the new research centre of the brazilian petroleum company in rio de janeiro, brazil: the...

The new research centre of the Brazilian Petroleum Company in Rio deJaneiro, Brazil: The achievements in the thermal performance ofair-conditioned buildings in the tropics

Rafael Brandao, Monica Pereira Marcondes, Gisele S. De Benedetto, Joana Carla Soares Goncalves *,Denise Helena Silva Duarte, Jose Ovıdio Ramos

Laboratorio de Conforto Ambiental e Eficiencia Energetica (LABAUT), Departamento de Tecnologia da Arquitetura (AUT), Faculdade de Arquitetura e Urbanismo,

Universidade de Sao Paulo (FAUUSP), Sao Paulo, Brasil, Rua do Lago, 876, Cidade Universitaria, 05508-900 Sao Paulo, SP, Brazil

Energy and Buildings 40 (2008) 1917–1930

A R T I C L E I N F O

Article history:

Received 9 March 2008

Received in revised form 16 April 2008

Accepted 21 April 2008

Keywords:

Architecture

Thermal-comfort

Energy-efficiency

Simulation

Tropics

A B S T R A C T

The study on the thermal performance of the air-conditioned buildings of the new research centre of the

Brazilian Petroleum Company, in the tropical climate of Rio de Janeiro, was part of a bigger research and

consultancy project involving environmental issues. The architectural design was the subject of a

national competition in 2004, encompassing over 100,000 m2. According to the design brief, out of the 10

buildings of the new research centre, 7 have to be either completely or partially air-conditioned, due to

specific occupation requirements. The challenge for better thermal performance was related to systems’

energy efficiency, to the introduction of natural ventilation and to the notion of adaptive comfort, which

were verified with the support of thermal dynamic simulations. At the early stages of the assessments,

the potential for natural ventilation in the working spaces considering the mixed-mode strategy achieved

30% of occupation hours. However, the development of the design project led to fully air-conditioned

working spaces, due to users’ references regarding the conventional culture of the office environment.

Nevertheless, the overall architectural approach in accordance to the climatic conditions still showed a

contribution to the buildings’ energy efficiency.

� 2008 Elsevier B.V. All rights reserved.

Contents lists available at ScienceDirect

Energy and Buildings

journal homepage: www.elsevier .com/locate/enbui ld

1. Introduction

This paper brings the achievements in the thermal performanceof air-conditioned buildings from the new research centre of theBrazilian Petroleum Company, in the tropical climate of Rio Janeiro,Brazil. Such environmental assessment was developed within thecontext of both consultancy and research, which was a rathercomprehensive project for new initiatives of environmentallyfriendly architecture in Brazil, in which the design processconsidered principles of environmental design. In that sense, thispaper is the third of a series of six including the topics ofarchitectural concepts and design process, outdoor thermalcomfort, thermal and energy performance of air-conditionedbuildings, thermal performance of free-running buildings, day-

* Corresponding author. Tel.: +55 11 3091 4538; fax: +55 11 3091 4539.

E-mail addresses: [email protected] (R. Brandao),

[email protected] (M.P. Marcondes), [email protected]

(G.S. De Benedetto), [email protected] (J.C.S. Goncalves), [email protected]

(D.H.S. Duarte), [email protected] (J.O. Ramos).

0378-7788/$ – see front matter � 2008 Elsevier B.V. All rights reserved.

doi:10.1016/j.enbuild.2008.04.009

lighting and, finally, buildings’ design and the search for a greenbuilding certificate.

The architecture proposal from Zanettini Arquitetura S.A., co-authored by Arch. Jose Wagner Garcia, was the subject of a nationalcompetition held in 2004.The building complex covers an area over100,000 m2 with laboratories, offices, a convention centre andother special uses. The winning scheme, planned to be partiallybuilt in 2006/2007 at the edges of the Guanabara Bay in Rio deJaneiro, was strongly influenced by bioclimatic concepts of the‘‘carioca’’ (local) architecture, showing a predominantly horizontalcomposition, in which transitional and open spaces have afundamental role in the environmental quality envisioned bypetroleum company and the design team, outdoors and indoors, inthe local hot and humid climate, located at latitude 22.53S.

The design process was informed by qualitative and quanti-tative environmental assessments since the conceptual stage,carried out by the team of specialists from the Laboratorio de

Conforto Ambiental e Eficiencia Energetica, do Departamento deTecnologia da Arquitetura da Faculdade de Arquitetura eUrbanismo da Universidade de Sao Paulo (Laboratory of Environ-ment and Energy Studies of the Department of Technology of the

mailto:[email protected]






http://www.sciencedirect.com/science/journal/03787788

http://dx.doi.org/10.1016/j.enbuild.2008.04.009

R. Brandao et al. / Energy and Buildings 40 (2008) 1917–19301918

Faculty of Architecture and Urbanism of the University of SaoPaulo). Focusing on the issue of the thermal performance of air-conditioned buildings, this paper summarizes the assessment’sprocess, starting with the presentation of key aspects of themethodology, which introduced the notion of adaptive comfort,followed by a number of in-depth simulation parametric studies toanalyze architectural design possibilities, which were carried outwith the support of advanced simulation tools. The climatic database that gave support to these assessments was the sameestablished for the overall environmental design of new researchcentre of the Brazilian Petroleum Company, which included theassessment of outdoors comfort and daylighting performance ofbuildings.

According to the design brief, 7 out of the 10 different buildingtypologies (to house different functions) have to be eithercompletely or partially air-conditioned due to specific occupationrequirements, these are named: Laboratories, Central Building(offices), Convention Centre, Laboratory for Virtual Reality (CVR),Restaurant and Greenhouse. The other 3 out of the 10 buildings

Fig. 1. Final masterplan including the existing research centre: (1) Central Building (offi

Workshop Building, (6) Staff and Maintenance Building, (7) Greenhouse, (8) Research an

(existing buildings).

that compose the new research centre were designed to have mostof their environments naturally ventilated: Staff and MaintenanceBuilding (bathrooms, showers, dinning areas, meeting areas andpersonal stock rooms) Research and Plant Building (warehouse forresearch and testing of physical models), Utility Central Building(entrance of the city utility systems in the complex, includingwater and electricity; self energy generation (gas) and cogenera-tion; plant rooms for the central air-conditioning system, andspecially utilities to support the laboratories with the provision ofgazes and liquids) and the Workshop Building (areas for testing ofmodels of petroleum platforms, offices, maintenance and equip-ment stock rooms) (see Figs. 1 and 2).

In the group air-conditioned buildings the thermal performanceof the architecture has a significant influence in the energyefficiency of the environmental control systems, whereas in thefree-running buildings, the issue of architectural thermal perfor-mance of buildings is only related to thermal comfort.

