Buying a house involves several months of research, financial decisions, and a series of technical checks, some of which have changed recently. Today, real estate projects are measured as much by energy performance as by price per square meter, and upstream framing errors can be costly at the signing of the agreement.
Energy audit and DPE: what concretely changes the value of a house
Competitors detail the budget, location, and visit stages. They quickly touch on a crucial point: the energy class of the property and its direct consequences on the sale price, negotiation, and even the feasibility of the project.
Since January 1, 2025, the sale of a single-family home classified as E, F, or G requires a regulatory energy audit in addition to the DPE. This document outlines the necessary work to achieve a better classification, including a timeline and cost estimate. For the buyer, it serves as a concrete negotiation lever.
Properties classified as G are already banned from rental. A buyer considering a rental investment in a G house must therefore factor in the cost of energy renovation even before making a purchase offer.
For apartments, the collective DPE has been mandatory since January 1, 2026, for all residential buildings built before 2013. This means that a buyer in a co-ownership can demand this document and assess the overall performance of the building, not just that of their unit.
Several resources allow for cross-referencing listings and diagnostics, for example on https://www.maison-immobilier.fr/, where the listings include the energy performance data of the referenced properties.
Old house, new house, or land to build: comparative table of constraints
The choice between old, new, and construction on land determines the timeline, financing, and level of risk of the project. Here is a comparison of the main constraints to anticipate.
| Criterion | Old house | New house (VEFA) | Land + construction |
|---|---|---|---|
| Entry delay | About 3 months after the agreement | Variable, often more than a year | The longest (permit + construction) |
| Energy audit | Mandatory if classified E, F, or G | Not required (recent RT/RE standards) | Not required |
| Work to anticipate | Frequent (insulation, roofing, compliance upgrades) | No short-term work | Included in the construction contract |
| Price negotiation margin | Higher on energy-inefficient properties | Low | Variable depending on the land |
| Notary fees | Higher (old scale) | Reduced | Old scale on the land, reduced on the construction |
Old properties requiring work offer the widest negotiation margin, especially for properties poorly rated on the DPE. In contrast, new builds or construction avoid unpleasant structural surprises, at the cost of often more rigid timelines and budgets.
Mortgage and PTZ: financing criteria to check before any offer
Making a purchase offer without checking borrowing capacity remains the most common mistake. Loan simulation with your bank or a broker should precede visits, not follow them.
The zero-interest loan has been expanded. The PTZ 2026 now covers the entire territory and also applies to new single-family homes, which changes the calculations for first-time buyers comparing old and new properties. This change in scope can represent several tens of thousands of euros in interest-free financing.
Three checks to conduct before signing anything:
- The actual debt ratio, including co-ownership charges, estimated property tax, and potential renovation costs, not just the loan monthly payment
- Eligibility for the PTZ based on geographic area, household income, and type of property (new, old with work, land + construction)
- The validity period of the mandatory diagnostics for the targeted property, to avoid having to redo them between the agreement and the signing at the notary
A loan refusal after signing the agreement triggers the suspensive clause and cancels the sale, but the lost time (often two to three months) resets the search to zero.
Sale agreement and signing at the notary: technical pitfalls
The sale agreement legally binds both parties. Two technical points deserve special attention.
Real estate diagnostics and their validity
The technical diagnostics file (DDT) must be complete and valid at the time of signing. An expired DPE or an absent asbestos diagnosis can delay the sale or open up recourse after the purchase. Each diagnosis has its own validity period, which varies from six months (risk assessment) to an unlimited duration (asbestos if the result is negative for a property built before 1997).
Suspensive conditions to customize
The suspensive condition for obtaining a loan is the most well-known, but other protections exist:
- Condition related to obtaining a building permit (for an extension or planned elevation)
- Condition related to the seller completing work before the final sale
- Condition related to the absence of undeclared easements, verifiable with the notary
The notary is not just an administrative stamp: they verify the property’s compliance, easements, urban planning, and any preemption rights. Choosing your own notary (in addition to the seller’s, at no extra cost) allows for a dedicated interlocutor to defend your interests.
The planned reform of the DPE on January 1, 2027, which revalues properties heated by electricity through a new calculation method, could change the energy class of certain properties without any work. For a purchase in 2026, anticipating this reclassification allows for evaluating the real potential of a currently poorly rated property.
