Case Study 7 - Detached bungalow - D to a C

This is a 3-bed detached bungalow built in the early 1960s.

The current EPC was produced in November 2025 using RDSAP 10, and the rating is 63D.

We are reviewing the current EPC, with a view to issuing our own, and seeing what would be required to get a 69C rating or better on this property.

Here is the features table from the existing EPC:

Wall

There is one wall type listed in the features table. A mistake has therefore been made in the EPC assessment because two wall types should be listed instead. This bungalow was built in the early 1960s, and a physical extension was added to it in 1984. This extension has a different floor type compared to the original building, and the floor area of the extension is more than 10% of the main building. It should therefore definitely be recorded as an extenson in the assessment, and as a result there would be two wall types listed. The walls of the original building and also the extension are both cavity walls. Drill holes on the outside of the main building indicate that cavity wall insulation was retrofitted to this building part, but the walls of the extension do not have any such drill holes, so CWI has not been retrofitted to the extension. By 1983 onwards, the predominant construction method with cavity walls was to include CWI in order to meet the thermal performance required by building regulations which had tightened up again just previously in 1982. We should therefore see wall entries for both:

• 'Cavity wall, filled cavity' - representing the main building (u=0.7)
• 'Cavity Wall, as built, insulated (assumed)' - for the extension (u=0.6)

When we re-assess this property, our EPC will indicate these two wall types. This is important because the assessment methdology uses slightly differente u-values for these two walls, as shown above.

Roof

The roof of both the main building and the extension are indeed pitched, with access to the loft, but from examination we can see the insulation depth is clearly only 100mm, not 150mm as stated. This is error number two in this EPC. The current EPC rating will have been inflated slightly due to this error, and when we produce our own EPC, the rating will be reduced slightly in comparison, when we declare the correct amunt of insulation. We will only see one Roof entry on our EPC because both the main building and the extension have the same level of insulation.

Windows

The EPC describes the property as being fully double glazed. This in fact is not true, and indicates error number three. There is one single glazed window present. The glazing is not the latest technology, the double glazed windows are all pre 2002, and there are a couple of metal framed windows (both are doors recorded as windows in fact), but when we produce our own EPC it will say 'Mostly double glazing'. This error will have inflated the rating slightly, but not by much at all.

Main Heating & Main Heating Controls & Hot Water

This looks fine, although we cannot see all the information recorded by simply looking at the Features table here. We do know that the thermostat used in the property is a Worcester Comfort 1 RF, which is a compensating controller. We will therefore make sure to register this in the assessment to take advantage of any small gain this provides.

Lighting

This looks fine. There are several incandescent and fluorescent bulbs in the property.

Floor

Most of the main building is indeed a suspended timber floor and we have looked underneath this to evaluate how much effort would be required to install insulation. However, the bathroom and the original kitchen floors are both solid floors, and these do not appear on the features table. Also, the flors of the extension are also solid as well. This includes the extended kitchen part and the dining room. This therefore is error number four. When we produce our own EPC we will see both types of floor represented in the features table.

Secondary Heating

If you ever see electric room heaters listed as Secondary Heating, and the main heating runs on gas, you have an outstanding opportunity to improve the EPC rating. In our case, the electric room heater recorded on the current EPC assessment was an electric feature fireplace heater in the living room. However this feature fireplace is a plug-in type and it is not fixed to the wall/chimney breast. It is therefore easily removeable and classed as a portable heater. This is error number five. The heater should not have been recorded in the assessment. Because this is the only source of electric heating in the property, and all habitable rooms are currently heated by the main heating system - radiators from the gas boiler - this will have reduced the current rating by a few points, likely five points, but we will confirm this later. When we produce our own EPC, there will be nothing listed under Secondary Heating.

to be continued...

Some limited additional information is available which is not present on individual EPC certificates.

We can check:

Construction Dateband: England & Wales: 1950-1966

Main building floor height

Habitable Rooms

Heated habitable Rooms