> ## 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.

# Material mapping

> Questions about mapping inventory items to EPDs and constructions, units, lifetimes, and quantities.

<AccordionGroup>
  <Accordion title="An EPD I need is missing from the library — how do I get it added?">
    Post a request in the pinned [EPD Requests topic](https://community.realtimelca.com/t/new-topic-for-epd-requests/138) on the community forum with a link to the EPD. The team adds it to the Real-Time LCA library and replies on the thread once it's in.
  </Accordion>

  <Accordion title="An insulation EPD is declared at a fixed thickness (e.g. Flexibatts 37 mm), but my wall uses a different thickness — how do I map it?">
    The declared unit is fixed by the EPD and can't be changed. The recommended workaround is to create a dedicated **construction** that wraps the EPD at your target thickness — e.g. *Flexibatts 37, 240 mm* — and set the amount per m² of construction.

    For 240 mm that's 240 / 37 ≈ **6.49 m²** of insulation per m² of wall. Mapping the wall to that construction then gives the correct quantity without you having to edit any areas.

    <Note>An updated construction feature is in progress to make m³ ↔ m² handling easier.</Note>
  </Accordion>

  <Accordion title="Can I change the declared lifetime of an EPD — e.g. set a window to 25 years for BR18?">
    Product-specific EPDs have a tested, fixed declared lifetime — that's what shows up as the default when you map. Generic and industry-average EPDs do let you enter your own lifetime in **Item properties → Lifetime (years)**.

    For compound items like windows, Revit can split out each part. You can map the glass separately with a product-specific EPD at 25 years while the overall generic window stays on the 50-year baseline.

    Field reference: [Material Mapping → Item properties](/user-guide/project/material-mapping#item-properties).
  </Accordion>

  <Accordion title="How is a layer's thickness handled in material mapping?">
    It depends on how the layer is modelled in your authoring tool and whether the quantity comes through as m² or m³.

    To check which unit a specific item is using, click the item in the mapping view to open **Item properties** — the **Preferred unit** row shows the unit the EPD's impact is multiplied by.

    See [Material Mapping → Item properties](/user-guide/project/material-mapping#item-properties).
  </Accordion>

  <Accordion title="Does Real-Time LCA convert model quantities to match the EPD's declared unit?">
    Yes. The model gives us the quantity in whatever unit it was measured in — square metres, cubic metres, length, pieces, and so on — and we automatically convert it to the **declared unit** of the EPD or construction you mapped to, using the mass and density values from the EPD.
  </Accordion>
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