25th August 2026
The majority of UK homes have one, but what is an EPC?
EPC stands for energy performance certificate. It is the official document that helps us understand how energy efficient a dwelling is. The more energy efficient your home is, the more you’re likely to save on energy bills, as well as having a greener impact on the planet and reducing your carbon footprint.
There are many ways to improve your EPC rating. These include reducing heat loss, improving heating and cooling efficiency, and using less electricity. Having a better EPC rating can even add value to your property. In fact, jumping from a low rating such as a G to a mid-range such as a C could increase your home’s market value by up to 15%. This INSULATION SUPERSTORE guide will take you through exactly what to do in order to achieve the best possible EPC rating.*
*Please note, listed buildings and older dwellings may struggle to achieve an excellent rating. This is due to preservation rules, permissions, and restrictions on replacing some materials, but we will advise on solutions where possible.
Table of contents
- What is an EPC rating, and how does it work?
- Improve your insulation
- Upgrade your heating systems
- Invest in a smart thermostat
- Prevent heat loss through windows and doors
- Consider renewable energy
- Switch to LED bulbs
- Final thoughts
What is an EPC rating, and how does it work?
An EPC rating is graded from A (highest efficiency) to G (lowest efficiency). It gives us an indication of how high energy costs will be for the property. In other words, it measures how much heat the property loses, which results in using more energy to maintain temperatures throughout the building. It also accounts for systems that may use up more energy to run. The table below explains how energy performance is measured in more detail.
| Rating | Score out of 10 | Energy Efficiency |
| A | 92-100 | Highest rating. Means the property has outstanding energy efficiency with practically no additions needed in order to improve. These properties can include features such as triple glazing, modern boilers, appropriate insulation, LED lighting, and even use renewable energy such as solar panels. |
| B | 81-91 | Highly efficient, very minor tweaks needed to achieve an A. Commonly found in new builds. |
| C | 69-80 | Above average in the UK, some minor improvements can be made. Also common in new build properties. |
| D | 55-68 | UK average energy efficiency rating. Improvements needed. |
| E | 39-54 | Below average energy efficiency with several improvements required. This is the legal minimum rating in order to rent out a property. |
| F | 21-38 | Poor energy efficiency. Many improvements needed. Often given to Victorian properties or older where there is little to no insulation, single glazing, and inefficient heating systems. |
| G | 0-20 | Extremely poor energy efficiency. Often given to listed buildings where energy efficient improvements are difficult to install due to restrictions and permissions. However, some additions are acceptable, such as installing breathable insulation, but always obtain Listed Building Consent before making any changes. |
In summary, the most likely ways you’ll achieve a D+ rating are:
- Having up-to-date heating systems
- Installing appropriate insulation, particularly in your loft
- Using LED lighting instead of incandescent or halogen bulbs
- Fitting a modern boiler that consumes less energy to run
- Installing windows that have either double, triple, or energy efficient glazing
- Relying more on renewable energy, such as solar power
You can find out your property’s EPC rating using the Government’s official Energy Performance Certificate Finder. All you need is your full address including your postcode. Explore the sections below to find out more about how to improve your current rating, and exactly what is available for your property.
Improve your insulation
If you’re going to make any of these improvements, installing insulation is by far the most important, as it is the best way to prevent heat loss. You should start by making sure you have the correct loft insulation, followed by insulating walls, then floors. This is the most fool-proof method of slowing down heat transfer and reducing your energy bills.
How does insulation make your home more energy efficient?
Insulation can be made from a range of materials. These include:
- Sheep’s wool
- Mineral wool
- Rock wool
- Wood fibre
- PIR board
- XPS board
- EPS board
- Phenolic foam
- Cork
- Multifoil
And many more. They each work in slightly different ways, and are engineered to work on different applications. But the one property they have in common is that they slow down heat transfer. This means they prevent warm air from passing through building materials such as brickwork and timber, acting as a barrier. For this reason, insulation is beneficial as it makes it harder for warm air to escape during Winter and prevents hot air from travelling inside throughout Summer.
Loft insulation
Often, the most common way heat escapes your property is through the roof. This is because heat rises, due to the air being ‘lighter’. Light, hot air can easily float upwards and escape via gaps and cracks. Cold air is much more dense, therefore easily sinking in through these crevices. Therefore, loft insulation is the most effective way to regulate indoor temperatures, but which type do you choose?
