Another point about the environmental performance of glass box offices that deserves attention is the acoustics. How is the acoustic comfort in these environments depending on their materials, the configuration and the uses of the internal spaces? And urban noise? How to open windows and not be bothered by external noise? If noise levels are high, employee performance and productivity will suffer. Exposure to excessive noise levels has a negative impact on the health, well-being, satisfaction, motivation and concentration of workers, and may even cause sick leave and extra expenses for medical reasons (2).

The compatibility between thermal and acoustic environmental comfort is a challenge, especially when considering office partitions in buildings. The openings as a passive system for thermal comfort in buildings are the ones that most influence the sound insulation of the partitions. In this way, opening the windows to provide natural ventilation can directly affect the acoustic environment of the workspaces. And even when closed, the windows are the weak point of the overall sound insulation of the facade, mainly due to the acoustic quality of the frames and the presence of gaps in window seals. Glass panels, on the other hand, are material components with low sound absorption coefficients and, therefore, are sound reflectors.

To obtain the desired facade sound insulation in relation to the local external noise, glass and frames suitable for each case must be used. Laminated and thermal insulation glasses have better sound reduction indexes than simple glass and, when arranged in multiple panes, separated by air chambers or special coatings, are even more acoustically insulating. However, from the thermal point of view, care must be taken regarding the shading of these glasses, noticing that double glazing is not advantageous for thermal and energy performance in hot climates. Therefore, the choice for this facade solution due to urban noise should be reserved for extreme cases.

A potentially effective strategy to solve the conflict between the advantages of natural ventilation and the needs of acoustic insulation, without causing discomfort to the occupants or reducing their productivity, is night ventilation, since the offices are unoccupied at this time, when the air-changes remove the heat accumulated during the day. However, despite reducing the thermal loads to be removed by air conditioning the next morning, this would not resolve thermal comfort during the occupation period, without opening the window or activating the air conditioning system on the hottest days. The ideal would be to “take care” of the external noise through an efficient public policy of noise management and control. This is to call for a Urban Sound Planning of the city.

Currently, noise maps are the main tool for this type of planning. They provide visual information about the acoustic behavior of a geographical area at a given time, diagnosing its distribution and quantification of noise. A municipal law published in 2016 establishes a period of seven years for the development of the noise map of São Paulo city (3). When the map is ready, it can be used to support urban planning decisions regarding noise management in the city, as it already happens in several European cities (4). Once the external noise is within acceptable limits, opening the window can no longer be a problem for the acoustic comfort.

Besides, it is important to highlight that, in many cases, acoustics can be solved (or at least improved) at the design stage. The geometry of the facades and their elements can contribute to reduce the noise incidence on them. External solar protections can be useful and there are even acoustic brises. Different internal layouts and office activities can also influence the acoustics. The open plan type office layout tend to have higher noise levels and less privacy than closed offices, the cellular type (5). Sound barriers (to block the sound from reaching the occupant directly), such as movable partitions, panels between work table, shelves and other types of separators, added to an adequate design of workstations can help in these cases as well.

Among the Brazilian standards, there is no specific one for office acoustics, but the ABNT NBR 10152 standard (6) establishes sound pressure levels ​​for different indoor environments, depending on their intended use, both for indoor sound evaluation purposes and for studies and acoustic design of indoor environments. In the case of offices, the standard presents values ​​for the following environments: call centers, private offices (management, directors etc.), collective offices (open plan offices), receptions, waiting rooms, meeting rooms and video conference rooms. For example, the recommended reference values for sound pressure levels for the purposes of studies and acoustic projects of private and collective offices are, respectively, 40 dB and 45 dB. For sound evaluation purposes, the standard recommends values equal to or less than the reference values presented above with a tolerance of up to 5 dB. According to the standard, measurements must be carried out in the environment in its usage configuration, but in the absence of its users. Therefore, the values do not reflect real situations of use, when noise generated internally by users is present (such as conversations, footsteps etc.).

In addition to the acoustic insulation of the space, its shape and dimension, its coating materials, and its internal noise influence the acoustic quality in the workplaces. In the case of glass-box buildings, the internal sound reflections caused by the glasses increase the sound reverberation in the place, which also impair speech understanding. To reduce such sound reflections, it is necessary to acoustically treat the environment, through the application of materials with high sound absorption coefficients, developed to absorb sound energy and consequently reduce sound reverberation and the internal noise level. Hence the “false ceiling lining” culture.

In most cases, the absorbent false ceiling linings are indiscriminately used as the perfect solution for acoustic comfort. Negative points of the ceiling liners are that, in addition to hiding the structure, which is thermal mass to absorb the heat generated internally, they accumulate dirt. The ceiling lining can be used to control the internal sound reverberation, but the acoustic treatment is not limited to this solution. Another common design error is to use the false ceiling to separate acoustically two environments. In these cases, basic concepts of sound absorption and sound insulation are confused.

