Case Study 3 - 1950s Terraced House - 30F to a C - No Heating to Gas Boiler

Context: The time of writing is September 2024 and the methodology for EPC assessments of existing dwellings is currently RDSAP 9.94. The much anticipated RDSAP 10 update has not happened yet and a significant methodology overhaul from RDSAP to the Hone Energy Model (HEM) is proposed for next year.

This is another 1950s 3-bed terraced house, of the same design as the ones featured in Case Study 1 and Case Study 2.

It's an auction property, and it stood out to me because it demonstrates how much impact the heating system of a property can have on the EPC rating.

This property currently has no heating system within it at all. There's no boiler, no radiators, no hot water cylinder, no heating of any kind. It's all been strippd out.

I've included it here to illustrate the really bad EPC rating it currently has (30F) and the massive improvement in EPC rating that is provided by just one Recomendation (fitting a gas boiler heating system).

The house was prepared for sale, and to comply with current legislation had to have an EPC in place in order for it to be sold. This just happens to be the condition that the current owners, the local housing association, decided to leave it in at the time of that assessment.

With the absence of any form of heating, the RDSAP methodology assumes the worst case use of peak rate electric heating (perhaps via portable heaters) in order to fulfil the heating requirements of the property.

Let's take a look at the Features List on the EPC to see this:

Looking at the table above we can see:

• The walls are cavity walls with insulation that has been added since construction (there's no 'assumed' after the words 'filled cavity) - Average (but as good as this property can be without additional internal or external insulation).
• 200mm of loft insulation - that's good
• Double glazed windows throughout - that' good
• Lighting - is very good with LED lights throughout

So all those items are looking really positive for the property.

What's left are the items related to heating which are all rated as Very Poor. This is due to the RDSAP methodology introducing a worst case scenario that electric heaters will be used to provide the required heating for the property. It's just this area of heating that is bringing the EPC rating down so low for this property - to a 30F.

Let's look at the Recommendations list:

(There are further recomendations but I have not included them here)

Ignore Step 1, the cost is very high for a relatively small gain in EPC rating.

Look however at Step 2, and the gain from fitting a central heating system based around a gas condensing boiler.

There is a 41 SAP point improvement to the EPC rating.

In reality, you'd be looking at the top end of that cost estimate range (~£7,000 or more), and the 74C rating displayed for Step 2 does actually include the 3 SAP point improvement from Step 1 as well - they are applied accumulatively in recomendations lists. If you didn't carry out Step 1 then you'd have to remove at least 3 points from that 74C, possibly more, as the presence of Step 1 might have helped Step 2 achieve so well.

We have seen however in Case Study 1 and Case Study 2 that this design of house with a filled cavity wall is capable of a C band rating when fitted with a gas combi boiler system and all other features are in good order. It's therefore likely that a condensing gas boiler on its own will still bring this particular property into the C band.

So, this case study really stands to illustrate how bad an EPC rating can be when peak rate electric heating is used. Use peak rate electric heating at your peril!

A final disclaimer: Note that for your own property, the change will be different than the values described above, due to many differences that will undoubtedly exist between this property and your property. Only an EPC assessment, or simulation, run on your property by a local energy assessor will give you accurate figures in oder to make informed decisions.