The renovation of a home encompasses very different realities depending on whether one seeks to reduce a heating bill, to bring an outdated electrical installation up to standard, or to adapt an old building to recent regulatory constraints.
Since January 1, 2025, homes classified as G in the energy performance diagnosis (DPE) can no longer be rented out, and this ban will extend to homes classified as F starting in 2028, and then E in 2034. This timeline changes the game for rental property owners, but it also raises questions for occupants about the relevance of renovating before the value of their property declines.
Energy performance and rental ban: what the DPE timeline imposes
The DPE is no longer just an informative document. By becoming a criterion for the decency of housing, it now conditions access to the rental market. A landlord whose property is classified as G faces a binary choice: renovate or withdraw the property from rental.
This constraint does not apply to owner-occupiers, who remain legally free to do nothing. However, the depreciation of a poorly classified property on the resale market is pushing more and more of them to undertake insulation or heating system replacement work, even without a legal obligation.
A point often overlooked: the Le Meur law of November 19, 2024, extends these energy performance requirements to tourist accommodations, with a dedicated timeline. Owners of seasonal rentals must therefore anticipate energy renovation work that was not included in their initial projections.
To better understand the work proposed by Habitat Guides, one must first understand which expense items weigh the most on the thermal performance of a building.
Thermal insulation of the building: the item that conditions all others
Renovating a heating system without addressing the building’s envelope is like heating a leaky home. Insulating the walls (walls, roof, ground floor) remains the primary lever for reducing heat loss, and it also determines the efficiency of all the equipment installed afterwards.
The roof represents the surface through which the largest share of heat escapes in a detached house. Insulating the attic, whether it is lost or converted, significantly changes thermal comfort in both winter and summer. Exterior walls come next, with two distinct approaches:
- External insulation (ITE) eliminates most thermal bridges and does not reduce the living space, but it alters the appearance of the facade and sometimes requires a prior declaration of work
- Internal insulation (ITI) is generally cheaper and better suited to condominiums or protected facades, but it encroaches on a few centimeters in each room and leaves some thermal bridges intact
- Replacing glazed surfaces (windows, bays, patio doors) complements the treatment of the envelope by limiting air infiltration and losses through joinery, which are often underestimated in older homes
Insulating without revising ventilation creates a risk of condensation and degradation of indoor air quality. A home made airtight by good insulation must be equipped with suitable mechanical ventilation (VMC), either single or double flow depending on the configuration.
Heating and domestic hot water: adapting the system to the renovated building
Once the thermal envelope is treated, heating needs decrease. The sizing of the new system must take this reduction into account, or else an oversized unit will be installed that will operate poorly and wear out prematurely.
The air-water heat pump remains the most installed system replacing oil or gas boilers in detached houses. It provides heating and, depending on the models, domestic hot water production. Field reports vary on this point: the actual performance of a heat pump varies greatly depending on the quality of the installation, the local climate, and the level of insulation of the home.
Wood pellet boilers are an alternative in rural areas with storage space. Wood log heating, via an insert or an efficient stove, can also serve as a supplement in a well-insulated home.
For hot water production, the thermodynamic water heater is gradually becoming the standard. It consumes significantly less energy than a conventional electric water heater, provided it is installed in a space with a stable temperature.
Global renovation or staged renovation: deciding based on the project and budget
The competitors of this article often present global renovation as the suitable solution. The available data does not allow for such a simple conclusion. It all depends on the budget available, the initial condition of the home, and the ability to coordinate multiple trades on the same site.
Global renovation, which combines at least two types of work (insulation and heating, for example), provides access to more advantageous financial aid. However, it requires a heavier initial investment and rigorous planning. A prior energy audit allows for prioritizing the items to be addressed first.
Staged renovation remains relevant when the budget is constrained, provided a logical order is followed:
- Treat the insulation of the envelope first to reduce the actual energy needs of the home
- Revise ventilation immediately afterwards to avoid humidity issues related to better airtightness
- Replace the heating system last, sizing it according to the new needs of the renovated building
Reversing this order amounts to wasting part of the investment, since heating installed before insulation will be oversized once the envelope work is completed.
DPE and disputes: an emerging legal risk for owners
The DPE has become a battleground between landlords and tenants. Cases of litigation are multiplying when the energy class displayed at the signing of the lease does not match the reality observed. This legal risk adds an additional dimension to the decision to renovate.
For a landlord, a reliable DPE carried out after work protects as much as it enhances. The diagnosticians themselves are subject to strengthened regulation, and the reliability of diagnostics remains a topic of debate within the profession.
The rental market is now clearly segmented between renovated homes, which find tenants quickly, and energy sieves, whose rental vacancy is increasing. This divide weighs on the property value in the medium term, regardless of any legal obligation.
