Minimum requirements, Ministerial Decree towards entry into force: 15 new features on building efficiency

The Ministry of the Environment's decree on minimum requirements

Appendix A of the decree introduces, in fact, coefficients for the five most common thermal bridges that the building must respect, depending on the climate zones. The appendix reports - as in the previous version of the Minimum Requirements Decree - transmittance values for dispersing opaque structures and for technical closures, always including the contributions of thermal bridges. In addition, however - as mentioned - spot checks on the most recurring thermal bridges are now introduced.

standard also specifies that the thermal bridge lengths to be used in the calculation of the reference building are equal to those of the real building. The verification of thermal bridges also becomes more accurate for major renovations on the second level, for which the calculation of thermal transmittance and limiting thermal transmittance, including thermal bridges, is introduced.

For the purpose of calculating the limiting thermal transmittance, linear transmission coefficients are given for eleven types of thermal bridges (pillar, intermediate floor, balcony, corner, etc.), depending on the climatic zone and the position of the insulation (on the external side, on the internal side, in the cavity).

An important influence on the verifications established for the different types of intervention and on the characterisation of the reference building is the change to always refer to gross external surfaces in the calculations.

For the reference building, in fact, it is foreseen that for all input data and for the parameters not defined by the DM, the values of the real building are used with reference to the gross external measurements. Reference is also made to the gross external measurements for verifications related to the global average heat transfer coefficient, as well as for the calculation of thermal transmittance including thermal bridges in major renovations of the second level.

This measure 'weighs' on the calculation of the dispersion surface and thus on the thermal requirements, with consequences on the results of the audits and also on the energy classes of the Energy Performance Certificates (Ape).

For major renovations of the second level, as specified, compliance with thermal transmittance limits, including thermal bridges, is required. In addition, an important simplification is achieved with the elimination of the obligation to verify the global average heat transfer coefficient (H'T), which was difficult to comply with in the case of envelopes with a good percentage of glazed surfaces.

For major first-level renovations, the maximum permissible values of the average global heat transfer coefficient are revised and calibrated according to the percentage of glazed components and the climate zone.

Furthermore, an important clarification is added: it is specified that, for the purpose of verifying the average global heat transfer coefficient for transmission, it is necessary to consider both the opaque and transparent parts of the building envelope subject to intervention only if both are owned by the same legal entity; if the opaque parts belong to a different legal entity from the one to which the transparent parts belong, the verification of H'T must be carried out only on the part on which the intervention is carried out.

The Ministerial Decree modifies the list of interventions that, for the purposes of verification, are assimilated to new constructions and must therefore follow stricter rules. In particular, interventions involving the recovery of existing volumes that were previously not air-conditioned or changes of use (such as the recovery of attics, warehouses and storerooms) are also considered new constructions, provided that the new portion has a gross air-conditioned volume greater than 15% of the existing one and in any case greater than 500 m3.

It is also specified that, if the new portion has a gross air-conditioned volume of less than or equal to 15% of the existing one, or in any case less than or equal to 500 m3, the extension is not considered new construction, but the requirements for major renovations or energy redevelopment must still be met, depending on whether the interventions insist on a shell surface greater than or less than 25% of the dispersing surface. The latter is to be understood as the total gross area of the building, resulting after the interventions and including the extended part.

By 3 June, non-residential buildings equipped with thermal systems with a nominal power output of more than 290 kW must install - if they do not have them - Building Automation and Control Systems (Bacs). In other words, they must be equipped with the technological infrastructure that enables the control and optimisation of air-conditioning, lighting and security systems, making the building a smart building.

Bacs systems must be of efficiency class B or higher, as defined by Uni En Iso 5210-1, provided their installation is technically feasible and guarantees, net of any incentives or tax benefits, a simple payback time of less than six years.

Failure to install such systems must be justified by the designer in the technical report certifying compliance with the requirements for limiting the energy consumption of buildings and their systems. This obligation, which was only foreseen for imported first level renovations and new buildings, is therefore considerably extended.

In defining the prescriptions for new constructions and for major renovation and energy requalification works, the Ministerial Decree provides, in the case of replacement of the heat generator, for the obligation to install self-regulating devices that separately control the temperature in each room or, where justifiable, in a specific heated or cooled zone of the real estate unit, provided that their installation is technically feasible and guarantees, net of any tax bonus, a simple payback time of less than six years.

