Resolving clashes between net-zero energy and acoustics engineering specifications, to enhance low-carbon building performance, regulatory compliance and future skills. Laws and standards comparison between Italy and UK Chiara Scrosati 1 , Lorenzo Belussi, Ludovico Danza and Fabio Scamoni ITC-CNR Via Lombardia 49, 20098 San Giuliano Milanese (MI), Italy Sean Smith 2 University of Edinburgh School of Engineering, Kings Buildings, Edinburgh, UK John Currie 3 Edinburgh Napier University School of Engineering & the Built Environment, Edinburgh, UK ABSTRACT Under the CNR (Italy) and RSE (Scotland) joint scientific cooperation agreement, the project deals with the development and enhancing understanding of the technical clashes and engineering solu- tions required to deliver net-zero outcomes across diverse construction systems both in new build and retrofit. This paper relates to the comparison between the two research groups about the acoustic and energy standards and low carbon measures in force in both countries. The sound insulation requirements and energy efficiency for residential buildings are mandatory in both Scotland and Italian building regulations. Sound insulation performance compliance is undertaken via on-site test- ing after completion of construction works. Importantly the specification for energy efficiency changes (and improvements) to the fabric of buildings often clash in terms of the material properties and performance functions for sound insulation. Thus, it is critically important for the specification changes in building materials for energy efficiency do not negatively impact noise and vibration sound insulation and vice versa. This can lead to non-compliance resulting in noise disturbance com- plaints by building occupants or loss of performance for energy efficiency. The paper characterizes some of the regulatory factors, clashes in material outcomes and recommends the importance of multi-factor knowledge across building performance measures. 1. INTRODUCTION

A key component of the net-zero delivery [1] is the compatibility between the future changes and improvements in energy performance of buildings and well-being of occupants [2] and the other key building regulations, such as fire resistance, sound insulation and structure. Scotland has set out target year of 2045 for net-zero carbon delivery and several Scottish local authorities, including City of Edinburgh have set a target of 2030. Italy has implemented the EU

1 scrosati@itc.cnr.it 2 Sean.Smith@ed.ac.uk 3 J.Currie@napier.ac.uk

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strategy of 2050. Also new net-zero design and construction systems also require alignment to future training and skills for their future installation as outlined in Smith’s report for Scottish government in May 2019. In both countries with over 25% of the net-zero target delivery residing with the built environment (residential, public, commercial and industrial buildings and energy processes), there is a significant step change required to deliver the future net-zero targets both in new build and specifically retrofit. The sound insulation requirements for residential buildings are mandatory in both Scottish and Italian Regulations. Sound insulation compliance is tested through on-site after completion of con- struction works whether new build or conversion/change of use. Importantly, the specification for energy efficiency changes (and improvements) to the fabric of buildings often clash in terms of the material properties and performance functions for sound insulation. Thus, it is critically important for the specification changes in building materials for energy efficiency do not negatively impact noise and vibration sound insulation. As this can lead to non-compliance and noise and disturbance com- plaints by building occupants. The need to build new buildings or to renovate existing ones from a Zero Energy Buildings (ZEB) perspective and to implement energy efficiency interventions leads to the use of new construction techniques and new materials that can lead to a conflict with acoustic needs. Therefore, it is necessary to study and validate the materials and construction techniques to avoid this conflict. Researcher from Construction Technologies Institute (ITC) of the National Research Council of Italy (CNR), the Centre for Future Infrastructure (UoE) and the Scottish Energy Centre (ENU) set a research project under the CNR (Italy) and RSE (Scotland) joint scientific cooperation agreement to resolve clashes between net-zero energy and acoustics engineering specifications. The paper presents the first outcomes of the project consisting of a preliminary analysis of the current legislation in both countries with the aim of paving the way for multi-factor knowledge across building performance measures. Due to the dimensions and the characteristics of the two countries involved, for the Italian side the analysis is mainly focused on Lombardy Region. 2. ITALIAN AND REGIONAL REGULATORY FRAMEWORK

