Ofgem, the administrator of the Great British Insulation Scheme (GBIS) and the Energy Company Obligation (ECO4), has confirmed its administrative approach to multiple insulation measures under GBIS. In a decision published on 26 June 2025, it states that solid floor insulation and underfloor insulation can both be installed together in the same project, and that this applies from 14 November 20241.
Ofgem received 18 responses in total, including from 9 suppliers, 5 installers and 4 from related industry bodies and consumers1. Of the 16 responses to the question on multiple insulations under GBIS, 12 agreed with the proposed approach1.
The decision sets conditions on how a second insulation measure can be delivered. Secondary insulation must be promoted by the same supplier as the first insulation measure, and a second insulation measure promoted by a different supplier from the first will be ineligible and face rejection1. Both insulation measures must take place in the same retrofit1. Ofgem states that from 14 November 2024 the two measure types can both be installed together, but that a third insulation measure could not1.
Two respondents felt the requirement for a single supplier to promote both measures went against the policy intent of increasing GBIS delivery and said it was inconsistent with DESNZ communications on the topic1. Ofgem said it would implement the proposals as outlined in its administration consultation, and that by minimising changes to the GBIS register and internal processes it expects the register to be ready to accept and approve secondary insulation measures as soon as the amended Order comes into force1. Measures will remain with "On Hold" status until the legislative changes come into effect1.
"From 14 November 2024 they can both be installed together"
The decision also covers smart thermostats, stating that only smart thermostats completed on or after 14 November 2024 are eligible to be notified as smart thermostat measures, and that they will only be eligible for a score where the specific product is listed in the PCDB for use with the heat source of the home where it is installed1. Ofgem says annual targets will not be removed1.
Why it matters for households
Floor insulation is one of the fabric measures that reduces heat loss through the ground floor of a home, and the ability to install solid floor and underfloor insulation together in a single GBIS retrofit affects what a householder may be offered when a supplier assesses a property. The decision confirms that the two measure types are treated as compatible within one project, subject to the same-supplier condition. For a home's energy independence, the practical effect is that a single project can address more than one insulation need at once, rather than requiring separate retrofits. The GBIS eligibility rules set out which homes and measures qualify, and the floor insulation guide explains the difference between suspended timber and solid floors. How insulation relates to a home's overall energy independence is covered in the insulation and energy independence guide.
What happens next
Ofgem states that measures will remain with "On Hold" status until the legislative changes come into effect, and that the register is expected to be ready to accept and approve secondary insulation measures as soon as the amended Order comes into force1. The draft legislative amendment was laid on 11 June 2025, and Ofgem alerted suppliers with an update by email on 13 June 20251. Final guidance will be published in due course1.