Functional/Declared Unit

Understanding Units in Building Life Cycle Assessment (LCA) and EPDs

In building LCA and Environmental Product Declarations (EPDs), the "unit" is how we measure and report the environmental impacts of a product or building. There are two main types:

• Functional Unit:
  • This focuses on the performance or service a product provides.
  • It answers the question: "What does this product do?"
  • Example: For insulation, a functional unit might be "providing a thermal resistance of 1.5 m²K/W for 50 years over 1 m²." This tells us how well the insulation performs over its lifespan.
  • Functional units are typically used when the EPD includes the product's use phase, showing how it performs in its intended application.
• Declared Unit:
  • This focuses on the quantity of the product itself.
  • It answers the question: "How much of this product are we talking about?"
  • Example: "1 kg of insulation" or "1 m² of 50 mm thick insulation."
  • Declared units are used when the product's function in the building is unclear (it might have multiple uses), or when the LCA doesn't cover the entire product lifecycle (e.g., just manufacturing).

In simpler terms:

• Think of the functional unit as measuring the effectiveness of the product.
• Think of the declared unit as measuring the amount of the product.

Which units does One Click LCA Support?

• Product Level:
  • You have flexibility. One Click LCA allows you to choose the unit that best suits your product and the lifecycle stages you're assessing.
• Building Level:
  • One Click LCA primarily provides results:
    • As a total impact for the entire building.
    • Per 1 m² of building area (with options for different area definitions).
  • Depending on the specific tool within One Click LCA, you may also find results:
    • Per 1 m² of building area per year of building use.
    • Per user.