The implementing decree of Italy's framework law on noise pollution (Law 447/1995), setting — for seven building categories — the passive acoustic requirements to be guaranteed in the finished building: airborne sound insulation between units, façade insulation, impact noise and building-services noise. It is the binding reference for acoustic comfort in Italian buildings.
It applies to buildings and their components as built — horizontal and vertical partitions — and to internal sound sources (building services), for the occupied spaces classified in the seven categories of Table A: residential (A), offices (B), hotels (C), hospitals and care homes (D), schools (E), recreational or religious uses (F), commercial uses (G). It concerns designers, works directors, contractors, builder-vendors and qualified acoustics professionals.
Four articles, one annex and two tables: the decree implements art. 3(1)(e) of the framework law on noise pollution (Law 447/1995) and determines the acoustic requirements of sound sources inside buildings and the passive acoustic requirements of buildings and their components as built, in order to reduce human exposure to noise. Table A classifies occupied spaces into seven categories — residential (A), offices (B), hotels (C), hospitals and care homes (D), schools (E), recreational or religious uses (F), commercial uses (G) — and Table B assigns the limit values to each, grouping the categories into four bands of stringency. It has been in force since February 1998, sixty days after publication in the Official Gazette.
The logic of the limits is graded on the sensitivity of the occupants. Hospitals are the most protected spaces: the highest airborne sound insulation between real-estate units (R'w of at least 55 dB, against 50 dB for all other categories) and the quietest continuous services. Schools have the strictest façade insulation (D2m,nT,w of at least 48 dB, against 40 for dwellings and hotels and 42 for offices, recreational and commercial uses). The permitted impact noise is most lenient for dwellings and hotels (L'n,w up to 63 dB) and strictest for offices, recreational and commercial buildings (55 dB), with hospitals and schools at 58 dB.
Three quantities concern the envelope and the partitions. The apparent sound reduction index R'w measures, in the finished building, how much an element separating two distinct real-estate units attenuates airborne noise — voices, television, music; it is "apparent" because it includes flanking transmission through adjacent structures, not the wall alone. The standardised façade sound insulation index D2m,nT,w describes protection from outdoor noise, traffic above all, with the outdoor level taken 2 metres from the façade and referred to a conventional reverberation time of 0.5 seconds. The normalised impact sound pressure level index of floors L'n,w quantifies the impact noise transmitted by floor slabs: here, unlike the first two, the measured value must stay below the limit.
Two quantities govern building services. LASmax is the maximum A-weighted sound pressure level with slow time constant, applied to intermittently operating services (lifts, waste-water drains, bathrooms, sanitary facilities and taps): the limit is 35 dB(A) in every category. LAeq is the equivalent continuous A-weighted sound pressure level, applied to continuously operating services (heating, ventilation and air conditioning): 25 dB(A) in hospitals and schools, 35 dB(A) in the other categories. Measurements are taken in the room where the noise is highest, which must differ from the room where the noise originates.
The decree expressly refers to components "as built": compliance with the limits is ascertained in the finished building, through sound measurements carried out by a qualified acoustics professional (tecnico competente in acustica), the professional figure established by Law 447/1995 itself. A product's laboratory certificate is a starting point for the design, not proof of the building's compliance.
As for liability, prevailing case law treats failure to meet the requirements as a defect of the property, which can ground a buyer's claims for damages or a price reduction against the builder-vendor. Several municipal building regulations also require acoustic documentation for building permits. The soundest defence remains design prudence: a predictive acoustic report, careful installation details, final acoustic testing.
UNI 11367 ("Acoustic classification of real-estate units", 2010 edition replaced by the 2023 one) is a voluntary technical standard: it measures the performance of the real-estate unit in the finished building and translates it into four classes, from I — the best — to IV. It does not replace the decree, which remains the binding minimum: it is a tool of qualification and transparency, usable in contractual relations and referenced by the Minimum Environmental Criteria (CAM) for public building procurement, which require Class II. In short: the decree states what the law demands, UNI 11367 states what the dwelling is acoustically worth.
The full text of the decree, freely reproducible, is published in Official Gazette General Series no. 297 of 22 December 1997 and can be consulted free of charge at the official source indicated on this sheet.
Where this rule shows up in past architect qualification exams — study the rule, not just the theme.
The decree does not expressly distinguish between new construction and work on existing buildings: it refers to buildings and components as built. In applicative practice and prevailing case law the requirements concern new buildings and renovations that affect the acoustic characteristics of the building (rebuilding of floors, partitions, façades, services); many local building regulations make this explicit. The municipal regulation should be checked case by case.
Sound measurements in the finished building are carried out by a qualified acoustics professional (tecnico competente in acustica), a professional figure established by Law 447/1995 and now enrolled in a national register. Final acoustic testing, although not always mandatory by law, is the strongest proof of compliance in the event of disputes.
The decree provides no specific penalty, but the concrete risk is civil: under prevailing case law non-compliance is a defect of the property, which can ground a buyer's claims for damages or a price reduction against the builder-vendor. Administratively, some municipalities require acoustic documentation for building permits.
They are complementary: the decree is the binding legal minimum, while UNI 11367 is a voluntary classification that measures the performance of the real-estate unit as built and expresses it in four classes (from I, the best, to IV). The classification does not replace compliance with the decree; it is referenced by the Minimum Environmental Criteria (CAM) for public buildings, which require Class II.
No, as far as airborne sound insulation is concerned: Table B refers the apparent sound reduction index R'w to elements separating two distinct real-estate units. Within the same dwelling the decree imposes no minimum insulation between rooms; any internal performance is a design or specification choice.
35 dB(A) LASmax for intermittently operating services (lifts, waste-water drains, bathrooms, sanitary facilities and taps) in all categories; for continuously operating services (heating, ventilation and air conditioning) 25 dB(A) LAeq in hospitals and schools and 35 dB(A) in the other categories. Measurements are taken in the room where the noise is highest, which must differ from the room where it originates.
Yes. Article 11 of Law 88/2009 envisaged a reorganisation of the rules on the acoustic requirements of buildings, never completed: the decree of 5 December 1997 remains fully in force and is still the binding national reference.
The decree is published in Official Gazette General Series no. 297 of 22 December 1997, freely available on the Official Gazette website (link on this sheet). As a legislative text, its reproduction is free.