The new buildings acoustic classification scheme in Spain: the standard UNE 74201 Amelia Romero Fernández 1 Teresa Carrascal García 2 Belén Casla Herguedas 3 Eduardo Torroja Institute for Construction Sciences. IETcc – CSIC. Serrano Galvache, 4. 28033 Madrid, Spain. ABSTRACT In September 2021, the document that develops an acoustic classification scheme was approved in Spain. It is the UNE 74201 standard that is described in this paper. The Spanish ACS is applicable to new and existing buildings for private or public residential use, for health/hospital and educational use. The development of this document has been a challenge which, requested by the construction sector, has been completed after 5 years of collaborative work, within the Technical Committee CTN74/SC2 - Building Acoustics of the Spanish Standardisation Body, UNE. It’s been achieved an ACS compatible with the “DB HR” Spanish building acoustics regulations and, in turn, in agreement as much as possible with ISO/TS 19488:2021. The standard defines different levels of noise protection by using a system of six classes for the requirements, A to F, where Class D defines the minimum requirements for acoustic quality that are mandatory to fulfil in the building code. Criteria for airborne, impact and façade sound insulation, for service equipment noise and for reverberation time are included. This paper shows in detail the verification, sampling and class assignment procedures developed in the standard. A comparison of the most general aspects with other European schemes is also shown. 1. INTRODUCTION

In Spain, the national standard UNE 74201 [1] approved in September 2021 has established an acoustic classification scheme, here in after ACS, 12 years after the entry into force of the new Spanish building acoustics regulations “DB HR” [2]. It is already known that building acoustics regulations specify minimum requirements that guarantee a certain level of acoustic quality for new buildings, but do not always guarantee satisfactory conditions for its occupants. 22,1% of the Spanish population has declared noise problems in their dwelling produced by neighbors or from outside [3]. DB HR gives limit values for acoustical conditions such as airborne, impact and façade sound insulation, reverberation time and noise from technical equipment, in a variety of building types. In this way, fundamental requirements in DB HR are a minimum airborne sound insulation of D nT,A (≈

1 aromero@ietcc.csic.es

2 tcarrascal@ietcc.csic.es

3 belench@ietcc.csic.es

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D nT,w +C 100-5000 ) ≥ 50 dBA and a maximum impact sound insulation of L’ nT,w ≤ 65 dB between two adjoining dwellings. As for the façades, the required sound insulation D 2m,nT,Atr (≈ D 2m,nT,w +C 100-5000 ) ranges from 30 to 42 dBA, depending on the use of the building and on the exterior noise levels. The required sound insulation increased, and consequently also the quality of Spanish dwellings; these requirements meant a huge and important change in regard to the previous regulation and an important leap towards the level of other European countries, with sound insulation indices that try to converge towards a harmonized proposal in Europe [4-6]; however, requirements in DB HR are still generally lower compared to those. In recent years, several studies have shown that in Spain it can be built with levels of quality and acoustic performance above the requirements defined in DB HR regulations [7]. Some examples can be found in [8], where more or less margin is seen depending on the construction system and the acoustic characteristic considered, airborne or impact sound insulation. Under this perspective, in 2016 work began on the development of an ACS within the Technical Committee CTN74/SC2 - Building Acoustics of the Spanish Standardisation Body, UNE. This project has been completed after 5 years of collaborative work. There are already 14 existing national acoustic classification schemes in Europe for dwellings [6] and in the international scope there is a technical specification, ISO/TS 19488:2021 Acoustics- Acoustic classification of dwellings [9], which can serve as a reference for countries that do not have their own regulations. The Spanish ACS standard achieved is compatible with the DB HR Spanish building acoustics regulations and, in turn, in agreement as much as possible with ISO/TS 19488:2021, which was considered as a starting point. The ACS includes criteria for airborne, impact and façade sound insulation, for service equipment noise and for reverberation time, by using a system of six classes for the requirements, A to F; Class A is the upper and Class F is the lower class, that is addressed to existing buildings that were designed with no commitment with acoustic performance, before the publication of DB HR in 2009. Minimum requirements that are mandatory to fulfil in the building code DB HR are classified as Class D. This paper shows in detail the verification, sampling and class assignment procedures developed in the standard. A comparison of the most general aspects with other European schemes is also shown. An application example on the ACS can be consulted in [10]. 2. OBJECT AND SCOPE OF UNE 74201