In Italy, the National Integrated Energy and Climate Plan 2030 was approved in December 2019. The construction sector must participate massively in the achievement of these CO 2 emission reduc- tion targets. The Italian Long-Term Strategy follows this direction pointing a renovation rate of ex- isting residential building of 1.9-2% (80% “deep renovation” with a reduction of primary energy consumption higher than 60% respect the current situation) per year to reach the goal of the Energy Roadmap 2050. The recent “Piano Nazionale per la Ripresa e la Resilienza” (PNRR), in accordance with the European Green Deal and the Renovation Wave, prioritizes energy efficiency and energy production from renewable energy sources. For this reason, a strong incentive plan was launched for the implementation of efficiency measures on public and private buildings. This plan is the Ecobonus, the Sismabonus and therefore the Superbonus at 110% funding towards retrofit measures, whereby an incentive of 10% to developers is provided as part of the refund for works undertaken. These measures have the aim of encouraging energy efficiency and anti-seismic interventions, as well as the installation of photovoltaic systems or infrastructures for charging electric vehicles in buildings. In addition, the Superbonus is a fundamental measure for the relaunch of the construction sector. The crucial aspect of this plan is the energy and anti-seismic redevelopment of the private residential heritage, while giving citizens a guarantee of being able to access those interventions without having to pay money. It is therefore, in particular renovations, rather than new buildings. New buildings and buildings that need to be renovated must also comply with the acoustic law requirements set out in

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Prime Ministerial Decree 5/12/97. At European level, the acoustic classification of building units is considered due to the need to protect citizens inside their homes, both from external noise and noise from neighbours, therefore the Italian standard UNI 11367: 2010 for the classification of building units is of stringent relevance.

2.1 Energy performance regulation The building energy performance regulation is presented in this paragraph for Italy and Lombardy Region, the main focus of the analysis. Figure 1 reports the topical Directives, Laws and decree that regulate the energy efficiency of buildings in Europe, Italy and Lombardy Region. Regional decrees DGR 8/8745 and DDUO 18546 are the last steps of a number of amendment of previous decrees, reported in Figure 1.

TOMBAROF

Figure 1: Topical Directives, Laws and decree that establish a general framework for the promotion of energy efficiency of the building stock in Europe, Italy and Lombardy Region. Before 2015, the regional law on energy efficiency and certification of buildings diverged from the national law in the assessment of the energy performance. Lombardy region, indeed, anticipated the national limits of energy performance by 2 years. The calculation procedure is the same and pro- vides the calculation of the minimum energy performance index for heating based on the surface-to- volume ratio (S/V) and the Heating Degree Days (HDD). The greatest difference between the national and regional legislation is the calculation of the limits of the classes for the energy certification of buildings. In the national law the energy classes are a percentage of an energy performance limit calculated as a function of the S/V ratio and the HDD. Instead, in Lombardy the energy classes are fixed for every S/V and HDD. The Primary Energy for heating (PEH) is the index used for the certification of buildings.Until 2015 about 1 million and half energy certificates had been collected. About half of buildings are in class G. The number of certifi- cates with A and A+ classes are the 1.25% and 0.21% of the total (Figure 2). With the DDUO 6480 30th July 2015, Lombardy Region aligns its regulation on energy efficiency of buildings with the national framework, although it provides more restrictive requirements, in rela- tion to the limits of the building performance. In Lombardy, all buildings built, refurbished or retro- fitted after 2016 must comply the requirements for near Zero Energy Buildings (nZEB). The energy certification is made comparing the non-renewable primary energy consumption of the real building with that calculated for the “reference building”. Since 2016 up to March 2019, about 500’000 of certificates have been recorded in the regional energy cadastre. The classes range from class G (the

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lowest performances) to class A (the best performances). Moreover, class A is subdivided in to 4 classes in order to better identify the upper class: from A1 to A4, the best. About 37% of buildings falls within class G. The percentage of buildings with A class is about 5% and only 1.85% of buildings falls within class A4. Data reported by the National Observatory on nZEB show that Lombardy is the region with the highest number of nZEB and with the highest percentage respect to the total number of buildings, even if this number is still low.

Figure 2. Left) Percentage of certificates per energy class. Right) Residential and non-residential EPH per energy class.