When internal particians stop at the ceiling height (instead of reaching the slab), noise can pass from one space to another via the ceiling. In this case, basic concepts such as absorption (achieved with the ceiling) and insulation are mixed up, because the ceiling absorbs the sound frequency of a specific space but it does not necessarily isolate the neighbouring one from such sound.

Nowadays, there is a wide variety of acoustic materials on the market, which can be installed not only on the ceiling; but also on workstations (acoustic particians installed at the height of the mouth); on walls and floors; suspended materials (acoustic baffles and clouds); micro-perforated and transparent materials installed in front of glass surfaces; besides acoustic furniture, such as folding screens, sofas, shelves, bookcases, lamps. Such solutions, in addition to being efficient, can lead to a more contemporary treatment of the image expected from a current workspace.

On the other hand, excessive sound absorption can cause everything that happens internally (like a simple fall of a pen) to be perceived, increasing distraction, generating discomfort and decreasing privacy

Ultimately, an adequate acoustic Project integrated with the other areas of comfort is the most indicated to the best general performance of the internal environment, keeping in mind that all design aspects (from building orientation to form and treatment of apertures and the furniture detail) have a role in the final acoustic. At the same time, it is fundamental that extremely unfavourable urban acoustic conditions to buildings´ performance are treated in the realm of urban planning and urban design, working in favour of a more significant integration between inside and outside.

notes

NA – A série de oito artigos intitulada “O pobre desempenho ambiental dos escritórios por trás da caixa de vidro” conta com os seguintes colaboradores: Amanda Ferreira, Ana Silveira, André Sato, Bruna Luz, Carolina Leme, Claudia Carunchio, Cristiane Sato, Eduardo Lima, Erica Umakoshi, Guilherme Cunha, João Cotta, Julia Galves, Juliana Trigo, Laís Coutinho, Larrisa Luiz, Marcelo Mello, Mônica Marcondes-Cavaleri, Monica Uzum, Nathalia Lorenzetti, Paula Abala, Sylvia Segovia.

NE – Este é o quinto de uma série de oito artigos sobre o tema do “desempenho ambiental”. A série completa é a seguinte:

GONÇALVES, Joana; et. al. The poor environmental performance of offices behind the glass-box. An overview (chapter 01/08). Drops, São Paulo, year 21, n. 158.08, Vitruvius, nov. 2020 <https://vitruvius.com.br/revistas/read/drops/21.158/7926/en_US>.

GONÇALVES, Joana; et. al. The poor environmental performance of offices behind the glass-box. Thermal comfort and energy demand (chapter 02/08). Drops, São Paulo, year 21, n. 160.02, Vitruvius, jan. 2021 <https://vitruvius.com.br/revistas/read/drops/21.160/7999/en_US>.

GONÇALVES, Joana; et. al. The poor environmental performance of offices behind the glass-box. The control of the thermal environment and air quality in times of pandemic (chapter 03/08). Drops, São Paulo, year 21, n. 161.02, Vitruvius, feb. 2021 <https://vitruvius.com.br/revistas/read/drops/21.161/8024/en_US>.

MICHALSKI, Ranny; et. al. The poor environmental performance of offices behind the glass-box. Acoustic comfort. Drops, São Paulo, year 21, n. 163.02, Vitruvius, apr. 2021 <https://vitruvius.com.br/revistas/read/drops/21.163/8073/en_US>.

GONÇALVES, Joana; et. al. The poor environmental performance of offices behind the glass-box. The transformation force of architectural strategies. Drops, São Paulo, year 21, n. 164.08, Vitruvius, may 2021 <https://vitruvius.com.br/revistas/read/drops/21.164/8186/en_US>.

1
Ver acima, na nota do editor, os demais artigos da série.

2
BASNER, M.; BABISCH, W.; DAVIS, A.; BRINK, M.; CLARK, C.; JANSSEN, S.; STANSFELD, S. Auditory and non-auditory effects of noise on health. The Lancet, 383 (9925), 2014, p. 1325-1332.

3
SÃO PAULO MUNICÍPIO. Lei n. 16.499, de 20 de julho de 2016. Dispõe sobre a elaboração do Mapa do Ruído Urbano da Cidade de São Paulo e dá outras providências. São Paulo, 2016 <http://documentacao.camara.sp.gov.br/iah/fulltext/leis/L16499.pdf>.

4
GEVÚ, N. V.; FERNANDES, W. C.; CORTÊS, M. M.; FAGERLANDE, G. C.; NIEMEYER, M. L. A. Mapa de ruído como ferramenta de diagnóstico e projeto. In Acústica e Vibrações, v. 50, 2018, p. 93-10.