Spanish Standard UNE 74201, published in September 2021, contains the classification scheme and the verification procedures for buildings. As with other existing classification schemes in other European countries, its main objective is to provide the construction sector, the market and the final users with a tool to specify a level of acoustic performance in buildings that is complementary to that defined in national regulations. It also aims at promoting the knowledge of occupants about the acoustic performance of buildings by using a scale from A to F. The use of this classification standard is voluntary in Spain and it is complementary to the current regulations [2]; however, an additional goal of this standard is to be a reference for authorities in order to set a specific class for future building regulations. The scope of the standard has been expanded with respect to ISO/TS 19488 and it applies to all type of dwellings (housing blocks, single family houses, detached and semidetached houses), public residential buildings, schools, medical centres and hospitals. It can also be used to assess the increase of the acoustic performance of an existing building after retrofitting works.

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Regarding airborne and impact sound insulation and noise transmitted from building services, UNE 74201 does not apply to: • Rooms adjoining unfinished premises or premises whose building use is not yet known, thus these situations cannot be classified. • Non-operational building services at the time of the classification. • Drain pipes. Waste water pipes are included in the classification. 3. DESCRIPTION OF THE ACS, ACOUSTIC CHARACTERISTICS AND ASSIGNED VALUES TO THE CLASSES

Six acoustics classes, A to F, are defined to specify different levels of acoustic conditions in dwellings. Class A is the highest class and Class F is the lowest one. Requirements defined in current acoustic regulation in Spain, DB HR [2], are guaranteed by Class D. Classes A, B and C provide higher protection against noise that will provide better acoustic comfort. Classes E and F correspond to inadequate noise protection and Class F is intended to classify existing buildings. The indication “ndp” can be used for dwellings where no acoustic performance is required or it is not determined. The performance areas in UNE 74201 are airborne and impact sound insulation, airborne sound insulation against outdoor noise, sound pressure levels from service equipment and reverberation time of certain spaces within buildings.

3.1. Airborne sound insulation Table 1 shows the minimum values for airborne sound insulation for each of the classes. Table 1: Airborne sound ins u l a t i o n b e t w e en protected rooms and other rooms. Class limits. Type of rooms C lass A Class B Class C Class D Class E Class F Between protected rooms and other rooms, both in the horizontal and the vertical directions D nT,A ≥ 60 D nT,A ≥ 57 D nT,A ≥ 54 D nT,A ≥ 50 D nT,A ≥ 46 D nT,A ˂ 46

Between protected rooms and service equipment or activity rooms D nT,A ≥ 65 D nT,A ≥ 62 D nT,A ≥ 59 D nT,A ≥ 55 D nT,A ≥ 51 D nT,A ˂ 51

Between protected rooms and common or access areas with an entrance door in the separating wa l l D nT,A ≥ 40 D nT,A ≥ 37 D nT,A ≥ 34 D nT,A ≥ 30 D nT,A ≥ 28 D nT,A ˂28

Note: Elevator shafts will not be included as facilities.

3.2. Impact sound insulation Table 2 shows the maximum values for impact sound pressure level for each of the classes. Table 2. Impact sound press u re l evels between protected rooms and other rooms. Class limits. Type of rooms C lass A Class B Class C Class D Class E Class F In protected rooms from other rooms or common access areas both in the horizontal and the vertical direc t i o n s L´ nT,w ≤ 47 L´ nT,w ≤ 53 L´ nT,w ≤ 59 L´ nT,w ≤ 65 L´ nT,w ≤ 70 L´ nT,w ˃ 70

In protected rooms from service equipment or activity rooms L´ nT,w ≤ 42 L´ nT,w ≤ 48 L´ nT,w ≤ 54 L´ nT,w ≤ 60 L´ nT,w ≤ 65 L´ nT,w ˃ 65

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3.3. Sound insulation against exterior noise Sound levels indoors depend highly on the outdoor source and sound insulation. Table 3 shows the minimum values for sound insulation for a specific environment characterised by L d for the relevant outdoor sound sources, for each of the classes. Table 3. Sound insulation a g a i n s t e x t e r i o r noise. Class limits. Type of rooms C lass A Class B Class C Class D Class E Class F Façades, roofs and floors in contact with exterior air in protected rooms; in specific environment with sound sources characterised by L d

D 2m,nT,Atr ≥ L d -21 D 2m,nT,Atr ≥ L d -24 D 2m,nT,Atr ≥ L d -27 D 2m,nT,Atr ≥ L d -30 D 2m,nT,Atr ≥ L d -34 D 2m,nT,Atr < L d -34

Notes: In the case of predominant aircraft noise, L d + 4 dBA should be considered. In any case, classes A, B, C and D additionally require compliance with the insulation levels required in the DBHR.