400 350 Residential [kWh/m?y] ities 6 oF £ D ¢ B Am sm Residential 18 Non-residential ° Non-residential [kWh/m*y]

2.2 Acoustic regulation Figure 3 and Table 1 reports the topical Directives, Laws and Decrees that regulate the building acoustics in Europe, Italy and Lombardy Region and the related requirement.

Figure 3 - Topical Directives, Laws and Decrees that regulate the building acoustics in Europe, Italy and Lombardy Region. Directive 89/106/EEC, later replaced by Regulation (EU) 305/2011, laying down harmonised con- ditions for the marketing of construction products, represent the background of the analysis; in fact they introduce the concept of “Protection against noise”: the construction works must be designed and built in such a way that noise perceived by the occupants or people nearby is kept to a level that will not threaten their health and will allow them to sleep, rest and work in satisfactory conditions. Following this concept, Italian Government inserted into the framework law 26 October 1995, n. 447, on the acoustic pollution, the mandate for the determination of the passive acoustic requirements of buildings and their components in order to reduce human exposure to noise. This mandate is actuated

0.21%. 1.25% 5.23% 7.13% 12.25% wAt+ A SB CBD BES

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by the Decree of the President of the Council of Ministers 5 December 1997 - Determination of building passive acoustic requirements, that provides mandatory passive acoustic requirements for all new buildings and refers to the Ministerial Circular 22/05/1967 n. 3150 for reverberation time limit values for schools. The most recent legislation is the Decree 11-1-2017 (updated in 11 October 2017), Adoption of minimum environmental criteria for interior furnishings, construction and textile products, valid only for public buildings (new, renovation and maintenance), which makes reference to UNI 11367 for the acoustic classification standard and to UNI 11532 for the requirements of indoor environments. Regional Law 10 August 2001, n.13, modified by Regional Law 21 May 2020 - n. 11, is an im- plementation of the national law n.447 and in particular of the D.P.C.M. 5 December 1997. Table 1 – Legal requirements concerning sound insulation and equipment noise (DPCM 5/12/97).

Activities or building use Parameter D 2m,nT,w [dB] R’ w [dB] L’ n,w [dB] L ASmax [dB(A)] L Aeq [dB(A)] Hospitals, clinics and nursing homes  45  55 ≤ 58 ≤ 35 ≤ 25 Dwellings, hotels and inns  40  50 ≤ 63 ≤ 35 ≤ 35 Schools  48  50 ≤ 58 ≤ 35 ≤ 25 Offices, commercial and recreational activities  42  50 ≤ 55 ≤ 35 ≤ 35 Standard UNI 11367-2010 (under revision) describes the procedures to define the acoustic classi- fication of single requirements. The determination of the acoustic classes [3] is based on the average values of the performance of all the in-situ measurements carried out on the various elements. The classification can be based on the measurements of all the measurable elements or a number of ele- ments through a sampling procedure for buildings with repeated elements (serial buildings); in the latter case the sampling uncertainty needs to be applied [4] (Table 2). Table 2: Limit values referring to the different acoustic classes of buildings according to UNI 11367 Acoustic class D 2m,nT,w (dB) R’ w (dB) L’ nw (dB) L ic (dBA) L id (dBA) I ≥ 43 ≥ 56 ≤ 53 ≤ 25 ≤ 30 II ≥ 40 ≥ 53 ≤ 58 ≤ 28 ≤ 33 III ≥ 37 ≥ 50 ≤ 63 ≤ 32 ≤ 37 IV ≥ 32 ≥ 45 ≤ 68 ≤ 37 ≤ 42 UNI 11444:2012 (under revision) contains the guidelines for selection of building units in the case of non-serial buildings, referring to the classification procedure given by UNI 11367. UNI 11532, which concerns the acoustic performances of indoor environments, is mandatory for new and refurbished public buildings where good speech perception is required (schools, offices, hospitals and other). 3. SCOTTISH REGULATORY FRAMEWORK

The current Scottish building regulations and the relative performance requirements for sound insulation and energy efficiency are encompassed in the Domestic Technical Standards Section 5:Noise and Section:6 Energy respectively.