5
BROCOLINI, L.; PARIZET, E.; CHEVRET. Effect of masking noise on cognitive performance and annoyance in open plan offices. In: Applied Acoustics, v. 114, 2016, p. 44-55.

6
ABNT – Associação Brasileira de Normas Técnicas. ABNT NBR 10152: Acústica – Níveis de pressão sonora em ambientes internos a edificações. Rio de Janeiro, ABNT, 2017.

about the authors

Ranny Michalski é engenheira mecânica pela UFRJ, mestre e doutora em Engenharia Mecânica pela Coppe UFRJ. Professora doutora da FAU USP, onde atua como docente no ensino e na pesquisa, e orientadora do programa de pós-graduação em Arquitetura e Urbanismo da FAU USP. Membro da Diretoria da Sociedade Brasileira de Acústica – Sobrac. Participa da elaboração de normas técnicas brasileiras em acústica da Associação Brasileira de Normas Técnicas – ABNT.

Joana Gonçalves é arquiteta e urbanista pela UFRJ, mestre em Environment and Energy pela AA School of Architecture, doutora e livre-docente pela FAU USP. Orientadora dos programas de pós-graduação Arquitetura e Urbanismo da FAU USP e Architecture and Environmental Design, School of Architecture and Cities, University of Westminster, Londres. Professora da AA School of Architecture, Londres. Diretora da Associação Plea.

Roberta Mülfarth é arquiteta e urbanista pela FAU USP, mestre pelo Programa Interdisciplinar de Pós-Graduação em Energia da USP, doutora e livre-docência pela FAU USP. Orientadora de pós-graduação em Arquitetura e Urbanismo da FAU USP e no Programa de Educação Continuada – Pece, no curso de especialização de Gestão em Cidades, junto a Poli USP. Vice-coordenadora do USP Cidades. Chefe do Departamento de Tecnologia da FAU USP.

Marcelo Roméro é professor titular da FAU USP. Arquiteto e urbanista pela UBC, mestre, doutor e livre docente pela FAU USP, pós-doutor pela Cuny (USA). Orientador e Professor dos Programas de Pós-Graduação da USP, do Instituto de Pesquisas Tecnológicas do Estado de São Paulo – IPT, da Universidade de Brasília, do Centro Universitário Belas Artes de São Paulo e da Peter the Great St. Petersburg Polytechnic University.

Alessandra Shimomura é arquiteta e urbanista pela PUC Campinas, mestre pela Unicamp e doutora pela FAU USP. Professora pela Faculdade de Arquitetura e Urbanismo e orientadora do programa de pós-graduação em Arquitetura e Urbanismo da FAU USP. Advisor no Student Branch ArchTech Labaut da Ashrae e Membro do Comitê Plea (Passive and Low Energy Architecture) Chapter Latin America and the Caribbean (Plea-LAC).

Eduardo Pizarro é arquiteto e urbanista, mestre e doutor pela FAU USP. Professor da Universidade São Judas. Pizarro é Embaixador do LafargeHolcim Awards e já desenvolveu pesquisa na Architectural Association Graduate School, em Londres, e na ETH, em Zurique. Ganhador de prêmios como o Jovem Cientista (Brasília, 2012) e o LafargeHolcim Forum Student Poster Competition (Detroit, 2016).

Sheila Sarra é graduada em Medicina pela Universidade de São Paulo e especialista em Medicina do Trabalho na Faculdade de Ciências Médicas da Santa Casa de São Paulo. Arquiteta e urbanista pelo Centro Universitário Belas Artes de São Paulo. Mestre e doutora em Arquitetura e Urbanismo pela Universidade de São Paulo, em Tecnologia da Arquitetura. Consultora em qualidade ambiental de edificações.

Aparecida Ghosn é arquiteta e urbanista pela UBC. Mestre pela FAU USP e professora do curso de pós-graduação da Anhembi Morumbi. Experiência nos setores privado, público e acadêmico no Brasil e exterior (EUA e Austrália). Atualmente atua com Avaliação Pós Ocupação em espaços de trabalho, com foco na qualidade ambiental Interna, saúde e produtividade dos ocupantes.

Beatriz Souza é técnica em Edificações pelo Centro Federal de Educação Tecnológica de Minas Gerais, arquiteta e urbanista pela FAU USP, com dupla formação pelo programa FAU Poli (USP). Foi bolsista de Iniciação Científica com apoio do CNPq e da Fapesp na área de Desempenho Ambiental e Eficiência Energética das Edificações. Atualmente é consultora da Arqio Arquitetura e Consultoria.

Karen Santos é aluna do curso de graduação em Arquitetura e Urbanismo da Faculdade de Arquitetura e Urbanismo da Universidade de São Paulo. Foi bolsista de Iniciação Científica com apoio da Fapesp. Atualmente, está cursando o Programa de Dupla Formação FAU USP – Escola Politécnica da USP.