A A A Applying Spanish Acoustic Regulations to Mechanical Ventilation with Heat Recovery Systems - Case Study Teresa Carrascal 1 Amelia Romero Fernández 2 Belén Casla Herguedas 3 Eduardo Torroja Institute for Construction Science, IETcc- CSIC Serrano Galvache 4 Madrid 28033. SPAIN ABSTRACT Due to recent changes in IAQ (Indoor Air Quality) and energy efficiency requirements, MVHR (Me- chanical Ventilation with Heat Recovery) has become increasingly common in Spanish new build dwellings. Regarding acoustics, Spanish Decree RD 1367/2007 sets out limits for sound pressure levels due to building services and describes the noise measurement and assessment procedure, which applies also to ventilation noise. The assessment procedure consists of a series of measurements of different noise parameters and the calculation of corrections due to tonal, low frequency and impul- sive components. This paper shows an example of a MVHR fan unit installed in the ceiling of a common dwelling, where some measurements were performed. Based on these measurements, this paper discusses the noise measurement and assessment procedures and proposes some improvements for the Spanish acoustic regulations. In addition, it also analyses the available calculation methods (ASHRAE and VDI 2081) and their application to comply with Spanish requirements 1. INTRODUCTION The aim of this paper is to analyse the application of Spanish Decree RD 1367/2007 [1] to Me- chanical Ventilation with Heat Recovery systems (MVHR) in dwellings. This decree is an environ- mental law transposed from [2], which applies to all environmental noise sources, including building services. RD 1367/2007 includes the requirements for sound pressure levels in dwellings due to building ser- vice equipment. It also specifies the measurement and assessment procedure which will be introduced in paragraph 2, which consists of several sound pressure level measurements and the application of corrections for tonal, impulsive and low frequency noise components. 1 tcarrascal@ietcc.csic.es 2 aromero@ietcc.csic.es 3 belench@ietcc.csic.es inter.noise 2-24 august scornsuevearcanmus )())D MVHR systems have become increasingly common in new build homes because they ensure an adequate airflow with minimum thermal losses specially in winter time. These ventilation systems work continuously, 24 hours, 7 days a week, and they consist of a heat recovery unit, equipped with a pair of fans which distribute fresh air to sensitive rooms, such as bedrooms and living rooms, while extracting air from toilet rooms and kitchens. Noise produced by the unit can be transmitted to the rooms though the ductwork and grilles. This paper shows the work of the Quality in Construction Unit to measure the noise produced by a typical MVHR system in a dwelling and the suitability of the of RD 1367/2007 [1] for the assess- ment of service equipment noise. In this work, measurements using the ISO 16032 [3] were per- formed too, because this standard is referenced in the regulations of several European countries. In addition, calculations were also performed to predict noise using [4], [5], [6] and the difficulties to assess components using the available manufacture data are shown. This paper does not intend to characterise noise produced by a particular ventilation system, but to discuss the procedures of Spanish RD 1367/2007 in relation to common MVHR. 2. NOISE REGULATIONS IN SPAIN Spanish Building Code, DB HR [7], refers to Spanish Decree RD 1367/2007 [1] which is the environmental law transposed from the Directive 2002/49/CE [2] on assessment and management of environmental noise whose purpose is to prevent and reduce noise pollution. Spanish Decree RD 1367/2007 contains the noise quality objectives applicable indoors that is, the noise limit level allowed in interior spaces, and specifically the noise immission rates for different sources. In addition, RD1367/2007 includes the requirements for sound pressure levels in dwellings due to building service equipment. These requirements are regulated according to articles 24 and 25 of RD 1367/ 2007 and table B.2 of Annex II of RD 1367/2007. Table 1. Noise limit values transmitted in dwellings due to building service equipment. Table B2 from RD 1367/2007. Building use Type of room Noise limits for building service equipment L K,d L K,e L K,n