RdSAP 10: Full Guide to the 2025 EPC Changes

RdSAP 10 is the new way of doing EPCs in the UK. It starts in June 2025. It’s more detailed, more accurate, and includes new technology. This means better energy ratings—but also more work for assessors.

1. What is RdSAP 10?

RdSAP stands for Reduced Data Standard Assessment Procedure. It’s the method used for EPCs (Energy Performance Certificates) in most homes across the UK.

The new version—called RdSAP 10—launches in June 2025. It replaces the current system (RdSAP 9.94).

This update changes how EPCs are done:

• More measurements
• More details
• New technologies included
• Less guessing, more evidence

In short, it’s designed to make EPCs more realistic, useful, and fair.

2. Why is RdSAP Changing?

The world has changed. Homes now have:

• Smart meters
• Solar panels
• Heat pumps
• Better insulation
• Smart heating

The old EPC method didn’t cover these well. That’s why the update was needed.

Main goals of RdSAP 10:

• Improve accuracy
• Reflect modern homes
• Help reduce carbon emissions
• Support the Net Zero target
• Give better advice to homeowners

3. What Are the 12 Main Changes in RdSAP 10?

Let’s break them down simply:

✅ 1. Windows

Before: Windows were based on property age.

Now:

• Every window is measured individually
• Record the width, height, type of glazing, frame, and draught-proofing
• Shading and orientation matter too

This means:

• No more guessing
• Better heat-loss results

✅ 2. Walls and Age Bands

New homes (built from 2023) now fall under Age Band M.

Also:

• Mixed wall types can be listed separately
• Walls shared with neighbours are treated differently

This makes EPCs more accurate for homes with extensions or renovations.

✅ 3. Roofs and Rooms in Roof

Rooms in the loft? These are now handled in more detail.

Assessors can:

• Choose basic or detailed entry
• Measure slope, insulation, wall types
• Add photos

Why this matters: Loft conversions can affect heat loss a lot. Now they’re properly counted.

✅ 4. Floors

Floors are no longer “one type fits all”.

Assessors now:

• Identify each floor type: ground, upper, or between
• Record floor build (timber, concrete, insulation)
• Add evidence if available

Helps avoid under/overestimating heat loss from floors.

✅ 5. Hot Water

Before: Basic info only.

Now:

• Record size of cylinder (litres)
• Measure heat loss
• State how many bathrooms the house has

Solar hot water and heat pump cylinders are also recognised.

✅ 6. Heating Systems

This is a big update.

Now assessors must collect:

• Boiler type and make
• Fuel used (gas, oil, LPG, electric)
• Number of heating zones
• Radiator types or underfloor
• Controls (thermostats, timers)

Multiple systems are now included (e.g. gas + electric room heaters).

✅ 7. Ventilation and Airtightness

Air movement is a big part of energy loss. Now included:

• Mechanical systems (MVHR)
• Passive vents, extractor fans
• Draught lobbies, chimney blocks
• Actual airtightness test results if available

✅ 8. Lighting

Before: Only light fittings were recorded.

Now:

• Each bulb is counted
• Types: LED, halogen, CFL, incandescent

This shows how efficient the lighting system is.

✅ 9. Smart Tech and Renewables

A big jump forward:

Now supported:

• Solar PV with battery storage
• Solar diverters (heat hot water using solar)
• Micro-CHP and hydro
• Smart meters and smart controls

This means homes that invest in green tech get proper credit.

✅ 10. U-Values and Heat Loss

Thermal performance of materials is now updated:

• Walls, floors, roofs have new U-values
• Reflects better insulation standards

This means EPCs are now closer to real-world performance.

✅ 11. Data and Evidence

Old system allowed guesses.

RdSAP 10 demands real data:

• Measurements
• Photos
• Documents
• Labels from appliances or insulation

No documents = use of default values = lower EPC scores.

✅ 12. New Calculation Engine

It uses SAP 10.2 logic:

• Real fuel prices
• Better CO2 factors
• Rewards low-carbon heating

Improves cost, emissions, and performance advice.

4. What Happens to EPC Ratings?

EPC results might go up or down based on:

• How much proof is given
• Age of property
• Heating system type
• Wall and floor insulation
• Renewable energy

Some homes may drop a rating because there’s no evidence. Others may go up thanks to low-carbon systems.

New EPCs will be:

• More realistic
• Better for planning upgrades
• More trusted by mortgage lenders

5. How This Affects Landlords

Things to know:

• EPC rules (MEES) still apply
• EPCs done after June 2025 will use new rules

What to do:

• Get EPC before June if you expect a drop
• Or wait until after June if you’ve upgraded insulation or added renewables
• Keep all paperwork: boilers, insulation, PV

You need:

• Evidence = better EPC = legal to rent

6. How This Affects Assessors (DEAs)

Survey Time:

• Old surveys: 30–45 minutes
• New ones: 60–90+ minutes

Training Needed:

• CPD course from accrediting body
• Learn new software
• Practice new measurements

Tools:

• Laser measure
• Torch
• Camera
• Access gear (for lofts, crawlspaces)

Cost:

• Most assessors will charge more
• 15–30% price increase expected

7. What Homeowners Should Do

Prepare Early:

• Find documents (heating systems, insulation, solar)
• Let assessor access roof, loft, underfloor
• Upgrade lights to LED

Why it matters:

• EPC can improve
• Better advice given
• Can apply for green loans or grants

8. Step-by-Step: How to Prepare for RdSAP 10

Step	Action
1	Check EPC expiry date
2	Decide if you want EPC before or after June 2025
3	Gather documents (manuals, install papers)
4	Replace bulbs with LED
5	Insulate loft and draught-proof gaps
6	Add smart heating controls if possible
7	Book an accredited assessor
8	Ask them about RdSAP 10 specifically

9. Simple FAQs

Q: When does RdSAP 10 start? A: 15 June 2025.

Q: Can I still use my old EPC? A: Yes, it lasts for 10 years. But new EPCs after June use the new method.

Q: Will my rating go up or down? A: Depends on evidence and property type.

Q: What is a good EPC rating? A: A or B. Most UK homes are D.

Q: Will it cost more? A: Yes. Surveys take longer and are more detailed.

Q: Can I do anything now? A: Yes. Gather proof, upgrade insulation, and switch to LED lights.

10. Final Thoughts

RdSAP 10 is a big step forward. It brings EPCs in line with how homes work today.

But it also:

• Requires more from assessors
• Puts pressure on homeowners to prove what they’ve done

The better your documentation, the better your EPC result.

Start preparing now so you’re not caught out after June 2025.

This is your chance to future-proof your home—and your compliance.