Correction Coefficients Methodology
How Mon Simulateur Immobilier moves from a theoretical savings calculation to a realistic estimate of what you will actually save.
Why this methodology?
When an energy performance certificate (DPE) calculates your future consumption after renovation, it makes a theoretical calculation: it assumes everything will go as planned, that materials will be perfectly installed, and that you will keep the same heating habits as before.
Reality is more nuanced. After insulating, people often heat a bit longer, or heat rooms they used to leave cold: this is called the rebound effect. When a heat pump is installed without prior insulation, its efficiency is not optimal. When windows are replaced without touching the rest, only a small share of losses is addressed (15-20% on average).
Mon Simulateur Immobilier applies correction coefficients to account for these gaps between theory and field. These coefficients come from scientific literature (IEA, ADEME, Effinergie, INSEE, plus international sources). They are not invented: they reflect what studies measure on hundreds of real projects.
This page explains in detail how these coefficients work, with their sources and limits. You will also find the 3 pieces of information you can provide to refine your estimate, and the corrective suggestions offered by our "Bouquet adjustments" panel.
The 3 correction layers
To go from the theoretical estimate to the number you see in the simulator, Mon Simulateur Immobilier applies three successive layers:
1Layer 1 — Per-work rebound coefficient
Each type of work has its own coefficient. Attic insulation — where the rebound effect is small (you don't heat your roof more!) — keeps 85% of its theoretical savings. A heat pump, where you may push the comfort dial up, can drop to 75%. These values come from international meta-analyses (Sorrell 2009, Aydin 2017, Belaïd 2018-2020).
2Layer 2 — Contextual modulators
If your home is rated F or G, you were probably restricting your thermal comfort (limited heating). After works, you will "catch up" this missed comfort: this is the comfort take-back, measured at around -15% on the gain. Same for very low-income households, who sometimes under-heated due to financial constraints (Madlener 2011).
3Layer 3 — Bouquet adjustments
This is the main subject of this page. Mon Simulateur Immobilier analyzes your bouquet (the set of works you selected) and applies bonuses or maluses based on interactions between the chosen works. A heat pump alone in a non-insulated home under-performs; the same heat pump combined with insulation and a heat-recovery ventilation over-performs (systemic synergy). 9 rules cover the most documented cases.
The 4 adjustment categories
The 9 rules are organized into 4 families. Each family covers a different type of interaction. At most one rule applies per family (the first one matching your case), so you will see at most 4 simultaneous adjustments.
Synergic
The bouquet shows overall coherence that amplifies gains (bonus), or a major imbalance between systems (malus). Positive example: heat pump + complete insulation + heat-recovery ventilation. Negative example: heat pump without prior insulation.
Implementation quality
The bouquet exposes a known implementation defect risk — typically thermal bridges (cold zones at junctions) or absence of ventilation after insulation (trapped moisture). Always a malus, unless you tell us the risk is mitigated.
Incompleteness
The bouquet is undersized relative to the installed system. Examples: heat-recovery ventilation in a non-airtight home (air bypasses the heat exchanger, you lose 60% of the nominal efficiency), or window replacement without touching the rest.
Staggering and labelling
The way works are carried out can amplify or reduce gains. Bonus for a BBC-Rénovation labelled site (third-party quality assurance, +15%). Malus for staggered works in multiple phases (-7% per deferred phase, interface defects).
Rules catalogue
Here are the 9 bouquet adjustment rules, ordered by category. Click on a rule to see its details (trigger, source, how to neutralize it).
Synergic
Implementation quality
Incompleteness
Staggering and labelling
Your declarations refine the estimate
Three pieces of information you provide via the simulator interface allow us to refine the applied adjustments. Without this information, we apply the statistical defaults (which are rather conservative).
Thermal bridge treatment (for interior insulation)
When you insulate from the inside, the junctions between your walls and floors/partitions remain cold if you do not specifically treat them. This creates zones where moist air condenses on the warm-side wall — the so-called interstitial condensation. The default penalty is 15% on the wall gain.
💡 If your contractor has planned bridge treatment (insulating spandrels, insulation returns at junctions), tick the box in the simulator sidebar. The penalty disappears.
Project labelling (BBC Rénovation)
The BBC Rénovation label (Effinergie) implies project assistance and third-party quality control. Effinergie observes that 85% of labelled projects reach the theoretical target, vs around 50% without the label. If your project is labelled, you get a 15% bonus.
💡 Tick the box if your project is BBC Rénovation, Effinergie or Dorémi labelled. An anti-absurd-declaration guard applies: a label without a coherent bouquet (≥ 2 insulation works OR heat pump + 1 insulation) is ignored to prevent over-declaration.
Works planning (grouped vs staggered)
ADEME observes that staggered renovations across multiple phases accumulate interface defects (sealing connections, thermal bridges at later-installed junctions). Count around -7% per deferred phase.
💡 Indicate via the radio button whether your works will be carried out as a single project or staggered over ≥ 2 phases. The default is "grouped" (no penalty).
Anti-regression logic
When our panel suggests adding a work to your bouquet to neutralize an adjustment, the engine checks that this addition does not introduce another malus of greater or equal severity. This is the so-called "deck of cards" logic: we don't want you to fix a -15% by triggering a -40%.
However, **net beneficial exchanges** are allowed. If you neutralize a -50% (windows only) by triggering a -15% (insulation without ventilation), the net is positive (+35 points), and the engine will still suggest it. You can then add a heat-recovery ventilation to neutralize the -15% in turn.
Bonuses (systemic synergy, BBC label) are always accepted if they activate alongside a suggestion — that's added value, no downside.
Confidence and limits
Each rule carries a confidence level reflecting the robustness of its calibration:
- high : Dedicated empirical study on a large panel of projects (typically IEA, TREMI, Effinergie). The coefficient is solidly documented.
- medium : Inference from several converging sources but no single study dedicated to this exact case (e.g. extrapolation of US studies to the French context).
- low : Conservative estimate based on physical principles or limited field observations. Wider uncertainty margin.
Our estimate remains indicative. For precise figures, get a regulated energy audit (RGE in France) that takes into account your home, your local climate, your heating habits, and your specific project. Our simulator is a pre-scoping tool, not a substitute for an audit.
Going further
If you want to dig into the methodology or sources: