Renovating a home involves several trades, various materials, and a budget that can spiral out of control within the first few weeks of construction. Between the regulatory changes of MaPrimeRénov’ in 2026 and the technical constraints specific to each area (insulation, electricity, plumbing), the success of a renovation project relies more on preparation than ambition. Which areas concentrate the risks of cost overruns, and how should they be prioritized before starting the work?
Energy renovation: what MaPrimeRénov’ 2026 changes for your project
The MaPrimeRénov’ scheme has been refocused since 2026 on large-scale renovations. The “Large-scale Renovation” component now targets homes rated E, F, or G on the energy performance certificate (DPE), with a clear requirement: to gain at least two energy classes after the work. For example, moving from G to E or from F to D.
A personalized appointment with a France Rénov’ advisor has become mandatory before submitting any aid request. This step aims to validate the technical coherence of the project and to avoid isolated works that have no real impact on the performance of the home.
From September 1, 2026, any subsidized large-scale renovation must also include the replacement of a fossil fuel boiler (gas, oil) with a decarbonized system: heat pump, geothermal energy, or another low-carbon solution. This point radically changes the initial cost estimate for homeowners still equipped with a gas boiler. It is better to integrate this item right from the project design rather than discovering it during the construction process.
Consulting the work on the Oh Brico site allows you to identify the various trades involved in this type of comprehensive renovation and to better anticipate the interactions between areas.
Home renovation areas: prioritize according to the risk of cost overruns
Not all renovation areas present the same level of budget risk. The table below compares the main lots based on their potential for overruns and their impact on the comfort of the home.
| Work Area | Cost Overrun Risk | Impact on DPE | Recommended Priority |
|---|---|---|---|
| Roof and attic insulation | Moderate | High | High |
| Replacement of fossil fuel boiler | High (depending on access and existing network) | High | High (mandatory for 2026 aid) |
| Electrical compliance | High (diagnosis often late) | None | Medium to high |
| Kitchen or bathroom renovation | Very high (finishes, plumbing) | None | Depending on comfort |
| Facade renovation | Moderate to high (scaffolding, weather) | Low to moderate | Variable |
Roof insulation offers the best ratio between investment and energy gain. In contrast, renovating a kitchen or bathroom generates the most frequent overruns, mainly due to embedded plumbing and changing material choices during the construction process.
The electrical diagnosis often comes too late in the schedule. Many homeowners discover it after opening the walls for insulation, which forces an urgent update of the electrical panel. Requesting a complete diagnosis before validating the first quote avoids this scenario.
Renovation budget: anticipate unforeseen events without inflating quotes
The margin for unforeseen events is included in all renovation guides. The real issue is not knowing that one should be planned, but understanding where overruns actually occur.
Three main sources of cost overruns frequently arise on residential construction sites:
- Structural discoveries after demolition (moisture in walls, weakened framework, outdated plumbing) that impose unplanned work not included in the initial quote
- Changes in material choices during the project, often motivated by a sudden preference or a stock shortage of the initially selected product
- Supply delays that extend the duration of the project and increase labor costs, especially for artisans charging by the day
Locking in material choices before starting the project significantly reduces the risk. This requires visiting showrooms, ordering samples, and confirming delivery times several weeks before the artisans’ intervention.
For large-scale renovations eligible for aid, the mandatory visit to a France Rénov’ advisor also helps validate the coherence between the projected budget and the actual work needed to achieve the required two-class DPE jump.
Artisans and work quotes: checks not to be overlooked
Requesting multiple quotes remains a common reflex. The problem rarely lies in the number of quotes obtained, but in the difficulty of comparing them effectively.
A detailed quote by area (with supplies separate from labor, brands and references of materials specified) allows for line-by-line comparison. A global quote without breakdown makes any analysis impossible and hides potential intentional omissions.
The RGE (Recognized Environmental Guarantee) mention conditions access to aid for insulation and heating works. Checking the validity of this certification on the official directory before signing avoids losing the benefit of MaPrimeRénov’ later on.
Another often underestimated point: coordination between artisans. On a site that combines insulation, electricity, and plumbing, the order of intervention matters. The plasterer cannot close the partitions until the electrician has run their conduits. A shared intervention schedule among all participants limits downtime and rework.
Thermal sieves and regulatory calendar: what weighs on housing renovation
The 2026 Housing Recovery Law tightens obligations for owners of homes rated F and G on the DPE. These properties, classified as thermal sieves, face increasing restrictions for rental.
This regulatory calendar changes the logic of prioritizing work. For a landlord, renovating the thermal envelope of the home becomes a condition for remaining in the rental market, not just a comfort choice. The gain of two DPE classes required by MaPrimeRénov’ aligns with this constraint.
For owner-occupiers, the regulatory pressure is lower, but the depreciation of a poorly rated property on the DPE during a future resale remains a factor to consider from the project design phase.
The area with the most impact remains insulation (roof, walls, ground floors), followed by the replacement of the heating system. These two lots, treated together, are usually sufficient to exceed the threshold of the two energy classes required to unlock aid and move out of the thermal sieve category.