software suite by downloading the free IES IMPACT complaint modules.
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 lifecycle is available within the tool, as required by the European Committee for Standardization CEN/TC 350 for integrated assessment of economic sustainability.
These costs are pulled into the IMPACT BIM through the BRE datasets. The datasets contain information with in each of the materials, products, constructions, etc. Previously the default data available within the VE was limited to thermal performance, now users can subscribe to the BRE data sets which also contain capital costs, life cycle cost and environmental impact data. This is assigned within the VE and a detailed picture of, not only the buildings thermal performance but also its cost and environmental impact is built up.
The datasets contain thousands of materials, products, systems, constructions. These are categorised by building type, to help with navigation specific to your project, which include Commercial, Domestic, Education, Healthcare, Industrial, Retail (frequent and infrequent).
The user assigns the data through quantities in respect to the model geometry. For example, you can apply floor finishes to the model by the Net Internal floor area, or glazing by glazed area. The user has the ability to assign in a finer grain of detail, for example the glazing on one façade may be different to another for security or solar gain reasons.
The Cost Consultant and Quantity Surveyor can submit their cost data directly into the model and can benefit from the data provided by the datasets or indeed where exact costs are known overwrite the default costs where appropriate.
IMPACT Methodology – LCA
IMPACT follows the BRE methodology, where each material and product which makes up the whole building is calculated using 13 environmental issues which culminate into 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 whole building. For example, does a product with a high global warming impact that does not pollute water resources have less overall environmental impact than a product that has a low global warming impact but produces significant water pollution? UK BRE Ecopoints help to enable this assessment.
This methodology has become an industry standard to evaluate the Environmental impact of a building and its elements and was derived following extensive consultation. The BRE Ecopoint is made up of 13 environmental issues, each normalised and with its own weighting. Each environmental issue is measured using its own unit, for example BRE measure mineral extraction using tonnes of mineral extracted and climate change in mass of Carbon Dioxide equivalent. Using these characterised impacts, it can be hard to make any useful comparisons. However, by comparing each environmental impact to a norm, each impact can be measured on the same scale. BRE have taken as their norm, the impacts of a typical UK citizen, calculated by dividing the impacts of the UK by its population.
The following are the 13 environmental issues calculated within IMPACT:
- Climate Change tCO2 (100yr) 21.6%
- Water Extraction m3 7%
- Mineral Extraction tonnes 8%
- Stratospheric Ozone Depletion kg CFC-11 eq. 1%
- Human Toxicity t1,4-DB eq. 6%
- Ecotoxicity to freshwater t1,4-DB eq. 6%
- High Level nuclear waste mm3 2%
- Ecotoxicity to land kg 1,4-DB eq. 0%
- Waste disposal tonnes 7%
- Fossil fuel depletion toe 3%
- Eutrophication kg PO4 3.0%
- Photochemical Ozone creation kg C2H4 0.2%
- Acidification kg SO2 0.05%
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.
This is undertaken by using a reference substance or unit, whereby the contribution of each measured emission is calculated by converting the amount of emission into the equivalent amount of the reference substance or unit. This conversion is done by using what are called characterisation factors. For example, for the impact category of climate change, the reference substance CO2 is used.
The use of a characterisation factor can be examined by taking methane as an example. We know that methane also contributes to climate change, but is measured to be 23 times more damaging than CO2 over a 100 year timescale. So, through the step of characterisation the effects of say 1kg of methane are converted into the amount of CO2 needed to cause the same effect. This equates to applying the climate change characterisation factor of 23 to the measured methane amount of 1kg which gives a figure of 23 kg CO2 equivalent.
The Environmental Profiles Methodology uses characterisation factors to cover the full range emissions and environmental impacts caused by the manufacture, use and disposal of construction materials. Making assessments based on normalised data means giving all the measured issues the same importance. BRE undertook an extensive study to identify weightings for a range of environmental issues.
Expert panels from across the industry’s stakeholder groups were used to judge the importance of many sustainability issues, covering environmental, social and economic issues. The results showed a surprising degree of consensus about the relative importance of different environmental issues across a broad range of interest groups. Currently, only data for the environmental issues can be measured and gathered on a UK basis, although IES hope to expand this to other location from around the World. The resulting weightings for the environmental issues measured by BRE have been used to weight the normalised environmental impacts to provide the Ecopoints score.
The BRE Green Guide to specification is also part of the BRE data sets which fuels the IMPACT complaint suite. Here there are thousands of materials and products contained within the IMPACT library each with their own specific rating from A+ to E. A+ represents the best environmental performance with E the worst. The Green Guide ratings are based on the ecopoint score achieved by each product and material.
Both these LCA and LCC assessments are combined with dynamic thermal simulation within the VE to take thermal performance into account. The IESVE model also delivers information on quantities.
The cost and environmental impacts of a project will ultimately remain with those who have the technical expertise; however through the phase change brought around by Building Information Modelling in the way we now work as an integrated design team, we can disseminate their analysis around the whole project table. It is the earliest stages of design where the design decisions have the greatest impacts and it is tools like the IES IMPACT Compliant suite which deliver the ability to quantify these metrics at this stage by architects and engineers long before the specialists arrive.