Home Insulation

Case study - 92 properties in SK31

Energy performance certificates (EPC) are a legal requirement when properties are built, sold or rented in the UK and the information is in the public domain. FLUKE has made a case study of 92 properties in the English East Midlands, ordnance survey grid area SK31. The housing stock consisted of a mixture older Victorian and early 20th century terraced housing and some more modern, estate built houses. (The data are anonymised and the grid area covers 100 square kilometres; this should provide adequate data protection to any individual householder). An EPC is issued following a detailed survey of the property and contains much useful information. This case study mainly focusses on the Standard Assessment Procedure (SAP) scores for the current and potential energy efficiency ratings. The latter score indicates the potential improvement in efficiency that might be achieved, if all the energy-conserving measures including insulation, low energy lighting, solar water heating etc. recommended in the report were indeed carried out. The comparison between these 'before' and 'after' SAP rating figures provides a simple method for assessing the potential improvement achievable if the entire housing stock were renovated to all the recommended measures in the EPC.

Histograms for the current and potential SAP ratings

The following two charts show the distribution of SAP ratings for the 92 houses:

Naturally, the distribution shifts to the (more energy-efficient) right, when the energy saving measures are implemented. Another way to view the data is to correlate the SAP ratings before and after improvements:

There is considerable scatter in the data. Some of the lowest rated properties would benefit greatly from insulation, on the other hand mid-range rated houses may be old stock that have already been insulated to a good standard - or new houses that haven't been improved.

The bolder, 45° line represents the current situat