Towards More Sustainability - Environmental Impact of Building Materials

Climate change has been a key focus for the architecture, engineering, construction, and operation (AEC/O) industry for some time. However, recently released figures from the United Nations Environment Programme (UNEP) send a stark warning: the industry is not on track to achieve its 2050 decarbonization targets. According to UNEP’s 2022 Global Status Report for Buildings and Construction, the sector still accounted for around 37% of energy and process-related CO2 emissions in 2021.

It's clear that more needs to be done. While no single approach ensures total decarbonization, the environmental impacts of new construction projects need to be assessed at a very early stage in order to minimize the building’s carbon footprint across its entire life cycle. In particular, choosing sustainable materials wherever possible is an excellent start. By assessing materials early in the planning process, more sustainable options can be specified which reduce the carbon emissions generated during manufacturing, construction, and operation. Typically, this is done using a life cycle assessment (LCA).

LCA is an established method used to identify the environmental risks of construction products, services, and even manufacturing processes. By doing so, it’s possible to compare different design options and ensure that the most sustainable solution is chosen. As the decisions made at the earliest stages have some of the biggest impacts on a building’s environmental performance, it is critical to use these assessment methods at the start of a project.

There are many different tools available to undertake life cycle assessment, each with different levels of granularity and complexity. Essentially, the tools draw environmental information from databases which is then used to calculate various environmental impacts of the building’s components for the whole life cycle of the structure. This provides a consistent basis for making design decisions that can optimize the performance of the building across all stages.

While an LCA considers the entire life cycle of a material – from extraction, manufacture, utilization, and disposal – different materials have different considerations that affect their sustainability. For example, timber is often considered to be more environmentally friendly than concrete. Yet to maximize the ecological benefits of timber, it needs to be sustainably produced from well-managed forests, optimally designed to maximize its service life, and appropriately disposed of at the end of its lifespan. Similarly, the Global Warming Potential (GWP) of bamboo is much less than traditional construction materials such as steel and concrete, but this can be significantly affected by the cultivation practices employed and energy supply used during processing and manufacturing.

Even for traditional construction materials, there is variability. For example, the environmental impact of concrete can be affected by any admixtures. These can extend the service life of the concrete or enable alternative and recycled materials to be used, which can lessen the material’s carbon footprint during its life cycle. The type of concrete used also significantly affects the carbon emissions generated by the material over its lifespan.

A Building Information Modeling (BIM) model is a good foundation for undertaking an LCA. Because BIM models are semantically rich, much of the information required for performing an LCA is already contained in the model. If the model uses OPEN BIM formats, such as IFC, this makes it much easier to exchange information using standardized representations (including element types, material layers, and properties), which allows mapping elements to their corresponding records in the desired ecological database to estimate their environmental impact.

Of course, at an early design stage there are numerous uncertainties that are yet to be resolved. An approach for overcoming those uncertainties could be by specifying materials more generically rather than specifically – such as using “concrete” rather than indicating the strength and type of concrete (e.g., C30). This can mean that an accurate LCA is more difficult to achieve at an early stage of the project when options are being evaluated. However, using different uncertainty mitigation approaches assist in estimating the impact of the decisions being made. There are research projects underway that are investigating how best to address this challenge, such as by using data from completed projects or finding ways to enrich the BIM data and automatically map its elements to an LCA profile or database. As these projects develop, the LCA’s evaluations will become increasingly accurate.

Creating a precise LCA is a complex task, but a critical one if the AEC/O industry is to reach it’s decarbonization goals. Digital tools can help make the assessment easier, and new methods are continuously evolving to streamline the process further.

For example, researchers are investigating how to improve the sound insulation of timber frames at an earlier stage in the design process. Typically, these analyses are undertaken when the project is already in detailed design. The problem with this is that these analyses can identify issues which usually require expensive and time-consuming changes. By using BIM models and IFC, the researchers have been able to shift the planning of the building physics, including acoustic analysis, to earlier stages where any changes have less of an impact.

Another area of development is how to increase the accuracy of calculated environmental impacts, such as embodied carbon or energy efficiency. Whilst these calculations can be carried out at an early stage, their precision is hindered as there are often still many unresolved uncertainties at this stage of the design. The relative “completeness” of the BIM model can often suggest that the design is more finalized than it really is. For example, material classification may be limited, the location or function of materials may be unknown, or there can be deficiencies in the decision process that hamper the design.

To address these issues, different approaches are being developed and trialed. One approach for improving carbon emission calculations is to enrich the life cycle building information, which then enables the assessment of a vast number of possible material combinations at once. Therefore, instead of single values for a particular material combination, a range of results are displayed which reveal the building parts with the greatest emission reduction potential.

To overcome not having accurate information (material or otherwise), one team of researchers has developed a solution using causal inference to improve design decisions for better environmental outcomes. Using a four-step process, a causal diagram with interventions is identified. This provides a nexus for integration domain knowledge with data-driven methods, providing a way to test and interpret design decisions.

Similarly, the Technical University of Munich has developed a model healing process using natural language processing (NLP) strategies. This automatically maps materials in a BIM model to a knowledge database with environmental indicators, to overcome any gaps in the information at an early design stage. This contains all the missing information required for a more accurate LCA to be undertaken.

As the industry races to reach net zero, it’s clear that digital tools are a key tool for decarbonization. These projects demonstrate that even at an early stage, it is possible to make more informed decisions – for better environmental outcomes.