Under BREEAM 2011, the Energy Performance Ratio (EPR) was introduced as a new methodology for calculating ENE 1 (CO2 reduction) credits.
The EPR is a triple metric, assessing energy demand, energy consumption and CO2 emissions, and represents a significant departure from the previous method, which assessed only CO2 emissions. It was introduced to promote energy efficient design rather than simply reducing CO2 emissions using renewable technologies.
Following introduction of the EPR however, many assessors have noted that achieving credits under ENE 1 has become far more challenging, and that certain buildings appear to unexpectedly underperform, even where efficient services such as combined heat and power (CHP), and efficient building fabric is incorporated in the design.
In June 2012, BRE updated the BREEAM ENE 1 calculation methodology in response to feedback from assessors and a review of energy data relating to over 500 buildings.
This article explains how this has made gaining credits under this issue more achievable for many typical building types, although achieving the BREEAM ‘Excellent’ minimum standards (6 credits, plus a 25% improvement on the Building Regulations Target Emission Rate) remains extremely challenging.
Summary of changes
The EPR has presented several challenges for design teams seeking to maximise the ENE 1 score.
- The triple metric approach makes it crucial that reductions in energy demand and consumption are a central consideration in all design decisions.
- It was evident that those buildings with low EPR scores had to make larger improvements in order to gain additional credits than those at the higher end of the scale.
- Buildings with CHP appeared to struggle to achieve credits, despite the reduction in energy consumption associated with this technology.
BRE’s review of these issues has resulted in the following updates to the ENE 1 calculation methodology:
- A new linear benchmarking scale has been introduced to award credits. This means that it is easier to progress from one credit to the next at the lower end of the scale (up until 6 credits). The previous calculator was weighted so that larger improvements were needed at the lower end of the scale, reflecting an assumption that is was ‘easier’ to make initial improvements to energy performance
- The Energy Consumption metric will now be based on primary energy, rather than delivered energy. This will provide greater rewards for buildings using CHP, which will be particularly relevant to developments in London.
- Due to the shift to assessing primary energy consumption, the performance weightings have been updated, shifting emphasis away from Energy Demand and CO2 Emissions, and towards Energy Consumption.
The table below outlines the ENE 1 credit scores achieved under both the original and revised BREEAM 2011 calculation methodology by different building types.
Our testing has demonstrated that in most cases the ENE 1 score of a building will benefit from using the revised methodology. For schemes already in progress (using the BREEAM New Construction 2011 guidance versions 1.0 and 2.0), the assessor can now choose which methodology to use, so a simple check is always worthwhile. In some cases, as demonstrated above, the overall score can increase dramatically.
It should be noted that achieving BREEAM ‘Excellent’ minimum standards will still be extremely challenging, despite this revision. This is because as well as the minimum requirement to achieve 6 ENE 1 credits, a building must also achieve a 25% improvement on the Building Regulations Target Emission Rate.