> For the complete documentation index, see [llms.txt](https://docs.betterbuilding.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.betterbuilding.io/user-guide/workflows/carbon/carbon-faqs/system-boundaries-en-15978.md).

# System Boundaries (EN 15978)

The following Life Cycle stages are included in a full-scope assessment against the EN 15978 standard. In building-level calculations, the idea is to consider all the meaningful impacts over the lifetime of the building. However, different certifications and calculation systems may limit the modules calculated.

**A1:** Raw material extraction and processing, processing of secondary material input (e.g. recycling processes)

**A2:** Transport to the manufacturer

**A3:** Manufacturing

Module A1, A2 and A3 are typically declared as one aggregated module A1-A3. All stages include the provision of all materials, products, and energy, as well as waste processing up to the end-of-waste state or disposal of final residues during the product stage. The assessment considers only the building and its parts, ignoring smaller items such as furniture or appliances.

**A4:** Transport to the building site

**A5:** Installation into the building.

Stages A4 and A5 include all impacts and aspects related to any losses during this construction process stage (i.e. production, transport, waste processing and disposal of the lost products and materials).

**B1:** Use or application of the installed product

**B2:** Maintenance

**B3:** Repair

**B4:** Replacement

**B5:** Refurbishment

**B6:** Operational energy use (e.g. operation of the heating system and other building-related installed services);

**B7:** Operational water use

Stages B6 and B7 also include the provision and transport of all materials, products, energy and water provisions, waste processing up to the end-of-waste state or disposal of final residues during this part of the use stage.

**C1:** De-construction, demolition

**C2:** Transport to waste processing

**C3:** Waste processing for reuse, recovery and/or recycling

**C4:** Disposal

All C stages include provision and transport, provision of all materials, products and related energy and water use.

**D:** Reuse, recovery and/or recycling potentials, expressed as net impacts and benefits

Module D allows supplementary information beyond the building lifecycle to be considered. For example, in construction projects, this includes the disposal of waste after demolition can be taken into account. The use of Module D is consistent with a cradle-to-cradle approach.


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