A homeowner who is renovating their roof discovers, when removing the old insulation, that the framework shows signs of moisture due to faulty ventilation. The project, initially planned to last three weeks, extends to two months, and the budget skyrockets. This scenario repeats itself in a large number of home renovation projects, and it is almost always explained by a sequence of poorly thought-out work from the outset.
Home Renovation: The Trap of Isolated Actions After September 2026
Since September 1, 2026, several insulation or equipment works carried out alone (attics, walls, mechanical ventilation, wood heating) are no longer eligible for MaPrimeRénov’ through the “by action” pathway. The aid is now refocused on a few actions for decarbonizing heating (air-water or geothermal heat pumps, removal of oil tanks, connection to a heat network).
For everything else, the work must be integrated into a larger renovation project. The decree of August 17, 2026, also modifies the rules for energy savings certificates (CEE): the aids are reserved for homes classified E, F, or G, and prohibit the project from resulting in the installation or maintenance of fossil heating.
In practical terms, insulating one’s attic alone no longer triggers public aid. It is in one’s best interest to combine insulation, ventilation, and heating system replacement in the same project. This is a constraint, but it forces a holistic approach to the project, which avoids discovering six months later that everything needs to be reopened to install a mechanical ventilation system. Resources like projet-habitat.fr help structure this overall vision before contacting craftsmen.
Order of Renovation Works: The Sequence That Avoids Rework
We see it on the ground: installing new joinery before addressing the insulation of the walls from the outside often requires redoing the finishes around the windows. The technical order is non-negotiable, and it does not always correspond to the aesthetic order one would like to follow.
Logical Sequence of a Comprehensive Renovation Project
- Structural work first: repair of the framework, treatment of cracks, waterproofing. There is no point in insulating a wall that absorbs moisture by capillarity.
- Thermal insulation next (roof, walls, ground floor), starting with the most heat-leaking envelope. In an old house, the roof generally represents the heaviest heat loss.
- Ventilation following the insulation. Insulating without reviewing the mechanical ventilation system means trapping moisture in the building, which generates mold in a few months.
- Replacement of the heating system, sized according to actual needs after insulation (and not based on the needs of the uninsulated house).
- Finishing work: interior joinery, coverings, electrical work if it has not been addressed beforehand.
In a new construction project, the logic is similar: the envelope is treated before the technical lots. The difference is that one starts from a plan, not an existing structure to diagnose.
Work Budget: Anticipating Invisible Costs
The budget displayed at the beginning of the project almost never covers the actual budget at the end of the work. Feedback varies on this point, but several items regularly emerge as sources of overruns.
Omitted Items in a Renovation Project
The asbestos or lead diagnosis, mandatory for buildings constructed before a certain date, can reveal costly asbestos removal. Soil studies, often neglected in renovations, become necessary as soon as one considers an extension of the house or a change in the use of a space.
Project management fees (architect or project manager) represent a significant percentage of the overall budget. They are perceived as an additional expense, but professional site supervision reduces coordination errors between craftsmen, which are the primary cause of cost overruns.
Another underestimated item: electrical compliance. In a 1970s house, the panel and wiring often need to be completely redone to meet the NF C 15-100 standard, which represents a project in itself.
New Construction or Major Renovation: Concrete Selection Criteria
The question arises when the cost of renovating an old house approaches that of new construction. This shift is particularly observed in houses with degraded structures (foundations, framework, networks) and whose initial energy performance diagnosis (DPE) is rated F or G.
In new construction, all thermal performance is controlled from the design stage. The RE 2020 imposes consumption and carbon emission thresholds that renovation struggles to meet without a substantial budget. On the other hand, available land in dense urban areas often pushes towards renovation by default, due to a lack of buildable land.
A rarely mentioned criterion: the duration of unavailability of the housing. A major renovation of an occupied dwelling requires phases of temporary relocation, with costs and logistical constraints that new construction (when living elsewhere during the project) does not generate in the same way.
Choosing Craftsmen and Companies: What Changes with the RGE Label
A decree published in August 2026 now regulates subcontracting in the context of energy renovation work. The company invoicing must itself hold the RGE label, and not simply be a subcontractor of a labeled structure. This change modifies the way professionals are selected.
Before signing a quote, one should verify the RGE qualification of the company on the official France Rénov’ directory. At a minimum, compare three detailed quotes item by item, ensuring that materials, insulation thicknesses, and joinery references are explicitly mentioned.
The choice between a general contractor and separate trades depends on the size of the project. Beyond three trades, coordination becomes a full-time job, and going through a project manager or general contractor simplifies the management of the schedule and interfaces between trades.
Regulations are evolving rapidly regarding energy renovation and construction. A project launched in 2026 cannot be set up like a project from 2023: aids, performance requirements, and subcontracting rules have changed. Checking each parameter before signing the first quote remains the best investment of time for the entire project.