RdSAP is the approved methodology used for assessing the energy performance of existing dwellings. RdSAP 10 introduced additional detail into the assessment process.
For homeowners and landlords, the practical effect is simple: more information is collected at the property, so the assessment reflects the building more closely — and some appointments take a little longer.
What changed
- 01
Window measurements
Windows are measured rather than estimated from standard assumptions.
- 02
Roof rooms
Rooms in the roof are measured in more detail, including their construction.
- 03
Newer age band
An additional, more recent property age band is available.
- 04
Solar PV & batteries
More detail is captured on photovoltaic arrays and battery storage.
- 05
Heat pumps
Additional heat pump data can be recorded, reflecting modern heating systems.
- 06
Pressure test data
Air pressure test information can be entered where it exists for the dwelling.
- 07
More data, sometimes more time
Extra detail means some appointments take a little longer on site.
What it means for your appointment
Expect more measuring — particularly of windows and any rooms in the roof — and more questions about heating, hot water and any technologies such as solar PV, battery storage or a heat pump. Documentation is more useful than ever, because the extra detail only helps where it can be recorded or evidenced.
The full visit is described in what happens during an assessment.
Book with the detail covered
Watt EPC assessments follow the current methodology and conventions. See prices or book online.