effect of thermal insulation systems on acoustic ...

EFFECT OF THERMAL INSULATION SYSTEMS ON ACOUSTIC PERFORMANCES OF ANCIENT BUILDING CONSTRUCTION ELEMENTS R. FORET; C. GUIGOU-CARTER; M. VILLOT Affiliation: { CSTB, 84 Avenue Jean Jaurès – Champs-sur-Marne, 77447 Marne-la-Vallée Cedex 2, France; CSTB, 24 Rue Joseph Fourier, 38400 Saint Martin d’Hères, France } e-mail: { [email protected] ; [email protected] ; [email protected] }

Abstract In this paper, the effect of current thermal insulation systems on acoustic performances of ancient building systems (between 50’s and 70’s) is investigated. Indeed, the thermal renovation of existent buildings will be essential in the next few years for energy savings considerations. However, the impact of thermal insulation composites on former and complex buildings systems (instead of traditional concrete walls) is different and not known. In a first step, the acoustic performances of different ancient building systems are predicted with CASC software (using a Transfer Matrix Method) and compared with laboratory measurements. In a second step, the effect of different thermal insulations – placed on the exterior (external thermal insulation composite system ETICS, added cladding, insulating wall panel) or in the interior (wall lining,…) on acoustic performances of ancient type walls is predicted and compared with the effect on a concrete wall (as current laboratory measurements, carried out according to ISO 140-16). In a last step, these data are used to study the effect of a thermal retrofit on acoustic performances of a 60’s building. The acoustic performances of the building before and after thermal retrofit are predicted with the ACOUBAT software. . Keywords: sound insulation, thermal insulation system, prediction, measurement.

1 Introduction In Europe, the majority of the energy consumption is used in the building sector. More specifically, space heating represents one third of the total energy consumption in moderate climate zones of central Europe. Thus, the saving potential for primary energy use is much

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INTERNOISE 2010 │ JUNE 13-16 │ LISBON │ PORTUGAL

higher in the field of building retrofit than in the field of new buildings. It is believed that in the future, essential energy savings can be achieved only through a high-quality comprehensive retrofit of the building stock. Since the number of building thermal renovation projects is going to largely increase in the next few years for these energy saving reasons, it is important to investigate thermo-acoustic solutions in order to develop the free dB concept in the coming buildings thermal regulation. This free dB concept relies on the development of thermal retrofit solutions that will improve at the same time the thermal (energy consumption) and the acoustic performance of the building; these solution will be referred to thermoacoustic solutions, evidently the economical aspect will have to be included. In this project, several types of buildings corresponding to different building periods, buildings techniques will be considered and the effect of thermal retrofit on acoustic performance of buildings is investigated. The French acoustic regulation does not usually apply when a building is renovated; it only suggests that in some cases the acoustic performance should not be degraded. For each type of building considered, the thermal renovation techniques will be classified as a function of the associated acoustic performance: a decrease in acoustic performance, no effect on acoustic performance, or an increase in acoustic performance. Global thermo-acoustic solutions will then be underlined. In-situ measurements should be performed to validate thermal and/or proposed thermo-acoustic solutions. In this paper, the effect of thermal retrofit on acoustic performance of buildings from the 60’s is investigated. Previous studies were made on 80’s building presented in [1][2]. The thermal renovation techniques usually implemented on such buildings are presented and their effect on acoustic performance is discussed.

2 Project description 2.1

Overview

The first goal of this project is to identify the impact on thermal retrofit solutions on acoustic performances of ancient building elements, indeed due to more stringent energy saving regulations new techniques are developed and it is important to assess their impact on ancient elements, because it could yield acoustic pathologies. First of all, the performances are assessed on standard wall (i.e. a 160 mm thick concrete wall), then this performance is predicted and compared with measurements to valid the modeling of the thermal insulation layer. Afterwards, using the previous results the performances of such systems implemented on ancient systems is predicted. That is why, after assessing the impact on ancient elements, these performances are used to predict the performances of a 60’s building and compared with acoustic regulation for new buildings.

2.2

Measurement methods

The measurements of the thermal insulation systems impact are carried out in the acoustics test laboratory of the CSTB (LABE, European Laboratory of Building Acoustics). The interior wall lining impacts are measured in accordance with the standard ISO 140-16 [3]. The impact of exterior wall thermal insulation is also measured using this standard.

