The modern construction world is transitioning towards sustainable methodologies. At the forefront of this evolution is the Life Cycle Assessment (LCA) of buildings. Adhering to standardized procedures not only advances consistency in assessment but also facilitates benchmarking, a cornerstone of progressive architectural and engineering practices. This guide revolves around the LCA model rooted in the structure specified by CEN TC 350 for construction work sustainability.

Foundations of the Life Cycle Assessment Model

The underpinnings of our proposed model are two pivotal standards:

• EN 15804 [18]: This standard addresses the product-level assessment.
• EN 15978 [19]: This zeroes in on the building-level assessment.

Choosing a standardized methodology is crucial for:

• Maintaining a uniform approach tailored for construction work evaluation.
• Ensuring comparability among different building evaluations.
• Upholding the key objective of benchmarking.

A Deep Dive into the Model’s Specifics

The intent is to furnish details on our adopted model, especially regarding sustainable design and its application in the LCA of buildings.

Basic Requisites for Conducting Analysis

When delving into the LCA, certain parameters and assumptions form the bedrock of calculations. This guide illuminates these requirements and illustrates any model variations from the referenced standards.

Any element or specific not covered herein should be sought from EN 15804 and/or EN 15978.

Integration with Professional LCA Software

Our model is seamlessly integrated into leading LCA software, ensuring that professionals have the tools they need for meticulous building assessments. The subsequent sections will elucidate on this software implementation.

The Model’s Expanse and Depth

Although our model can serve the LCA of an entire building, our benchmarking primarily concerns the building’s structural system. Therefore, subsequent discussions will cater to this essential component.

4.1 Objectives and Limits of the Analysis

4.1.1 Primary Aims

The LCA’s crux is to evaluate the environmental footprint of a building’s structural system over its entire lifecycle, from material inception to its ultimate end. The overarching ambition is the creation of a uniform LCA tool, pivotal for benchmarking residential and office structures.

4.1.2 Defining Functional Equivalence

Here, functional equivalence encompasses:

• Building’s purpose (residential or office).
• Total Gross Floor Area (GFA).
• A defined time span.

For office spaces, an alternative functional equivalent considers the number of workstations over the GFA. The results are normalized based on the building’s GFA and year.

A significant component is the estimated building lifespan, rooted in the design code or structural system regulations. In the absence of explicit lifespan documentation, a 50-year period is the norm, aligning with EN1990 [41] for residential and office structures.

4.1.3 Boundaries of LCA

Every phase, from product inception to the end-of-life stage, is encapsulated in the model. The modular concept, introduced by CEN TC350 standards, demarcates the LCA’s system boundaries. A notable exception is Modules B6 and B7, focusing on operational energy and water consumption during a building’s lifecycle. Since these do not influence the building’s structural framework, they are omitted.

Furthermore, to align with the model’s objectives and bolster EU resource efficiency directives, Module D finds its place in our building’s LCA. This is a divergence from the conventional CEN TC 350 standards, which view Module D as an optional inclusion.

Table 1. Scope of the LCA

Product stage	Process stage	Use stage	End-of-life stage
A1 A2 A3 A4	A4	B1 B2 B3 B4 B5 B6 B7	C1 C2 C3 C4 D
Raw material supply	Transport	Manufacturing	Transport