Recommendation 11

The public need to have confidence that homes stated to be net zero are as promised. Therefore, the Government should review the metrics used to measure energy efficiency in homes. This should include considering how energy performance certificates are calculated, how embedded carbon could be better incorporated into the calculations of the carbon emissions of properties, and how the in-use performance of properties can be accurately measured. The Government should introduce measures to close the performance gap, including post-occupancy evaluations, which assess whether the actual energy output of new properties meet the standards promised by the developers once they are being lived in. This is particularly important as evidence indicates that new homes can lose 50% more heat than expected.