Residential Living rooms 40 40 30 Bedrooms 35 35 25 Table 1 considers only the noise transmitted by a certain service equipment to an adjoining area, it deals with the noise level that each service equipment individually must not exceed. It shows the noise index L Keq, T, that is the equivalent continuous sound pressure level weighted A, (L Aeq, T ), cor- rected by the presence of emerging tonal components, low frequency components and noise impul- sive character, according to the following expression: L Keq, T = L Aeq, T + K t + K f + K i (1) Where: - K t is the correction parameter associated with the L Keq, T index to assess the discomfort or ad- verse effects due to the presence of emerging tonal components. - K f is the correction parameter associated with the L Keq, T , index to assess the discomfort or adverse effects due to the presence of low-frequency components. - K i is the correction parameter associated with the L Keq, T , index to assess the discomfort or harmful effects by the presence of impulsive noise. The maximum value of the correction resulting from the sum K t + K f + K i will not be greater than 9 dB. Figure 1 shows the procedure to obtain corrections: K f , low frequency correction, K i , impulsive correction and K t , tonal correction. Figure 1. L Keq,T evaluation level and correction calculations according to RD 1367/2007. 3. DESCRIPTION OF THE SYSTEM Decentralized ventilation systems are usually installed in multifamily dwellings in Spain, the HR unit is usually installed inside the ceiling of certain rooms, which are usually the non-sensitive rooms, such as corridors, halls or kitchens. Ductwork is placed within the ceiling to conduct supply air to living rooms and bedrooms, through grills. Exhaust air is extracted from kitchens and toilet rooms. The main sources of noise are the two fans inside the heat recovery unit, which must work contin- uously. Airflow controls rely on CO 2 detectors, humidity detectors or manual controls, which occu- pants can activate manually to set the airflow to different points to meet the ventilation necessities of the rooms, for instance, when the dwelling is not fully occupied or at unoccupied periods. In this work, a common MVHR system was measured in a 4-bedroom dwelling. The unit was installed inside the kitchen ceiling and two mineral wool duct silencers were placed in the supply and exhaust ducts. Document DB HS-3, Indoor Air Quality [8] of the Spanish Building Code sets minimum airflow requirements for dwellings. In this case, minimum airflow is 120 m 3 /h when the dwelling is fully occupied. 4 RESULTS OF THE MEASUREMENTS PERFORMED 4.1 Description of the measurements Measurements were performed to both characterise sound pressure levels produced by a MVHR system according to the engineering method in ISO 16032 [3] and to assess noise level indexes asso- ciated with user annoyance in relation to decree RD 1367/2007 [1]. Compliance with requirements is also verified. According to Annex IV in RD 1367/2007, measurements must be made in the most unfavourable receiver and under the most unfavourable operating conditions, and the final evaluation value will be that in the most unfavourable position which means the highest value obtained among different sam- ples of all the measurement positions. This differs from the ISO 16032 as measurements are made during a specified operation cycle and in addition, the final result is the average of all measurements made in all the positions. The measurements were performed in a multifamily dwelling, sited in a town in the north of Ma- drid capital, at night to guarantee the lowest background noise. Once the distribution of the dwelling was studied, the living room was chosen as receiver room, as it is adjacent to the kitchen and the duct distance to the supply grille is shorter, as depicted in Figure 2. RD 1367/2007 evaluation level > Lxeg,r = Lieg, r+ Kit Kp+ Ki eC) eC Ne : Ls 10 0 K; low frequency correction | >} y= L cay r= L toy > we o T= 1s 6 LB) KGB) : : : 110 0 \—>| K;, impulsiveness correction | >} Li = L cay.ri = L tea.r > bos $ T= 1s 6 Ly SPL of band f, which contains the emerging tone —>|_K,, tonal correction > | LH ly- 1, | >| Learithmetic average of the next two ad levels, the one in the band immediately above f, and that of the band immediately below f f(H2) L(dB)_|_K.(aB)_| _f(ttz) L(aB)_|_K.(aB)_|__ f(z) L(aB)_|_K,(aB) Ls8 0 0 0 20-125 Hz [_812 6 6 6 Figure 2. Location of the ventilation central equipment, the receiving room and the measurement positions: P1, P2, P3 and corner position To jointly satisfy the conditions of both measurement standards [1], [3], a certain procedure was established and the following series of criteria were adopted: - 4 measurements positions, that is a corner position and 3 positions in reverberant field; - 3 repetitions of measurements, this implies recording 3 measurement cycles of the system in operation. These 3 measurements give us a margin of 3 repetitions in each position depending on the differences between consecutive measurements according to ISO 16032; - The measurement at each position starts and ends with the measurement of the background noise for at least 30 seconds; - Frequency range: 16 Hz to 12500 Hz, as tonal correction in RD 1367/2007 is applied from 20 Hz to 10000 Hz; 31,5 Hz to 8000 Hz, according to ISO 16032; - Registered and processed parameters, with 1 second sampling period: o Octave bands spectrum from 31,5 Hz to 8000 Hz; o One-third octave bands spectrum from 16 Hz to 12500 Hz; o RD 1367/2007 global parameters: L Aeq , L Ceq , L AIeq , of the most unfavourable 5-seconds sample, to calculate corrections due to components; o ISO 16032 global parameters: L Aeq , L AFmax , calculated from octave bands values, in a measurement period of 30 seconds within the operation cycle. Emitted noise was also registered in order to characterise noise levels and spectra in one position in the centre of the emitting room (kitchen). Two working regimens were used to make the measurements and to set comparisons: 120 m 3 /h airflow, which is the minimum required for this type of dwelling when it is fully occupied, and 200 m 3 /h airflow, which is the maximum airflow the unit is able to provide 4.2 Emission and reception spectra obtained The following graphs in Figure 3 show the emission and reception SPL spectra for the two working airflows. These spectra correspond to the most unfavourable samples of 5 second duration under the criteria of RD 1367/2007 [1]. fe Comer position @R2 Living room Reception Emission 60 60 50 50 40 40 SPL (dB) SPL (dB) 30 30 20 20 10 10 0 0 16 25 40 63 1000 1600 2500 4000 6300 16 25 40 63 2500 4000 6300 1000 1600 100 160 250 400 630 10000 100 160 250 400 630 10000 Frequency (Hz) Frequency (Hz) Figure 3. Emission and reception spectra measured with 120 m 3 /h and 200 m 3 /h airflows. 120 m3/h 200 m3/h 120 m3/h 200 m3/h Looking at Figure 3, it can be seen that there is a difference of 10 dB approximately in the SPL generated in emission with both airflows in almost the entire spectrum; logically, the higher the air- flow is, the higher the sound pressure levels. This difference can also be seen in the receiver room, except from 2.000 Hz when the levels are equalized. Figure 4 shows the emission and reception spectra together for a 120 m 3 /h airflow. It indicates the effect on the received noise levels of the acoustic insulation and the properties of the room. It is worth mentioning that received levels will be predictably lower when the dwelling is in use since during the measurements the room was unfurnished. Based on the temporal registration graph obtained with both airflows, it was seen that noise levels were very stable with no significant variations over time; SPL was about 10 dB higher in the case of the maximum airflow. Emitted vs received SPL - 120 m 3 /h 50 40 SPL (dB) 30 20 10 0 100 125 160 200 250 315 400 500 630 800 16 20 25 40 50 63 80 10000 12500 31,5 1000 1250 1600 2000 2500 3150 4000 5000 6300 8000 Frequency (Hz) Figure 4. Emission vs reception spectra with 120 m 3 /h minimum airflow. 