3.4. Noise from building services Table X shows maximum values for A-weighted time-averaged or the maximum sound pressure levels due to service equipment, for each of the classes. Table 4. Sound pressure levels in protected rooms due to building service equipment. Class limits. Type of room and sources Quantity Class A Class B Class C Class D Class E Class F In protected rooms from outdoor and indoor service equipment producing continuous noise in adjacent rooms.

L A,eq,nT ≤ 24 ≤ 27 ≤ 30 ≤ 33 ≤ 36 ˃ 36

In protected rooms from outdoor and indoor service equipment producing intermittent or irregular noise in adjace nt rooms.

L AF,max,nT ≤ 28 ≤ 31 ≤ 34 ≤ 37 ≤ 40 ˃ 40

3.5. Reverberation time Table X shows the maximum values allowed for the reverberation time in empty and unoccupied rooms for each of the classes. These values only apply to public residential, health and teaching uses. Table 5. Reve r beration time. Class limits. Type of room Class A Class B Class C Class D Class E Class F In common access areas sharing an entrance door with protected rooms ≤ 0,6 s ≤ 0,9 s ≤ 1,2 s ≤ 1,5 s ≤ 1,8 s ˃ 1,8 s

Empty classroo m s ≤ 0,7 s - - 0,7

During the development of the ACS the working group had to deal with many challenges, both administrative and technical [7]. One of the most troublesome technical point to discuss was the definition of the verification and sampling-plan procedures intended to facilitate the implementation

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of this classification scheme. The idea was to define these procedures without leaving many options or choices open so that if two different entities were to classify the same building, two different classification results would not be obtained due to the sampling carried out. For this, a compromise had to be reached between simple enough guidelines to encourage the use of the standard, and a statistically representative sampling procedure and with an adequate level of detail. The guidelines, structured in sequential steps, suggest a prioritization process depending on different factors. A summary of the guidelines is exposed hereinafter.

4.1. Conformance verification procedures Two alternative verification procedures A and B may be applied to the verification of conformance with an acoustic class. This conformance with an acoustic class may be done for an entire building, an individual dwelling, a specific room or even a specific acoustic characteristic. Procedure A consists of three stages; firstly, a design and calculation stage according to ISO 12354 [11] is defined; where a preliminary sampling plan is designed and sensitive rooms are identified. Secondly, in the construction stage visual inspections must be made on site to ensure that the installation of the elements is made according to the specifications of the project. And thirdly, field measurements are made. Procedure B consist of verification by field measurements only.

4.2. Identification and counting of cases and subcases A case is defined by a given adjacency situation between rooms for a given acoustic characteristic (airborne sound insulation, impact sound pressure level, noise from service equipment, reverberation time). So, all protected rooms existing in the building and all different cases have to be identified, according to Table 6. Next, identified subcases to count are related to different construction systems for each identified case. Table 6: Identification of p o s s i b l e c a s e s

Acoustic characteristic Possible cases

C01: Protected rooms horizontally adjacent to other rooms that are not service equipment or activity C02: Protected rooms horizontally adjacent to service equipment or activity rooms C03: Protected rooms adjacent to common or access areas with an entrance door in the separating wall C04: Protected rooms vertically adjacent to other rooms that are not service equipment or activity C 0 5: P r o tected r o oms vertically adjacent to service equipment or activity rooms

Airborne sound insulation

C06: Protected rooms horizontally adjacent to other rooms that are not service equipment or activity C07: Protected rooms horizontally adjacent to service equipment or activity rooms C08: Protected rooms vertically adjacent to other rooms that are not service equipment or activity C 0 9: P r o tected r o oms vertically adjacent to service equipment or activity rooms

Impact sound insulation

Sound insulation against exterior noise C10: Façades in protected rooms

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Acoustic characteristic Possible cases

