‘My house is more than 100 years old – how can I achieve a top energy rating?’

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In a leafy suburb in Surrey just off the M25, Simon Skinner has been steadily investing in his Victorian home. The 59-year-old, who works in the aerospace industry, has extended his property twice – once in 1993, and again in 2001.

The original building dates back to the late 1800s, but has since tripled in size due to Mr Skinner’s investment. 

So far, the energy crisis has not had a noticeable effect on Mr Skinner, who handily fixed his energy deal for two years in 2021. 

He currently pays 20p per kWh for electricity and 3p for gas – far below the rates dictated by the price cap. But his deal expires next month – and his bills will inevitably soar.

“It would be good to see what we can do with energy efficiency measures to mitigate the impact of the price rises,” he says. “Especially for our winter heating bill with three home workers living in the house.”

Given the two extensions differ drastically from the original house, with varying insulation levels, Mr Skinner wonders how an assessor could possibly generate an accurate energy performance certificate (EPC) that covers the whole property. 

EPCs rank the energy efficiency of a home on a scale of one to 100, and homeowners can move further up the scale by making improvements. 

Ratings run from A (extremely efficient) to G (extremely inefficient).

As part of Telegraph Money’s Net Zero Makeover series, we enlisted the help of energy provider Ovo, and comparison site Checkatrade, who arranged for an EPC assessor to visit Mr Skinner’s home and see what could be done to make the property more energy efficient.

Greig Millar, energy expert at Ovo, says:

As it was built before 1900, the original building of Mr Skinner’s home will have been built with little-to-no insulation. 

While decorating the property, he installed wall insulation himself in parts of the building including the living room. It was a hot day and the wall insulation was helping to keep the room fairly cool.

However, we always recommend that people work with accredited contractors when installing internal wall insulation to make sure it meets building standards and to avoid issues down the line.

Poorly fitted wall insulation can lead to cold bridging, where gaps in the insulation can lead to condensation and dampness. I didn’t see any evidence of condensation or dampness during my visit but this is something to look out for.

I then went up into the loft and found the loft insulation was under 100mm. This is much lower than it could be and I recommend Mr Skinner increases this, in line with current recommendations, to 380mm, which typically costs £8 per m2.

Loft insulation is one of the most cost-effective ways to retain heat in a property – saving up to £475 a year according to the Energy Savings Trust charity – and this should help to prepare the home for winter and reduce heating bills.

Moving on to the extensions. Both cavity-built extensions will be relatively well insulated due to the building regulations during the period of construction.

There is still some room for improvement though. For example, the loft hatch was not insulated or fitted with draught-proofing. These are two simple and cost-effective measures that can help keep homes warm.

Both the original building and extensions have older, aluminium framed double-glazed windows. 

When the time is right for Mr Skinner, replacing these with modern PVC framed double glazing with trickle vents will help to improve heat retention and ventilation throughout the property. It is important that buildings can breathe and trickle vents enable this without making homes too draughty.

The heating system is currently controlled by individual smart TRV’s (Thermostatic Radiator Valves) – this is a good move by Mr Skinner to monitor and control his heating system so it is only producing heat as and when required via the thermostat. 

Outside the property, Mr Skinner has had rooftop solar PV fitted. There’s a good space to put a solar battery on the first floor of the original building, which will maximise the efficiency of the system and this would be a good option to explore further. A solar battery costs from £2,500 depending on size, according to specialist publication the Eco Experts. 

Mr Skinner has taken lots of positive steps to improve the insulation and efficiency of his home. 

However, there is room for improvement and I recommend focusing on insulation and draught proofing to start with, before moving on to more expensive updates such as replacing the windows, installing a solar battery and electrifying the heating system.

Chris Grant, of EPC Choice, says: 

Thankfully the owners had to hand the Building Control sign-off documents, which crucially allowed the correct build dates to be run through the EPC software. 

We advise all homeowners to obtain these before an EPC survey, as local authority records can be sketchy. An incorrect build date can cost a homeowner up to 10 EPC points.

This included a measured survey and a complete record of all property elements that affect how the property “uses and loses” energy. 

With the original building and two extensions, we effectively produced three mini EPCs to record the different construction types accurately. 

These will be merged into one to provide an overall rating. Potentially challenging for a property with solid and cavity brick walls, differing wall types can affect an EPC rating by anything between 8 and 12 points. 

Mr Skinner is raising the EPC bar by installing internal wall insulation in the original house. 

Whilst not immediately visible from the exterior, a check from the roadway revealed a six-panel array of solar photovoltaics (PV) facing due south. 

Whilst not the largest PV install, the MSC certificate confirmed a 1.05 kW peak system installed in 2010 at the peak of the Government’s Feed-in-Tariff rate. 

Solar PV can add anywhere between 10 and 15 EPC points, dependent on the number of panels installed. The benefits of double-glazed windows are well established, extending to all windows at this property. 

However, they are the older type installed between 2004 and 2007. The EPC software will suppress the recommendation to replace the windows, but typically, more modern UPVC frames with argon-filled double or triple glazing will show an EPC rating improvement of four to six EPC points. Estimates suggest upgraded windows save a typical homeowner £425 over five years.

With wall Insulation and solar PV, this homeowner is attuned to saving energy but has yet to extend this to the heating for the property. 

An Ideal Classic FF250 boiler lurked in the bathroom cupboard; this virtually bomb-proof boiler, known to have a lifespan of 25 years, is the weak link. 

Non-condensing, and with a seasonal efficiency rating of just 76.7pc, replacing this should be a high priority, bringing a three point EPC rating improvement and a potential £349 annual saving on heating and hot water costs. 

However, the boiler’s negative impact has been partially offset by using a hi-tech Drayton Wiser zone control, which allows individual time and temperature control of all rooms and is linked to external weather reports. 

So what next for this property on its energy efficiency journey? An air source heat pump would complement the solar PV, but with little uplift to EPC rating, this technology is essentially an electric form of heating. 

Still a rarity in the UK, Mr Skinner is eying a ground-source heat pump with the associated saving on heating and hot water, but again little impact on the EPC rating. 

This property achieved an EPC rating of B81 and the potential to reach 90, which is just two points short of the magical A rating.