4.3 Results applying RD 1367/2007 and ISO 16032 This section shows final values obtained in measurements of the MVHR system working with the two airflows. Compliance with the sound pressure limit values due to service equipment noise in dwellings is also verified for the minimum required airflow. Results are grouped as follows: Emission Reception - Evaluation levels ( L Keq,Ti ) according to Annex IV of RD 1367/2007 [1] and verification of compliance; - L Fmax , L AFmax , and L CFmax octave band spectra and global parameters L Fmax , L AFmax , L CFmax and L Aeq according to ISO 16032 [3]. Tables 2 and 3 show, for each measurement position, the final evaluation level L Keq,Ti (with T i = 5 s) obtained from parameter L Aeq,Ti and corrected for the presence of emerging tonal components ( K t ), low frequency components ( K f ) and impulsive noise ( K i ) as explained in section 2. Results in bold (position 2) correspond to the highest value of those obtained to be taken as the final evaluation level of the measurement. Table 2. Final eval uat i on l evel, L Keq,Ti , for 120 m 3 /h required airflow. RD 136 7/ 2007 val ues – Minimum 120m 3 /h required airflow Position L A,eq,Ti Component corrections Evaluation level L Keq,Ti (1) K t K f K i Total 1 25,2 dBA 6 3 0 9 34 dBA 2 25,9 dBA 6 3 0 9 35 dBA 3 23,7 dBA 3 3 0 6 30 dBA (1) L Keq,Ti must be rounded to an integer number. Table 3. Final evaluation l evel , L Keq,Ti , for maximum 200 m 3 /h provided airflow. RD 1367/ 2007 values – Maximum 200m 3 /h airflow Position L A,eq,Ti Component corrections Evaluation level L Keq,Ti (1) K t K f K i Total 1 34,0 dBA 0 3 0 3 37 dBA 2 33,0 dBA 3 3 0 6 39 dBA 3 31,5 dBA 3 3 0 6 38 dBA (1) L Keq,Ti must be rounded to an integer number. In relation to the detected components with 120 m 3 /h airflow (Table 1), emerging tonal compo- nents have been detected at 250 Hz and at 1.000 Hz, implying corrections of 3 dB and 6 dB, respec- tively. In case there is more than one tonal component, the highest value will be adopted as the value of the correction parameter. In this case the correction would be 6 dB due to the frequency of 1.000 Hz. In all cases, low frequency components that imply corrections of 3 dB have been detected; and no impulsive components have been detected. Therefore, the final correction to apply obtained as the sum of the previous ones is 9 dB. Regarding maximum airflow (Table 2), an emerging tonal component has been detected at 1.000 Hz which implies a correction of 3 dB. This component appears in two of the three measurement positions in a single measurement sample, so the correction is on the edge. Penalties of 3 dB are also applied due to low frequency components in all cases and there are no impulsive components either. Therefore, the final correction to apply obtained as the sum of the previous ones is 6 dB. If we verify compliance with sound pressure limit values due to service equipment noise in dwell- ings as specified in RD 1367/2007 (Table B2 in Annex 3 and hints in Article 25 in [1]), in a living room the following values in Table 4 must be met. Table 4. Verification of compliance for minimum 120 m 3 /h required airflow. Measurement RD 1367/2007 requirements Annual average level Daily average level Sample level ( L K,eq,Ti ) (2) (dBA) Day Evening Night Day Evening Night Day Evening Night 40 40 30 43 43 33 45 45 35 L Keq,Ti (dBA) 35 ( L Keq,year ) (dBA) ( L Keq,T ) (1) (dBA) Evaluation level N/A N/A N/A Ok Ok Ok - L K,eq,T (3) (dBA) 35 Ok Ok Nok N/A N/A N/A (1) Annual values increased by 3 dB (2) Annual values increased by 5 dB (3) Since the equipment works stably throughout the complete day, the daily average value L Keq,T coincides with the calculated value L Keq,Ti with T d = 12 hours, T e = 4 hours, T n = 8 hours. Bearing in mind that the final evaluation value L Keq,Ti includes a 9 dB correction due to compo- nents, if this correction were not applied or if it were applied in a different way, this installation would comply with the normative limit values. The final evaluation value L Keq,Ti would also be different if it were not based on the highest measurement value but on an average of the different measurement positions, as ISO 16032 does. See proposals and comments in this regard in section 5. As for results according to ISO 16032, values in Table 5 were obtained. Ta ble 5. ISO 16032 results (1) . Averaged values for all measurements positions and all cycle s. Minimum 120 m 3 /h required airflow Maximum 200 m 3 /h airflow Frequency (Hz) L CFmax (dBC) L Fmax (dB) L AFmax (dBA) L Fmax (dB) L AFmax (dBA) L CFmax (dBC) 31,5 42,0 - 37,2 43,8 - 40,8 63 36,9 10,7 36,1 39,3 13,1 38,5 125 29,9 13,8 29,7 34,9 18,8 34,7 250 32,8 24,2 32,8 39,7 31,1 39,7 500 21,0 17,8 21,0 32,0 28,8 32,0 1000 17,4 17,4 17,4 22,2 22,2 22,2 2000 15,7 16,9 15,5 13,4 14,6 13,2 4000 13,6 14,6 12,8 14,1 15,1 13,3 8000 15,6 14,5 12,6 15,9 14,8 12,9 Weighted 43 27 41 47 34 45 (1) Results were not