LEARNING FROM BUILT EXAMPLES IN RIO DE JANEIRO

Oscar D. CORBELLA1 Simos YANNAS2

1 Faculdade de Arquitetura e Urbanismo Universidade Federal Rio de Janeiro

corbella@gbl.com.br 2Environment & Energy Studies Programme Architectural Association Graduate School,

36 Bedford Square, London WC1B 3ES, UK Tel. + 44 20 7887 4000 Fax + 44 20 7414 0782

simos@aaschool.ac.uk

ABSTRACT: The paper summarises the main findings from a series of short-term measurements and observations on a number of representative buildings in Rio de Janeiro. Conference Topic: 3.6 Education, Technology Transfer and Design Support

INTRODUCTION

Few contemporary buildings in Rio de Janeiro (Latitude 22.9º S Longitude 44º E), are capable of providing thermal and visual comfort to their occupants without a heavy dependence on conventional energy systems. The development of an environmental architecture that can free itself from such dependence is one of the challenges facing the present generation of Brazilian architects. For a short period starting in the 1930’s and lasting little more than twenty years a previous generation embraced the principles of modernism together with a certain concern for environmental design. From the 1960’s most new commercial buildings were fitted with air-conditioning, or would have needed to be so, to achieve adequate indoor conditions for occupant comfort.

As part of a collaborative project on the environmental attributes of buildings and outdoor spaces in the tropical climates of Brazil [1], we have studied buildings from different periods in Rio de Janeiro and conducted a series of measurements in some of the city’s street canyons and landscaped open spaces. Some of the latter are reported elsewhere [2] [3]. The buildings we studied include:

− Casa Rui Barbosa, a mid-19th century building of

heavyweight masonry construction, and its annex which was added in 1967.

− Palacio Gustavo Capanema (previously known as Ministry of Education and Culture); architect: Lucio Costa and team including Oscar Niemeyer and A. E. Reidy, 1936.

− Housing at Parque Guinle; architect: Lucio Costa, 1948.

− Museum of Modern Art; architect: A.E. Reidy 1953.

− Petrobras HQ building; architect: RL Gandolfi and team, 1968.

− Apartment building in Ipanema; architect: C. & I. Ferraz 1979.

− Fashion Mall, São Conrado, Maria Alice Marcillac 1982.

BUILDING STUDIES

Short-term measurements of air temperature, relative humidity and other environmental variables were undertaken in and around the selected buildings, mainly during warm summer periods. The air temperature measurements taken at the Palacio Gustavo Capanema, Fig.1, are summarised in Fig.2.

Figure 1: Palacio Gustavo Capanema North (left) and South (right) elevations.

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Figure 2: Air temperature readings, Palacio G. Capanema (Source: [1])

The graph shows that with the outdoor air temperature exceeding 35oC, the northern (equatorial) side of the building, which is protected by fixed horizontal external louvers as shown in Fig. 1, rarely rose above 30oC whereas on the southern side, which is fully glazed and has no solar protection, the temperature frequently exceeded that outside the building. This result highlights the need for systematic and effective solar control which should combine several strategies, i.e. selective use of orientation, control of glazed areas and shading of outdoor spaces, as well as solar control measures on apertures of all orientations for this climate [4]. There is a clear indication also from these measurements that a certain amount of thermal inertia is desirable to modulate the fluctuations driven by the outdoor air temperature, as well as those resulting from solar and internal heat gains.

The effects of incremental levels of thermal inertia are illustrated by Fig. 3. This compares readings of the outdoor air temperature with those taken in three spaces of the Casa Rui Barbosa complex in Botafogo. The original building, Fig. 4, which is currently functioning as a museum, is of masonry construction with relatively small windows protected by wooden louvred shutters. The more recent annex building, which houses the museum’s administrative offices, has no protection from the sun and is fitted with air-conditioning. The measurements were taken over a weekend when the air-conditioning was switched off in the annex and the building was unoccupied. The original building is not air-conditioned. The annex office on the third floor can be seen to rise in temperature as solar gains take effect over time eventually reaching peaks above the outdoor temperature. The Cozinha space (not a functioning kitchen) in the main building shows the effect of the building’s thermal inertia as well as a high rate of air exchange. The third space is the basement area of the annex which has no solar or internal heat gains and its coupling with the ground provides it a very stable temperature that stays close to the daily mean outdoor temperature throughout the period of the measurements.

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Figure 3: January air temperatures in two spaces of Casa Rui Barbosa and Annex basement (Source: [1])

Figure 4: Casa Rui Barbosa original building

The modulating influence of a building’s

thermal inertia is also highlighted by the measurements that were taken in the Petrobras Headquarters building in the commercial centre of Rio. As can be seen from Fig. 5, the building is fitted with adjustable solar control, horizontal louvers on the north elevation, vertical louvers on east and west, reduced glazing on south. Another feature of this building are the landscaped openings it has on alternating positions of the plan at each floor. The building is, fully air conditioned, which makes the environmental function of these spaces less clear. The measurements, Fig. 6, were taken over a weekend period in the month of January with the building’s air conditioning system switched off.

Figure 5: Petrobras HQ building with its different, adjustable solar control devices on northern (left) and western (right) orientations and the deep setbacks of the floor plans.

