Understanding your EPC.

EPC EXPLAINED

What does EPC data tell you?

A domestic EPC shows a current energy rating from A to G, a potential rating and recommended improvements. The rating is calculated using standard assumptions about occupancy and use.
It does not come from your actual energy bills, and it cannot predict exactly what your household will spend.

The familiar energy efficiency rating is based on modelled energy costs. Carbon emissions are a separate result. A measure can reduce emissions or improve comfort without producing the largest increase in EPC points.

An assessor records the home’s dimensions, age and construction, together with details of insulation, windows, heating, controls, hot water and other relevant systems. Different extensions and building parts can have different construction and insulation levels.

“Assumed” usually means the calculation uses a prescribed default where direct inspection or acceptable documentary evidence is unavailable. It does not prove that insulation is absent. “N/A” against a floor or roof does not automatically mean it has been left out of the calculation.

Check the assessment date, address, floor area and descriptions before relying on an old certificate. Work completed since the assessment will not appear automatically. Keep installation records and photographs of concealed insulation so an assessor can check whether they meet the evidence requirements.

Source: Government guide to domestic EPCs.

EPC EXPLAINED

Insulation: material, thickness and installation

Mineral wool, rigid foam boards, blown materials and wood-fibre products have different properties and applications. Thickness alone does not establish thermal performance: thermal conductivity, continuity, fixings, gaps and the complete construction all matter.

A U-value describes heat transfer through a building element in W/m²K. A lower U-value means less heat passes through each square metre for the same temperature difference. Thermal bridges at junctions can still lose heat and create cold surfaces even where the main wall or roof is insulated.

EPC EXPLAINED

Heating, water and controls

Boilers burn fuel to heat water for radiators, underfloor heating or domestic use. The appliance, fuel, efficiency, storage, distribution and controls affect the assessment. A boiler charachteristics and rating can be found here.

Heat pumps transfer heat from air, ground or water. Their performance depends on design, flow temperature, emitters and operation. A room-by-room heat loss calculation is needed for system sizing; the EPC alone is insufficient.

Direct electric heaters turn electricity into heat at the point of use. Storage heaters store heat for later use and depend on suitable charging controls and tariffs. Neither should be treated as having the same performance as a heat pump. Communal heating supplies heat from a shared system. Its assessment depends on the system information and applicable methodology.

A programmer sets heating times. A room thermostat regulates temperature where it senses it. Thermostatic radiator valves regulate individual radiators; zoning can provide separate control for different areas. Weather and load compensation can adjust heating operation to demand. Smart controls are useful where they add appropriate functions, but an app alone does not guarantee extra EPC points.

Hot water also matters: the source, cylinder insulation and controls can affect energy use. Record what is actually installed and provide product details where available.

Source for heating design: Energy Saving Trust heat loss guidance.

EPC EXPLAINED

Which improvements should come first and why?

Every home is different, so there is no single package of improvements that works for everyone. Whether you’re a homeowner looking to reduce bills or a landlord aiming to improve your EPC rating, it’s important to spend your money wisely.

Here’s a sensible approach:

1. Start with your EPC. Check your existing certificate or arrange a new assessment. Look at what’s already installed, what’s missing and where improvements could make a difference.
2. Fix problems first. Damp, leaks, damaged walls and poor ventilation should be addressed before making energy improvements. An EPC doesn’t assess the overall condition of a property, but there’s little point insulating a wall if you’re simply covering up an existing problem. Fix the cause, not just the symptoms!
3. Look at the simple improvements. Loft insulation, heating controls, hot water cylinder insulation and LED lighting can be relatively inexpensive ways to improve efficiency. However, their impact on your EPC will vary.
4. Consider bigger insulation upgrades. Cavity wall, solid wall, floor and roof insulation can significantly reduce heat loss. Always consider the cost, disruption and potential effects on ventilation and moisture before committing.
5. Get the heating right. A new boiler or heat pump isn’t automatically the best answer. The heating system needs to suit the property. Proper heat loss calculations and energy modelling can help identify the most suitable options.
6. Explore solar panels. Solar PV can help improve your EPC rating and reduce electricity bills. However, roof condition, orientation, shading and available space all matter. Battery storage should be considered separately based on your electricity usage.
7. Check the results before spending. This is particularly important for landlords working towards a target EPC rating. Improvements don’t always deliver the points you expect, and their individual benefits cannot simply be added together. An accredited assessor can model different options to help you choose the most cost-effective combination. Ask us about EPC improvement modelling.

Spend Wisely, Not Necessarily More

Replacing every window or installing an expensive heating system might sound like a good idea, but neither is guaranteed to provide the best return.

The cheapest route to a better EPC rating isn’t always the best route to a better home and the most expensive improvements don’t necessarily deliver the biggest benefits.

The key is finding the right balance between cost, energy savings, comfort and EPC performance.

For homeowners, that means a warmer, more efficient property. For landlords, it means protecting your investment, improving tenant comfort and planning for energy efficiency requirements without unnecessary expense.