From 3 August 2026, anyone who presents the building permit to build a new building or undertake a major energy renovation will have to integrate a minimum share of renewable sources into the project. The thresholds change with the construction site: it reaches 60% in new buildings, it drops to 40% for deeper renovations and 15% for less extensive interventions or for the substantial renovation of the heating system.
The rules are contained in the legislative decree of 9 January 2026, number 5, which implements the European directive RED III. The provision came into force on 4 February and grants 180 days before the obligations apply to buildings: therefore the request for the building permit submitted from 3 August counts, even when the construction site begins later.
The word “renovation” can include very different jobs; the decree deals with those capable of truly changing the behavior and energy efficiency of the building. Bathroom remodeling, a new kitchen or flooring replacement, taken alone, are left out.
Which restructurings trigger the obligations?
The major first level renovation involves more than 50% of the gross dispersing surface and also includes the renovation of the winter or summer air conditioning system of the entire building. It could be, for example, an extensive intervention on the roof, facades, external walls and windows accompanied by the renovation of the systems.
In the second level the works affect more than 25% of the dispersing surface, without reaching the conditions envisaged for the first. A very extensive thermal coat or a major intervention on the roof can therefore fall under the new regulations even when the boiler remains where it is. The updated definitions come from the decree of the Ministry of the Environment of 28 October 2025, which revised the minimum energy requirements for buildings.
The dispersing surface does not coincide with the walkable surface of the apartment. It includes walls, roofs, floors and windows that separate air-conditioned spaces from the outside or non-air-conditioned spaces. In condominiums the calculation concerns the building, not just the living room of the owner who has decided to start the work.
Another category concerns the restructuring of the heating system, that is, a substantial modification of the system that produces and distributes heat. Simply replacing the boiler with a new appliance does not automatically coincide with renovating the entire system. Changing the generator and redesigning the home’s energy system are jobs of different weight, even when they both end up under the “systems” heading in the estimate.
The dimensions change with the depth of the construction site
For a new building, renewable sources must cover at least 60% of the consumption expected to produce domestic hot water. The same percentage must be achieved by considering hot water, heating and cooling together.
In major first level renovations the threshold goes to 40% for hot water and 40% for the sum of the three energy services. For second level interventions it drops to 15% of the expected consumption for heating and cooling; hot water, in this calculation, remains outside.
The 15% quota also applies when an existing building undergoes a real renovation of the heating system. For public buildings all percentages increase by five points: 65% for new buildings, 45% for first level renovations and 20% in the other two cases.
These numbers do not describe the part of the bill that is destined to disappear. They are percentages calculated on the conventional energy consumption foreseen by the project. The technician will insert accounts and checks into the energy report, while the Municipality will check compliance with the obligations through that document.
How much renewable power will need to be installed?
In addition to the consumption quotas, there remains the obligation to install a minimum electrical power from renewable sources on or inside the building, or in its appurtenances.
For new buildings the coefficient is equal to 0.05 kW for each square meter of the building’s plan surface area. In existing buildings it drops to 0.025 kW. On a ground level of 100 square metres, this means at least 5 kW for a new building and 2.5 kW for one already built. In public buildings the result increases by 10%.
The surface area of the appurtenances does not enter into the calculation, but it can accommodate the systems. The area must abut the building and cannot exceed three times its footprint. The decree also specifies that photovoltaic systems installed on the ground do not contribute to achieving the obligation. A solar field located elsewhere, therefore, cannot be borrowed to fix the project’s numbers.
The solution can combine photovoltaic, solar thermal, heat pumps, geothermal energy and other permitted technologies, according to the characteristics of the house and the services to be covered. A few panels on the roof may be insufficient when the project must also reach the thermal quotas.
The decree also prevents fulfilling the obligations by producing only renewable electricity intended for devices that generate heat with a simple electrical resistance, the so-called Joule effect. An exception is made for real estate units already classified in energy class B or higher.
The exemption
An architectural constraint, an unsuitable roof or a particularly difficult system configuration can prevent full compliance with the thresholds. The decree also considers the lack of economic convenience, but requires the designer to document it in the energy report, examining the non-feasibility of the different technological options available.
When the report is not required, the information must still be communicated to the Municipality according to the methods established by the administration. In short, the technical impossibility must come accompanied by checks and signatures: writing that the system is “not convenient” takes up one line, proving it requires something more.
For new buildings and first-level renovations, the exemption also involves a compensatory requirement. The project must obtain a non-renewable primary energy value lower than the limit calculated for the reference building. The renewable share can only be reduced when energy performance recovers elsewhere.
The percentage obligations do not apply to buildings connected to an efficient district heating or cooling network, provided that this covers the entire energy needs of the service concerned.
From August 3, therefore, renewable sources will enter projects first and then construction sites. For those who build from scratch or intervene heavily on the casing and systems, the technical report must already contain quotas, installed power, chosen technologies and any reasons that make it impossible to fully comply with the obligations.
