The construction industry is one of the largest exploitations of both renewable and non-renewable natural resources. It is therefore crucial to select materials with low impact and examine their embodied impacts.
An LCA is a study of a material or product from its extraction to its use in building construction. It can also be used to assess a whole building.
Energy
Construction and the operation of buildings have long-lasting impacts on the environment. These impacts can be reduced with the use of sustainable building materials that have low embodied energy. These can include those that are extracted locally and manufactured with renewable energy.
A building’s energy consumption is a large portion of its overall carbon footprint. The life cycle assessment can provide a clear picture of this. This begins with an accurate bill of quantities for each material and its components. Then the data can be fed into a computer model to perform the LCA.
The model will calculate the impact of each material during its cradle to grave stages. This includes the extraction of raw materials, their transportation to the manufacturing site, labor and equipment use, etc. It will also determine the emissions from each of these processes, such as global warming potential (GWP), ozone depletion potential, acidification of land and water and other impacts.
Once the data is compiled, it will be presented in a database known as an LCI or Life Cycle Inventory. Different databases have varying focuses. A common one is Gabi, which is used by many providers of construction materials and products in the US.
Water
The LCA of a building begins with a list of all the materials used in that building, such as bricks, concrete, glass, PVC, electrical components, etc. This list is analyzed to obtain a total mass balance, and from there, emissions are calculated for each material, including those from energy, chemicals, or processes that lead to environmental impacts like global warming potential; photochemical smog formation; depletion of the stratospheric ozone layer; acidification of soil and water; eutrophication; and direct human respiratory impact.
This step is sometimes referred to as the “cradle-to-gate” stage. Next, the process of manufacturing the building material or product takes place, followed by the construction phase. Finally, when the building is no longer being used, the LCA analyzes the end of life phase, determining where the materials will go for recycling or disposal and the associated emissions.
Various methodologies exist for conducting an LCA, and the choice depends on the goals of the assessment. A streamlined assessment uses generic datasets to reduce costs and time, while detailed assessments use system-specific data for more comprehensive analysis and greater accuracy.
Air
Air emissions incurred by building materials during their service life can significantly affect the environment. These include carbon dioxide, methane, nitrous oxide, sulphur dioxide, volatile organic compounds and particulate matter. Controlling these emissions can help improve the overall environmental performance of a building.
A life cycle assessment (LCA) evaluates the environmental impact of a product, from raw material extraction through manufacture, distribution and use to disposal. The impacts are assessed in six impact categories: global warming potential; ozone depletion potential (from the release of ozone-depleting substances); acidification of land and water sources (from the release of acidifying pollutants such as sulphur dioxide, nitrogen oxides and ammonia); nonrenewable resource depletion; and eutrophication (from the release of nutrients such as nitrogen and phosphorus into waterways).
Designers can compare the impact of different building materials by using an LCA tool such as Tally or Gabi. They can also choose building materials with a low environmental impact based on their properties such as high recyclability, longevity and local production, which reduces transport costs and carbon footprint. These strategies can reduce overall building costs.
Materials
The material choices in a building have a significant impact on environmental and human wellbeing. These impacts include global warming (greenhouse effect), ozone depletion, acidification of land and water, and smog.
The best way to reduce these impacts is through designing a building with closed-loop cycles where materials are reused and in a sense recycled at the end of their useful life, rather than being sent to the landfill. This reduces the need to extract further resources from the earth’s limited natural resources.
LCA helps to identify where a building’s impacts are being made by interrogating the procedures that a product goes through during its use phase, from raw materials extraction, manufacturing and construction to the final disposal or recycling of a material or a whole building. A cradle-to-grave approach is usually used in LCA, with a focus on the environmental impact and cost of a product or building throughout its entire life cycle.
Waste
The energy and raw materials required to produce a product or building material are not always used efficiently. Thus, there are atmospheric emissions and waterborne wastes produced through all stages of the production process. These byproducts can be useful or harmful and the waste materials may need to be recycled or disposed of in some way.
Life cycle assessment helps to identify and understand environmental impacts of products, materials, buildings and industrial systems. It helps to determine the best ways of producing these goods and services. It is also a tool that provides data for companies seeking to improve their eco-friendly potential within design processes (eco-design) and for complying with internal environmental policies, legislation or certification.
LCA uses a four-step method: scoping and goal definition; life cycle inventory (LCI); LCIA or Life Cycle Analysis and interpretation; and comparing alternatives. It can be applied at a range of scales, from cradle-to-grave or gate-to-gate. A cradle-to-grave approach examines all the stages of a product’s production, use and disposal whereas a gate-to-gate LCA only considers the extraction, materials processing, manufacturing, packaging, transportation and distribution phases but does not include the end-of-life or disposal phases.