Consider EPC Mistakes

At the time of writing the methodology for EPC assessments of existing dwellings is 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 2025.

Some EPCs are unfortunately issued where a mistake is made by the Energy Assessor during the assessment. Sometimes it's possible for the EPC rating to be skewed one way or another by this.

Ideally, assessment methodology should be applied equally to a single building by any energy assessor, and result in a pretty consistent rating, and to support this ideal, the occasional auditing of EPCs was introduced in 2018 by the Government approved accreditation schemes.

Mistakes however do happen even at the best of times. Many can't be spotted from just looking at the EPC certificate, but here are some examples that you might possibly be able to spot by checking the EPC Features list.

For an EPC assessment, each of the following parts of a property need to have a dateband assigned for when they were built:

• The main building
• Any real or 'notional' extension
• Any 'Room In Roof' (where you have a room within a pitched roof).

There are a number of pre-defined datebands available to choose from. For England & Wales, these are currently (in RDSAP 9.94):

before 1900, 1900-1929, 1930-1949, 1950-1966, 1967-1975, 1976-1982, 1983-1990, 1991-1995, 1996-2002, 2003-2006, 2007-2011, 2012 onwards

As parts of the assessment calculation are based on the building regulations in force at the time of construction, if the wrong date band is entered, the system may produce an EPC rating that is overly positive or negative as a result, potentially significantly.

Consider for example a property that has external cavity walls. Perhaps it's built in 1971, but the energy assessor enters a date band after 1983 instead.

If the building's cavity wall in fact does not have insulation within it, and there are no visual fill holes externally, the assessor will declare the wall 'as built' (ie as it was originally built).

However, because the date band applied is post 1983, the system will assume that the cavity wall does actually have insulation within it and the EPC rating will be inflated.

After 10 years, another energy assessor is asked to assess the same building, and perhaps they enter the correct date band, the EPC rating is assessed correctly and it goes down by a number of points. The present owner is then disappointed.

The same thing can happen in the other direction of course, particularly around the 1983 threshold. In this case the EPC rating would be lower than in reality until again another EPC is produced based on the correct date band.

This problem can sometimes be spotted by checking the 'Wall' type in the Features list of an existing or expired EPC. For a cavity wall, 'Insulated (assumed)' would generally indicate post 1983 and 'no insulation (assumed)' would generally indicate before 1983. If what is indicated does not represent the actual dateband of the building then perhaps an error might have been made.

As a property owner you can reduce the chances of this occuring on a new EPC by carrying out some research on your property and making the energy assessor aware of your thoughts of the age of the building. They can take your opinion into account. Present them with any evidence you have been able to gather. You could for example include a copy of the Land Registry Title Register for the property (this often, but not always, contains information that can accurately date the age of construction) - if you dont have a copy of this from your conveyancer when you purchased the property, just download a copy from the Land Registry website for £3. Other evidence could include copies of any Building Control completion letters for extensions of building works done etc. This would be particularly important for Rooms in Roof.

A recent property I assessed had a cavity wall which had been manually declared on a previous EPC by the energy assessor as having insulation present, (the EPC feature list did not include the word 'assumed').

In fact, the property was built in 1973 when cavity wall insulation was not fitted as standard, it was a second floor flat, and there was no visual or documentary evidence that any insulation was present. I had to declare the insulation status of the wall as 'As Built' and the EPC rating reduced as a result, somewhat reducing the effect of the energy improvements that the owner had made elsewhere in the property in the meantime.

There is a position towards the top of Energy Performance Certificates where the internal floor area of the property is indicated. It's calculated by the software summing up the floor areas of all the separate building parts. The value should reflect fairly accurately the real floor area of the property.

I came across one property where the previous EPC indicated a floor area of 180m2, but after measurement onsite I could only account for 120m2. Clearly the rating of the previous EPC would have been affected in some way in the case of this discrepancy.

If you were interested in checking, you could measure the actual internal floor area of your property and compare this against the value indicated on your previous EPC.

Note that EPC assessmnets will not include thermally separated conservatories, un-heated garages, and basements if they do not qualify.

In the upcoming RDSAP 10 update, the way 'Room In Roof' is assessed will change a bit. Here in this example we'll mention only the current (RDSAP 9.94) conventions.

Take the example of this pair of semi-detached properties:

These properties were clearly built at the same time, and both have large dormer windows in the roof, with those first floor rooms entirely built within the sloping structure of the pitched roof.

These first floor storeys are a case of what is called 'Room in Roof' and are handled differently within the EPC assessment compared to a standard storey.

As a quick guide, RDSAP 9.94 Convention 2.06 describes the inclusion of 'Roof Rooms' as:

• Include when accessed via a permanent fixed staircase such that one is able to walk downwards facing forwards.
• Does not necessarily contain habitable rooms.
• For a roof room to be classed as such and not a separate storey, the height of the common wall must be less than 1.8 m for at least 50% of the common wall (excluding gable ends or party walls). The common wall is a vertical continuation of the external wall of the storey below.

There are further instructions for when the area of dormer windows account for more than 20% of the floor area, and also for overiding the default insulation elements, but the common wall measurement mentioned above is the well known indicator.

In our photo above, the pitched roof slopes all the way down to the floor level of those roof rooms, leaving a common wall height of zero. Therefore, even without considering the rear elevation and looking only at the front elevation as shown in the photo, we have already reached the threshold of the 50% rule for Room In Roof.

The ceilings in these roof rooms are likely to be sloping (vaulted), possibly with a horizontal ceiling section of a smaller area compared to the floor area, and possibly with or maybe without a hatch to access the area above that horizontal ceiling.

Normally, it is not possible to visually assess the level of insulation in the sloping parts of the ceiling. Also, if there is no hatch in the horizontal ceiling part, then it will not be possible to assess the depth of insulation in that either. If there are vertical internal walls around the perimieter of the room in roof, and there is no access behind them, then it will not be possible to assess the insulation levels there either.

In the absence of such access, the assessment falls back on minimum building regs that were in place at the dateband that the assessor applies to the Room In Roof. This dateband is normally the construction date of the rest of the property unless significant documentary evidence is available that proves the Room In Roof complies with more recent regulations (such as if it has been refurbished to newer building regs).

Anyhow, you would expect to see a reference to 'Room in Roof' in the Features table of the EPCs for both of these two properties.

Let's compare them and see what we find:

This is the Features List from the EPC for the property on the left:

There is no mention of 'Room In Roof', and the Roof section indicates a standard pitched roof, likely with no access available, because it says 'Insulated (assumed)'.

In comparion, this is the Features List from the EPC for the property on the right:

This looks much more like what you'd expect. There is reference to 'Room in Room' in one of the Roof entries, and the mention of a timber frame wall is consistent with a Room In Roof where the floor area under the dormer windows is more than 20% of the floorspace of the whole floor.

In summary, it would concern me that the Room In Roof on the left hand property may well have been included as a standard storey in it's EPC. If so, it's quite possible that the EPC rating might be higher on that EPC than it would be had the EPC been assessed correctly.

It's possible to enquire with the energy assessor if you are concerned that an EPC might be incorrect. If you are still not happy after contacting them, you can contact the accreditaton scheme they are a member of (Elmhurt, ECMK, Quidos etc.).

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