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Figure 6. Air temperature measurements, Petrobras Building (Source: [1])

It can be seen from the graph that the internal

temperature is very stable. On the Monday morning the drop in temperature reflects the switching on of the air conditioning. At the end of the working day the internal temperature start to rise again as the equipment is switched off.

Figure 7 shows summer and winter temperature measurements taken in non-air conditioned areas of the Rio’s Museum of Modern Art, Fig. 8.

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Figure 7 Museum of Modern Art: summer and winter measurements (Source: [1])

Figure 8 Museum of Modern Art

The measurements near the entrance of the museum (Portaria) reflect the convective coupling with the outdoor. The Atelier space is better protected and its thermal inertia allows it to maintain a lower daytime temperature than the outdoor. The effect of night-time cooling by ventilation is also shown quite strongly on the temperature of the atelier space.

At Parque Guinle Lucio Costa’s use of perforated blocks (cobogo) on the elevation of the balconies of the apartments provided a striking formal device whilst also contributing to solar control without inhibiting air movement, Fig. 9. A strong permeability of the building envelope has always seemed to be a desirable feature for buildings in tropical climates. It is often prohibited by concerns for privacy, security, noise and pollution. Built some thirty years after Parque Guinle the apartment building in Ipanema, Fig. 10, illustrates an adjustable version of the same principle.

Figure 9 Apartment buildings at Parque Guinle, Laranjeiras

Figure 10 Apartment building in Ipanema One of the building studies was followed by a comparison between the Fashion Mall shopping centre in São Conrado and the Rio Sul shopping Centre in Botafogo [5]. The Fashion Mall, Fig. 11, had been selected for study because of its contact with the outdoor that makes it unlike the conventional sealed box type of shopping centre. Although

measured temperature and humidity values were fairly high in summer, interviews with visitors suggested that the majority found the environmental conditions agreable and liked the building. Since the circulation areas of the building are partly daylit and not air-conditioned, it was initially surprising to find that the Fashion Mall used more electricity than the fully air conditioned and permanently artificially lit Rio Sul. This resulted mainly from the high coupling to the outside air of the building’s air-conditioned shops, owing to the large exposed envelope area and open shop doors.

Figure 11 Fashion Mall shopping centre, São Conrado LESSONS FROM THE BUILDING STUDIES

The issue of solar control requires designers to pay closer attention to the spatial and temporal distribution of incident solar radiation. The table below gives comparative summary data that can help assess the respective solar control requirements on different building orientations. The data are expressed in kWh per square metre over the three months of summer and winter periods of the year. Table 1. Incident Solar Radiation on vertical surfaces

in Rio de Janeiro, kWh/m2 season

Winter Summer North 340 180 East / West 220 305 South 95 220 Source: [6]

It can be seen from Table 1 that the summer values of incident radiation, which correspond to mean daily values in the range 2.0-3.5 kWh per square metre, combined with daytime outdoor air temperatures exceeding 30oC can lead to high levels of thermal discomfort. In summer, the winter hierarchy gets reversed and south-facing openings require more protection than north-facing one in summer.

In summary, the lessons from the building studies are:

− The combination of effective solar control on all orientations, with adequate thermal inertia and the ability to make use of cooling breezes and night-time ventilation can allow buildings to achieve acceptable conditions of thermal comfort without need for air conditioning.

− Adjustable elements, and air and daylight permeability, are desirable and can also lead to interesting formal expression.

− Better use of the available daylighting may require installation of automatic lighting controls.

− People like open spaces and thermal comfort conditions can be achieved with careful design.

− Coupling with the outside environment may be desirable for this climate provided a building is protected from the sun, makes good use of daylighting, and is not air conditioned.

− When a building is to be air conditioned the size of the AC plant and its electricity consumption can be reduced considerably by paying attention to solar control and thermal inertia and by lessening the external envelope’s thermal sensitivity to the outside environment; both the air conditioning and lighting loads can be reduced by controlled access to daylighting.

ACKNOWLEDGEMENT We acknowledge the support of the British Council, CNPq, and FAPERJ that has permitted the undertaking of the measurements and collaborative work reported in this paper. REFERENCES [1] Corbella, O.D. and S. Yannas (forthcoming 2001)

Em Busca de uma Arquitetura Sustentavel para os Tropicos. UFRJ.

[2] Corbella, O.D. and S. Yannas Posto 3 Copacabana Rio de Janeiro. Proc. of IV Encontro de Conforto no Ambiente Construido, Salvador.

[3] Corbella, O.D., V. Corner, S. Yannas (2001) Outdoor Spaces and Urban Design: Case studies of two Plazas in Rio de Janeiro. Proc. of PLEA 2001 Conference, Florianopolis.

[4] Yannas, S. (1990). Solar Control Techniques. Workshop on Passive Cooling, EC Joint Research Centre, European Commission.

[5] Corbella, O.D. and S. Yannas (1998). Environmental Study of Two Shopping Malls in Rio de Janeiro. In Proc. PLEA 98 Environmentally-Friendly Cities, James & James (Science) Publishers, London.

[6] Castanheira, R. G. (2001) Radiação Solar Incidente em Planos Inclinados Fachadas e Telhados no Rio De Janeiro. Masters Dissertation, UFRJ.