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Smarter investment for housing associations – CROHM vs EPC recommendations

If you are looking for a way to improve the energy efficiency of your worst-performing stock then you might turn to your EPC certificate for recommendations. However, Parity have shown impressive savings can be made by using the minimum SAP analysis as part of the CROHM (Carbon Reduction Options for Housing Managers) stock assessment service.

Our minimum SAP scenario looks at the cumulative costs and savings associated with bringing your stock up to a minimum SAP target by modelling energy saving initiatives in order of cost effect (£s per SAP). Whilst EPC certificates also report the costs and savings, we believe that the fixed order of application is somewhat inefficient. Consequently we thought it would be interesting to see what the actual cost saving differences are between the two services – noting that we used the same pricing set for both for ease of comparison.

Our investigation showed that to achieve a minimum SAP C (SAP 69) the resultant average SAP, CO2 and fuel bills were very similar for both services. Yet CROHM estimated a 28% lower investment – equating to a £1.4 million saving for a medium sized housing association of approximately 4,800 properties. One example property shows that an EPC recommendation of external wall insulation produces similar average energy savings to the much cheaper CROHM suggestion of adding an actual boiler model (typically saving 1 SAP point) and upgrading inefficient lighting – saving an estimated £2,819. Higher %age savings can be achieved for lower SAP targets, where more invasive (and expensive) measures (such as installing solid wall insulation) are recommended early on that result in significant overshoot of the target SAP.

Cost comparison of CROHM vs epc reccomendations



Surprisingly for the higher SAP targets we noticed that the number of properties that failed to achieve the desired target SAP score after all possible measures were applied was actually higher within the CROHM analysis. After a bit of investigation, we discovered that this is mainly because EPC certificates suggest wind turbines as an upgrade option – see graph above.  Whilst this is possible with CROHM, the cost and practicality of the measure means housing managers often choose to rule this out of the assessment.

Number of properties missing SAP target


Furthermore, we found that a lot of the measures on the EPC certificate are more restrictive than the CROHM minimum SAP measures and therefore limiting the number of upgrade options. Examples of these include:

  • Not upgrading regular boilers to more efficient combi boilers – CROHM has the option to upgrade all regular boilers to combi
  • Upgrading single glazing when there is less than 80% multiple glazed on the property – CROHM has the option to upgrade any remaining single glazing
  • Applying cavity wall insulation to properties pre 1982 – CROHM would also investigate the application of insulation to properties between 1983-1995

In summary, the financial savings were calculated as being between 23%-53% across different SAP targets, demonstrating the significance of applying measures in a logical and cost effective order and shows that the investment required can be significantly reduced by minimising the amount of overshooting and offering less restrictive initiatives.