To repeat that old statistic, the Sustainable Development Commission claim that in 2050, homes existing in 2006 will still make up 70% of the total housing stock. Although the non-domestic sector has a higher rate of demolition than the housing sector, today’s non-domestic buildings will also be in use for many years.
In 2009 the Committee on Climate Change assessed the UK’s potential carbon emissions reductions. They estimated that new homes could contribute 4 MtCO2 towards the target, while refurbishment of existing homes could contribute between 9 and 18 MtCO2. An additional saving of 5 to 9 MtCO2 was projected to be achievable from non-domestic buildings.
It’s not cheap to refurbish buildings to high levels of efficiency, and there’s no requirement to match new build performance. It is therefore worth considering whether the benefits of refurbishment are sufficient to offset the upfront costs, both environmental and financial.
This post is an introduction to life cycle thinking approaches used in the construction industry which can help to address this question.
Life cycle thinking in buildings
The impacts of a building can be split into impacts associated with waste and impacts associated with energy. The energy use can be both direct and indirect. Dixit et al define direct energy use is that used on site during construction, during pre-fabrication, and in transportation of materials to site. Indirect energy use is that used in producing building materials, maintaining the building, demolishing the building, and the operational energy used throughout the building’s life. The same distinction applies to material resources.
Life cycle cost
Life cycle thinking is not new to the building design community, as demonstrated by the large number of tools shown in the image above. Many construction projects will consider LCC at some point, partly encouraged by schemes like BREEAM which awards credits for demonstrating that the whole life cost of building elements was studied at the design stage.
The relevant standard for LCC of constructed assets is BS/ISO 15686-5.
Life cycle assessment
Although life cycle cost could be seen as a type of LCA, the term “life cycle assessment” is generally only applied to the assessment of environmental impacts as described in BS/ISO 14040.
There are several outstanding areas where the practice of LCA on buildings differs from other LCAs. A paper by Erlandsson and Borg in 2003 identified “service coverage, life-cycle definition, time dependence (coverage), life-cycle inventory and life-cycle impact assessment” as needing development.
Work has continued including several recent papers. A simple LCA tool called ENSLIC has also been published which is designed to fit with the work of CEN TC 350, a life cycle assessment standard which is currently under development.
Life cycle carbon footprint
Carbon footprinting is probably the best known and most discussed environmental LCA approach. In the UK the standard for life cycle carbon footprinting of products (with buildings seen as a particularly complicated type of product) is PAS 2050.
Several companies including dcarbon8 and Sturgis Carbon Profiling now carry out embodied carbon and life cycle carbon footprinting of buildings. There are a number of tools aimed specifically at built assets, such as the BRE’s Envest II which also covers LCC, and more in development, notably some of the successful applicants for Technology Strategy Board funding on the Design & Decision Tools for the Low Impact Buildings programme.
Whole life value
Whole life value (WLV) assessment is the comprehensive use of life cycle thinking. The costs and benefits to all stakeholders are weighed up in a process based on LCC (and subject to the same ISO standard). Non-market LCA impacts are accounted for by assigning financial values or by non-financial weighting methods (there could be a whole series of posts on the pros and cons of the different approaches to values and weightings).
The National Audit Office has recommended that this process should be followed for Government funded works. Although the term “whole life value” is not mentioned explicitly, the Treasury’s “Green Book” also advocates a similar process in examining the whole life costs and benefits to a range of stakeholders.
Summary
So that’s an overview of the types of tools available and a whole lot of further sources for the interested reader. Over the next few weeks I’ll be posting more on methodological issues around applying life cycle thinking to buildings, particularly the difficulties connected with length of life of buildings.