Why is my EPC rating so low?

This is one of the most common questions we get asked as Energy Assessors and there’s generally a few common issues that crop up time and time again.

Firstly is the construction type of the property. Older solid brick or stone built properties will generally produce poorer ratings than their cavity wall equivalents. Solid brick and stone walls by their very nature aren’t particularly efficient at retaining heat and therefore this is reflected in the EPC rating they are given.

Mid terraced properties where you’ve got just a relatively small amount of exposed walls to the front and back will come out better than end of terraced or detached properties of the same construction type simply because they have less heat loss perimeter.

Earlier built cavity wall properties from generally the 30s to the late 70s were built with unfilled cavity’s and those that have not been subsequently retro-filled will also do relatively poorly on the EPC, however the EPC will show that these walls should be suitable for being filled and this will be reflected in the properties recommendations report.

The property’s heating system also plays a major part in the final rating and the EPC is weighted heavily in favour of properties heated by main gas. This has always been the case since the introduction of the EPC as mains gas has always been one of the most readily accessible and most cost effective methods of producing space and water heating.

Things though are beginning to move slightly on this front with the on-going focus on reducing our reliance on fossil fuels and the pressure from governments on reducing carbon emmisions, there is a very clear shift towards more what are deemed eco friendly alternatives such as heat pumps and solar PV.

What can often be surprising though, particularly to those who have had expensive heat pump systems fitted, is that they often don’t make any significant difference to the EPC rating. This is due in part to the bias in the algorithm towards mains gas which at present doesn’t particularly give heat pumps, an in particular air source heat pumps, the result they may deserve when mains gas is there as an alternative option. If the current system is LPG or heating oil however, the result will be slightly more favourable towards the heat pump.

I’ve found it not uncommon, particularly in properties where owners have moved from mains gas to an ASHP, for the rating to stay very similar and sometimes to even reduce, this is very hard for homeowners to accept, particularly those doing it for primarily ecological reasons as they expect to see the EPC go through the roof but currently this just does not happen.

This is more often than not down to the fact that an ASHP heats hot water in a similar way to an old fashioned immersion system and this is the way the EPC views it and therefore it sees heating hot water by electricity as inherently expensive and therefore doesn’t give it the rating it possibly deserves. Also a heat pump will often need to be run for 24hrs a day, albeit at a lower intensity than a gas boiler would, but this still has a bearing on the rating.

Heating controls are also very important in your final rating so try wherever possible to have a programmer, room thermostat and also TRVs (thermostatic radiator valves) on all of your radiators. Modern zonal heating systems where each radiator or floor can be programmed individually are also gaining in popularity and are a great way to reduce consumption and also produce a good rating.

Final things are loft insulation, make sure ideally to have 270-300mm of insulation, draught proof any single glazed windows and aim to have low energy light fittings throughout the property.

See our blog article here which explains the different factors which influence your final rating.

Contact us.

NN Home Energy Surveys

12 Battle Close, Wootton
Northampton, NN4 6RP

Opening hours: Monday - Saturday

8am - 8pm / Sat 9am - 5pm

Tel: 07851 957628

Email: david@nnhes.co.uk