Energy Efficiency, Sustainability and Retrofit
Energy performance, retrofit and unintended consequences
Energy assessment begins with the Energy Performance Certificate (EPC), produced using SAP or RdSAP and valid for ten years. The EPC gives an asset rating A–G, an environmental impact rating and recommendations, but it is not a condition survey and relies on assumed data. The Minimum Energy Efficiency Standards (MEES) require domestic private rented property in England and Wales to reach at least band E before letting, subject to exemptions; owner-occupied homes are not caught in the same way. Listed buildings and some other properties have exemptions, but the rules are narrow.
Retrofit must follow a whole-dwelling approach. PAS 2035 sets the framework for risk assessment, a medium-term improvement plan and appropriate oversight; PAS 2030 covers installer competence, and TrustMark registration supports quality. The 'fabric first' principle prioritises insulation, glazing, draught-proofing and airtightness before changing heating systems. But improving airtightness without planned ventilation can cause condensation, mould and poor indoor air quality. Solid-wall insulation, internal or external, changes dew-point risk; external insulation can alter appearance in conservation areas; internal insulation reduces room size and can create thermal bridges. Heat pumps need correct sizing, emitter design and insulation.
Traps: treating an EPC as proof of condition; assuming MEES applies to all homes; recommending insulation without ventilation and moisture risk assessment; ignoring planning and party wall issues; overstating savings.
Worked rule of thumb: assess the building, the occupancy and the moisture risk before specifying measures. A fabric-first measure that traps moisture is not an improvement.