With the exception of the of the specialized rooms of theLaboratories, the Centre of Virtual Reality and the Greenhouse,

ces), (2) Laboratories, (3) Convention Centre, (4) Laboratory for Virtual Reality, (5)

d Plant Building, (9) Restaurant, (10) Utility Central Building, (11) Research Centre I

Fig. 2. Physical model of the complete architectural composition of new research

centre of the Brazilian Petroleum Company seen from the south–east orientation.

Source: Zanettini Arquitetura S.A.

R. Brandao et al. / Energy and Buildings 40 (2008) 1917–1930 1919

where the building functions demand highly controlled environ-mental conditions (not only related to comfort), the concept of themixed-mode environmental approach was tested and the possi-bility of 30% of natural ventilation in working environments wasfound at the first stage of the environmental studies. In orderwords, the notion of fully air-conditioned environment (stated inthe design brief) was challenged. However, with the developmentof the buildings’ design, followed by the constant reviews ofPetrobras, the mixed-mode strategy was refused in all workingspaces for the adoption of the fully air-conditioned mode.

All buildings with air-conditioning systems were evaluatedaccording to the same methodological procedures. Based on suchassessments, this paper highlights the assessment of the thermalperformance of specific office cells within the Laboratories andworking areas in the Central Building, in which thermal comfortwas a priority for the architectural design that was conceived andoptimized for the best possible energy efficiency.

2. Method for buildings’ thermal assessment

In the harsh conditions of the hot-humid climate of Rio deJaneiro, the architectural design and its related environmentalstrategies for a better buildings’ thermal performance, aiming forthe maximization of free-running periods of occupation, arelimited by climatic conditions and occupation parameters. Inregards to the design of the air-conditioned buildings andconsidering the introduction of the mixed-mode strategy, it isimportant to note that no fixed benchmarks were established inthe assessment of the thermal performance. This is due to thereasonably recent application of such strategy as well as the

shortage of references from both local and similar climaticconditions and the architectural innovative aspects of the entireproject, including the design process. Therefore, these studies weremostly based on the comparative analysis of alternative designsolutions, specially related to the architectural features andspecifications of the buildings’ envelop. In the same way, aminimum number of hours within the pre-defined thermal-comfort zone for the free-running mode (according to the notion ofadaptive model) as well as maximum acceptable internal loads didnot have pre-established thresholds. As a consequence, adequatevalues to qualify the building’s performance and to decide for themixed-mode or the fully air-conditioned approach were carefullyconsidered on a case-by-case basis.

The buildings’ thermal performance was assessed according tothe following steps:

� E
stablishment of comfort parameters and design criteria for free-running and air-conditioned environments. � P reliminary building studies to test the selection of the critical
rooms, thermal zoning, simulation schedules, materials andinternal loads.
� C omputer fluid dynamic simulations from air flow around
buildings for the establishment of pressure coefficient, windspeed at the openings and exterior convective heat exchangecoefficient.
� T hermal dynamic simulations of free-running environmental
conditions to the establishment of the potential of hours withoutthe need for active cooling systems (reinforcing that the maingoal was to maximize the free-running period of occupation).
� S pecification of mixed-mode settings for rooms with specific
occupation requirements or with insufficient potential fornatural ventilation.
� S imulations for both mixed-mode and fully air-conditioned
strategies.
� E valuation of the simulation results and proposal for changes in
architectural features, materials and buildings’ operation cri-teria.

2.1. Comfort parameters

Regarding the internal environmental conditions in generalworking spaces in Brazil, there are two buildings’ regulations: NR-15 [1] and NR-17 [2]. The first one refers mainly to extremely hotenvironments, such as factories, and recommends resting periodsrelated to people’s exposure to above certain indoor temperatures,whereas the second one says that the environment must beadequate to the psycho-physiological characteristics of the work-ers and to the nature of the task. For working spaces in whichintellectual demand and constant attention are required, NR-17recommends the following design parameters: effective tempera-ture between 20 8C and 23 8C; air relative humidity not inferior to40%; air speed not superior than 0.75 m/s.

With respects to the assessments of thermal performance of thebuildings from research centre to be partially of fully air-conditioned, NR-15 was not applied, as there were no cases ofgeneration of extreme internal loads. On the other hand, eventhough NR-17 applied theoretically to all environments of interestin this assessment, its parameters were impossible to be attainedin a free-running mode, in any time of the year, considering thereference year. Based on a particular 5-year weather file, areference year was created, which was used to support thebuildings’ environmental assessments. The hottest month and asummer reference design day were picked out of the original 5-year file, February 2003, for in-depth assessments of buildings’thermal performance.

Table 1RH and DBT combinations for PPD � 10%, considering M = 70 W/m2, Iclo = 0.5 clo,

to = DBT

va (m/s) RH (%) DBT (8C)

0.1 50 26.4

65 26.0

0.2 50 27.0

65 26.6

0.5 50 27.8

65 27.5

0.8 50 28.3

65 27.9


Instead, the notion of the adaptive model was explored as apossibility of achieving periods of natural ventilation in variousspaces, therefore setting up the case for the mixed-mode strategy.In that respect, the periods of natural ventilation were identifiedusing the adaptive model of Dear, Brager and Cooper [3], whilstnational and international standards and references were used forthe air-conditioned periods.

The Brazilian practice for air-conditioned design is based ontwo standards: NBR 6401, Instalacoes Centrais de Ar-Condicionado

para Conforto: Parametros Basicos de Projeto (Central Air Condition-ing Facilities for Comfort: Basic Design Parameters) [4], and onOrientacao Tecnica sobre Padroes R eferenciais de Qualidade do Ar

Interior (Technical Orientation on Air Quality Standards) by theNational Sanitary Supervision Agency (ANVISA, 2003), [5]. In bothcases, the recommended ranges for dry bulb temperature (DBT)and relative humidity (RH) are: DBT = 23–26 8C and RH = 40–65%;DBTmax = 26.5–27 8C and RHmax = 65%; DBTmax = 28 8C andRH = 70% (for access areas); and considering air velocity (va) at1.5 m: va1:5 m ¼ 0:025� 0:25 m=s.

From the international context, the following references werealso used: ISO 7730, ‘‘Moderate thermal environments: determi-nation of the PMV and predicted percentage of dissatisfied (PPD)indices and specification of the conditions for thermal comfort’’ [6]and ASHRAE-55 (1992), ‘‘Thermal Environmental Conditions forHuman Occupancy’’ [7].1

The first one, ISO 7730, estimates the PPD in a given thermalenvironment and recommends a PPD value inferior to 10–15%.However, such design parameters are limited to the followingconditions: DBT between 10 8C and 30 8C, RH between 30% and 70%and air velocity under 1 m/s. As opposed to that, ASHRAE 55 (1992)establishes a winter and a summer comfort zone, allowing for a20% PPD, which is more appropriate to the local tropical climaticconditions.

