Materials Efficiency Metric

The eTool Materials Efficiency Metric (MEM) was created to calculate material circularity and apply it to a whole asset analysis. The metric is calculated based on the mass of material that is virgin or reused, and the amount of renewable and non-renewable primary and secondary material. After calculating the mass, a discount factor (weighting) is applied to reused materials and materials with higher renewable content. The lower the materials efficiency metric number the better or more “circular” the material is.

eTool users are able to report on the Materials Efficiency Metric as they would normally report on an indicator so that is visible in the same reports alongside other environmental indicators. Material efficiency metric can be calculated at the asset level which takes into account the design life achieved with materials (years). 

There is a procedure for obtaining the MEM (as per HS2’s requirement) that requires that users report the MEM per year (using the time scale when generating the report). What the user is reporting is actually MEM.year as an indicator, so reporting this per year when generating the report will get the ME asset indicator (ME.Year/Year = ME).


For each asset, the materials efficiency using eTool should be calculated using the following equation:

ME.Year = Mv + 0.7*Mrec + 0.35Mren + 0.245Mrenrec + 0.1Mreu + 0.35Mrenrec


ME.Year = Materials Efficiency Mass = The materials efficiency (with no time component)
Mv = Mass of non-renewable primary material (t)
Mrec = Mass of non-renewable secondary (recycled) materials (t)
Mren = Mass of renewable primary material (t)
Mrenrec = Mass of renewable secondary (recycled) material (t)
Mreu = Mass of reused non-renewable materials (t)
Mrenrec = Mass of reused renewable materials (t)

Each mass of material should include the materials required for any associated temporary use (i.e. those consumed during construction plus the construction waste generated). At design stage, for materials that have variable recycled/renewable/reused content, the industry average rates should be used until the specifications have been confirmed.

eTool Indicators & Processes

Material processes in eTool library were updated to include:

  • Mass of non-renewable primary material (t)
  • Mass of non-renewable secondary (recycled) materials (t)
  • Mass of renewable primary material (t)
  • Mass of renewable secondary (recycled) material (t)
  • Mass of reused non-renewable materials (t)
  • Mass of reused renewable materials (t)

New indicators were added to the eTool for:

  • Total Mass
  • Mass of recycled materials
  • Mass of reused materials
  • Materials Efficiency Mass

Reporting Indicators with the LCA Report

These indicators are available only when using eTool default LCI Source but are not available in the IMPACT database. To turn on these indicators when generating the LCA report, please refer to the setting below:

Below is an example of how the material efficiency metric indicators are displayed as shown in page 3 of the LCA report:

Reporting Indicators via ‘All Impact Details’ Report

If you want to report on these indicators via the ‘All Impact Details’ report, you will need to turn on these indicators in the Project Level under the ‘Indicators’ tab.


Related articles: New Materials Efficiency Metrics, Links between LCA and the Circular Economy, Are we running out of building materials?, BREEAM Mat-06 Material Efficiency


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