Introduction

Building Information Modelling (BIM) is playing a vital role in achieving the goals of sustainable construction. With BIM it is now possible to tone down the environmental impact and elevate energy performance of the buildings by controlling harmful greenhouse gas emissions, consumption of resources, waste production, and pollutants during all construction phases.

However, the challenge is, an enormous amount of data is needed to leverage the full potential of BIM in sustainable construction. The data includes but is not limited to information about building materials energy consumption, resource consumption, and the environmental impact it will have during its entire life cycle from raw material extraction to disposal. To overcome this challenge Life Cycle Assessment (LCA) can be utilized coupled with BIM to achieve the desired sustainability goals for buildings.

What is Life Cycle Assessment?

Life Cycle Assessment, unremarkably referred to as LCA, is a methodology that aims to quantify the environmental impacts of products, taking into consideration the entire life cycle since the extraction of raw materials, manufacturing and transportation to the site, construction, operation, and maintenance, till the end-of-life and recycling or demolition.

As per ISO 14040.2 LCA is a technique to assess the environmental aspects and potential impacts associated with a product, process, or service, by:

• Compiling an inventory of relevant energy and material inputs and environmental releases
• Evaluating the potential environmental impacts associated with identified inputs and releases
• Interpreting the results to help decision-makers make a more informed decision.  

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The LCA is a systematic process that comprises four key components, Goal and Scope, Inventory analysis, Impact Assessment, and Interpretation. Within goal and scope the product, process, or activity is described and boundaries are identified to avoid any over estimations that lie beyond the scope of assessment. Inventory analysis identifies and quantifies resources (water and material usage) used and environmental releases (air emissions, disposal of solid waste). While Impact Assessment examines the potential ecological and human effects of resource usage and environmental releases, in simple terms Life cycle inventory(LCI) can be thought as ‘INPUT’ and the Impact Assessment can be thought as a resulting ‘OUTPUT’. Getting the results is pointless if the results are not interpreted to yield valuable information, Interpretation is the last component of LCA where the  LCI and Impact Assessment information is evaluated to select the preferred product, process, or service.

To assess the results and make informed decisions about choosing a product, service, or Process over another it is necessary to establish a linkage between them and their potential environmental impacts. Therefore life cycle assessment is categorized into various impact categories to study the potential environmental impact a particular product, service, or process might have on the environment. Commonly used life cycle Impact categories are listed below

• Global Warming
• Stratospheric Ozone Depletion
• Acidification
• Eutrophication
• Photochemical Smog
• Terrestrial Toxicity
• Aquatic Toxicity
• Resource Depletion
• Land Use
• Water Use

The listed impact categories include atmospheric releases, energy usage, solid waste, and resource usage. For decision making quantification of these categories is essential therefore every impact category is measured in quantitative units, for instance, the atmospheric releases are measured in kgCO2e (Carbon dioxide equivalent ), energy is measured in Kilowatt Hours (KWh), Water usage in Gallons or cubic meter. The challenge is, suppose 9 tons of Methane and 2 tons of Nitrogen oxide is released into the atmosphere, which could have a greater potential impact? To overcome these characterization factors are used to convert different elements of the Impact category into a common unit to ensure better decision making. To answer the above question simple calculation is required,

Quantity of Methane - 9,000 kg

Quantity of Nitrogen Oxide - 2,000 Kg

Methane Characterization factor (Global Warming Potential) - 26

Nitrogen Oxide  Characterization factor (Global Warming Potential) - 265

Methane Global warming Potential Impact - 9,000 * 26 = 2,34,000 KgCO2e

Nitrogen oxide  GWP Impact - 2000 * 265 = 5,30,000 KgCO2e

From the above example, even though the quantity of Nitrogen oxide is released less it has more potential to cause global warming than Methane that is released in abundant quantities relative to Nitrogen oxide.

In this way, LCA can facilitate Designers, Architects, and Engineers to select the product or process that results in the least environmental impact

Integrating LCA with BIM

BIM and LCA can be considered as two faces of the same coin, while on the one side BIM supports the integrated design and improves information management and coordination between the different stakeholders throughout the building life cycle

. On the flip side, LCA is an effective technique for assessing the environmental performance of the building/building materials. . Both LCA and BIM should be integrated into the decision-making process in the initial stages for achieving a comprehensive overview of the project from the beginning. LCA can simplify the data input into the BIM model for various building materials to carry out a detailed study about the sustainability of the building. The quality of energy analysis and environmental impact study can be drastically improved with huge data from LCA and the ability of BIM to qualitatively manage such huge data.

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Even Though getting a green building rating for the building is a step towards sustainability many environmental experts argue that these rating systems have many shortcomings. For instance, Leadership in Energy and Environmental Design (LEED) which is a renowned green building rating system, in which some LEED credits are provided for having bicycle racks in the parking area within the facility. The argument is that, suppose the bicycle racks are added just to earn extra LEED credits so that the monetary value of the property is increased and have no functional value within the facility, in such cases the fundamental intent of the green building gets defeated. In the above case, the LCA of bicycle racks within a BIM model in no time could show the additional environmental impact it could potentially cause throughout its life cycle.

Performing LCA within  BIM authoring tools provides a number of advantages, when the designers design their buildings in a BIM authoring tool, they assign building materials and quantities to create a Bill of Materials (BOM) for the full building or constituent parts. This BOM updates automatically as the design changes, allowing engineers and architects to assess the environmental impact of their design choices on the overall sustainability of their projects in real-time. This flexibility to perform LCA at the speed of design is what has made BIM and  LCA integration a trending topic in the BIM community.

There are a number of tools that bring the strength of LCA to a BIM authoring tool both as a plugin to an existing BIM authoring tool as well as standalone web applications, these tools contain information regarding the building materials required to perform LCA, mapping the materials from BIM model to LCA database creates a link for information flow from BIM model to LCA plugin or web application and then further calculations are performed by LCA tool to quantify a building or material's embodied environmental impacts to land, air, and water systems.

Challenges in the Integration Process

Although the BIM and LCA Integration brings mammoth value in sustainability, still there are some challenges that need to be addressed to make the process more robust.

• Insufficient data about material properties in BIM models in terms of LCA analysis.
• Less expertise about BIM and LCA processes and tools with the stakeholders.
• Quality of data input for performing LCA “an LCA is as good as data it uses”
• Less availability of data for unconventional building materials
• Additional resources, Time, and cost associated with data gathering and management

Conclusion

BIM-LCA is an optimal process towards achieving sustainable development, environmental protection, and ameliorating the decision-making process in the construction sector by combining rich data about building materials through LCA databases and easy information management with the BIM processes and tools.

Integration of BIM and LCA provides significant potential for the industry’s long-term sustainability goals.

Using all available building information and connecting it to existing LCA databases offers the ability to illustrate the environmental impact of the decisions taken by construction professionals and can bring sustainable development in the early stage of the planning, where the changes are minor and still affordable. Additionally, with the update of the LCA database with alternative building materials and the  6D BIM (sustainability and energy efficiency), the future of BIM-based LCA appears bright.

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To know more about BIM LCA integration reach out to us at www.desapex.com