In the office building of the glass box, a great part of the impinging solar radiation passes through the façade due to its transparency. In order to deal with the excessive lighting levels upon the work plan, various types of internal curtains are a necessity for the visual comfort of occupants, however, in many cases making the internal spaces darker, besides blocking views to the exterior.

Coloured glass facades and, or reflective glass are even worse to the penetration of daylight, because they allow the incidence of the part of solar radiation associated exclusively with heat (the long waves), at the same time that block a significative part of the solar radiation that creates daylight, again resulting in darker internal environments. It is worth mentioning that there are today available in the Brazilian market, internal blinds of the rolo type, that control the access of daylight without it blocking totally. However, from the thermal perspective, once the solar radiation goes through the glass, the cooling load will be the same as if there were no solar blinds at all.

Technically, the use of external shading continues being the ideal solution for a better environmental performance not only from the point of view of thermal performance, but also for daylight, because it blocks the direct component of solar radiation (the actual sun), which brings glare risks, and also for moderating the penetration of diffuse light coming from the sky in the perimeter of the floor plans, around the facades.

About the glass with milky aspect, as the so called U-glass (that has recently reached the Brazilian Market), due to the multiple layers of this type of glass component, the hypothesis for its performance would be of a good control of glare caused by the incident solar radiation, resulting in a homogenous daylight in the interior, however, with the implications of overheating that are related to the other types of double glazing (mentioned in the previous texts of this series).

In addition to that, in the office buildings of glass facades, the artificial lighting systems are normally designed without any consideration to the possible contribution of daylight. This happens for several reasons, including the need of blocking the impacts of solar radiation by means of internal shading (as already previously mentioned), the depth of the floor plan and, also, the simple belief that artificial lighting is always necessary, regardless the time of the year, the hour of the day and the type of the sky (overcast, partially cloudy or clear). What is missing in these cases is the understanding of those who occupy the building and manage its systems of the possibilities of energy savings and the advantages of daylight to the well-being and health of the occupants.

A series of studies carried out in the past two decades, in Brazil and abroad, proved that the exposure to artificial light has relevant consequences to occupants´ health. Fieldwork in office buildings in Brazilian cities showed that people that work only under the influence of artificial light have higher chances of presenting symptoms of psychiatric disorder, depression, anxiety and negatively-affected sleep quality (1). On the other hand, other case-studies demonstrate that a building design of good daylight qualities can reduce headaches and all the other symptoms of the so called Sick Building Syndrome up to 25%, furthermore, it can improve individual productive up to 23% and reduce annual energy demand for artificial lighting in up to (2). It was also verified that the stress level in people exposed only to artificial light during the entire day is higher in those that are exposed to a combination between daylight and artificial light (3).

Besides the characteristics of the facades, the proximity of the workstation to the facade is an relevant parameter of the layout to visual comfort, in particular due to the possibility of visual communication with outside (4). Looking to the architectural building design as a whole, the glass facade is not the only component responsible for the lack of daylight (and of the poor thermal performance, as already mentioned in previous texts of this series). The depth of the know “deep-plan” floor plates result in a significant fraction of the usable floor area away from the influence of the facades and, for this reason, being distant from the reach of daylight.

In quantitative terms, whilst the Brazilian standard that deal with lighting requirements in workspaces puts forward the figure of 500 lux to be kept on the work-plan (5), a number of international references point put to the preference of occupants for varying conditions, being the range between 300 lux to 3.000 lux characterized by none or very low probability of additional need for artificial lighting (6), what raises questions about the pertinence of the 500 lux threshold given by the current Brazilian standard, and the range between 100 lux and 300 lux, being of complementary use of artificial light.

Analytical studies developed for office buildings of glass facades in the city of São Paulo, but with external shading, identified a good access of daylight, according to international criteria, showing minimum lighting levels oscillating between 100 lux and 300 lux up to 9 metres deep, in the North and South sides of the building, and in depths between 10 and 12 metres on the East and West sides (7). This is to say that depths deeper than those, in their respective orientations, for the local climatic and sky conditions of São Paulo, imply in higher dependency of artificial light in offices.

It is important to highlight that the form and depth of floor plans of a building have a central role in the efficacy of facade-strategy and to an overall building environmental performance, encompassing thermal and lighting. Nevertheless, in the case of the deep-plan buildings, in which the influence of facade is limited to a small portion of the usable floor area, improvements in the design of the facades with the insertion of external shading devices for thermal and visual performance are less relevant to the reduction of cooling demand as well as artificial lighting demand.

In office buildings from the last decade in São Paulo, for example, it was seen that the bigger ones have floor plates as wide as 30 by 70 metres (8), significantly surpassing the adequate dimensions for a satisfactory daylight performance as well as for energy savings, regardless the façade design. In this way, it is necessary to rethink the economic formula that produces the building, pushing for the relation between the maximum usable floor area to the minimum facade area, resulting in deep-plan floor plates of restricted access of daylight and natural ventilation, exclusively to save construction costs, ignoring the consequences on the environmental and energy performance of the final building.

But what is the real increase of facade area for a potentially favourable relation between facade area and floor plan to daylight penetration? Taking as an example a building of squared floor plate of 1,000 m2(of 32 metres side), the same usable area in a narrower rectangular shape (of approximately 18 by 55 metres side), would have the facade area increased by 16,5%, as a function of the increased of the perimeter of the floor plate.

