Assessing the environmental impact of a building or of materials used to build it can be complex. There are different factors to consider and the ideal choice will often be the best balance between them. The effect on energy efficiency of the building must be balanced with the energy used to produce a material and any possible toxicity issues surrounding the extraction of raw materials and manufacture of a product.
This is the first of a series of blogs that will look at examples to highlight some of the issues and choices involved. It sets out some key definitions and criteria to consider. Some of it is re-written from assignments originally part of my MSc SABE, and I’ve left references to source material in, so you can fact-check if you like.
What does sustainability mean anyway?
Minimising a buildings’ environmental impact is essential. In construction and in use buildings contribute substantially to CO2 emissions [1,2]. The construction industry is responsible for approximately 40% of global energy use  and is the second largest consumer of raw materials .
The World Commission on Environment and Development defines sustainable development as that which “meets the needs of the present without compromising the ability of future generations to meet their own needs” . This emphasises the need to be aware of future consequences of any actions. The need to look after the wider environment is implied, but with human survival at the heart.
The International Standards Organisation (ISO) more explicitly acknowledges biodiversity: humans must “carry out their activities in a way that protects the functions of the earth’s ecosystem as a whole” . Sustainable development goals should combine with requirements of function and efficiency ; in order to be sustainable buildings must not only be energy and resource efficient – they must meet their users needs. Essentially – even if a building is constructed with materials that are energy efficient and with low impact on biodiversity and resource depletion – if it doesn’t meet the needs of its users it’s still not sustainable.
Simon Fairlie uses “low-impact” rather than “sustainable”, seeking development that “through its low negative environmental impact either enhances or does not significantly diminish environmental quality” and as such may be allowed where conventional development should not be . Low-impact developments according to this definition could ultimately be removed without a lasting impact on the land.
Criteria for assessing materials
Sustainable materials must minimise the use of energy and natural-resources, while maximising recycling potential . Chosen materials should not contribute to habitat or biodiversity loss.
Social impacts should be considered such as noise, disturbance and damage to the amenity of the built and natural environment. Climate change resilience should be considered.
Building materials contribute to energy use and CO2 release during production of the material, and in construction, operation and deconstruction of a building [1,3]. Choice of materials must address each of these.
Embodied Energy and Carbon
Energy use and emissions associated with production and transportation of materials are described as Embodied Energy (EE) and Embodied Carbon (EC) [2,9]. These are key gauges of the sustainability of a material, in the light of climate change.
As the operational energy-efficiency of buildings increases, so does the importance of EE/EC  – so the greater insulated a building is, and less energy it needs to run it, the greater the proportional significance of EE/EC in overall lifetime emissions associated with that building.
Using EE and EC to compare materials is complicated by different approaches [3,10]. I mostly use figures from the Inventory of Carbon and Energy (ICE) . This uses data from peer-reviewed sources, and itself underwent peer-review and revision . Using a single database allows comparison of materials based on consistent criteria. Where data is not available in ICE then Environmental Product Declarations from the manufacturer can include useful information.
Embodied energy relates to embodied carbon dependant on the carbon intensity of primary energy sources . High EE may not mean high EC, for example where renewable energy is used. Because of this I tend to concentrate on embodied carbon as it relates directly to global warming potential (GWP).
Where possible embodied CO2e (equivalent) figures are used – expressing total greenhouse gas (GHG) emissions from different gases as the amount of CO2 that would have an equivalent GWP .
Examples coming soon…
References M.J. González, J. García Navarro, Assessment of the decrease of CO2 emissions in the construction field through the selection of materials: Practical case study of three houses of low environmental impact, Build. Environ. 41 (2006) 902–909. doi:10.1016/j.buildenv.2005.04.006. J. Monahan, J.C. Powell, An embodied carbon and energy analysis of modern methods of construction in housing: A case study using a lifecycle assessment framework, Energy Build. 43 (2011) 179–188. doi:10.1016/j.enbuild.2010.09.005. M.K. Dixit, J.L. Fernández-Solís, S. Lavy, C.H. Culp, Identification of parameters for embodied energy measurement: A literature review, Energy Build. 42 (2010) 1238–1247. doi:10.1016/j.enbuild.2010.02.016. B. Berge, The ecology of building materials, 2nd edition, Architectural Press, Oxford, 2009. World Commission on Environment and Development (WCED), Report of the World Commission on Environment and Development: Our Common Future, United Nations, 1987. www.un-documents.net/our-common-future.pdf (accessed March 3, 2015). BSI, BS ISO 15392:2008 : Sustainability in building construction. General principles, 2008. https://bsol.bsigroup.com/Download/SubscriptionPdfDocument?materialNumber=000000000030084695&documentNumber=BS%20ISO%2015392%3A2008 (accessed August 14, 2015). J. Pickerill, L. Maxey, Low impact development: the future in our hands, University of Leicester, Dept. of Geography], Leicester, 2009. https://lowimpactdevelopment.files.wordpress.com/2008/11/low-impact-development-book2.pdf (accessed August 5, 2015). C. Thormark, The effect of material choice on the total energy need and recycling potential of a building, Build. Environ. 41 (2006) 1019–1026. doi:10.1016/j.buildenv.2005.04.026. C.I. Jones, G.P. Hammond, Embodied energy and carbon in construction materials, Proc. ICE – Energy. 161 (2008) 87–98. doi:10.1680/ener.2008.161.2.87. L.F. Cabeza, C. Barreneche, L. Miró, M. Martínez, A.I. Fernández, D. Urge-Vorsatz, Affordable construction towards sustainable buildings: review on embodied energy in building materials, Curr. Opin. Environ. Sustain. 5 (2013) 229–236. doi:10.1016/j.cosust.2013.05.005. G. Hammond, C. Jones, Inventory of Carbon and Energy (ICE), (2011). http://www.circularecology.com/embodied-energy-and-carbon-footprint-database.html (accessed November 28, 2014). L.K. Gohar, K.P. Shine, Equivalent CO2 and its use in understanding the climate effects of increased greenhouse gas concentrations, Weather. 62 (2007) 307–311. doi:10.1002/wea.103.