Determination of the Passive Acoustic Requirements of Buildings

What it requires

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.

The five quantities

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.

On-site verification and liability

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.

The relationship with UNI 11367

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.