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3.1 Acoustic Standards The Scottish sound insulation standards for attached houses and apartments (flats) significantly increased in performance in 2011. Using the D nT,w weighting criteria it provided some of the highest airborne sound insulation standards in Europe for apartments, using minimum 56dB as indicated in Scottish Government - Building standards technical handbook 2019. In 2013 a new series of technical standards were introduced for ‘sustainability’ under the Section 7. This provided a range of building performance requirements encompassing three primary levels of bronze, silver and gold. Bronze is the equivalent level to meeting the minimum sound insulation requirements with higher performance for Silver and Gold levels as outlined below in Table 3. Sound insulation testing is required for new attached housing and there are set requirements for specific ratios of houses to be tested, dependent on the number of total attached houses on a new construction site. The incorporation of enhanced standards under the Section 7: Sustainability technical standards may be requested as part of the planning application by the local authority or by the client. Under- standably achieving a minimum airborne sound insulation of 60 D nT,w requires a design target for the construction specification to be aiming for 64dB, to facilitate site variations and measurement uncer- tainties. This significantly impacted the concrete separating floor construction options, resulting in increasing floor slab thickness or removal of specific designs due to an inability to meet the compli- ance performance standard. Table 3: Sound insulation requirements in Scotland for minimum technical standards and enhanced sta ndards for sustainability.

Separating

Airborne Sound

Impact Sound

Technical Standards Sound Testing

Structure Floor/Wall

Insulation dB (D nT,w )

Transmission dB (L' nT,w )

Mandatory sound testing with set quota of testing

Floors 56 56

Section 5: Noise Building Standards

Walls 56 n/a

Floors 56 56

Section 7 (Bronze)

Walls 56 n/a

Mandatory sound testing with set quota of testing

Floors 58 54

Section 7 (Silver)

Walls 58 n/a

Floors 60 52

Section 7 (Gold)

Walls 60 n/a

3.2 Energy performance standards Whilst the majority focus of this paper relates to acoustic standards, the changes in energy perfor- mance of new build housing over the last decade in Scotland have led to significant changes in con- structions being used. Enhanced energy efficiency levels with external wall U-values less than 0.21 and 0.18 have resulted in the switch by industry to either rigid board insulations, away from mineral wool, or the thickness of the external wall increasing, in some cases by 40-80mm. Many blockwork

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wall constructions had difficulty in achieving the required U-values consistently and the increasing switch to more sustainable construction, using timber framed homes, also provided the opportunity to comply with higher energy performance. Timber frame housing represents 85% of all new annual homes built in Scotland. The increased thickness of external walls also led to increased stiffness, for example moving from 90mm depth timber studs to minimum 140mm. External wall cavities are now fully filled with min- eral wool and the relative effect of flanking transmission on overall performance has been reduced.

3.3 Changes in energy performance affecting sound insulation outcomes The facades of buildings for walls and windows with higher energy performance constructions and increasing airtightness led to a reduction in external noise entering the dwellings. The higher energy efficiency standards were adopted before enhanced Silver or Gold levels for sound insulation for separating walls and floors. The thicker external walls coupled with more insulation increased the external wall sound insulation and reduced the internal background noise levels. Consequentially this has also reduced the potential for external noise to mask sound transmission from adjoining dwellings through separating walls and floors. Whilst this was dependent on the location of the dwelling relative to the external noise environment, anecdotally some house builders reported more sound transmission complaints of residents stating they could hear their neighbours, even though it was the same acoustic separating wall or floor they had built in the years before with little or no complaints. In some new build designs external wall mineral wool based insulations were changed to rigid board insulations, with higher energy performance. This allowed the developer / designer to maintain the same external wall dimensions for existing house type designs and achieve the energy efficiency performance. However, the shift towards rigid polymer based insulation (much lower acoustic ab- sorption) materials resulted in a weakness for sound transmission and for flanking transmission. Some developers incorporated additional straps or resilient bars on wall linings to reduce flanking trans- mission via the external walls. A further interesting factor emerged related to enhancing the air tightness of dwellings. As reduc- ing air leakage can improve both the design calculations and in-situ energy performance it can also affect pressure displacement within a volumetric space. A number of developers stated an increase in noise complaints from flatted dwellings, even though the in-situ sound insulation performance of the separating floors was high. Some dwelling occupants stated they could ‘sense’ where the upstairs occupants were as they moved around the property and they found this to be annoying or disturbing. This was more common in lightweight frame buildings but some cases were also recorded in concrete frame buildings, again with high levels of sound insulation for separating walls and floors. Potentially the increased airtightness, coupled with reduced masking noise, due to increased external wall insu- lation and higher performance windows, resulted in a lower internal background noise levels and higher sensitivity by occupants to minor deflections or displacements/movements of the separating floor system. More recently, as Silver and Gold levels of sound insulation have been incorporated for separating walls and floors this may reduce some of the ‘sensitivity’ complaints, but not all. 4. NET ZERO HOUSING

