The Medium Term Plan (MTP) has become a critical document in the PAS2035 retrofit assessment process. Unlike the initial Energy Performance Certificate, the MTP demands far greater technical depth and justification. Building Control inspectors, lenders, and insurers now scrutinise these documents with unprecedented attention, making the difference between approval and rejection.

Understanding the MTP's Purpose

A Medium Term Plan outlines the retrofit strategy for a property over a defined period—typically 3 to 5 years—addressing energy efficiency, fabric improvements, and heating system upgrades. Under PAS2035, the MTP must demonstrate that work will progressively improve the property's performance while managing moisture, condensation, and unintended consequences.

This isn't simply a list of recommendations. Inspectors expect to see evidence of:

Structuring for Scrutiny

Start with Robust Baseline Data

Your MTP's credibility rests on the initial assessment. Document everything: thermographic surveys, moisture testing, air leakage measurements, and material specifications. Vague statements like "poor insulation" won't survive scrutiny. Instead, specify: "cavity wall insulation absent; U-value calculated at 1.8 W/m²K; proposed mineral wool cavity fill targets 0.27 W/m²K."

Explain the Intervention Logic

Building Control inspectors want to understand why you've sequenced interventions in a particular order. Some improvements must precede others. For example, addressing air leakage typically comes before upgrading heating systems, as it reduces heating demand. Explain these dependencies explicitly.

If recommending external wall insulation before cavity closure, justify why this sequencing minimises risks such as interstitial condensation. Reference relevant standards and industry guidance.

Address the Unintended Consequences Head-On

This is where many MTPs fail scrutiny. PAS2035 specifically requires assessment of potential negative outcomes. These might include:

Don't assume these won't arise. Explicitly assess each and propose management strategies. If a property shows elevated moisture readings, your plan should detail how you'll monitor the situation during retrofitting.

Documentation Standards

Clarity and Precision

Use technical language appropriately, but avoid jargon without explanation. "MVHR system with summer bypass and defrost cycle" is clearer than "advanced mechanical ventilation." Specifications must be measurable: a target fabric energy efficiency (FEE) percentage, specific U-values, air tightness figures (m³/h/m² at 50Pa).

Cross-Reference to Standards

MTPs that reference relevant guidance strengthen their position against challenge. Cite Building Regulations guidance, Approved Document L, PAS2035 itself, and relevant British Standards. When recommending a particular approach, show that it aligns with recognised best practice.

Visual Documentation

Include annotated photographs, floor plans showing intervention locations, and thermal images where they illustrate problems. These make technical reasoning transparent and harder to dispute.

Managing Phasing

The phased nature of MTPs creates unique challenges. Building Control needs assurance that intermediate stages won't create unsafe or non-compliant conditions. Your plan should confirm:

Some inspectors ask for post-phase inspection protocols. Specify what measurements will be taken after each stage to confirm expected outcomes are being achieved.

Managing Stakeholder Expectations

MTPs increasingly face scrutiny from mortgage lenders and insurance providers. A well-documented plan demonstrates professional competence and reduces perceived risk. Include:

Conclusion

A robust Medium Term Plan reflects thorough assessment, technical competence, and risk awareness. Properties are unique; generic templates won't withstand scrutiny. The time invested in detailed analysis and clear documentation now prevents disputes later and demonstrates the rigour that PAS2035 demands.