For this project, air-conditioning settings were determined byapplying ISO 7730 and correlated standards (ISO 7726 [8]; ISO8996 [9]; ISO 9920 [10], which were then confronted to theBrazilian national regulation NBR 6401 [4] and ANVISA [5].Exploratory studies were carried out in order to determine variablearrangements of DBT, RH and va with PPD inferior to 10%, to whichthe following conditions were assumed:

(a) M

1

curr

conc

asse

etabolic rate (M) for sedentary activity M = 70 W/m2 (1.2met), according to ISO 8996 [9].

(b) C
lothing thermal resistance (Iclo) of 0.5 clo. According to ISO9920 [10], the resistance of 0.5 clo is equivalent to: shirt withshort sleeves, light trousers, underwear, socks and shoes.
(c) M
ean radiant temperature assumed to be the same of the airdry bulb temperature, since roofs and walls are overshadowedand insulated. Therefore, according to ISO 7726 [8], theoperative temperature is equivalent to air temperature.
(d) A
ir velocity under 0.25 m/s for light or sedentary activitiesduring summer, if operative temperature is under 26 8C (ISO7730 [6]; ASHRAE 55(1992) [7]. For operative temperaturesabove 26 8C, air velocity should be under 0.8 m/s [7].
Based on the scenarios from Table 1, it was recommended thatthe air-conditioning settings of DBT = 26 8C, RH = 65% and va ¼0:1 m=s should comply with ISO 7730 as well as with Braziliannational regulations, what resulted in higher thermal conditionsthan the ones usually adopted by the current Brazilian practice.

During the development of this research and consultancy project (2004), the

ent version of ASHRAE 55 dated from 1992. The latest version, including the

ept of adaptive model was only officially published after the conclusion of the

ssments.

Some exploratory simulations were carried out in order todetermine the reductions in thermal loads and the consequentimpact on energy consumption of such set points. However, thefinal simulations for annual loads considered the environmentalscenario of 24 8C and 50%, as determined in the engineering designas an operation parameter for the cooling system, whereas thesettings for the sizing of the cooling systems were 22 8C and 50%.

Whether the ISO and ASRHAE standards apply to free-runningor mixed-mode spaces, it is highly debatable within the academicfield. Dear, Brager and Cooper discussed the issue in ASHRAE (RP-884) [3], based on a research experiment with 20,700 occupants of160 buildings in 9 climatically different countries, including casesfrom The United States, England, Thailand and Indonesia. Theoutcomes indicated that occupants of free-running buildings dopresent higher tolerance to internal condition variations, which areresults that Fanger adaptations in ASHRAE-55 (1992) and ISO 7730did not predict. The referred ASRHAE report (RP-884) proposes anadaptive comfort index, which brings an empirical model thatincorporates acclimatization, clothing options, behavior patternsand tolerance to climatic variability. Indoor comfort is linked to themean outdoor condition, meaning that people in hotter climatestend to accept higher temperatures than those from temperateclimates [11].

The adaptive model reflects on a more energy-efficiencyapproach, since it expands the comfort zone and increases thefree-running period. So, for free-running spaces, the comforttemperature (tc) is related to the outdoor temperature according tothe mean external effective temperature (meET*), presented as:

tc ¼ 18:9þ 0:255meET� (1)

In this case, the comfort zone ranges from (tc � 2.5 8C) to(tc + 2.5 8C) for no more than 10% of the users dissatisfied withthe thermal conditions. The results for the effective temperaturesalong the year are presented in Fig. 3.

2.2. Mixed-mode settings

Based on the recognized European know-how applied in recentprojects, indoor environments that prove to offer the minimum of30%2 of the occupation time within thermal-comfort conditions inthe free-running mode were recommended to run in mixed-mode.This means that the air-conditioning would only be switched onwhen thermal comfort cannot be achieved purely by passive means,including solar shading, thermal inertia and natural ventilation, dueto harsh external climatic conditions. Although the figure of 30% wastaken as a reference, it could not be a benchmark, since economic

2 This value is based on a general cost–benefit analysis for European projects,

since there are no benchmarks for tropical climates or for the Brazilian economic

reality.

Fig. 3. Comfort zone throughout the year, considering 90% and 80% of satisfied people.


criteria including air-condition running costs and costs of openablefacades have to be considered in the definition of such a target.

As mentioned before, among the buildings to have air-conditioning in the new research centre, the exception toacceptance of the mixed-mode approach were the special roomsfrom the Laboratories and the auditorium and the events’ roomsfrom the Convention Centre and the Center for Virtual Reality,where the requirements for a controlled environment are stricter.In the final design of buildings and systems, despite the studies onthe possibility of the mixed-mode strategy, all environments inwhich air-conditioning should be necessary for any period of theyear became fully air-conditioned due to technical, economic andcultural reasons.

The mixed-mode approach, with all the architectural featureswhich implies to it, is a new concept in Brazil. Still today most air-conditioned buildings are sealed boxes, usually with raised floorsand false ceilings, completely isolated from the exterior. Thestrategy of central air-conditioning combined with automaticoperation of windows to make natural ventilation viable in certainperiods of the year is not considered in many cases of thecommercial architecture, for technical and economic reasons.However, a similar mode of environmental control of theconventional mixed-mode is the insertion of the window air-conditioning to old free-running buildings which, despite itsextremely energy inefficiency, is still commonly found among thebest regarded clusters of office towers in Sao Paulo and Rio deJaneiro.

Nevertheless, the mixed-mode strategy brings obvious eco-nomical and environmental advantages, since it reduces air-conditioned periods and allows for subtle fluctuations of theinternal environmental conditions, which are told to be wellreceived by occupants, given the limits of a comfort zone. It alsoincreases user interaction with the outdoors environment, whichhas been proven to have beneficial psychological effects [12].Moreover, the simulation studies proved that the mixed-modestrategy results in reductions of thermal loads during the air-conditioned periods, as an effect of the natural ventilation thatprevents heat accumulation, especially during nights. Therefore,night ventilation was recommended even in environments that arefully air-conditioned during occupation time.

In this assessment, the mixed-mode strategy was characterizedby the opening of windows from an internal air temperature of20 8C, opening gradually in order to allow higher naturalventilation rates. When air temperature exceeds 26 8C all windowsare shut and air-conditioned is switched on to keep the 26 8C ortake the internal conditions down to 24 8C (according to comfortcriteria established for each occupation area). Since internal airvelocities above 0.8 m/s may cause disturbance in working

environments, the windows are also closed when external windspeed exceeds 5.0 m/s, as found in the ventilation assessments asthe threshold for acceptable internal air velocities.