As countries transition into super-high energy efficiency for the fabric of the new housing, and very high performing airtightness values in the delivery of very low carbon or net zero homes, the interactions with other standards such as sound insulation and occupant sensitivity and comfort may be useful to track and monitor. A further dimension will be carbon reduction objectives for both the selection of construction materials and the low or zero carbon heating systems adopted.

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Whilst many countries with net zero standards focus on the operational carbon there is a growing shift by specifiers, public bodies and clients to include embodied carbon also within the reporting matrix. The use of recycled materials or low embodied carbon materials will increase also resulting in lighter weight structures. This will affect the dampening mass of many structures and introduce new materials and components, which will alter the energy and acoustic ‘system’ performance of walls, floors and roofs. A recent study in 2021 [5] illustrated the influence on carbon emissions by altering specific construction elements of separating walls built in the UK. The rapid increase in the use of air source heat pumps and accompanying 24/7 noise outputs also introduces adjacent noise sources close to external walls and windows. Architects and acousticians when specifying such services equipment, particularly in areas with very low ambient background noise levels, will have to be cautious of the practicalities and influence of such noise outputs and the effective window and door insulation measures to be adopted. 5. CONCLUSIONS

This paper has provided an overview of some of the key changes in energy and sound insulation standards occurring in both Scotland and Italy. Whilst the types of construction and materials used may be different, the complexity of addressing ‘technical compatibility’ across different technical performance requirements is similar. Over the coming decade as new housing and retrofit construction of housing accelerates to deliver net zero or lower carbon outcomes, the combinations and clashes between some technical standards is likely to increase. In effect, the specifier or designer is now required to address a triple helix of energy, acoustics and carbon emissions and still comply to the more rigid structural and fire safety technical requirements. The combination of construction materials with lower embodied carbon, new innovative products, higher regulatory performance standards, closer monitoring and reporting sets the scene for designers and specifiers to require an enhanced knowledge and awareness of the potential technical clashes and building performance outcomes which may occur. 6. ACKNOWLEDGEMENTS

The authors gratefully acknowledge the international knowledge exchange funding and support from the CNR (Italy) and the RSE (Scotland) scientific cooperation agreement towards this study. 7. REFERENCES

1. Smith, S., The role of building sustainability and the delivery of horizon net-zero. Keynote presentation. United Nations Economic Commission for Europe (UNECE). November 2020. 2. Danza, L., Barozzi, B., Bellazzi, A., Belussi, L., Devitofrancesco, A., Ghellere, M., Salamone, F., Sca- moni, F., Scrosati, C. A weighting procedure to analyse the Indoor Environmental Quality of a Zero- Energy Building, Building and Environment , Volume 183 , 107155 (2020) 3. Fausti P, Di Bella A, Santoni A, Scamoni F, Secchi S, Semprini G, The Italian classification scheme of buildings -application to apartments and schools. Proceedings of 2020 International Congress on Noise Control Engineering, Seoul, Republic of Korea, 23-26 August 2020. 4. Scrosati, C., Scamoni, F. Managing measurement uncertainty in building acoustics. Buildings , 5(4) , 1389–

1413, (2015). 5. Smith R.S., Scrosati C. and Arora M. Enhancing sustainability of acoustic architectural specifications whilst also improving building performance. Proceeding of CEES 2021 , Coimbra, Portugal, 12-15 October 2021.

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