For overall efficiency, the best type of insulation for pitched roofs is either glass wool or mineral wool, and comes in the form of either bats or rolls. To achieve efficient thermal performance, we recommend to lay it at a depth of 270mm, with a layer of 100mm underneath and 170mm on top, perpendicular. It is also essential not to compress glass or mineral wool insulation, as the trapped air gaps provide additional thermal resistance. These insulation types are also flexible, meaning they can fit around joists, as well as being cost effective.
If you’re looking for a more sustainable and renewable solution, sheep’s wool is a fantastic alternative. It is actually more breathable than glass and mineral wool, making it excellent in more humid environments. Sheep’s wool loft insulation can also be installed at slightly thinner profiles whilst still achieveing excellent thermal efficiency. However, it is not as budget-friendly.
For flat roofs, you’ll need rigid board insulation such as PIR or XPS. They are laid directly on top of the roof deck, and are durable enough to withstand weight on top of them, such as a weatherproof membrane. Insulation board is also highly moisture resistant to any rain water coming through gaps. It helps to create a ‘warm roof’ which essentially keeps the space between the roof deck and the top of the roof warm. This prevents any surfaces from getting cold, which would otherwise cause condensation when hit with the warm air rising from your house.
Cavity wall insulation
Cavity walls are commonly found in new build houses and properties constructed after 1930 in the UK. They are much more thermally efficient compared to solid walls, even without insulation. This is because they are technically made up of two walls, with a gap in between them. This gap reduces the chance of heat loss from inside the property, as well as preventing any moisture being absorbed by the inner wall, keeping your home warm and dry.
The gap or ‘cavity’ can be taken a step further and filled with insulation. On new builds, this gap is normally already filled, but on older homes is normally filled with mineral wool insulation.
Solid wall insulation
Solid walls are much less thermally efficient. This is because they easily absorb rain water. Usually, when the rain stops, the warmth of the sun extracts this water out of the wall externally, creating a ‘sponge effect’ as it dries. However, in the UK, when it can rain for days on end, solid walls absorb more and more water without any relief, causing internal damp patches. The best way to prevent this is to install external wall insulation in the form of rigid boards, or internal wall insulation. This is normally the case for period or listed buildings, but you must always check before installing, as restrictions do apply.
Floor insulation
Like walls, there are two types of floor. One is a solid floor, and the other is a suspended floor. A solid floor relies on strong, durable insulation boards, including XPS and PIR, in order to withstand load-bearing weight. Meanwhile, suspended flooring can be insulated with glass and mineral wool, which is flexible enough to fit around timber framework.
Upgrade your heating systems
Investing in contemporary heating and cooling systems is much more energy efficient, as they use modern technology to regulate indoor temperatures without using energy unnecessarily. For example, installing a thermostat automatically switches off your heating once it detects the desired temperature has been reached.
Ensure you have modern central heating rather than open gas fires, as these consume large amounts of energy. Having said this, relying on central heating alone isn’t enough…
Replace your boiler
Swapping your old boiler for a brand new one can be more beneficial than you think. Boilers actually have their very own energy efficiency rating on an A-G scale, with A being the most efficient. Modern boilers use energy that would otherwise be wasted thanks to their condensing design. Unlike older boilers, they use the hot exhaust gases to pre-heat the cool water running back into the system. In other words, more dated boilers would have sent this gas outside via flue, thus using additional energy to heat the water running back from taps and radiators. We recommend the Viessmann Vitodens 100-W combi boiler for ultimate energy efficiency, as well as the Vaillant ecoFit range to help you improve your overall rating.
Install a heat pump
Heat pumps can provide you with 300-400% energy efficiency. They are the future standard rather than boilers for this reason, as they only rely on electricity. They use a refrigerant to draw in warm air from outdoors, which boils into a gas. This gas is then heated up, and passed into your home’s water system via a condenser. Heat pumps transfer heat that already exists in the air outside, whereas a boiler must create heat by burning fuel, such as gas. This is what makes them distinguishably more energy efficient.
Fit thermostatic radiator valves
A thermostatic radiator valve, also known as a TRV, allows you to control the temperature of individual radiators. This means that you can essentially prevent rooms that are not in use from being heated, saving on both energy use and bills.