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2.3

Prediction methods

The ACOUBAT software based on the NF EN 12354-1, -2, -3, -5 and -6 standards [4] is used to compare the building acoustic performance to the French acoustic regulation, based on the measured or predicted acoustic performance of the thermal retrofit systems. Indeed, if the acoustic performance of the thermal retrofit system on ancient systems is not part of the ACOUBAT database or available from laboratory measurements, it has been predicted with CASC software developed at CSTB and used to predict sound transmission, sound absorption, impact noise and rainfall noise of building elements. This computer program uses an infinite multilayered structures model based on a transfer matrix approach [5]; the different infinite isotropic layers of constant thickness can be either solid, fluid or porous (following Biot’s theory [6]) elements.

3 Effect of thermal insulation systems on acoustic performances of elements In the 60’s, in France, the main building elements used for the walls were 200 mm hollow bricks walls, 14 cm thick concrete walls and prefabricated sandwich elements (e.g. concrete/EPS/concrete or aluminum/insulating layer/aluminum). The prefabricated sandwich considered in this study is composed of a 7 cm thick concrete layer, 3 cm thick EPS layer and 10 cm thick concrete later. Therefore the performance of exterior and interior wall linings implemented on such building elements are investigated and presented in this section. The performances of the supporting walls are extracted from ACOUBAT software for the concrete and brick wall, and predicted using CASC for the prefabricated sandwich.

3.1

Interior wall thermal insulation systems

In this section, the effect of thermal insulation systems placed on the interior of a wall is investigated. This thermal insulation lining considered is composed of a 80 mm glass wool layer and 13 mm plasterboard bounded on it. The results of the sound reduction R with the interior wall lining are presented below. 100

Sound reduction index R (dB)

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Frequency (Hz) Concrete wall 14 cm + interior wall lining 13+80 mm Hollow bricks + interior wall lining 13+80 mm Sandwich 7/3/10 + interior wall lining 13+80 mm

Figure 1 – Sound reduction index for ancient building systems with an interior wall lining

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3.2

Exterior wall thermal insulation systems

In this section, the effect of thermal insulation systems placed on the exterior of a wall is investigated. These systems can be added claddings, insulating wall panels or ETICS. In this study, we focus on ETICS – literally meaning External Thermal Insulation Composite Systems – composed of an insulating layer (mineral wool or EPS) and a plaster finishing. The insulating layer can be bounded on the wall or fixed mechanically by anchors. First of all, ∆R measurement was carried out on a 160 mm ETICS (with EPS) bounded on 160 mm thick concrete wall according to ISO 140-16 [3]. The results are presented below; those are also compared with the prediction made with CASC software. We can observe a good agreement between measurement and prediction all over the frequency range 100-5000 Hz and the trends seem to be well captured. The resonance frequency of the system is at 500 Hz and decreases the sound reduction R by 13 dB. 40

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Figure 2 – Sound reduction index for ancient building systems with an exterior wall lining Afterwards, the sound reduction R for a 100 mm thick ETICS (minimum recommended by heat physicist to reach thermal regulation) implemented on different supporting walls is predicted. The computations are made using CASC software. The results are presented in Figure 3.

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100

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Frequency (Hz) Concrete wall 14 cm + ETICS 100 mm Hollow bricks 20 cm + ETICS 100 mm Sandwich 7/3/10 + ETICS 100 mm

Figure 3 – Sound reduction index for ancient building systems with an exterior wall lining

4 Application to 60’s building thermal retrofit The goal of this section is to assess the effect of a thermal retrofit on the acoustic performances of the building thanks to previous results (components performance). The selected building corresponds to the 60’s building period.

4.1

Building description

The selected building corresponds to the 50’s-60’s building period. A general view of the floor distribution is presented in Figure 4. The external walls are made of 14 cm thick concrete as well as the internal wall. The dwelling separating walls are made of 6 cm thick concrete wall. All the floor slabs are constructed of 14 cm thick concrete.

Dwelling #1 Dwelling #2 Figure 4 – Floor building description. A description of the different building elements is proposed in the Table 1.

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Table 1 – Elements description. Elements External wall Inside wall Separating wall Floor slabs Floor covering Door Window

Description 14 cm thick concrete 14 cm thick concrete 6 cm thick concrete 14 cm thick concrete wall PVC floor covering Distribution door Window with simple glass pane 4 mm

The building configurations considered to evaluate the acoustic performances are presented in Figure 5. The configurations (a) and (b) represent 2 bedrooms and a living room placed on two adjacent floors, respectively. The dimensions are given in Figure 5. (a)

(b)

Bedroom Living room (4.2x3.2 m2) (4.3x4.2 m2) Figure 5 – Building configurations for acoustic performance evaluation.

