PAS2035 is the UK standard for the retrofit of domestic buildings. Published by the British Standards Institution, it defines the process that must be followed when retrofitting energy efficiency measures in homes — covering everything from the initial assessment through to installation and handover.
For housing associations, understanding PAS2035 is no longer optional. The standard is a condition of all major UK retrofit funding schemes, and non-compliance creates legal, financial and reputational risks that are difficult to recover from.
In plain English: PAS2035 is the rulebook for how retrofit should be done in the UK. It doesn't prescribe exactly which measures should be installed — that's determined by the assessment and design stages. What it does prescribe is the process that must be followed to ensure those measures are the right ones, installed correctly, and that residents are properly informed throughout.
Why was PAS2035 introduced?
Before PAS2035, there was no mandatory standard governing the whole-house retrofit process in the UK. Individual measures had installation standards (like MCS for heat pumps), but nothing governed the overall process — the assessment, the design of a package of measures, and the coordination between parties.
The result was patchy quality, measures being installed without proper assessment of the building as a whole, and a genuine risk of harm — particularly around ventilation, moisture and overheating. PAS2035 was developed to address this, drawing heavily on the work of the Each Home Counts review.
The four stages of PAS2035
PAS2035 divides the retrofit process into four stages, each with defined outputs and compliance requirements:
- Stage 1 — Pre-Retrofit Assessment: A qualified Retrofit Assessor conducts an RdSAP-based assessment of the property. This forms the evidential basis for all subsequent decisions. Condition data — ventilation, damp, mould — is captured here.
- Stage 2 — Improvement Option Evaluation: The Retrofit Coordinator produces an IOE document modelling the available measures, their costs, projected savings and impact on SAP score. A Medium Term Plan is produced showing staged delivery over time.
- Stage 3 — Retrofit Design: A Retrofit Designer produces detailed specifications for the chosen measures. Ventilation and overheating strategies are confirmed. The RC reviews and approves the design before work begins.
- Stage 4 — Installation and Handover: Measures are installed by PAS2030-accredited installers. The RC oversees and signs off. A complete handover pack is produced and the works are lodged with TrustMark.
The key roles defined by PAS2035
The central role — the RC manages the whole process, coordinates all parties and takes responsibility for PAS2035 compliance across all four stages. All works must have an RC.
Carries out the pre-retrofit assessment (Stage 1). Must be accredited by an approved scheme. Produces the RdSAP report and condition data that underpins the IOE.
Produces the detailed specification for the measures to be installed (Stage 3). Must be appropriately qualified and take responsibility for the design.
Must be PAS2030 accredited for the specific measures being installed. Works under the direction of the RC and in accordance with the approved retrofit design.
What does compliance actually mean?
PAS2035 compliance means that a qualifying project has followed the defined process correctly — with the right roles in place, the right documentation produced at each stage, and the works lodged correctly with TrustMark.
It does not mean that measures will definitely perform as projected, or that residents will be satisfied with the works. Compliance is about process, not outcome. But a properly followed process significantly increases the probability of good outcomes.
For housing associations, the practical meaning of compliance is: all four stages have been completed, all required documents have been produced, all works have been carried out by accredited installers under the oversight of an accredited RC, and all works have been lodged with TrustMark.
The most common compliance failures
The non-conformities that surface most frequently at lodgement stage — when they are most disruptive and costly to resolve — are:
- Ventilation not properly assessed before insulation is installed
- IOE produced without adequate assessment data
- Stage advice letters not issued to residents at the correct times
- Design not reviewed and approved before installation began
- Handover pack incomplete or issued after the lodgement deadline
All of these are process failures. Every one of them is preventable with proper coordination.
How PASDOC helps
PASDOC is built around the PAS2035 process. The platform guides every project through the four stages, with automated compliance checking at each gate — so non-conformities are identified at the point when they can still be corrected, not at the point of lodgement.
Assessment data is imported directly from all major accreditation bodies. Documents are auto-generated from project data. Stage advice letters are triggered automatically. TrustMark lodgement happens directly from the platform.
The result is a retrofit coordination process that is inherently more compliant, more consistent and significantly less labour-intensive than manual coordination.