Councils typically choose a Warm Homes: Local Grant delivery partner by checking four things: the certifications that make an installer eligible to do publicly funded retrofit work at all, the quality assurance arrangements that sit behind those certificates, the practical delivery model (including local presence and social value), and whether the partner can help fill the programme with eligible residents.
This guide sets out each of those four areas in plain English, with the questions procurement and sustainability teams tend to work through and the evidence worth asking any prospective partner to show. It is written for local authority officers and managing agents weighing up delivery options for Warm Homes: Local Grant (WHLG) or similar retrofit programmes.
What certifications does a WHLG delivery partner need?
Government-funded retrofit work in England is delivered under the PAS 2035 framework. In practice, that means an installer needs to be TrustMark registered and PAS 2030 certified, with the work overseen under PAS 2035 by a qualified retrofit coordinator. These are the table stakes: without them, a contractor cannot lawfully deliver the fabric measures a WHLG programme funds.
It is worth being precise about the wording when checking credentials. An installer is “PAS 2030 certified” and “works to PAS 2035”; PAS 2035 certification itself belongs to retrofit coordinators, not installation firms. A partner that describes its own status accurately is usually a partner that treats compliance seriously elsewhere too.
What about heat pumps, solar and batteries?
WHLG is not only a fabric scheme. Where low carbon heating and generation measures are in scope, the relevant certification is MCS, and it is technology-specific: an MCS certificate lists the exact technologies a firm is certified to install. If your programme includes air source heat pumps, solar PV or battery storage, ask to see the certificate and check those technologies are actually on it, rather than accepting the MCS logo at face value.
A partner that holds both sides, the PAS-certified fabric work and the MCS-certified low carbon technologies, can deliver whole-home projects without splitting the job across contractors, which simplifies both accountability and resident experience.
Who checks the work, and who chose the checker?
Certification is a floor, not a guarantee. The government’s own review found that 92% of external wall insulation installations delivered under ECO4 and GBIS had major defects requiring remediation (written ministerial statement HCWS953, 13 October 2025). Every one of those installations was done by a certified installer. That is why the quality assurance arrangements behind the certificates matter more than the logos themselves.
Useful questions to put to any prospective partner: What proportion of your installations is physically inspected, and by whom? Did a funder or framework require that inspection regime, or did you set it up yourselves? Who pays for it? What happens when an inspection finds a problem?
The answers vary widely across the industry. Some installers are inspected only on the sample basis their scheme requires. Others go further: at Pyramid Eco, for example, 100% of our high-risk installations are physically inspected by the Installation Assurance Authority at our own invitation and cost. We mention it not because the arrangement is unique to us, but because “who checks the work, and who chose them” is a question that quickly separates delivery partners on paper from delivery partners in practice.
Material choices tell a similar story. Specification decisions made on quality or safety grounds, and held to even when they cost the installer margin, are good evidence that the quality culture is real. Ask what materials the partner specifies for external wall insulation and why.
Does local delivery matter?
Retrofit is disruptive, resident-facing work in occupied homes. The delivery model determines how well that goes: who is on site every day, how quickly problems are escalated, and how residents are treated when something unexpected turns up behind a wall.
Questions worth asking: Is there a dedicated site manager on every project, and are they employed by the partner or subcontracted? How far do crews travel? What is the escalation route when a resident raises a concern? Local delivery also carries social value weight in most council scoring frameworks: local employment, local supply chains and money staying in the area are all scoreable benefits that distant crews cannot offer.
Can the partner help fill the programme?
A WHLG allocation only becomes delivered projects if eligible residents come forward, and finding them is consistently one of the hardest parts of running a scheme. The scheme’s design recognises this: DESNZ’s WHLG policy guidance (July 2026) allows participating authorities to use up to 15% of funding for administration and delivery support, which can include resident identification and engagement.
So a fair question for any prospective delivery partner is what they will do to help find eligible households, not just install measures once households are found. We have written separately about how WHLG funding can support resident finding, including what that looks like in practice alongside a postcode-level eligibility checker.
What does a remediation track record tell you?
One further signal is whether a partner is trusted to put failed retrofit work right. Remediation of defective installations is procured carefully, because the buyer has already been let down once. An installer working on insulation remediation through recognised routes such as the IAA’s remediation procurement framework has, in effect, been through a second layer of due diligence by organisations whose whole concern is installation quality.
Frequently asked questions
Do WHLG installers have to be TrustMark registered?
Yes. Government-funded domestic retrofit work in England, including WHLG, is delivered under PAS 2035 by TrustMark-registered, PAS 2030-certified installers.
Is MCS certification needed for every WHLG project?
Only where MCS-scope technologies are being installed, such as air source heat pumps, solar PV or battery storage. MCS certificates are technology-specific, so check the certificate covers the measures in your programme.
Can WHLG funding be used to find eligible residents?
DESNZ’s WHLG policy guidance (July 2026) allows up to 15% of funding to be used for administration and delivery support, which can include resident identification. Individual eligibility always has to be checked case by case; no household or organisation can be guaranteed funding.
What is the difference between PAS 2030 and PAS 2035?
PAS 2030 is the installation standard that installers are certified against. PAS 2035 is the wider framework covering assessment, design and coordination of domestic retrofit, overseen by a retrofit coordinator. An installer is PAS 2030 certified and works within PAS 2035.
If it is useful to see how one delivery partner answers all of the questions above, we have put our own answers in one place on our Warm Homes: Local Grant delivery partner page. And if a conversation would help with a programme you are planning, we are happy to talk it through.