Noise from building service equipment C11: Service equipment rooms horizontally or vertically adjacent to protected rooms

Reverberation time C12: Common access areas sharing an entrance door with protected rooms C13: Empty classrooms C14: Empty canteens and restaurants

4.3. Quantification of sampling Once we have counted all the subcases in the building, we have to determine the sampling to apply and the number of field measurements to do. In general, as for sound insulation, at least a percentage of 5% of subcases have to be selected for verification procedure A and 10% for procedure B. In case of vertically adjacency between rooms, these percentages are reduced to 3% and 6% respectively, due to the large number of resulting rooms obtained in these situations. For both procedures it is indispensable that all the activities/service equipment rooms are tested in, at least, one case. In cases where the reverberation time must be verified, both percentages of 5% and 10% will be applied, with a minimum of one measurement per subcase. In relation to sound from building service equipment, the sampling to apply was one of the most troublesome issue to define [10], since the casuistry that can be found in a building and the number of cases that can be obtained is very large. It was finally agreed that, at least, one test will be carried out for each installation. In case there is more than one common installation of the same type (for example, lifts) at least one measurement will be made for each of them. In addition, for each installation (boilers, air conditioners) sound pressure levels will be measured in at least one vertically adjoining protected room and in another horizontally adjoining one. For the particular case of waste water installations, the criterion will be to measure 1% of the detected cases (those with a change of direction in the pipe adjoining the protected room), with a minimum of one test. With regard to sanitary ware (bath and shower, lavatory, bidet, washbasin, kitchen sinks, etc.), measurements will be made in at least 1% of the vertically adjoining rooms, 1% of the horizontally adjoining rooms and 1% of the diagonally adjoining rooms. For each type of adjoining, at least the noise level due to one sanitary element of each type will be measured.

4.4. Criteria for the selection of the rooms to be tested The ACS guidelines define some criteria to arrange the order in which the test cases should be selected in order to prioritise the most unfavourable situations. These criteria take into account the type and use of the rooms, geometric characteristics and other parameters. In case of sound insulation, the first criterion to apply is the type of the receiving room and the adjoining emitting room. Table 7 shows the selection order in the case of private residential housing. For each of the subcases, combinations of rooms will be sequentially selected from the table. As many combinations as necessary will be selected to complete the number of tests obtained in the sampling procedure.

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Table 7. Room selection order.

Adjoining emitting room

Activity/service

Protected

Adjacent

Common or access areas Outside

Use of the

Selection

equipment

receiving

dwelling

building

order

premises

room

C01, C04 C06, C08

C02, C05 C07, C09 C03 C10

1 st

Kitchen

2 nd Dining room

Bedroom

Private residential (housing)

Activity/service equipment Common or access areas Outside

3 rd Bedroom

4 th Dining room Kitchen

5 th Dining room Next, to specifically select the rooms to be tested, the general and the geometric criteria are applied, for example, cases with no expansion joint in separating walls, with no elastic coverings in separating floors, façades exposed to the higher exterior noise and rooms with lower volume/surface ratio and for façades those with higher windows ratio. Additional criteria for service equipment noise and reverberation time are defined, for example, selecting the protected rooms closest to the main sound sources, and in case of reverberation time the highest volume rooms will be selected first.

4.5. Criteria for assigning classes Class assignment is done sequentially, that is, firstly, measurements results from the cases are classified individually; then each of the complete acoustic characteristics; and finally, the complete dwelling or the whole building. The final class to certify will be the minimum class obtained. To assign a class to a specific case, each and every one of the test results of that case must comply with at least the assigned class, accepting a maximum unfavorable deviation of 2 dB/dBA, for each individual result. The average results of that case must also comply with class limits. The class assignment for each of the acoustic characteristics is done by assigning the most unfavorable class of the corresponding cases. Finally, the classification of a dwelling or an entire building is done by assigning the most unfavorable class of the acoustic characteristics. The Spanish ACS standard includes, in an annex, a suggested report template detailing the minimum contents that it should contain. 5. COMPARISON WITH OTHER EUROPEAN SCHEMES

