The Improvement Option Evaluation is the document at the heart of PAS2035 Stage 2. It is the RC's professional analysis of the options available to improve the property — modelling different measure combinations and presenting a clear basis for the client to make informed decisions about what to commission. Get it wrong and the project is on unstable foundations from Stage 2 onwards.
Despite its central importance, the IOE is one of the most commonly incomplete documents in retrofit project records. Understanding what it must contain — and what the most common omissions are — is essential for any RC or housing association running a funded programme.
The Mandatory Content
PAS2035 requires the IOE to present a genuine range of improvement options, not a single preferred option dressed up as a comparison. Each option must include:
- The specific measures included in the option
- Predicted improvement in SAP score and EPC rating
- Estimated capital cost
- Projected annual fuel bill saving
- Projected carbon saving
- Any relevant risks or constraints associated with the option
The options must be genuinely different — varying in scope, cost and outcome — so that the client has a real choice. An IOE that presents three variations on the same measure package, or models only the measures the RC intends to recommend, does not meet the standard.
Important: The IOE must address ventilation. Where any proposed option would reduce the property's air permeability, the IOE must identify the ventilation implications and indicate the compensating strategy required. IOEs that model insulation measures without addressing ventilation are non-compliant regardless of how well the SAP modelling is done.
The Medium Term Plan
The IOE feeds directly into the Medium Term Plan — the agreed phased approach to improving the property over time. The MTP sets out which measures will be installed in the current project phase, which are planned for future phases and the sequencing logic that ensures earlier measures do not compromise later ones.
The MTP must be consistent with the IOE. Where the client selects an option that differs from what the RC recommended, the MTP must document this and record the RC's professional view on the implications.
Common IOE Failures at Lodgement
- Only one option presented — or multiple options that are not genuinely distinct
- SAP scores not calculated — savings estimated rather than modelled from RdSAP data
- Ventilation implications not addressed
- No documentation of which option was selected by the client and why
- MTP inconsistent with the selected option — measures installed differ from those agreed
- IOE not updated when scope changes during design or installation
The last point is particularly important. Where the measure package changes between Stage 2 and Stage 4 — because of technical constraints, budget changes or resident preferences — the IOE and MTP must be updated to reflect the actual scope. An IOE that does not match what was installed is a non-conformity that will be flagged at lodgement.
How PASDOC Handles the IOE
PASDOC generates complete IOE documents directly from the imported RdSAP XML data. SAP scores, cost projections and carbon savings are calculated automatically across multiple option scenarios. The platform flags ventilation implications as part of the compliance audit, and maintains consistency between the IOE, MTP and Stage 4 documentation throughout the project lifecycle.