Thinking about the value of the building and the usable area of the floor plate, the financial impact of such an increase has to be counterbalanced with the benefits in the health, satisfaction and productivity of the occupants, as already mentioned here, and also the savings associated to the reduction of energy demand. In sum, it is undeniable that access to daylight and views towards the exterior result in healthier, more comfortable and more productive conditions for the workspace, justifying the environmental and social value of architectural alternatives to the form of the deep-floor building and glass facades, without treatment against glare.

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, André Sato, Aparecida Ghosn, Beatriz Souza, Carolina Leme, Claudia Carunchio, Eduardo Lima, Erica Umakoshi, João Cotta, Julia Galves, Juliana Trigo, Karen Santos, Laís Coutinho, Larissa Luiz, Monica Uzum, Marcelo Mello, Nathalia Lorenzetti, Paula Abala e Sheila Sarra.

NE – Este é o quarto 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
MARTAU, ‪Betina Tschiedel. A luz além da visão: Iluminação e sua relação com a saúde e bem-estar de funcionárias de lojas de rua e de shopping centers em Porto Alegre. Tese de doutorado. Campinas, FEC Unicamp, 2009.

3
LOFTNESS, B.; HAKKINEN, O.; ADAN, A.; Elements that contribute to healthy building design. In: Environmental Health Perspective, n. 115, p. 965-970, 2007.

4
KERKHOF, G. A. “Licht en prestatie”, Proceedings. Symposium Licht en Gezondheid. Amsterdam, 1999.

5
NEWSHAM, G. R. C.; MANCINI, S.; BIRT, B. J.; Do LEED-certified buildings save energy? Yes, but.... Energy and Buildings, n. 41, p. 897-905. Elsevier, 2009.

6
ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. NBR ISO/CIE 8995-1:2013: Iluminação de ambientes de trabalho. Parte 1: Interior. Rio de Janeiro, 2013.

7
MARDALJEVIC, John; ANDERSEN, Marilyne; ROY, Nicolas; CHRISTOFFERSEN, Jens. Daylighting metrics: is there a relation between useful daylight illuminance and daylight glare probability? In: BUILDING SIMULATION AND OPTIMIZATION CONFERENCE, 1., 2012, Loughborough. Proceedings […]. Loughborough: Loughborough University, 2012, p. 189-196.

8
MARCONDES-CAVALERI, Monica Pereira; CUNHA, Guilherme Reis Muri; GONÇALVES, Joana Carla Soares. Iluminação Natural em Edifícios de Escritórios: Avaliação Dinâmica de Desempenho para São Paulo. In PARC: Pesquisa em Arquitetura e Construção, v. 9, p. 19-34, 2018.

9
PEREIRA, D. C. L. Iluminação natural em edifícios de escritório: metodologia para a avaliação do desempenho luminoso. Tese de doutorado. São Paulo, FAU USP, 2017.

about the authors

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 e 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-docente 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 e chefe do Departamento de Tecnologia da FAU USP.

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.

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, na graduação e na pós-graduação. Coordenadora da Regional São Paulo da Sociedade Brasileira de Acústica (Sobrac). Participa da elaboração de normas técnicas brasileiras em acústica da Associação Brasileira de Normas Técnicas – ABNT.

Marcelo Roméro é professor titular da FAU USP. Arquiteto e urbanista pela UBC, mestre, doutor e livre docente pela FAU USP e 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.

Eduardo Pizarro é arquiteto e urbanista, mestre e doutor pela FAU USP e 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).

Cristiane Sato é arquiteta e urbanista, mestre e doutora pela FAU USP. Especialista na área de Conforto Ambiental e Eficiência Energética das Edificações. Atualmente é Pesquisadora de Pós-DOC da FAU USP e Consultora de projetos de iluminação e eficiência energética.

Mônica Marcondes-Cavaleri é arquiteta e urbanista, doutora e pós-doutora pela FAU USP. Mestre pela AA Graduate School, Londres. Há 15 anos é consultora e pesquisadora em desempenho ambiental e eficiência energética da arquitetura. Especialista no uso de ferramentas avançadas de simulação computacional em avaliações dinâmicas e integradas de desempenho ambiental e eficiência energética. Auditora Aqua-HQE.

Bruna Luz é arquiteta e urbanista, mestre e doutora pela FAU USP, na área de Tecnologia da Arquitetura, com ênfase em Iluminação Natural e Eficiência Energética das Edificações. Tem pós-doutorado pela FEC-Unicamp, onde é professora colaboradora. Foi bolsista da Fapesp. Também é professora do Programa de Pós-Graduação da faculdade Belas Artes.

Guilherme Cunha é arquiteto e urbanista pela FAU USP. Cursou o programa de dupla formação 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, com ênfase em iluminação e térmica. Atualmente é consultor da Inocatech Engenharia.

Ana Silveira é aluna do curso de graduação em Arquitetura e Urbanista da FAU USP, com estágio na Polimi de Milão. Foi bolsista de Iniciação Científica com apoio do CNPq e da Sonfy na área de Iluminação Natural.