It is seen in a series of works from theory and practice that the first step to the achievement of significant reductions in the energy demand for space cooling and artificial light of office buildings of the present time is associated with a review of architectural features based on the understanding of the local climate (1). In a simple way, the architectural parameters that will make a difference in the thermal, lighting and energy performance of these buildings are the building form and the dimensions of the typical floor plates  (which will determine how far into the internal space daylight and natural ventilation can reach), combined to the facade´s configuration (including area, distribution and physical characteristics of the illuminating surfaces – normally in glass) and to the shading strategies, which are important not only to reduce solar gains, but also to daylight control and eventual risks of glare (as seen in text 4 of this series).

A research in more than 5.000 commercial buildings in the United States showed that the shading of the facades can reduce, in average, 64% of the cooling loads of the building sector in the country (2). In the United Kingdom, guidelines to energy conservation in office buildings point out to the possibility of approximately 60% of energy demand minimization as a function of natural ventilation (3).

As explained by Anésia Barros Frota e Sueli Ramos Schiffer (4), the efficacy of natural ventilation in removing internal gains depends on the minimization of these gains. João Leal Vieira (5) identified by means of analytical studies the possibility of cooling demand reductions of up to 75% in a typical tall office building of rectangular floor, central core and glass facades in Rio de Janeiro (latitude 23ºS), showing 42kWh/m2per year in the best case versus 167kWh/m2in the base case scenario – the worst case. This performance is a result of the combined effect of external shading, thermal mass exposed to the internal space, night-time ventilation and, finally, of the rectangular plan that facilitates the cross ventilation during those hours in the year when the external climatic conditions are mild – which corresponds to approximately one-third of occupational hours.

In many contemporary projects, external shading protections are taken as components separated from the building´s envelope, hence, these are wrongly treated as an additional item, generating the false impression that putting external protection is an expensive measure. Such an approach misses a more systemic understanding, in which the return of the envelope´s investment is seen as a whole, encompassing energy savings, as well as the qualitative gains for thermal and visual comfort, in particular in the occupied zone around the perimeter of the floor plane (as seen in the previous texts of this series).

However, the contemporary production of office buildings in cities of emerging economies such as São Paulo, it is common to see little interest in the good use of daylight and none interest in natural ventilation, not even in the night-time ventilation (that happen when the buildings are empty), that has the potential to cool the internal spaces with the benefit of the lower external temperatures of the night, previous to the occupation starts in the following morning.

With all the implications for the comfort and well-being of the occupants and for the cooling and artificial lighting energy demand (discussed in detail in the previous texts of this series), we should go back to the initial question: Why are we perpetuating the glass-box model for the office building? Whilst the environmental and energy impacts of the glass facade are commonly not-considered, from the point of view of the image that is expected from this building type, a great part of the Market believes that the glass facades depict an aspect of technical progress and high status to the buildings (a rather old-fashion idea from 1970s that persists). In addition, many design decisions taken in the context of commercial developments are based on the belief (many times, a wrong belief) that the plain “curtain glass” façade is more economic than the alternative with external shading control.

Nevertheless, according to the experience of Brazilian architects involved in the elaboration of better climatic inserted office buildings, there are already built examples with in the Brazilian market with the design Project to which differentiated alternative façade solutions were technically studied, in search for design solutions more adequate to the climate, without impacting on additional construction costs (information based on the consultancy and design practice of the authors). In these cases, it was verified that, when it is possible to position the buildings with their main facades facing north and south, external horizontal protections in the form of structural-slab extensions of the building can be sufficient to block a great deal of global solar radiation and significantly reduce internal temperatures.

Aiming to compensate any additional cost created by the horizontal shading, based on the same experience, it is recognized that alternatives to the reduction of the overall cost of the buildings are: utilization of clear glass, which is up to 50% cheaper than those with special colour or insulation treatments, and the adoption of opaque components on the areas below the window sill-height, targeting the reduction of glass areas on the facades, which is unnecessary to the penetration of daylight, only allowing for higher solar gains.

Applying such alternatives, the result is a building of less thermal load and better daylight conditions, as a function of the higher lighting transmittance of the transparent glass, with a cost of the buildings´ envelop similar to the conventional curtain wall of some kind of differentiated glass type.  It is Worth mentioning here that even when the building´s orientation is a difficult one for the success of an effective shading without blocking totally the external views, because of the heights of the solar angles, as it happens in the East and West, smaller glazing areas, achieved with the placement of opaque panels, will limit the need of external large vertical shading devices, therefore reducing the cost of the facades.

