1970s Ground Floor Flat - 46E seeking a C for MEES

At the time of writing, the current methodology for EPC assessments of existing dwellings is RDSAP 10. The old EPC for this property was conducted under an older version of the methodology. In the future, the Home Energy model will replace RDSAP and government consultations indicate their desire to change EPC measurement metrics. This will therefore change approaches to EPC rating improvement in the future.

This is a 1970s Ground Floor Flat rented out in the PRS (Private Rental Sector).

The last EPC was issued in 2009, expired in 2019 and the rating was 46E.

The plan is to try and increase the EPC rating to a C now as cheaply and as reasonably as we can.

The government here in England & Wales have issued two consultations around changes they are proposing to EPCs.

Firstly, the format of EPCs is likely to change, with multiple metrics replacing the single cost-based metric used currently.

Secondly, MEES requirements are likely to be tightened to a 'C equivalent' rating across two of the multi-metrics, a building fabric metric and either the heating system metric or the smart-readiness metric. This would come into force in 2028 / 2030.

As part of the proposed changes, any existing EPCs with a C band rating or better would be deemed to comply with the tighter MEES requirement and allowed to remain valid until the end of their 10 year validity period.

We hope that by getting a C rated EPC now, we will then have plenty of time to work out whether the property will pass the future MEES requirements using the future EPC metrics.

The expired EPC was carried out in January 2009, and the floor areas was recorded as 38m2.

2009 was fairly early in the history of EPCs.

EPCs were first introduced in 2007 and there have been several changes in the methodology over the years although I don't expect the rating to be much different now if the property were to be re-assessed today as it was back in 2007.

Let's take a look at the Features table from the expired EPC:

We notice there are two wall types declared, both cavity walls, one with assumed partial insulation and one without. I'm not exactly sure where two wall types might be present in the flat. One of those wall types might be the party wall, although as the property is a flat so it's not possible to determine the party wall type.

The main heating is provided by 'Modern Slimline' Electric Storage Heaters. There are actually two of these in the property, one in the living room and one in the bedroom.

There is also an entry for Secondary Heating where it says: Room heaters, electric. This is because there are two fixed electric towel rail radiators in the property - one in the kitchen and one in the bathroom. This actually won't bring the EPC rating down because the main heating is storage heating.

Hot water heating is provided by electric immersion heaters in a 'Fortic' style hot water cylinder, and the Features table indicates the heating is off-peak (ie lower cost).

Finally, notice the floor is recorded as a suspended floor, but this is actually wrong. The ground floor in fact is a solid floor with perhaps 20mm polystyrene insulation laid between batons and then floorboards on top. I believe this is as it was originally built.

There are three Recommendations listed on the EPC certificate:

With all three of these recommendations applied, the EPC rating would be 65D. This would leave us just 4 points short of a C rating where the target is 69C or better.

The modern recommendation for storage heaters would now be for High Heat Retention Storage Heaters and these would result in a higher EPC rating compared to the slightly older Fan assisted type.

Looking now at work that has been carried out on the property since 2007.

Cavity wall insulation has been installed in the external walls and the hot water cylinder has been replaced completely.

The replacement cylinder has factory fitted foam insulation rather than the old mineral wool jacket of the original.

This means the first two recommendations have already been implemented, so we may only have one recommendation left which is the one to upgrade the storage heaters.

However, we have also fitted a Positive Input Ventilation (PIV) system in the flat which resolved a damp issue. As we will see this reduces the EPC rating.

We need to gain access to the property, and conduct a new EPC to see what the rating is now.

Options that might be available to us:

• Remove all storage heaters, fit one High Heat Retention Storage Heater to the living room and an electric panel heater in the bedroom.. or
• Fit a gas combi boiler with radiators.. or
• Fit a heat pump with radiators and a new hot water cylinder

A gas meter box is actually available alongside the property, but it is not connected to either the ground floor flat or the first floor flat and the incoming pipe has been capped off.

Our preferred option is likely to be the installation of one High Heat Retention Storage Heater (HHRSH) to replace an existing 'modern slimline' storage heater. We would remove any other storage heaters in the flat and fit an electric panel heater in the bedroom. This is likely to be the most cost effective option.

The way HHRSHs work in the EPC rating calculation is interesting. You only need one so long as there are no other types of storage heater present. Adding additional HHRSHs does not result in a better rating.

Also, the declaration of Secondary Heating sources such as electric panel heaters does not seem to result in a reduction of EPC rating like it would if the main heating system was a gas boiler. The same also appears to be true of un-heated habitable rooms in the property.

We've gained access to the property and have simulated a fresh EPC assessment to see where our current baseline rating is....

The result is 59D.

There are only two recommendations that would appear on the certificate:

So there is a floor insulation recommendation where there wasn't before. That's partly because the floor type was wrong on the previous EPC.

We would be very reluctant to implement solid floor insulation for several reasons.

The second recommendation however is for High Heat Retention Storge Heaters which we would be happy doing.

If we implemented the High heat Retention Storage Heaters without the floor insulation then we would get a rating of 66D.

This is just 3 points shy of a C band rating, and the certificate would only indicate one recommendation which is the one for solid floor insulation to bring us up to 71C.

I notice the primary energy useage with the HHRSHs would then be 222 kWh/m2/yr.

With the HHRSHs in place, can I think of any further options that would bring up up to a C:

Interestingly, removing the PIV would bring us up to a C.

If we went down this path, we should implement other measures to mitigate against condensation. This would be by replacing the PIV with a passyfier vent, adding trickle vents to the windows (none present currently) and increasing door undercuts.

We would prefer to leave the PIV present as we wish to rent the property again soon.

We are a little limited in options because the building fabric in a few areas is reasonable already. From the RDSAP 10 Specification document we can see that:

• A party wall declared as 'unable to determine' has a u-value of 0.0 (no heat loss).

• Also, for a roof declared as 'another dwelling above', the methodology also assumes there is no heat loss upwards.

• We have cavity walls with retrofitted cavity insulation, with an original 1967-1975 (band E) construction dateband (England & Wales) for which a u-value of 0.7 is used (it would have been 1.5 without the CWI).

For more information, see our pages on Heating Systems and
High Heat Retention Storage Heaters