> ## Documentation Index
> Fetch the complete documentation index at: https://docs.realtimelca.com/llms.txt
> Use this file to discover all available pages before exploring further.

# ISO standards

> The parent ISO standards that underpin whole-building LCA in Real-Time LCA.

Real-Time LCA aligns with three families of ISO standards: the parent LCA methodology in *[ISO 14040:2006](https://www.iso.org/standard/37456.html)* and *[ISO 14044:2006](https://www.iso.org/standard/38498.html)*, the building-level framework in *[ISO 21931-1:2022](https://www.iso.org/standard/74518.html)*, and service-life planning in the *[ISO 15686](https://www.iso.org/standard/59018.html)* series. All are available for purchase from [ISO.org](https://www.iso.org). The European calculation method [EN 15978](/methodology-and-compliance/en-15978) operationalises these for buildings in Europe.

## ISO 14040 and ISO 14044 — LCA principles

ISO 14040 sets out the principles and framework of life cycle assessment; ISO 14044 specifies the requirements and guidelines. Together they define the four LCA phases used implicitly across every calculation in Real-Time LCA:

* **Goal and scope definition** — captured per project (functional equivalent, reference study period, system boundary).
* **Life cycle inventory analysis** — built from the Building Component Inventory and the linked EPD or generic dataset for each material.
* **Life cycle impact assessment** — characterisation per EN 15804+A2 indicator factors.
* **Interpretation** — presented through the project dashboard, emissions-over-time view, and report exports.

## ISO 21931-1:2022 — framework for buildings

ISO 21931-1 provides the international framework for environmental performance assessment of buildings and civil engineering works. It defines *what* a building-level assessment must cover (functional equivalent, system boundary, modules, indicators) without prescribing the calculation rules themselves.

[EN 15978](/methodology-and-compliance/en-15978) is the European calculation method that conforms to this framework. Real-Time LCA implements EN 15978, so projects produced in the platform are simultaneously consistent with ISO 21931-1.

The 2022 revision of ISO 21931-1 aligns more closely with the *EN 15804+A2:2019* indicator set; the in-progress revision *prEN 15978-1* is expected to bring EN 15978 into the same alignment.

## ISO 15686 — service life planning

The ISO 15686 series covers service life planning for buildings and constructed assets. The data relevant to Real-Time LCA is the **reference service life (RSL)** of each construction product, which drives module B4 (replacement) calculations: a product with an RSL shorter than the project's reference study period is replaced one or more times within the study period, and each replacement event re-emits the embodied carbon of the new product.

Real-Time LCA uses national lifetime tables — for example the BR18 lifetime table for Denmark — as the source of RSL values. See [Assumptions and defaults](/methodology-and-compliance/assumptions-and-defaults) for how overrides work at project level.