The construction industry is one of the largest exploiters of renewable and non-renewable resources. Its impact on the environment is enormous.
Life Cycle Assessment (LCA) is a method for examining cradle-to-grave environmental impacts produced by building materials. It can help in choosing eco-friendly building materials. Despite its usefulness, many impediments hinder its use in practice.
Inputs
Inputs are all the raw materials and energy that are used to make a building. They include things like the embodied energy of materials and building component combinations, their production, transportation to the construction site, their use in the building, waste disposal and maintenance of the building. Inputs can also be indirect such as the impact of fossil fuel depletion and eutrophication caused by nitrogen and phosphorus entering waterways.
Depending on the goal of the LCA, different information will be included or excluded. For example, a wood panel reused in another building is an externality, but the carbon stored within that panel enters the system boundary of the second building as a reduction in carbon emissions from extraction of new raw material.
There are few direct comparison studies of the different LCA methods. However, in the building sector, Nassen et al. found that IO analysis led to 2-times-higher estimates than process LCA. This may be due to the fact that IO LCAs tend to be more cement-intensive than their counterparts, which could bias the results towards higher emissions.
Outputs
Building materials create environmental impacts throughout their life cycle. Those impacts include reducing non-renewable resources and degrading the environment. To reduce these impacts, designers need to examine how each material is produced and used in a construction project. A building life cycle assessment, or LCA, is a way to do that.
A LCA examines the building process from raw materials extraction to the end of a building’s useful life. Depending on the scope of the study, it can look at a whole building, a product or just one type of material or component.
Typically, a building LCA begins with a list of all the materials used in a building. Then, the mass balance of those materials is calculated. The results of that calculation are then used to determine the impact of those materials. The impact is measured in terms of potential environmental damage, such as global warming, ozone depletion and acidification of land and water. An LCA can also assess a material or product’s supplier by looking at the provider’s Environmental Product Declaration (EPD) or an Environmental Profile.
Energy
The energy and water inputs and outputs in the building life cycle are determined by conducting an LCA study of a material or building component combination (BMCC). Generally speaking, an LCA includes the following phases: embodied energy, transport to the construction site, usage phase, reprocessing where necessary, disposal and demolition [18].
A full LCA takes into account a wide range of impacts, but most commonly they include greenhouse gas emissions, ozone depletion, acidification of land and water, eutrophication of lakes and rivers and non-renewable resource depletion. The impact assessment is divided into Modules A, B and C and an additional optional Module D which allows the consideration of external impacts beyond a project’s system boundary.
Using less energy intensive materials during the building process is one of the most effective ways to reduce overall environmental impacts. In addition to reducing operational energy use, it can also reduce waste generation, energy and water consumption and optimize costs. Manufacturers of construction materials and products can make their lifetime impacts known by declaring them in an EPD or environmental profile, which helps designers find suitable alternatives.
Water
The building materials that make up a structure must be sourced, processed and transported. This results in water inputs and outputs that must be taken into account as part of a life cycle assessment. This information can be used to minimize the impact of a material and its processes, such as reducing GHG emissions or minimizing embodied water.
While GHG emissions have received the most attention, they are only one of a range of environmental impacts that must be considered when choosing materials for construction. Other impacts include ozone depletion, water consumption and eutrophication of lakes and rivers.
Life Cycle Assessment is an important tool that should be used by builders and designers to reduce the environmental burden of building materials. Using LCA allows designers to select materials that are both functionally and aesthetically appropriate while lowering the total cost of ownership. However, the lack of a comprehensive and internationally-accepted data inventory hinders the use of this tool in the United States. Until this is addressed, it will be difficult to reduce the environmental impacts of building materials.
Waste
The LCA of building materials includes all the procedures that a material or product undergoes from its raw state to its final destination at the end of its life. This includes its extraction from the earth as well as all of the energy that it consumes. The process of calculating the embodied carbon of materials is also included in the LCA.
The cradle-to-grave process is often broken down into four stages: production, construction, use and end of life. While GHG emissions have gained the most attention, there are a wide range of other impacts that need to be evaluated such as ozone depletion, resource depletion and water toxicity.
Until recently, the availability of data on the life cycle of a material or a building was limited. There are now several public database developments and other academic, commercial and industrial databases available. However, they still have many problems such as boundaries, energy supply assumptions and the complex nature of economic activities. This can make it difficult to compare LCA results. This is a major issue that needs to be resolved in order to enable the wider adoption of LCA for sustainable building design.