The amount of recycled and/or secondary aggregate must be greater than 25% of the total amount of high-grade aggregate specified for the development. In order for the recycled/ secondary aggregate in each high-grade application to be included in the calculation of the 25% amount, the minimum percentages in the relevant table must first be met.
Note: not all high-grade applications must meet the percentages in the table in order to award a credit, however all high-grade aggregate must be included in the total.
The following example is taking figures from UK NC 2014. The applications and percentages vary with each scheme version.
If only Structural Frame, Building foundations and Granular fill/capping are present. The following calculation would be carried out to confirm compliance:
Structural Frame = 50 tonnes of aggregate; of which 5 tonnes is recycled/ secondary aggregate
Building foundations = 50 tonnes of aggregate; of which 8 tonnes is recycled/ secondary aggregate
Granular fill/capping = 80 tonnes of aggregate; of which 80 tonnes is recycled/ secondary aggregate
Table 54 minimum percentages are:
Structural Frame must have 15% recycled/ secondary aggregate for 1 credit, i.e. at least 15% of 50 = 7.5 tonnes. In our example we have 5 tonnes, therefore this amount cannot be included in the total calculation, and all 50 tonnes must be considered as primary aggregate.
Building foundations must have 20% recycled/ secondary aggregate for 1 credit, i.e. at least 10 tonnes. We have 8 tonnes, so again, this must all be considered as primary aggregate.
Granular fill/capping must have 100% recycled/ secondary aggregate for 1 credit. In our example all 80 tonnes is, therefore this amount can be considered as recycled/ secondary aggregate.
To determine if a credit can be awarded, the following calculation is then carried out:
Total aggregate; 50 + 50 + 80 = 180 tonnes
Aggregate to be included in calculating % = 80 tonnes (Granular fill/capping only)
% therefore is 80/180 = 44% which exceeds the 25% minimum
This shows that despite two high-grade applications not meeting the minimum threshold percentages, the overall % is sufficient to award the credit.
The same principle applies to the calculation of the Exemplary level criteria.