2.3. Simulation procedures

The assessment of the thermal performance of buildings,including the potential for natural ventilation and the resultingthermal loads during the air-conditioning periods were deter-mined by advanced thermal dynamics’ computer simulations. Thesimulated environment is divided in a number of thermal zones,whilst the influence of neighboring rooms is taken into account. Inthat way, several thermal phenomena can be evaluated in terms ofsimultaneity, location and interaction. Building modeling is carriedout in two stages: geometry characteristics, materials specificationand occupation schedules.

For free-running environments the results from dry boldtemperature (DBT), RH and mean radiant temperature (MRT)were used in order to calculate the effective temperature for eachhour, which was compared against the comfort temperature andclassified as ‘‘Comfortable’’, ‘‘Hot’’ or ‘‘Cold’’. Air-conditionedrooms were evaluated based on annual and maximum thermalloads.

2.4. Assessment method

The results allowed for the evaluation of the thermalperformance and energy efficiency according to the followingcriteria:

1. T
he thermal-comfort periods achieved during the free-runningmode were determined according to the adaptive modelpresented in ASHRAE (RP-884) [3], considering both the 10%and 20% tolerance. The number of hours of thermal comfort aswell as discomfort for heat and cold were calculated for eachzone during occupation time.
2. T
he maximum cooling load was determined by the highestthermal load in the summer reference day, 9 February 2003, inorder to guide the design of the air-conditioning systems [13]. Itonly accounts for sensible and latent loads inside the room(disregarding serpentine loads due to air renovation). Sincethere were cases in which maximum loads in the annualsimulation were higher, these results were also presented fordemonstrative reasons. However, it is important to note that dryand wet bulb temperatures for the reference day werecompatible with the ones proposed in air-conditioning regula-tions. Adding to that, the number of hours in which the heatloads in the annual simulation exceed the ones in the reference


day simulation is never above 5% of the occupation period.Therefore, the recommendations for the sizing of mechanicalsystems followed the studies for the reference summer day.

3. A
n annual load profile was drawn by calculation of thefrequency (by intervals and cumulative) of thermal loadsyear-round. Based on that, it was recommended that thechillers would be designed to be either switched off or operatingclose to their maximum capacity, i.e., with their highest coolingefficiency.
4. T
he thermal loads breakdown for the selected environments ispresented, also for the summer reference day. It accounts forthermal loads contributions from the different buildingcomponents, allowing for the more effective changes, speciallyrelated to the design and specification of buildings’ envelope.
3. Preliminary parametric studies

The information about the preliminary parametric studies andthe building thermal assessments were taken from the technicalreport entitled CENPES-II, Arquitetura e Eco-eficiencia: Conforto e

Desempenho Termico das Edificacoes II [14].In order to inform the first stages of the architectural design in

terms of strategies for the control of the thermal conditions, anexploratory study was carried out to assess the potential for free-running buildings in the climate of Rio de Janeiro as well as thechanges in energy performance due to different air-conditioningsettings of operation. For these purpose, one of the office cells ofthe Laboratories was simulated, a typical space of the project,repeated alongside the rows of the laboratories, and where naturalventilation was accepted.

The model included three laboratories, each one defined by twooffices and one specific research room, covering from engineeringto biological themes. The case study is a typical office room,designed for two people and user’s control of air-conditioningsettings and window openings. The chosen office cell has only thenorth facade in contact with the external environment, howeverprotected from the direct solar radiation by the externalcirculation, and a top technical room. Externally it is paintedwhite, following the specifications of color as well as buildings’components applied to the other buildings of the architecturalcomplex.

The occupancy period was established from 7 a.m. to 5 p.m.,excluding weekends, according to the standard Petrobras workinghours.

The occupancy parameters considered in the thermal dynamicsimulations of the typical office space of the Laboratories’ officecells were: 2 people, plus 15 W/m2 equipment load, plus 12 W/m2

lighting. The materials and building components applied were asfollowed: windows were specified as aluminum frame andtransparent float glass of one sheet of 6 mm; the door was ofwooden panel of 3 cm; walls were of cellular concrete panel of15 cm; the floor was of concrete 2000 kg/m3 and 15 cm, plus an aircavity of 50 cm and concrete layer of 400 kg/m3 and 15 cm incontact with the soil and; the roof was plasterboard of 2 cm, plusan air cavity of 50 cm, concrete 400 kg/m3 (15 cm) and another aircavity of 100 cm and, at last, a sandwich metal panel of 15 cm.

3.1. Free-running simulations

It should be noted that design was still in an early stage and thatchanges in architecture and materials have been made afterwards(not only for the benefit of thermal performance). However,environmental design principles were already applied to this roomfor this preliminary assessment, from which the results indicate aninteresting potential for the free-running mode, ranging from 13%

to 30% of the time. With 10% of windows’ opening for 24 h a day,the comfort criteria was met for 13.50% of the occupied hours.Whereas increasing this opening for 100% of the window area theresult goes up to 30%. In the cooler months of the year, such as June,having 50% opening of the windows would led to 50% of theoccupation period in comfort hours. If internal loads aredisregarded, comfort hours can rise up to 48% of year. As apreliminary conclusion, it is possible to say that the mixed-modestrategy was proved to be a viable option for this climate,especially in cases of low internal loads.

3.2. Assessment of air-conditioned spaces

Aiming to analyze the potential for energy saving in theoperation of the air-conditioning systems, simulations werecarried out for different thermostat settings. Two environmentalscenarios combining air temperature and relative humidity wereproposed: 24 8C with 50% and 60% RH and, 26 8C with 60% and 65%RH, during the standard period of occupation (from 7 a.m. to5 p.m.).

Based on the results, it was recommended that air-conditioningshould operate to provide 26 8C of air temperature and 65% RH,which showed a reduction of 15% in the maximum cooling load and30% in the maximum dehumidification load, when compared tothe scenario of 24 8C of air temperature and 50% RH. In that context,it is worth mention that no heating loads are required giving thecharacteristics of the local climate. Given the representative area ofworking spaces in the entire project, these savings represent asignificant impact on the size of the cooling systems, which wouldimply in a series of environmental, spatial and economicadvantages.

4. Buildings assessment

Simulations of thermal dynamics were carried out in order toquantify the thermal performance of the architectural designagainst the need and the efficiency of the air-conditioning, in agroup of selected working spaces (offices) within the Laboratories,Central Building (office spaces), Convention Centre, Centre ofVirtual Reality, Restaurant, Workshop Building and the Green-house, which were spaces qualified in the design brief with therequirement of air-conditioning systems. Throughout the designprocess, a number of design changes were assessed, to optimize thethermal performance of the buildings. The most relevant cases inthe issue of modes of environmental control are described in detail,being the two main buildings of the architectural composition,which also sum up the biggest area of working spaces with thepotential to incorporate natural ventilation: the Laboratories andthe Central Building, the big office building.