4.2

Proposed thermal retrofit

The thermal retrofit proposed by heat physicists to reach thermal regulation of existing (ancient) building is presented below for each “wall”. Table 2 – Elements description and thermal description. Elements

Before thermal retrofit

External wall

14 cm thick concrete

Inside wall Separating wall Floor slabs

14 cm thick concrete

After thermal retrofit ITI ITE (ETICS) 80 mm glass wool ∆(Rw+Ctr)heavy 100 mm EPS ∆(Rw+Ctr)heavy wall = -4 dB wall = 7 dB -

6 cm thick concrete

None

14 cm thick concrete wall PVC floor covering ∆Lw = 13 dB Distribution door

None

Floor covering Door Window

Window with simple glass pane Rw+Ctr=23 dB

None None Window with double glass pane 4/16/4 (low emissivity and 85% argon gas) Rw+Ctr=29 dB

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4.3

Acoustic performances before thermal retrofit

The acoustic performances (façade insulation, airborne sound insulation, impact noise level) of the building are calculated with the ACOUBAT software and compared with measurements carried out in 1969. The results are computed with the 60’s French regulatory indexes for acoustic performances of a building presented below, which are DG “bass frequency insulation”, DM “mid frequency insulation” and DA “high frequency insulation”. They correspond to an arithmetic average of one-third octave bands.

D100 + D125 + D160 + D200 + D250 + D320 6 D + D500 + D640 + D800 + D1000 + D1250 = 400 6 D1600 + D2000 + D2500 + D3200 DA = 4

DG = DM

4.3.1 Façade sound insulation The façade sound insulation is computed and the results are presented below. No measured data were available, thus the results are only compared with 60’s recommended values. We can note that the predicted values are above the regulation. Table 3 – Façade sound insulation – Initial performances. Bedroom 1964 level Measured Predicted Living room 1964 level Measured Predicted

DG 15 27 DG 15 22

DM 20 30 DM 20 24

DA 25 32 DA 25 24

4.3.2 Sound insulation between dwellings The sound insulation (airborne sound and impact noise) in the building is computed with the ACOUBAT software and compared with measurements carried out in 1969. We can notice a good agreement between the predicted and measured values. The ACOUBAT model seems to be valid to describe the acoustic performances of such building. The values are close to the 60’s regulatory values. Table 4 – Airborne sound insulation – Initial performances. Vertical insulation Bedroom-Bedroom 1964 level Measured Predicted Living room-Living room 1964 level Measured Predicted

DG 36 38 36 DG 36 38 36

Bedroom-Bedroom 1964 level Measured Predicted

DG 36 38 36

DM 48 49 50 DM 48 47 50

DA 54 59 63 DA 54 54 63

DM 48 48 51

DA 54 60 64

Horizontal insulation

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Table 5 – Impact noise level – Initial performances. Vertical impact noise level Bedroom-Bedroom 1964 level Measured Predicted Living room-Living room 1964 level Measured Predicted

LG 66 64 66 LG 66 64 64

Bedroom-Bedroom 1964 level Measured Predicted

LG 66 59

LM 62 65 66 LM 62 65 65

LA 51 51 52 LA 51 51 50

LM 62 58

LA 51 43

Horizontal impact noise level

4.4

Acoustic performances after thermal retrofit

4.4.1 Façade sound insulation The thermal retrofit impact is predicted and the results are compared with current acoustic regulation. As expected the change of the simple glass pane window by a double glass pane has the major influence on the façade sound insulation. The addition of an interior lining has low or no effect on the façade sound insulation. The addition of an exterior lining lightly decreases the performances it is due to the resonance frequency of the system which could strongly lower the performances of the supporting wall (as presented previously). It appears important to study the effect of such systems on low performance supporting walls, because the sound transmission through opaque wall begins to be noticeable and limiting the global acoustic performances. However, in this study in all cases (bedrooms or living rooms) the performances are above or equal the current French regulation for new buildings (ie DnT,A,tr ≥ 30 dB). Table 6 – Global index DnT,A,tr in dB for façade sound insulation – After thermal retrofit. Rooms Regulation value for new building Initial performances Window with double glass pane Window with double glass pane + ITI Window with double glass pane + ITE Window with double glass pane + ITI + Certified air inlet 1 Dne,w+Ctr=36 dB Window with double glass pane + ITI + Certified air inlet 2 Dne,w+Ctr=42 dB

Bedroom 30 29 35 35 34 32 34

Living room 30 26 32 32 31 31 31

4.4.2 Sound insulation between dwellings In this section, the effect of thermal retrofit on acoustic performances between dwellings is assessed. It should be noted that the concrete floor is assumed to be covered with a basic plastic floor covering that has no effect on the sound insulation direct path. Furthermore, it should be noted that for the interior sound insulation the external thermal insulation ETICS is not considered to have any effect since it will not modified the lateral transmission paths. The interior wall lining induces a 1 dB gain for vertical sound insulation and has no effect on other insulations. It is interesting to notice that in all cases the acoustic performances of such building are really lower than the current acoustic regulation values for new building, either for sound insulations between dwellings or impact noise levels.

