Ofgem added Hybrid Wall Insulation (HWI) measure types to the Great British Insulation Scheme scores matrix on 20 July 2023, in what the regulator records as Version 2 of the document1. The matrix sets out the scores energy companies receive for measures installed under the scheme1.
The scheme adopts the ECO4 partial project scores framework, so the matrix is identical to the ECO4 partial project score matrix, with the exception of ineligible measure types being removed1. The matrix was originally published on 30 May 2023 as Version 11.
Ofgem's own record of the change reads:
"An update was provided, with Hybrid Wall Insulation (HWI) measure types being added."
The page lists three versions in total. Version 1 (30 May 2023) was the original publication; Version 2 (20 July 2023) added the Hybrid Wall Insulation measure types; Version 3 (22 April 2025) added scores for Smart Thermostat measures1. A further update is noted as applicable to Version 3 (06 August 2025), covering how a product qualifies to be notified as a smart thermostat depending on the version of RdSAP used in the pre-retrofit assessment1.
| Version | Date | Change recorded |
|---|---|---|
| Version 1 | 30 May 2023 | Matrix originally published |
| Version 2 | 20 July 2023 | Hybrid Wall Insulation (HWI) measure types added |
| Version 3 | 22 April 2025 | Smart Thermostat measure scores added |
On smart thermostats, Ofgem states that where the pre-retrofit RdSAP assessment uses RdSAP 10, a product can only be notified as a smart thermostat where it is listed in the SAP 10 PCDB as a smart thermostat, for use with the heat source of the home where it is installed1. The PCDB currently lists smart thermostat products only for condensing gas boilers, non-condensing gas boilers, condensing LPG boilers and non-condensing LPG boilers as pre-main heat sources1.
The scores matrix is published alongside the scheme's Delivery Guidance, whose Chapter 6 covers how the scores work1. Ofgem directs questions about the scores or their application to ECO@ofgem.gov.uk1.
Why it matters for households
The scores matrix is the mechanism that determines how much credit an energy company receives for a measure installed in a home under the Great British Insulation Scheme1. Adding Hybrid Wall Insulation measure types to that matrix is what makes those measures scoreable within the scheme's framework, rather than sitting outside it. For a household, the practical effect is that a hybrid wall insulation measure can be counted by the company delivering it, which is the condition under which such work is put forward under the scheme at all.
The matrix does not set what a household pays, and no costs, grant levels or eligibility thresholds for Hybrid Wall Insulation appear in the published material1. What the document does establish is that the scoring framework is shared with ECO4, minus ineligible measure types, so the treatment of a given measure is not unique to this scheme1. Households weighing insulation and energy independence will find the measure types listed in the matrix rather than in the guidance text.
What happens next
No next steps for Hybrid Wall Insulation are dated in the material. The only later dated item is the update applicable to Version 3 (06 August 2025) on smart thermostat eligibility1.