4.1. Laboratories

As previously mentioned in item 3, each laboratory environ-ment is defined by one special room, two adjacent offices cells forthe researchers and a top technical room, under the roof. Two officecells located at the ends of one building (one of the laboratoryrows) facing opposite solar orientations (north and south) weresimulated (see Figs. 4 and 5).

4.1.1. First simulation scenario: analysis of the free-running mode

In the first moment, simulations were carried out to quantifythe potential for natural ventilation in the selected office cells.Based on the conclusions from the preliminary simulationassessments (which adopted the same environments as casestudies), more insulation was provided, especially regarding the

Fig. 5. Section of a typical wing of the Laboratories facing north and south orientations.

Fig. 4. Plan of a typical wing of the Laboratories highlighting the main office spaces simulated in the thermal dynamic assessment.


internal walls dividing the office cells from the special laboratoryrooms. Due to the strict environmental requirements, the speciallaboratory rooms were considered as to be fully air-conditioned atlower temperatures than the adjacent offices, therefore, the heatflow between these two spaces became an important issue for thebuilding’s thermal performance. Table 2 shows the differentmaterials and building components tested in each stage of the

Table 2Materials and building components tested of the two laboratories’ office cells

Rooms/offices First round of simulations

free-running analysis

Second round of simulatio

mixed-mode vs. full a/c

Materials

North/south Walls

Office/special room: ceramics + cement +

50 mm concrete + air gap + 50 mm

concrete, d = 2.200 kg/m3

Office/special room: cerami

cement + 50 mm concrete +

gap + 50 mm concrete,

d = 2.200 kg/m3

Office cell/office cell: gypsum + 50 mm

air cavity + gypsum

Office cell/office cell: gypsum

+ 50 mm air cavity + gypsu

External: 25 mm gypsum + 50 mm glass

wool + 25 mm concrete, d = 2.200 kg/m3

External: 25 mm gypsum +

50 mm glass wool + 25 mm


Floor

110 m concrete + 700 mm air cavity +

150 mm concrete, d = 2.800 kg/m3

110 m concrete + 700 mm

air cavity + 150 mm concre

d = 2.800 kg/m3

Ceiling/roof

Gypsum + 400 mm air cavity + 110 mm


Gypsum + 400 mm air cavi

+ 110 mm concrete, d = 2.2

Windows

Clear glazing 6 mm, aluminium frame Clear glazing 6 mm

environmental assessment, following development of the buildingdesign.

The results from the free-running mode simulations for theselected laboratories’ office cells showed the possibility of 88% thetotal yearly hours of occupation within the proposed thermal-comfort zone, without the air-conditioning on, therefore, justifyingthe introduction of the mixed-mode strategy. The changes in

ns Third round of simulations

mixed-mode analysis

Final simulations

cs +

air

Office/special room: office

cell/office cell: cellular concrete

120 mm, 500 kg/m3, plasterboard

Office/special room: office

cell/office cell: gypsum +

50 mm air gap + gypsum

m

External: light concrete 140 mm,

500 kg/m3, plasterboard

External: 120 mm laminated


te,

200 mm aerated concrete slab

d = 2.500 kg/m3, no air cavity +

impermeabiliz + cement + ceramics

200 mm aerated concrete

slab d = 2.500 kg/m3, no air

cavity + impermeabiliz +

cement + ceramics

ty

00 kg/m3

12.5 mm gypsum ceiling +

1500 mm air cavity + 150 mm

concrete slab + sandwich panel

12.5 mm gypsum ceiling +

1530 mm air cavity +

sandwich panel

Clear double-glazing 10 + 28 +

6 mm clear glazing 6 mm,

aluminium frame

Clear glazing 6 mm, aluminium

frame

Table 3Total annual loads and maximum loads of the Laboratories’ office cells: air-conditioned 26 8C–65% RH

Office/room Total annual load (MW) (air condition, a/c) Maximum load (W)

Full a/c single

glazing

Mixed-mode

single glazing

Mixed-mode

double-glazing

Full a/c single

glazing

Mixed-mode

single glazing

Mixed-mode

double-glazing

North 2.7 2.4 2.4 2.281 1.604 1.620

South 1.2 1.1 1.1 1.383 772 722

Table 4Maximum loads and total annual loads for the Laboratories’ office cells: assessment of the mixed-mode strategy

Office/room Maximum load (kW) Total load (MW)

February Annual Annual

22 8C/50% 24 8C/50% 24 8C/50% 26 8C/65% 24 8C/50% 26 8C/65%

North 1.48 1.21 1.82 1.12 2.2 1.1

South 1.57 1.29 1.87 1.26 2.2 1.2

3 The lowest air-conditioning settings studied were established in the mechan-

ical and electrical engineering design: 22 8C and 24 8C, 50% RH. Those were tested

against more tolerant thermal conditions, proposed by the environmental design,

considering 26 8C and 65% RH.


materials’ specification had a positive impact on the Laboratories’thermal performance, enabling the researchers’ office cells to relyon natural ventilation during a reasonable percentage part of theyear. This is especially significant for the case of the south-facingrow, where the better performance compared to the north-facingoffice cell is due the minor exposure to direct solar radiation andbetter exposure of its openings to the wind. Other positive aspectsof design that contributed to the results for both cases were themoderate internal loads and the relative small dimensions of theroom.

Considering the north-facing office room, the percentage of theoccupied hours of the year within the comfort zone is 55.3%,followed by 37.9% of hours when the thermal conditions areclassified as warm and 6.8% of hours classified as cold. Looking atthe south-facing room, 88.6% of the occupied hours of the year arewithin the comfort zone comfort, whereas 6.5% are classified aswarm and 4.9% as cold. Nevertheless, even though a positivethermal performance was identified, the hours of comfort could beexpanded with the introduction of internal higher thermal mass.

4.1.2. Second simulation scenario: mixed-mode versus full air-

conditioned

Following the simulations of free-running mode, this phase ofthe assessment addresses the energy efficiency of the mixed-modestrategy, comparing against the full air-conditioned operation ofthe office cells. The opening for the natural ventilation was 50% ofthe total window area. When the external climatic conditions werenot favorable, the windows would be closed and the room’sthermal conditions would be controlled with the operation of theair-conditioning system, set up at 26 8C and 65% RH (as mentionedpreviously in item 2). At this phase, the performance of cleardouble-glazing was tested against clear single glazing on theexternal windows of the rooms, for the mixed-mode strategy. Interms of integration between the environmental strategies andarchitecture, at this point of the design process, it is important tocite that the recommendation for higher internal thermal masswas not incorporated in the building’s design.

