Introduction

Going live on 15th June 2025, RdSAP10 represents the largest change to the methodology in roughly 13 years. The changes are part of the Government’s aim of eliminating fuel poverty, lowering carbon emissions and creating healthier and more comfortable dwellings.

The changes will improve the accuracy of assessments and ensure that modern technologies have become more commonplace over the last ten years represented.

Whilst in our opinion it does not resolve all the industry’s difficulties, it should be seen as an exciting and much-needed steppingstone towards the Home Energy Model, EPC reform and minimum energy efficiency standards (MEES) changes we expect to see in the next few years.

So, what’s changing…

Measurement of all windows, new window age bands and the presence of shutters

All windows must now be measured in RdSAP10. This brings the methodology in line with SAP, non-domestic and retrofit. As part of the changes to measuring windows, there are new glazing age bands for different window types and the ability to enter the presence of shutters.

Information needed to be collected on windows:

• Draughtproofed
• Orientation
• Glazing Type
• Glazing location
• Wall location
• Dimensions
• Presence of Shutters

Walls, roof, floors – new types and insulation thicknesses

RdSAP 10 brings about numerous changes for walls. Walls see the introduction of new wall types (curtain walls, basement walls). It also sees the ability to add two alternative walls per building part. Wall insulation thicknesses see an upgrade with more thicknesses to choose from and the ability to select the thermal conductivity of solid walls.

For roofs, there is a new roof type for “non-residential or unheated spaces” above a property and more precise insulation thicknesses have also been introduced.

For floors, there is a new floor type in “basement floor” and the introduction of more precise insulation thicknesses.

Refined data entry for Hot Water Cylinder (HWC)

The exact cylinder size can now be identified in RdSAP10. This alongside the ability to input declared cylinder heat loss allows for a more accurate water heating entry.

Changes to roof rooms

Roof rooms have had a major overhaul in RdSAP10. Roof rooms now have two types depending on the type of build. Type 1 is a “true roof room” and type 2 is where there is a common wall (more of a short storey). When selecting these we have additional information to collect such as the dimensions for the gable walls and common walls.

Ventilation & air pressure testing

Ventilation in RdSAP10 has been brought in line with full SAP and sees the introduction of multiple new mechanical ventilation options as well as data collection being needed for open fireplaces, chimneys, extract fans, passive stacks etc.

Mechanical ventilation can also be selected from the database.

Finally, air pressure test results can be included. This allows for the properties building performance to be measured much more accurately and will likely have a significant impact on ratings.

New age band

In line with upgrading building regulations a new age band has been created. This will allow the modern properties to have the correct assumptions made about them in line with the building regulations from when they were built.

New technologies

PV batteries and PV diverters can now be accounted for and selected in RdSAP. These additions come alongside recommendations for both too.

A less common, but no less important technology, small-scale hydro generation, is now able to be recognised within the methodology.

Changes to lighting

In the previous version of RdSAP, we identified the total number of light fittings.

Going forward, in RdSAP10, we must identify the number of light bulbs. From here we also need to identify the type between incandescent, CFL and LED.

New recommendations

RdSAP10 finally sees the introduction of a heat pump recommendation. This recommendation is only given on “fairly insulated” properties and where the rating to install a heat pump is better than that of a gas boiler.

The other recommendations added are PV batteries and diverters, which will be recommended when there aren’t any.

Gathering Evidence

If a measure is not visible or hard to identify, we are required to gather documentary evidence to confirm its existence at the property. Documentary evidence is required for;

• Age of extension(s)/roof rooms
• Floor Insulation 
• Solar PV size and panel types
• Wall Insulation
• Windows

If you are unsure of what might be deemed as suitable documentary evidence, please get in touch