Tip: Just make sure you don’t fit these in your ‘master room’. This is the room that houses your thermostat, and turning off radiators in this room will interfere with its temperature detection and signal to the boiler to keep using energy to heat your entire home.
Invest in a smart thermostat
A smart thermostat can help you improve your EPC rating by reducing unnecessary energy usage. Many use something called geofencing, which detects your location on your phone, turning off any heating that does not need to be running whilst you’re out of the house. Smart thermostats can also help you heat individual rooms, or rooms that are in use, rather than allowing systems to use energy and supply heat to the whole of your property. They can even adapt to your living patterns, detecting when you make up and when you return home from work, gradually adjusting temperatures at just the right time.
Prevent heat loss through windows and doors
Doors and windows are thought to be responsible for 15-20% of a property’s heat loss. Heat transfer via gaps around windows and doors often gets overlooked, and sometimes, you might not even need to replace your doors and windows at all. In fact, simple sealing can easily improve your home’s energy efficiency by blocking off those little nooks and crannies where heat may be escaping without you knowing.
Upgrade your glazing
Having just single glazing is likely going to bring your EPC rating down drastically. Investing in double, triple, or even energy efficient glazing is the more efficient alternative. Thanks to modern technology, most companies have double or triple glazing as their standard, and it can even be found in roof windows. Double and triple glazing contains gas between each layer of glass, usually Agron, Krypton, or Xenon. These noble gases are all denser than air, they make heat much more difficult to pass through the layers of glass, maintaining indoor temperatures.
If you have a listed or period property where replacing windows isn’t an option, secondary glazing is installed to the inside of an existing window, which traps air and slows down heat transfer. This means you’ll be relying less on systems that require energy consumption to heat and cool your home, reducing your carbon footprint and improving your EPC rating.
Add draught proofing
Draught proofing your home improves energy efficiency as it seals off any small gaps where heat could be escaping. It is an especially good method as it is low-cost and low-effort. Simply installing draught excluders and weather seals to external doors can reduce heat loss by 10-15%.
Consider renewable energy
Renewable materials create energy sources that are replaceable. In other words, they will not run out, as we have the natural capability to continue creating more. Fossil fuels such as oil and coal are the opposite of this, as they have a limited supply. Renewable energy is much more efficient as it does not require burning materials that release harmful toxins into the atmosphere. Instead, the source can be turned directly into power, such as electricity, without this step.
Solar panels
Whilst they can be quite an investment initially, solar panels are one of the best ways to generate renewable energy directly for use in your home. Solar power converts sunlight into electricity to power household appliances. Depending on which model you opt for, some solar panels can convert up to 23% of sunlight into electricity.
Natural insulation
Whilst the actual material doesn’t affect your EPC rating directly, natural insulation can have very effective energy efficiency. Sheep’s wool, hemp, and wood fibre insulation are all considered renewable. This is because they can continue to be remade naturally without burning fossil fuels. Each of these materials has an energy efficiency within the units of around 0.35-0.45 W/mK, which is even better than fibreglass or mineral wool! They are also extremely breathable, meaning they can absorb heat from the air inside your home, and slowly release it when the temperature drops.
Switch to LED bulbs
This is probably the quickest and easiest way to improve your EPC rating. It is also incredibly budget-friendly. If your property currently has halogen bulbs, they’re actually wasting most of the energy they make as heat, as they only convert 2-3% into light. The same goes for incandescent bulbs, they also waste most of their energy converting to heat, with just 5-10% being turned into light. On the other hand, LED lighting triumphs in energy efficiency. It uses the least amount of watts to produce the same level of brightness as other bulbs, and converts almost all of the energy it produces into light.
Final thoughts
Improving our EPC ratings isn’t just about meeting a legal requirement on paper. It’s about reducing our carbon footprint and doing what we can for a greener, more sustainable future. Making these changes to our everyday environments can have a big impact, while also reducing the cost of household energy bills. Having newer, updated systems can also give us peace of mind that they are running effectively, and can even be cheaper to fix and maintain, with fewer faults overall. Needless to say, the benefits are plentiful, and we can all agree that having an improved EPC rating is an asset to any property.
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