The introduction of the mixed-mode strategy has proved toenhance the thermal performance of the rooms and, therefore, itwas strongly recommended. Moreover, in-depth analyses of thethermal loads from the air-conditioning period highlighted thatthe mixed-mode caused a decrease of around 10% in the totalannual loads of both rooms, in comparison to the full air-conditioned model (with single glazing, see Table 3). Regarding themaximum loads for the system, the same trend was pointed out,

with a reduction of 30% for the north-facing office cell andapproximately 50% for the south-facing one.

On the other hand, the choice for the double-glazing against thesingle glazing did not cause a relevant reduction in terms ofinternal loads. The extra insulation effect expected from the secondlayer of glass had no significant impact during natural ventilationperiods. In this case, the double-glazing was not necessary for theimprovement of the rooms’ thermal performance. The mixed-mode results could be enhanced if higher internal thermal masswas incorporated in the design, as recommended on the previousphase of environmental assessment.

4.1.3. Third simulation scenario: mixed-mode analysis

For the following simulations, design changes regarding thecomposition of the walls of the office cells were proposed by thedesign team, by which both the external walls and the interiorpartitions were replaced by less insulated building’s components.The potential of the mixed-mode strategy in the researchers’ officecells was carried out in a greater level of detail in this stage of theenvironmental assessment. During the periods of natural ventila-tion the windows were 80% opened. For the air-conditioned hours,two different environmental scenarios were compared in anannual basis: 26 8C–65% RH and 24 8C–50% RH. With regards to thecritical summer, February 2003, two other scenarios were tested:24 8C–50% RH and 22 8C–50% RH.3 The study of lower airtemperatures and relative humidity levels during the hottestsummer month was related to environmental parameters definedin the mechanical and electrical systems’ design, especially due topick summer loads.

Regarding the air-conditioned period, the outcomes from thenorth-facing studied room showed a better performance than thesouth-facing one in terms of maximum loads (see Table 4). This factis explained by the lack of effective solar protection on the southfacade of the Laboratories’ rows, as opposed to what is seen in thenorth face, which is efficiently protected by the overhanging roof.For both office cells, significant reductions in the maximum loadswere found by comparing the two air-conditioning scenarios. Inthat sense, the raise in temperature from 24 8C to 26 8C during thehottest month impacts in a reduction equivalent to 20%, moreover,considering the rest of the year, this figure reaches 35%.

Fig. 6. Plan of the second floor of the Central Building, highlighting the main office

spaces simulated in the thermal dynamic assessment.


Following the same trend, the analysis of the total annual loadsshow a reduction of 42% by changing the air temperature settings(sensible loads), whereas the decrease of 60% is identified byincreasing the RH from 50% to 65% (latent loads). According to theresults, the potential period of natural ventilation within themixed-mode during working hours, happens between May andSeptember, keeping the air-conditioning design parameters at24 8C and 50% RH. Pushing the air-conditioning energy perfor-mance higher, the operation at 26 8C and 65% RH proved to expandthe natural ventilation period by one extra month, which isequivalent to a 10% reduction in the air-conditioning hours.

The windows were considered fully opened for nighttimeventilation from 17 h to 7 h, therefore, it is understood that the realtotal period of natural ventilation is expected to be higher than theresults from the simulations. It is worth highlighting that thenighttime ventilation has the positive impact in the reduction ofloads during the air-conditioning hours. Having said that,considering 24 8C of air temperature and 50% of RH, the resultsof annual percentage of natural ventilation during the occupiedhours in the north-facing room is 12.2%, being similar in the south-facing room, 13.3%. Changing the set point parameters for 26 8C ofair temperature and 65% of RH, the results of annual percentage ofnatural ventilation during the occupied hours are better, raising to21.2% in the north-facing room and 23.1% in the south-facing one.

However, the simulation studies consider the number of hoursof natural ventilation only during the occupation time, therefore, itdoes not add the number of nighttime natural ventilation.

4.1.4. Final simulations

Final analyses were developed to evaluate changes introducedby the architectural design, which were mainly recommendedbased on construction criteria. The external walls of the office cellswere replaced by pre-cast concrete panels of 12 cm thick, withplasterboard cladding on the internal surface and cement on theexternal. On the other hand, the internal walls were specified as thedry wall system (Fig. 7). Following these changes, the potential ofthe mixed-mode strategy in the office cells was re-assessedthrough simulation. Another major change in the simulationmodel was the opening of the windows for the natural ventilationwhich was decreased to 50%, instead of the previous 80%, based onthe detail of window frames’ design. Regarding the air-condition-ing hours, the final assessment of the rooms’ annual performanceconsidered the conditions of 24 8C and 50% RH. The thermostatsettings were also assessed for the maximum loads during thehottest month, including a second scenario of 22 8C and 50% RH, asdefined in the mechanical and electrical design.

The results showed an increase in the thermal loads during theair-conditioned periods with the changes in the building’smaterials and air-conditioning operation parameters in bothrooms. The maximum loads were still higher in the south-facingoffice cell, as a result of the impinging direct solar radiation. Inorder to optimize its performance, there should be provided astrategy to block the direct radiation during some hours of the day,and consequently reduce the solar gains in the room. It is possible

Table 5Maximum loads and total annual loads for the Laboratories’ offices: final

simulations

Office/room Maximum load (kW) Total load (MWh/)

February Annual Annual

22 8C/50% 24 8C/50% 24 8C/50%

North 2.29 1.76 2.3

South 2.45 1.91 2.3

to see in Table 5 the maximum loads for the hottest month,February 2003, represented the most significant raise in both casestudies, reaching up to 50% compared to the previous results. Inparallel to that, the annual total loads increased in 5%, equivalent to1 MW h for each office.

Regarding the natural ventilation periods within the mixed-mode strategy, the changes in building’s material specificationscaused an increase of around 15% on the potential periods fornatural ventilation, occurring between May and October, in bothoffice cells due to changes in the final thermal balance, with the air-conditioning set at 24 8C and 50% RH. In addition, such increase hasa compensatory effect against the raise in thermal loads for the air-conditioned periods.

4.1.5. Design parameters for the air-conditioning system4

The air-conditioning systems of the Laboratories including theattached office cells, the air temperature of 22 8C (�1 8C) wasadopted as the design criteria for thermal comfort, with no control ofrelative humidity and 100% intake of fresh air, due to use’srequirements. In this case, it is observed a relevant discrepancybetween the parameters tested in the environment and energy andthe final mechanical and electrical design. It was argued by both theconsultant engineers and the client that the occupants of thelaboratories will use heavy cloths, as a consequence of the specificityof such spaces; therefore, the set up of 24 8C for the air temperaturewas likely to be perceived as hot and uncomfortable by the occupants.On the other hand, the fact that there is no control of relativehumidity, will bring a significant positive impact in the overall energyconsumption of the system, especially given the hot-humid condi-tions of the local climate. In terms of intake air, the air-conditioningsystem provides 100% of fresh air.