corrected with reverberation time, which the standard 16032 leaves as optional. According to ISO 16032, the spectra in octave bands correspond to the moment in which the max- imum A-weighted or C-weighted sound pressure level occurs during an operation cycle. These spec- tra have been appropriately corrected with background noise. A-weighted and C-weighted values are calculated from octave-band measurements. Fast time weighting has been used for the measurements. Additionally, as indicated in ISO 16032, it has been decided to also determine the equivalent con- tinuous sound pressure level with an integration time corresponding to an operation cycle (30s, for equipment with continuous sound level). As seen in Table 6, the average SPL measured is 25 dBA for the required airflow and 33 dBA for the maximum airflow the heat recovery unit is able to provide. Table 6. L Aeq,30s values for the 3 measurement positions and the 3 cycles per position. Minimum 120 m 3 /h and maximum 200 m 3 /h airflows. Minimum 120 m 3 /h required airflow Maximum 200 m 3 /h airflow Cycle 1 Cycle 2 Cycle 3 Cycle 1 Cycle 2 Cycle 3 L Aeq,30s (dBA) (dBA) (dBA) (dBA) (dBA) (dBA) Position 1 23,8 23,9 23,9 32,0 32,1 32,0 Position 2 25,7 25,8 25,4 33,7 33,7 33,9 Position 3 25,5 25,7 25,7 32,8 32,7 32,8 5. DISCUSSION ON THE MEASUREMENT AND ASSESSMENT METHOD ISO 16032 [3] results vary widely from results obtained by applying RD 1367/2007 [1]. This is due to the differences in the measurement methods and to the 9 dB correction due to tonal and low frequency noise in this specific study case. The following ideas are essential to understand these differences: - RD 1367/2207 evaluation result is the highest corrected SPL measured in the room, whereas ISO 16032 result is an average of the SPL measured in several positions. RD 1367/2207 measurement method consist of SPL measurements for at least 5 s long, in at least 3 positions. Corrections for background noise, tonal, impulsiveness and low frequency noise are applied in each position. The highest corrected sound pressure level corresponds to L Aeq,T , the evaluation level, which must be compared with requirements. Given that there may be differences of 2 dB or more between positions, and that in each position, corrections must be applied, the resulting L AeqT values vary significantly for the same room: 5 dB in this case study for the 120 m 3 /h airflow as seen in table 2. No spatial and temporal averaging make repeatability and reproducibility conditions difficult to meet for RD 1367/2007. - RD 1367/2007 corrections are applied in 3 dB steps, which means that small differences of just one decimal in L f , L t and L i , as seen un Figure 1, imply no correction or corrections of 3 or 6 dB, which in addition to what it has been already said, compromises the repeatability and reproduci- bility of the results. - In RD 1367/2007 low frequency corrections are applied but no comparison with the hearing threshold is required. In this specific case-study, most of the low frequency energy is below the hearing threshold [9], only frequencies above 125 are audible. But the difference between L Ceq,Ti and L Aeq,Ti is more than 15 dB, so according to RD 1367/2007 a 3 dB correction is applied. If we only analyse the part of the spectra which exceeds the hearing threshold, no correction should be applied. See Figure 5. SPL vs hearing threshold 80 70 60 50 SPL (dB) 40 30 20 10 0 100 125 160 200 250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000 6300 8000 31,5 20 25 40 50 63 80 10000 12500 -10 Frequency (Hz) SPL (120 m3/h) Hearing threshold (ISO 226) Figure 5. SPL measured and the hearing threshold. Local regulations in Catalonia [10] and the Basque Country [11] in Spain include a different procedure that apply corrections only to the part of the spectra that is above the hearing threshold, which is very valuable to assess equipment whose noise emission is low. 6. CALCULATION METHODS Part of the work also consisted of calculating SPL from the manufacturer data, who provided the sound power levels of the MVHR unit radiated into ducts, as well as the sound power level from ducts to the unit and from the unit case to the free space, in third octave bands from 160 Hz to 10.000 Hz, for different airflows and pressures. The insertion loss of silencers was also provided. The rest of the data