Energy Performance Diagnosis (DPE)

The Energy Performance Certificate (EPC) assesses a dwelling's/building's energy consumption and greenhouse gas emissions, then assigns it a rating from A to G. It is based on technical characteristics (building envelope, insulation, windows and doors), systems (heating, hot water, cooling, ventilation), and a standardized calculation methodology. Beyond the energy label, the EPC provides recommendations for work with estimated impacts (energy, emissions, comfort), useful for prioritizing a multi-year energy performance plan (PPT), defining the scope of an energy performance contract (CPE), or preparing for a renovation.

Energy Performance Certificate (EPC): Operational definition and report content

A "regulatory" Energy Performance Certificate (EPC) produces:

- an energy label (kWhEP/m².year) and a climate label (kgCO₂/m².year);

- a summary of the building envelope (walls, roofs, floors, glazing): surfaces, resistances, thermal bridges;

- a status of the systems: heating, DHW, air conditioning, ventilation (flow rates/performance);

- indicators of summer comfort (sensitivity to overheating) and an estimate of the bill;

- improvement scenarios (insulation, regulation, generators, RES) with estimated gains and order of investment.

Methodologically, the calculation relies on conventional usage assumptions to compare properties under similar conditions (it is not a compilation of actual bills). In the service sector, the Energy Performance Certificate (EPC) is often combined with submetering and load curves to effectively manage sites.

Advantages, limitations and points to consider regarding the Energy Performance Certificate (EPC)

Interests

• Standardized vision for comparing goods and communicating simply (A→G).
• Technical basis for prioritizing insulation/building envelope vs. equipment replacement.
• Work roadmap: scenarios with estimated gains and effect on classes.
• Dialogue tool for co-ownership/general assemblies (readable for non-technical people).

Boundaries

• Conventional assumptions ≠ actual uses (schedules, density, instructions).
• Sensitive to the quality of input data (thickness, materials, sealing).
• Labeling alone is insufficient to accurately quantify OPEX.
• In complex tertiary sectors, an audit + STD/SED is preferred for fine-grained arbitration.

Points to consider

• Precise on-site surveys (photos, plans, wall composition, joinery, bridges).
• Systems: actual yields, regulation, balancing, maintenance status.
• Ventilation & IAQ: hygiene flow rates, airtightness, impact on needs.
• Summer comfort: sun protection, thermal inertia, night ventilation.
• Cross-reference DPE with metering data (kWh, DH of discomfort) to prioritize.
• Planning: coordinate DPE, energy audit, PPT and opportunities for aid (e.g. CEE).

Anecdote — “The DPE (Energy Performance Diagnosis) that brought common sense back to Toulouse”

In Toulouse, a 1980s-era condominium building had just received an "E" energy performance certificate (EPC). The temptation: to replace the boiler. However, the report detailed a roof insulation defect and the original windows on the west side. At the general meeting, the building manager compared the EPC rating with load curves: high peaks in the late afternoon during the summer and long winter warm-up periods. The decision: external thermal insulation on the parapets/roof + solar shading + load balancing as a priority. The result the following year: improved summer comfort, lower kWh consumption, and only then, a lower-capacity air-to-water heat pump. The moral of the story: the EPC provides guidance; the measurements confirm the correct order of priorities.