4 Information provided by the engineers from MHA Engenharia, from Sao Paulo,

the consultant engineers for the design of the mechanical and electrical systems of

research centre’s new buildings.

Fig. 7. Section of the Central Building facing east and west orientations.


With special regards to the office cells, the mixed-modeapproach was also discarded in the design of the air condition,based on the same argument of risks of discomfort. However, withthe design of operable windows and the zoning of the distributionof air (one fun coil to each laboratory unit), the choice for naturalventilation is ultimately given to the occupants.

As a last point, it was highlighted by the mechanical andelectrical consultants that the energy efficiency of the air-conditioning systems in the Laboratories depends on a final

Table 6Materials and building components tested on the simulations of the offices from the C

Building Rooms/offices First round of simulations

free-running analysis

Second round of sim

mixed-mode vs. full

Materials

Walls

Central Building External: 25 mm gypsum + 50 mm

glass wool + 25 mm concrete,

d = 2.200 kg/m3

External: 25 mm gyp

glass wool + 25 mm

d = 2.200 kg/m3

Internal: gypsum + 50 mm air

gap + gypsum

Internal: gypsum + 5

gap + gypsum

West 1st floor/

east 2nd floor

Floor

Raised carpet floor (metal +

120 mm concrete d = 2.200 kg/m3

+ 375 mm air gap + metal + carpet)

Raised carpet floor (

120 mm concrete d

+ 375 mm air gap +

Ceiling

Gypsum + 400 mm air gap + 110

mm concrete d = 2.200 kg/m3

Aluminium + 950 m

steel + 150 mm con

d = 2.500 kg/m3

Windows

Clear glazing 6 mm,

aluminium frame

-Clear glazing 6 mm

-Clear double-glazin

Canopy 51 sandwich

panel

Clear glazing 6 mm Perforated metal pa

sandwich panel and

glass in the center

refined set up of its criteria, accordingly to the specific purpose ofeach Laboratory, which were not revealed by Petrobras during thedevelopment of the design project.

4.2. Central Building

Composed by working spaces, this is a lifted linear building245 m long, orientated towards east and west. The building designis defined by two parallel wings divided by an internal open

entral Building

ulations

a/c

Third round of simulations

mixed-mode and a/c analysis

Final simulations

sum + 50 mm

concrete,

External: aluminium + 200

mm air gap + 50 mm rock

wool + aluminium

External: gypsum + 50 mm

rock wool + 200 mm air

gap + aluminium

0 mm air Internal: idem. Partitions:

10 mm foam/textile + 15 mm

metal sheet + 25 mm rock

wool + 7 mm air gap + 15 mm

metal sheet + 10 mm

foam/textile

Internal: idem. Partitions:

idem

metal +

= 2.200 kg/m3

metal + carpet)

Raised carpet floor (metal +

120 mm concrete

d = 2.200 kg/m3 + 375 mm

air gap + metal + carpet)

Raised carpet floor

(metal + 120 mm

concrete d = 2.200 kg/m3

+ 375 mm air gap +

metal + carpet)

m air gap +

crete

Aluminium + 950 mm air gap

+ steel + 150 mm concrete

d = 2.500 kg/m3

Aluminium + 950 mm

air gap + steel + 150 mm

concrete d = 2.500 kg/m3

-Clear glazing 7 mm -Clear glazing 8 mm

g 10 + 28 + 6 mm -Green glazing 7 mm -Green glazing 8 mm

-Clear double-glazing 10 + 28 + 6 mm

nel (40%void) +

6 mm green

Perforated metal panel (40%void) +

sandwich panel and 7 mm green

glass + central shed (30% opening)

Perforated metal panel

(40%void) + sandwich

panel and 7 mm green

glass + central shed

(30% opening)


corridor, supported by vertical circulation axis. Non-symmetric,the east wing of offices is a two-storey high block and the westwing is only one storey, with terraces at the top level of each wing.A big roof covers the entire building, shadowing the terraces belowand, therefore, the office blocks. Due to its central position, thisbuilding crosses the site and the building complex on the north–south direction, linking the Convention Centre, the Laboratoriesand the big Restaurant at ground level (Figs. 6 and 7).

4.2.1. First simulation scenario: analysis of the free-running mode

Initially, simulations to assess the potential of the free-runningmode were carried taking two selected office spaces of the CentralBuilding, located in different floors and opposite orientations, asillustrated in figure. Each selected office space has 665 m2 of usablearea and a floor to ceiling height of 2.80 m. At the first phase of thearchitectural design, the office spaces in the Central Building weremainly characterized in construction terms by light weight andinsulating materials, with external white metallic cladding andclear single glazing windows.

The choice of materials was in accordance with the firstqualitative evaluation of the building’s exposure to the acousticconditions of the site. Acoustic issues were especially significantdue to the building’s orientation, facing a heavy traffic highwaywhere an elevated rail line will be placed in the near future. Theissue of acoustics’ performance in the working space is aggravatedby the open plan configuration.

With special regards to the roof, it was firstly conceived as a bigmetallic perforated layer over the building, allowing some‘‘filtered’’ light to reach the terraces beneath as well as air flow,defining a partially covered open space. Still in this first stage of theenvironmental assessment, the original roof was tested against amore enclosed solution, in which opaque sandwich panels withglass panels would protect the terraces from rain and still allow forthe penetration of some solar radiation, however, minimizingenvironmental diversity (see Table 6).

The simulations considered 50% of the windows’ area openedduring the working hours, which went up to 100% during the non-occupied hours, that is to say, the nighttime period (i.e., from 17 hto 7 h). During weekends and holidays, the windows were set tobe fully opened as well, allowing for natural ventilation 24 h aday.

The simulations of the free-running mode for the office spacesin the Central Building resulted in a considerable percentage ofhours in the year within the comfort zone, highlighting theimportance of having openable windows in the offices. Anotherrelevant outcome was the increase in the thermal performance ofthe office rooms considering the big roof of sandwich panels, whichwas 20% higher than the results obtained with the solution of glassand metallic perforated panels. Nevertheless, the positive results inthermal comfort of the office rooms have to be evaluated againstthe impact of such design solution in the quality, meaningenvironmental diversity, of the open environmental of the terraces,including the losses in daylight penetration. The options for thedesign and specification of the big roof over the Central Buildingwere also assessed according to outdoor comfort criteria anddaylight performance. % of the year (working hours) west (first

Table 7Total annual loads and maximum cooling loads for the east and west office rooms of t

Office/room Total annual load (MW)

Full a/c single glazing Mixed-mode single glaz

East 37.9 39.4

West 40.3 42.1

floor) 2.2% cold 59.3% warm 38.5% comfort east (second floor) 1.3%cold 62.2% warm 36.5% comfort.

