PAS 2035 is the British standard that governs how domestic energy retrofit is assessed, designed and managed, and since 31 March 2025 the updated PAS 2035:2023 has been the mandatory version for every publicly funded project (Elmhurst Energy, 2025). If you install insulation, heat pumps or solar under any government scheme, this standard now decides whether your work is fundable.
This pillar guide is written for installers and contractors, not policy teams. It explains what PAS 2035 covers, how it differs from PAS 2030, what changed in the 2023 revision, the retrofit coordinator role, the risk paths, and which funding schemes gate on it. The goal is to help you win compliant work without tripping over the paperwork.
Key Takeaways
- PAS 2035:2023 has been mandatory for all newly registered funded retrofit since 31 March 2025, when PAS 2035:2019 was withdrawn (Elmhurst Energy, 2025).
- PAS 2035 is the whole-house planning and risk framework; PAS 2030 is the installation certification that sits under it (NEF, 2025).
- A retrofit coordinator is mandatory on every domestic project delivered under TrustMark and government funding (Retrofit Academy, 2025).
- The standard applies to ECO4, GBIS, SHDF, HUG and the Warm Homes Local Grant, all feeding the £13.2bn Warm Homes Plan confirmed for 2025-26 to 2029-30 (Energy Saving Trust, 2025).
- Every project is assigned a risk path (A, B or C) that sets how much assessment, design and oversight is required.
What is PAS 2035 and why does it matter in 2026?
PAS 2035 is the overarching specification for retrofitting dwellings for improved energy efficiency, covering assessment, design, and the management of a whole retrofit project. It sits at the centre of the retrofit framework and defines strategy, assessment, risk management and design before any measure is installed (Retrofit Academy, 2025). In plain terms, it forces a whole-house view instead of bolting on a single measure and hoping for the best.
It matters in 2026 because compliance is now the gate to funded work. Compliance with PAS 2035 is a requirement of all retrofit programmes that deploy government funding, so an installer outside the framework simply cannot access the largest pipeline of domestic work in the country (Retrofit Academy, 2025). With the Warm Homes Plan committing £13.2bn to upgrade up to five million homes, that pipeline is only growing (Energy Saving Trust, 2025).
The standard also protects the installer. Its whole-house approach and moisture rules exist to stop the unintended consequences, damp and condensation being the classic ones, that follow a poorly planned fabric upgrade. Done properly, PAS 2035 is as much a defence against callbacks as it is a funding requirement.
PAS 2035 vs PAS 2030: what is the difference?
The two standards do different jobs, and mixing them up is the most common source of confusion on site. PAS 2035 is the strategic planning and risk assessment framework for the whole project, while PAS 2030 is the installation certification standard that ensures the measures are fitted correctly, safely and to a high standard (NEF, 2025). One plans and manages, the other installs.
Put simply, PAS 2030 focuses on the quality of the installation process, while PAS 2035 ensures the retrofit is appropriate for the building as a whole (Brighter Compliance, 2025). The design and risk decisions live in PAS 2035; the physical execution of those decisions is certified under PAS 2030.
The table below sets out the split for installers deciding what certification they actually need.
- Aspect: PAS 2035 · PAS 2030
- Purpose: Whole-house planning, assessment, design, risk · Installation of individual measures
- Who it covers: Coordinator, assessor, designer, evaluator · The installing contractor
- Output: Retrofit strategy and medium-term plan · Measures installed to certified standard
- Funding role: Overarching framework for compliance · Certification required to access funding
What changed in PAS 2035:2023?
The 2023 revision tightened the standard in several practical ways that installers feel directly. It now requires a medium-term improvement plan for every project, strengthened guidance on airtightness, moisture and ventilation, and specific provisions for traditional or historic buildings in line with BS 7913 (Elmhurst Energy, 2025). Ventilation is no longer an afterthought; it is assessed up front.
Assessment methodology also moved on. Assessors now use enhanced ventilation assessments, and SAP 10 becomes the new methodology, bringing assessments closer to a full SAP calculation with metrics such as air permeability (Elmhurst Energy, 2025). Projects must now include post-retrofit evaluation, including a resident feedback questionnaire within three months of completion and a full record of inspections.
For the contractor, the honest summary is that the 2023 version adds cost and admin. Stricter site inspections, revised ventilation requirements and updated design responsibilities all add to project overhead, so pricing needs to reflect the extra assessment and evaluation work rather than absorbing it silently.
The retrofit coordinator role and Level 5 requirement
The retrofit coordinator is the linchpin of PAS 2035, and the role is mandatory on every domestic retrofit delivered under TrustMark and government funding (Retrofit Academy, 2025). The coordinator liaises with the client, assessor, designer, installer and evaluator to keep the project coordinated and quality-assured from first survey to final sign-off.
Becoming one is a formal step, not a badge. Anyone wanting to act as a retrofit coordinator must hold the Level 5 Diploma in Retrofit Coordination and Risk Management before joining one of the approved TrustMark scheme providers (Retrofit Academy, 2025). Only once accredited can they lodge projects and deliver retrofit under publicly funded programmes.