needed for calculations was estimated using either ASHRAE Handbook [4] or standard VDI 2081 [5], [6], such as attenuation though plastic ducts, elbows, Ts and the self-generated noise. The frequency range for both procedures is 63 Hz to 8.000Hz in octave bands. According to ASHRAE, the uncertainty of this calculation method is ±2 dB, due to the uncertainties of the test data and the possible cumulative errors of the calculation process. The most significant variations between calcu- lations and test results occur at low frequencies (63 Hz), where variations can reach 5 dB. Table 7 show that there is a good agreement between calculated and measured values, as the big- gest difference for positon 3 is 1,8 dB, which agrees with the ASHRAE specifications. Calculations were performed 3 m from the supply grill. Table 7. SPL measured Vs calculated SPL. Position Measured L A,eq,T Calculated L A,eq Difference P1 25,2 dBA -0,3 P2 25,9 dBA 0,4 P3 23,7 dBA -1,8 However, there is not enough information to determine tonal and low frequency corrections, be- cause the octave band spectra do not allow to predict tones. In the frequency of 250 Hz and 1.000 Hz there are tones in the measurements, however, this is impossible to predict with the sound power data in octaves. 25,5 dBA Regarding low frequency corrections, data bellow 63 Hz is needed. In general, consultants may apply corrections based on their own experience to satisfy requirements during the design process. 7. CONCLUSIONS This paper shows the results of different measurements of a decentralized MVHR using the Span- ish RD 1367/2007 [1] and ISO 16032 [3] in a typical housing block located in the area of Madrid. RD 1367/2007 is the Spanish regulation for environmental noise and it applies also for service equip- ment noise. It also includes the measurement and assessment procedures which include corrections for tonal, low frequency and impulsive noise, whereas ISO 16032 is the standard referenced by the regulations of many European countries. The paper discusses the suitability of this method to assess noise produced by MVHR systems, three main conclusions regarding the measurement and assessment method of RD 1367/2007 are shown: - Spatial and temporal averaging will be beneficial for repeatability and reproducibility. - To improve repeatability, corrections for low, tonal and impulsive noise should be applied according to a linear equation instead of in 3 dB steps, as little differences in the measurements lead to very different results of the evaluation level, L A,eq,T . - Corrections need to be applied only when the SPL is above the hearing threshold, to avoid penalties when the sounds are not audible. It is significant that L Aeq,T is 35 dBA whereas L A,eq according to 16032 is 25 dBA for 120 m 3 /h. That means that this system will comply in many European countries [12]. To the date this paper has been written, the public comment process of RD1367/2007 has already finished, which means that any member of the public has been able to submit comments or proposals on RD 1367/2007. The intention of this work is also to support the modification of RD 1367/2007 regarding service and equipment noise. 8. ACKNOWLEDGEMENTS The authors are thankful to Santiago Pascual and Alberto Rodríguez from Siber Zone, S.L.U., a Spanish manufacturer of ventilation systems, who funded this work and provided technical infor- mation about their equipment. 9 REFERENCES 1 Ministerio de la Presidencia, RD 1367/2007de 19 de octubre, por el que se desarrolla la Ley 37/2003, de 17 de noviembre, del Ruido, en lo referente a zonificación acústica, objetivos de calidad y emisiones acústicas. 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D 176/2009. 2009, pp. 85734–85797. 11 Departamento de medio ambiente, planificación territorial, agricultura y pesca, Decreto 213/2012, de 16 de octubre, de contaminación acústica de la Comunidad Autónoma del País Vasco, vol. 222. 2012. https://www.legegunea.euskadi.eus/eli/es-pv/d/2012/10/16/213/dof/spa/html/webleg00-contfich/es/ 12 Carrascal García, Teresa, A. Romero Fernández, and M. B. Casla Herguedas, ‘Noise from Building Ser- vices: Comparison of Technical Requirements in Sixteen Countries’, in Proceedings of the Forum Acus- ticum FA2020 Conference, Dec. 2020, p. 255. DOI: 10.48465/fa.2020.0210. Previous Paper 227 of 769 Next