The non-installation is argued by the professional in the technical report.

The decree lays down stricter obligations for the integration of electric vehicle charging stations in non-residential buildings. Compared to Decree 48 of 2020, for non-residential buildings a higher number of charging points is foreseen, both in the case of new construction and major renovations.

The Ministerial Decree not only tightens up the rules introduced by Legislative Decree 48 of 2020, but also goes into the technical characteristics of columns and conduit infrastructure, and does so for residential buildings.

The Ministerial Decree proposes a holistic approach, inviting - when designing to contain energy consumption - to also look at fire and seismic safety and thermo-hygrometric well-being. In particular, the Ministerial Decree introduces the obligation to follow fire safety standards when carrying out major renovations at the first level.

In more detail, the decree provides a link to the fire prevention regulations in the first annex and more precisely in the chapter on the performance of new buildings and major renovations of the first level.

According to the Dm, for new buildings and for those undergoing major first-level renovations, in the case of interventions involving the opaque parts of the building envelope, the relevant fire prevention provisions apply. A provision that - for civil dwelling buildings - must be brought into line with the Viminale's Dm (Dm 25 January 2019) that deals with the fire safety of apartment buildings, where the obligation to comply with the fire prevention rules for new constructions and for interventions affecting more than 50% of the total surface of the façades is provided for.

For new buildings and buildings undergoing major renovation, a safety assessment in accordance with the Technical Building Regulations is mandatory. The objective is to determine whether structural safety needs to be increased through targeted interventions or whether the use of the building can continue without intervention.

The Ministerial Decree introduces the Carnot method to define the factors for converting the energy supplied by district heating networks and cogeneration plants into primary energy, with the aim of determining the efficiency of such systems more precisely.

The technical project report is lightened in the case of energy requalification involving only the replacement of windows and doors.

In this case, the report can be completed in a partial manner, dealing with declarations concerning: the air permeability and thermal transmittance of new windows and doors, the fulfilment of the transmittance verification, the transmittance of replaced windows and doors, and the verification of the total solar transmittance factor of the window component for transparent technical closures with an east-west orientation.

Furthermore, again in the case of energy requalification, in the presence of darkening closures or types of transparent surfaces for which the verification of the total solar transmission factor is satisfied, the technical report may be replaced by the declaration of the contractor certifying the Ce marking of the newly supplied windows and doors. In case of replacement of the heat generator, the report must also contain the designer's asseveration of compliance with the obligation to install Bacs systems and self-regulating devices for the control of indoor temperature. Finally, for the purposes of the obligation to draw up the technical report, the decree states that the replacement of a traditional gas boiler with a gas condensing boiler does not constitute a change in the type of generator.

The chapter defining the requirements common to new buildings, major renovations and energy upgrades introduces the obligation to equip lifts and escalators with a specific technical data sheet drawn up by the installation company.

For lifts this must include: the type of technology, the capacity, the stroke, the rated motor power, the energy consumption per reference cycle and the standby power. For escalators and moving walkways, the data to be included in the sheet are: the type of technology, the rated motor power, the energy consumption in continuous operation. The sheets must be kept by the person responsible for the installation.

At the design stage, for the construction of new buildings or major renovations of first level, the designer must take into account the technical, functional, environmental and economic feasibility of alternative high-efficiency systems, if available. The assessments of merit must be included in the report under Law 10.

The list of exceptions to the minimum requirements DM is extended, which does not apply in the case of work on the existing heating system involving the renovation of a layer of a component of the envelope (e.g. the floor).

If the replacement of this layer is not functional for the installation, no limit on the transmittance of the component is required. Interventions on existing installations aimed at maintaining their efficiency and safety are also excluded from the scope of application, provided they do not involve any replacement of the installation or its parts.

For the purposes of the definition of a nearly zero-energy building, it is stipulated that the mandatory quota of integration of systems from renewable sources is to be assessed either for the entire building, if the individual energy services of summer and winter air-conditioning and domestic hot water production of all building units are satisfied exclusively by centralised thermal systems, or per individual building unit if the individual energy services are satisfied only or also by systems serving, exclusively, individual building units.