For a small installer, the practical decision is whether to train someone in-house or subcontract coordination. Either works, but the coordinator has to be engaged from the start. Bringing one in after the measures are chosen defeats the whole-house logic the standard is built on, and it is a frequent cause of rework.
Risk paths A, B and C explained
PAS 2035 does not treat every home the same. Each project is assigned a risk path, A, B or C, depending on its complexity, and the chosen path dictates the level of scrutiny, oversight and documentation required (Brighter Compliance, 2025). A simple single-measure job carries less assessment burden than a deep multi-measure retrofit of a hard-to-treat home.
Path A covers the lowest-risk work, typically simpler dwellings and straightforward measures, with the lightest documentation. Path B sits in the middle. Path C applies to the most complex cases, including protected or traditional buildings and extensive fabric work, where the design detail, moisture risk assessment and oversight are most demanding.
Knowing the path early changes your quote and your programme. A path C job carries far more coordinator and design input than path A, and pricing it as if it were a simple loft top-up is how margins evaporate. Confirm the path with your coordinator before you commit to a fixed price.
Which funding schemes require PAS 2035?
Effectively all of the current domestic retrofit funding routes require it. PAS 2035 is mandatory for ECO4, the Great British Insulation Scheme, the Social Housing Decarbonisation Fund, the Home Upgrade Grant and the Warm Homes Local Grant (Retrofit Academy, 2025). If a homeowner or landlord is accessing public money for insulation or clean heat, the PAS 2035 process applies.
These schemes now sit under one national umbrella. The government confirmed £13.2bn for the Warm Homes Plan across 2025-26 to 2029-30, aiming to upgrade up to five million homes and cut bills by as much as £600 per household (Energy Saving Trust, 2025). For installers, that is a multi-year demand signal, and PAS 2035 is the entry ticket.
If you already deliver under ECO4 or the Warm Homes Local Grant, the framework is the same. The measures and funding pots differ, but the assessment, coordination and evaluation spine is PAS 2035 in every case.
How installers get compliant and win funded work
Getting compliant is a sequence, not a single certificate. You need PAS 2030 certification for the measures you install, registration with a TrustMark-approved scheme provider, and access to a qualified retrofit coordinator for every job (NEF, 2025). Registering as a TrustMark business is the step that ties your certified work to the funding portal.
Route the work in the right order. The retrofit assessor surveys the home, the coordinator sets the strategy and risk path, the designer specifies the measures, you install to PAS 2030, and the evaluator checks the outcome. Skipping straight to installation without the assessment and design in place is the fastest way to have a lodgement rejected.
Many installers pair PAS work with adjacent routes, becoming an ECO4 installer or offering EPC improvement advice, because the customer conversation overlaps. A household chasing a warmer, cheaper home rarely cares which scheme pays; they care that the job is done once and done right.
Common PAS 2035 pitfalls for installers
The most expensive pitfall in the field is engaging the coordinator too late. When the coordinator arrives after measures are already promised to the customer, the whole-house assessment often flags a ventilation or moisture issue that forces a redesign, and the installer eats the delay. Bring coordination in at the survey stage and this largely disappears.
The second recurring problem is underpricing the assessment and evaluation load introduced by the 2023 revision. Stronger ventilation checks, SAP 10 assessment and the three-month post-completion evaluation are real hours that many quotes still ignore. Treat them as line items, not goodwill, and build the coordinator's fee into the job from day one rather than discovering it at lodgement.
Frequently Asked Questions
Is PAS 2035 a legal requirement?
PAS 2035 is not a law in itself, but it is a mandatory requirement for accessing government-funded retrofit schemes such as ECO4, GBIS and the Warm Homes Local Grant (Retrofit Academy, 2025). Private, self-funded work does not legally have to follow it, though the whole-house and moisture guidance is still strong practice for any fabric upgrade.
When did PAS 2035:2023 become mandatory?
PAS 2035:2023 became the required standard for newly registered funded projects on 31 March 2025, after an 18-month transition, and PAS 2035:2019 was withdrawn on 30 March 2025 (Elmhurst Energy, 2025). Assessments under the old version could not be lodged with inspection or handover dates after 29 March 2025.
Do I need both PAS 2030 and PAS 2035?
As an installing contractor you need PAS 2030 certification for your measures, and your project needs to sit within the PAS 2035 framework managed by a retrofit coordinator (NEF, 2025). You do not personally hold PAS 2035, but you cannot deliver funded work without a coordinator applying it to the job.
What is a retrofit coordinator and do I have to hire one?
A retrofit coordinator manages the whole project against PAS 2035 and is mandatory on every TrustMark and government-funded domestic retrofit (Retrofit Academy, 2025). You can train someone in-house to Level 5 or subcontract the role, but the project cannot be lodged for funding without one.
What are the PAS 2035 risk paths?
Risk paths A, B and C classify a project by complexity, and the path sets how much assessment, design and oversight is required (Brighter Compliance, 2025). Path A is the simplest, path C covers complex and traditional buildings. Confirming the path early is essential for pricing the coordination and design work accurately.
Reonic's installer platform helps UK retrofit teams keep survey, design and compliance evidence for each job in one place, so PAS 2035 lodgements are easier to assemble.