There are several differences between the European national schemes for the acoustic classification of dwellings [6] and, specifically, with the Spanish one. These differences are based on a range of criteria such as: acoustic insulation descriptors, number of quality classes, range of quality classes or relation to regulatory requirements. Spanish Building Code [2] and Spanish ACS, logically, use the same sound insulation descriptors, that is, D nT,A (≈ D nT,w +C 100-5000 ) for airborne sound insulation and L’ nT,w for impact sound pressure level. In comparison with other European countries, a total of 15 existing ACS (including ISO/TS 19488), in case of airborne insulation, half of them use in their national schemes a descriptor based

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in D nT,w (with or without any of the available spectrum adaptation terms) and the other half use R’ w . As for impact sound insulation, practically half of the countries are using a descriptor based in L’ nT,w , as Spain does (3 of them adding the spectrum adaptation term); and the other half is using L’ n,w . Differences obviously multiply when considering different frequency ranges for the application of spectrum adaptation terms. Regarding the number of quality classes, the Spanish classification includes criteria for 6- quality classes as another four more countries do; nevertheless, 4-classes schemes are the most common in Europe. Two classes above regulations and one below is the most usual configuration in the European ACS whilst the Spanish one has three classes above the requirements and two below them; this is a consequence of having our regulatory requirements corresponding to a Class D, whereas European limit values generally correspond to a Class C (taking into account the differences between the schemes and that the comparisons are not so immediate). And on the other hand, we have a Class E and an additional Class F below regulations; this Class F was included to classify existing buildings and to consider all those cases that remain below a certain level of performance. Finally, the Spanish scheme uses the indication “npd”, not counted as a class, the same as well as the ISO/TS 19488 standard, but only two other countries have it incorporated in their ACS. 6. CONCLUSIONS

The ACS recently approved in Spain UNE 74201 has been exposed in this paper. A tour has been made throughout the standard explaining its object, scope, assigned values to the classes for the different acoustic characteristics and the verification procedures. Comparisons have also been made with other existing ACS in Europe, making clear the many unwanted differences that exist between them (high variety of descriptors, frequency margins, number of quality classes, etc.). A European directive that could encourage the different countries to harmonize all these issues would be desirable, as it was already tried once [4,9]. Once we have an approved ACS standard the next challenge will be to promote the use of it encouraging investors and developers to see the ACS as an opportunity to enhance acoustic insulations above regulatory levels and to provide an added value to their buildings, paying more attention to users’ satisfaction. This challenge would be made much easier if existing national building regulations enforced the application of the ACS by setting a specific class to be met. It would be desirable that in a few years the use of the ACS will be generalised and will stimulate construction market to improve the acoustic quality of buildings. 7. REFERENCES

1. UNE 74201: 2021. Acústica. Esquema de clasificación acústica de edificios. AENOR. 2. Real Decreto 1371/2007, de 19 de octubre, por el que se aprueba el documento básico DB-HR Protección frente al ruido . 3. National Institute of Statistics. Living Conditions survey . July 2021. https://www.ine.es/ 4. COST Action TU0901: Integrating and Harmonizing Sound Insulation Aspects in Sustainable Ur-ban Housing Constructions, http://www.costtu0901.eu/ 5. B. Rasmussen, M. Machimbarrena. Developing an international acoustic classification scheme for dwellings – From chaos & challenges to compromises & consensus? Proc. Internoise 2019 . 6. B. Rasmussen. Sound insulation between dwellings - Comparison of national requirements in Europe and interaction with acoustic classification schemes. Proc. International Congress on Acoustics. ICA 2019 .

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7. M. Machimbarrena, A. Romero, J. A. Trujillo, M. J. De Rozas, A. Arenaz, E. García. The development of a Spanish Acoustic Classification Scheme for residential, sanitary and docent buildings: Challenges and potential impact. Proc. Internoise 2019 . 8. A. Romero, M. T. Carrascal, M. B. Casla: “Airborne and impact sound insulation performance in Spanish multi-storey housing: 10 years of the protection against noise regulations in the Building Code (2009-2019)”. Proc. Internoise 2019 . 9. ISO/TS 19488:2021 Acoustics-Acoustic classification of dwellings. ISO. 10. A. Romero Fernández, M. Machimbarrena, M.J. De Rozas López. Analysis of the draft Spanish standard PNE UNE 74201: Acoustic classification scheme for buildings. Proc. Forum Acusticum 2020 . 11. ISO 12354: 2017. Building acoustics. Estimation of acoustic performance of buildings from the performance of elements.

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