Minimum energy-performance requirements for buildings (the 'minimum requirements decree')
Summary
TAV. 00The 'minimum requirements decree': it implements Legislative Decree 192/2005 by defining the methods for calculating the energy performance of buildings and the minimum requirements they must meet. It introduces the reference-building method and the NZEB (nearly zero-energy building) obligation for new construction. Published in Official Gazette no. 162 of 15 July 2015.
Scope of application
TAV. 01It applies to new buildings and to works on existing ones (major renovations of the first and second level, energy upgrades), grading the requirements according to the type of works. It is accompanied by the twin decrees of 26/06/2015 on technical-report templates and on the EPC (energy performance certificate) guidelines.
In depth
TAV. AThe reference building: the heart of the method
The decree does not only set absolute threshold values: it introduces a comparison. For every real building a 'reference building' is constructed, identical in geometry, orientation, use and climate context, but fitted with standard energy parameters set by the decree. The real building complies if its performance is no worse than that of its reference twin. It is a performance-based method, not a simple checklist of thicknesses.
What is checked
The requirements concern two fronts: the envelope and the systems. On the envelope, the transmittances of the elements, the mean heat-transfer coefficient (H'T) and the summer equivalent solar area (overheating control) are checked. On the systems, efficiencies and the global energy-performance indices (EPgl) are verified, distinguishing renewable from non-renewable energy.
| Front | What is checked |
|---|---|
| Opaque and glazed envelope | thermal transmittances U of the elements |
| Overall behaviour | mean coefficient H'T; equivalent solar area (summer) |
| Systems | efficiencies; EPgl indices (renewable/non-renewable) |
| Renewables | minimum share from renewable sources (coordinated with D.Lgs. 199/2021) |
NZEB: the standard for new buildings
Since 1 January 2021 every new building (and many major works) must be NZEB: very high energy performance and a need covered to a significant extent by renewable sources, largely on site. The decree traces the transition that D.Lgs. 192/2005 and the EPBD directive had set out, and that the new EPBD (Dir. (UE) 2024/1275) pushes towards the zero-emission building.
- 01Type of worksDefine the works (new construction, major renovation, energy upgrade).
- 02CalculationBuild the reference building and compute performance with the UNI/TS 11300 methods.
- 03ComparisonCompare the real parameters with the reference ones and with the minimum requirements.
- 04CertificationDraw up the technical report (the former 'Law 10' report) and the EPC at the end of works.
Why it matters
This is the decree that translates efficiency goals into design numbers: without the 'minimum requirements', the great frameworks (D.Lgs. 192, EPBD) would remain principles. It is here that the designer finds the yardstick to prove that a building really does consume little.
Key points
TAV. K- Implements D.Lgs. 192/2005: it defines how energy performance is calculated and the minimum requirements to meet.
- Reference-building method: requirements are checked by comparing the real building with a standard-parameter 'twin'.
- Since 2021 every new building must be NZEB (nearly zero-energy building).
- Requirements on the envelope (transmittances, H'T, equivalent solar area) and the systems (efficiencies, EPgl).
- Three levels of works: new construction, major renovation (1st/2nd level), energy upgrade.
- Compliance is certified by the technical report under art. 8 (the former 'Law 10' report).
Frequently asked questions
TAV. QWhat is the reference building?
A virtual building identical to the real one in geometry, orientation and use, but with standard energy parameters set by the decree. The real building complies if it performs no worse than its reference.
What does NZEB mean and since when is it mandatory?
NZEB is the nearly zero-energy building: very high performance and large use of renewables. Since 1 January 2021 it is mandatory for all new buildings (since 2019 for new public buildings).
Which works on existing buildings are subject to it?
The decree distinguishes major renovations of the first and second level (based on the share of the dispersing surface affected) and energy upgrades, with progressively less extensive requirements.
How does it relate to D.Lgs. 192/2005?
D.Lgs. 192/2005 is the framework; D.M. 26/06/2015 is the implementing decree that makes its calculation methods and minimum requirements operational. Without the decree, the law would remain a principle.
What is the 'ex Law 10' technical report?
It is the report certifying compliance with the energy requirements, required by art. 8 of D.Lgs. 192/2005 (heir of Law 10/1991). One of the twin decrees of 26/06/2015 sets its templates.
Glossary
TAV. G- Edificio di riferimento
- Virtual building with standard parameters used as the term of comparison to verify energy compliance.
- NZEB
- Nearly zero-energy building: very low energy need, covered to a significant extent by renewable sources.
- EPgl
- Global energy-performance index: it sums the needs of the building's energy services, split into renewable and non-renewable shares.
- H'T
- Mean heat-transfer coefficient: it measures the envelope's dispersion per unit of dispersing surface.
- Ristrutturazione importante
- Works affecting a significant share of the dispersing surface; the decree distinguishes a first and a second level.