How to improve an EPC rating from F to C

A realistic starting point

An F-rated home has more than one serious weakness. Start with your certificate, and note the current score, the potential score and the list of recommendations. If the potential rating is D, the assessor's own list stops short of C, and that is useful information before you budget.

Think of it as two projects: first F to D, which often removes the worst heat loss and running costs, then D to C. Many homes get the largest comfort gain from the first stage, and our D to C guide picks up from there.

Why F-rated homes score so low

Scores this low usually come from a combination of these problems, which your EPC's description lines will show.

• Solid walls with no insulation, so heat escapes through the largest surface in the home.
• Little or no loft insulation, or a roof room or flat roof that is harder to treat.
• Costly heating, such as older electric heaters, room heaters, or an old oil or LPG boiler.
• Single glazing and draughty floors, which add to the problem but rarely cause it alone.

The heating line matters more here than in other bands. The Energy Saving Trust notes that electric heating can make a rating look worse because electricity usually costs more per unit than gas. Check that the system and tariff were recorded correctly.

Get a whole-home plan before you start

At this scale, one job affects the next. Insulation and airtightness change how moisture moves through a building, and heating should be sized for the home after the heat loss has been reduced. Under the PAS 2035 retrofit standard, a retrofit coordinator assesses the home and sets out a plan, including ventilation. TrustMark explains how this works for homeowners.

Poor installation is a real risk. The National Audit Office reported in 2025 on high levels of non-compliant external wall insulation, and issues with internal wall insulation, installed under government schemes. Ask for evidence of certification, guarantees and an explanation of how moisture will be managed.

For older solid-walled homes, take advice from someone familiar with traditional buildings. Historic England notes that putting fabric upgrades first is often neither practicable nor desirable in a historic building. If the home is listed, get advice before changing it, as you may need consent.

An EPC does not assess condition. If you are buying, a survey should come before any of this planning.

A typical order of work

1. Repair the building first: roof, gutters, damp and failed pointing.
2. Sort out ventilation, then seal the worst draughts.
3. Insulate the loft or roof.
4. Insulate the walls, if the plan shows this is safe and practical.
5. Insulate floors, ideally when they are already being disturbed.
6. Replace the heating, sized for the improved home.
7. Add solar panels if a gap remains and the roof suits them.

Typical costs

These are the Energy Saving Trust's typical figures, mostly for a semi-detached home in Great Britain. Costs vary with the home, the region and the installer, so treat them as a starting point and get quotes.

Solid wall insulation and a heat pump alone come to around £24,000 or more before any grant, so judge a full F to C project on comfort and condition as well as bill savings.

What is unrealistic from F

• Reaching C with one measure, whichever one it is.
• Fitting a heat pump into a home that still loses heat badly. It may be possible, but running costs can suffer, so reduce the heat loss first.
• A fixed price before anyone has assessed the home. Hidden repairs are common in this kind of property.
• C in every case. For some homes, reaching D or E and stopping is the sensible outcome, particularly where walls cannot be insulated safely.

Landlords and funding

In England and Wales, an F or G home cannot be let on a new or existing private tenancy unless a valid exemption is registered. The current cost cap is £3,500. Planned rules would raise the target to a C equivalent by 1 October 2030 and the cap to £10,000, subject to legislation.

Eligible lower income households may get free upgrades through the Warm Homes: Local Grant in England, or Nest in Wales. The Boiler Upgrade Scheme offers £7,500, or £9,000 for eligible oil or LPG homes without mains gas until March 2027. Warm Homes loans cover clean energy technology such as heat pumps, solar and batteries, so check whether your work qualifies.