And how much are the costs of the design project of these type of buildings? In general, the “glass-box” building is associated to simplified architectural designs, with building solutions easily to be replicated, generating design projects relatively cheaper to those who build them.  On the opposite of that, the interest for better environmentally responsive buildings is directly related to more elaborated design projects, with more technical knowledge and assessments of environmental and energy performance, since the beginning of the concept stage.

This has to do with the development of advanced analytical studies of computer simulations, associated to the architectural and building systems´ design, in the exploration of passive strategies and technical solutions of air-conditioning and artificial light more energy efficient, which are aligned with the environmental performance of the architectural proposal. Having said that, it is worth asking how much the insertion of this kind of studies would add to the overall cost of the design Project in comparison to the common practice? In the current moment, in the Brazilian market, specialists from the field estimate an extra cost between 5% and 20% of the total architectural value of the project, depending on the complexity of the referred studies (information based on the consultancy and design practice of the authors).

Going back to the critical review of the conservative approach, it is necessary to design the building of the future and not of the past, which will include specialized technical studies of environmental and energy building performance, considering that the shading, the thermal mass of the construction, daylight and natural ventilation are architectural/building design features that will make a difference both in the environmental and energy performance of the occupied office building.

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, Aparecida Ghosn, Ana Silveira, André Sato, Bruna Luz, Carolina Leme, Claudia Carunchio, Cristiane Sato, Eduardo Lima, Erica Umakoshi, Guilherme Cunha, Julia Galves, Juliana Trigo, Karen Santos, Laís Coutinho, Mônica Marcondes-Cavaleri, Monica Uzum, Nathalia Lorenzetti, Paula Abala, Sheila Sarra, Sylvia Segovia.

NE – This is the first in a series of eight articles on the topic of “environmental performance”. The complete series is as follows:

1
GONÇALVES, Joana Carla Soares, UMAKOSHI, Mitie, Erica. The Environmental Performance of Tall Buildings. Londres, James & James, Earthscan, 2010.

2
GRIFFITH, Brent; TORCELLINI, Paul; LONG, Nicholas; CRAWLEY, Drury; RYAN, John. Assessment of the technical potential for achieving zero-energy commercial buildings. Washington, DC: National Renewable Energy Laboratory, 2006 <https://bit.ly/33cNJxX>.

3
CIBSE – CHARTERED INSTITUTION OF BUILDING SERVICES ENGINEERS. Energy efficiency in buildings: CIBSE Guide F. 2. edição. Londres, CIBSE, 2004.

4
FROTA, Anésia Barros; SCHIFFER, Sueli Ramos. Manual de conforto térmico. 7ª edição. São Paulo, Nobel, 2005.

5
VIEIRA, João Leal. O desempenho térmico de ambientes de trabalho nas cidades de São Paulo e Rio de Janeiro. In: Edifício ambiental. GONÇALVES, J. C. Soares; BODE, Klaus (Org.). São Paulo, Oficina de Textos, 2015.

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. Profa. 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-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. 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-Doc 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 FAUUSP. 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, 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.

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).

João Cotta é graduado em Arquitetura pela Pontifícia Universidade Católica de Campinas, mestre em Sustainable Environmental Design pela AA School of Architecture, Londres, e doutorando pela FAU USP. Sócio do escritório Oliveira Cotta arquitetura. Em seu portfólio destacam-se o novo centro de P&D da empresa Siemens na Ilha do fundão, no Rio de Janeiro e a Ampliação da estação de metrô Santo Amaro.

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.

Larissa Luiz é arquiteta e urbanista pela FAU USP. Pesquisadora do LABAUT desde 2014, com pesquisas em ergonomia, desempenho térmico e luminoso. Foi Bolsista de Iniciação Científica da Fapesp na área de Desempenho Ambiental e Eficiência Energética das Edificações. Atualmente é aluna de mestrado da FAU USP na área de Tecnologia da Arquitetura e consultora em conforto e desempenho ambiental e eficiência energética da CA2.

Marcelo Mello é engenheiro civil pela Politécnica-USP, arquiteto e urbanista pela FAU Mackenzie, mestre em Sustainable Environmental Design pela Architectural Association School of Architecture, Londres, e doutor pela FAU USP. Trabalhou com consultoria em sustentabilidade no Centro de Tecnologia de Edificações – CTE, e hoje atua como Diretor na Arqio Arquitetura e Consultoria.