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Table 7 – Global index DnT,A in dB for sound insulation between dwellings – After thermal retrofit. Vertical insulation Rooms Bedroom - Bedroom Living room – Living room Horizontal insulation Rooms Bedroom - Bedroom

New building regulation 53 53

Initial performances 47 47

Retrofitted with ITI 48 48

Retrofitted with ITE 47 47

New building regulation 53

Initial performances 49

Retrofitted with ITI 49

Retrofitted with ITE 49

Table 8 – Global index L’nT,w in dB for sound insulation between dwellings – After thermal retrofit. Vertical level Rooms Bedroom - Bedroom Living room – Living room Horizontal level Rooms Bedroom - Bedroom

4.5

New building regulation 58 58

Initial performances 65 64

Retrofitted with ITI 65 64

Retrofitted with ITE 65 64

New building regulation 58

Initial performances 57

Retrofitted with ITI 57

Retrofitted with ITE 57

Improvement of acoustic performances by thermal and acoustic retrofit

As previously noticed, the acoustic performances of the building are really low and to keep a balance between sound insulation from the exterior and the interior it seems necessary to improve the acoustic performances of the floors and the separating walls. Two solutions can be considered to improve the interior acoustic performances. The first one consists in replacing the PVC floor covering by a concrete screed on a thin acoustic underlayer (with ∆Lw ≥ 20 dB); on the inside wall an interior lining (∆(Rw+C) heavy wall =6 dB) should be installed (with ∆(Rw+C) = 10dB). The second one is to add thin acoustic linings on the inside walls and the floors ((∆(Rw+C) heavy floor = 7 dB). These two solutions will allow reaching the current acoustic regulation (for new buildings in terms of impact noise level and airborne sound insulation.

5 Conclusions The effect of thermal insulation systems on acoustic performances of ancient building elements was investigated. The interior wall lining considered increases the acoustic performances in terms of airborne sound insulation. The exterior wall lining system considered, an ETICS, strongly decreases the performances of the supporting walls, which are really low. That is why in a second step, a building from the 60’s construction was considered to assess the impact of these systems. The thermal renovations proposed by heat physicists permit to be conform to the thermal regulation for existing building. Globally, the effect of thermal retrofit is positive on façade sound insulations, yet the acoustic quality of the building is really weak for other noise sources (interior airborne or interior structure borne sound) before thermal retrofit. The proposed renovation does not improve these points. Through this study test it is also important to notice that the decrease yielded by an exterior thermal insulation (e.g. ETICS) can begin to influence the façade sound insulation. Indeed, the addition of such systems on low performances ancient systems can be prejudicial, as well as such system

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can be used after removing of a whole façade, the lateral transmission can be important. It is necessary to be careful during a renovation. Therefore, an acoustic renovation of the intermediate floors and inside wall is necessary to improve the acoustic comfort and to keep balanced contributions between noise from indoor or outdoor. The proposed acoustic treatment could permit to be in accordance with current acoustic regulations for new buildings (in terms of airborne sound insulation and impact noise level). The costs of these solutions are currently assessed to create a concept of free dB for example.

Acknowledgments We gratefully acknowledge the CSTB Research and Development Department as well as the DHUP (French ministry for Housing, Urban planning and Landscape Department) for financially supporting this project.

References [1] Guigou-Carter, C. Foret, R. Villot, M. Chéné, J.-B. Effect of thermal renovation on acoustic performance of buildings. Proceedings of Euronoise 2009, Edinburgh, United Kingdom, 2009. [2] Guigou-Carter, C. Foret, R. wetta R. Ducruet P. Villot, M. Comparison of measured and predicted sound insulation for a thermal retrofitted building. Proceedings of Internoise 2010, Lisbon, Portugal, 2010. [3] ISO 140-16, “Acoustics – Measurement of sound insulation in buildings and building elements – Part 16 : Laboratory measurement of the sound reduction index improvement by additional lining”, 2006. [4] NF EN 12354, “Building Acoustics – Estimation of acoustic performances of buildings from performance of elements”, 2000. [5] Munjal, M.L. Response of a multilayered infinite plate to an oblique plane wave by means of transfer matrices. Journal of Sound and Vibration, 162, 1993, pp 333-343. [6] Biot, M.A. Theory of elastic waves in a fluid saturated porous solid. I. Low frequency range, II. Higher frequency range. J. Acoust. Soc. Am., 28, 1956, pp 168-91.

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