In those simulations, the windows were considered openedduring the total period of time, and because of that it might beconsidered that the ‘‘cold’’ hours could become ‘‘comfort’’ hourssimply by controlling the room ventilation rates. Hence, it ispossible to say that there is a potential for those offices to rely onnatural ventilation for approximately 40% of the year. Finally, itwas concluded that a great deal of thermal loads has been gainedthrough the glazed surface area of the internal facades of the officewings, which face the opened long circulation.

4.2.2. Second simulation scenario: mixed-mode versus full air-

conditioning

Based on the results of the simulations for the free-runningmode, in this phase it was tested the potential of the mixed-modeenvironmental strategy, in comparison with the option of fully air-conditioned offices, in terms of energy efficiency. Following thesame parameters used on the simulations for the Laboratories’office cells, it was also tested the double-glazing in comparisonwith the clear single-glazing windows. For acoustic reasons thewindows placed on the west facade of the west wing of thebuilding were considered all fixed, therefore, the possibility ofnatural ventilation on these offices could only be possible throughthe windows facing the internal open circulation.

As the architectural design developed, changes regarding thebig roof of the Central Building were proposed and tested. In thatrespect, a composition of the two previous options was technicallyassessed in terms of its environmental performance, looking atdaylighting, glare and thermal conditions. The roof’s overhangingtowards the west orientation was kept permeable to some solarradiation and, therefore, to daylighting penetration, as a linearcontinuous louvered brise soleil (see and Table 6).

As concluded in the assessment of the Laboratories’ office cells,the option of double-glazing windows instead of the single glazedones did not show relevant improvements in terms of thermal-comfort conditions, therefore, it was not recommended in theenvironmental report. On the other hand, the roof solution of thecentral part (half of the roof’s area) covered by sandwich panelsand the rest in perforated metallic panels had a positive impact inthe reduction of solar gains.

Regarding the energy efficiency of the control of the thermalenvironments, the mixed-mode approach was proved to con-tribute to the reduction of the offices’ thermal loads, as shown inTable 7. On the other hand, the total annual loads were slightlyincreased in the case of the mixed-mode strategy against the fullair-conditioning, being 1% in the east office room and 5% in thewest office (which presents fixed external windows and conse-quent smaller rates of natural ventilation, extending the air-conditioned period within the mixed-mode strategy). In thatrespect, it must be underlined that the results for the west roomwere also influenced by the shading devices’ permeability to solarradiation.

Concluding this phase of the assessment, the architecturaldesign configuration and the operation parameters of the roomshad a great impact on the mixed-mode results. According to that, it

he Central Building: a/c: 26 8C and 65% RH

Maximum load (W)

ing Full a/c single glazing Mixed-mode single glazing

33.738 32.010

34.703 33.962


was strongly recommended that specific aspects of the building’sdesign should be reviewed. The most significant case for changewas the reduction of the glazed area facing the internal opencirculation, through which the most relevant solar gains wereidentified. In terms of control of the thermal conditions, it wasstressed in the environmental recommendations that west wing ofthe offices should be fully air-conditioned. Particularly in this case,the double glaze windows were recommended for both facades ofthe west wing to improve energy efficiency of the air-conditioning.

4.2.3. Third simulation scenario: mixed-mode versus air-conditioning

For the following studies there have been tested lightweightwalls with external aluminum cladding and internal thermal andacoustic insulation, together with ceilings with acoustic absorbersand floor to ceiling internal partitions, according to last designchanges. In addition, it was included an linear opening in the bigroof, along the building’s length of 245 m, for exit of air flows asrecommended in the assessment of outdoors’ comfort. This wasintended to avoid possible heat accumulation underneath thatlarge surface (see Table 6). According to the latest conclusions, theapplication of green glass on the internal facades of both east andwest office wings, oriented towards the internal open circulation,and clear glass on the external facades, was tested and compared tothe application of clear single glaze on all windows.

Based on the previous results, the west office was consideredfully air-conditioned, having the windows closed during all theoccupation time. For this case, the use of double-glazing was testedagain, in order to increase thermal insulation against the externalclimatic variability. On the other hand, the mixed-mode strategywas still investigated for the office room in the east wing of thebuilding. An evaluation of the potential natural ventilation withinthe mixed-mode strategy was also carried out.

Considering the east office wing operating in the mixed-modestrategy, the use of green glass on the windows of the internalfacade, having the air-conditioning set at 26 8C and 65% RH,resulted in a 3.8% reduction in the total annual cooling loads, asopposed to the use of clear glazing on both facades of this officewing, as shown in Table 8. This was similar to the performance ofthe double-glazed windows tested for both facades, equivalent to a2.7 kW h/m2 savings; therefore, the choice for the single greenglass was emphasized.

The evaluation of the different environmental control strategieswithin the mixed-mode showed that the east office would rely onnatural ventilation just for the first morning hours of the day,representing almost 10% of the year. During the rest of the year, theair-conditioning would be switched on. Regarding the mixed-mode performance, the limitations of computer modeling must betaken into account (see Section 4.1.3). Having said that, the resultsshould be more optimistic in the real situation than it waspresented for the simulations. As expected, the air-conditioningsettings that were tested caused relevant impacts on the east wingoffice. A change in the operation parameters from 26 8C and 65% RHto 24 8C and 50% RH reflected in 28% increase in the room’s totalannual loads.

Table 8Total annual loads for the east and west office rooms, with different glazing types

and air-conditioning settings

Office/room Total annual load (MW h)

Clear single glazing Clear + green single glazing

26 8C/65% 26 8C/65% 24 8C/50%

East (mixed-mode) 58.8 57.0 79.1

West (full a/c) 62.9 61.8 81.3

Regarding the west office, which was recommended to be fullyair-conditioned, the test with the double-glazing presented areduction of 2.% of the total loads compared to the option of clearsingle-glazing on both facades, one facing the west orientation andthe other one facing the internal circulation. Nevertheless, thethermal performance of the room in terms of total annual loadscould be considered similar to the outcomes with double-glazing onwindows on both facades, or also to the use of green glass only on theinternal facade (which showed a reduction of 2.%). In parallel to that,technical assessments on daylighting were carried out for the offices,showing minor impact in terms of daylighting access into this roomwith the green glass windows, compared to the simulationsapplying clear double glazed windows on both facades.

Likewise, as a consequence of the balance between thermal andlight performance, green glass windows from the internal facadesof the office room from east wing is highly recommended. In termsof energy performance of the air-conditioning, the two differentsettings resulted in relevant impacts on the west wing office. In thiscase, 24% increase was in the total annual loads was identifiedaccording to the conditions of 24 8C and 50% RH, compared to 26 8Cand 65% RH. Therefore, the more tolerant condition wasrecommended for both east and west offices.

4.2.4. Final simulations

The final simulations focused on two changes in the specifica-tion of building’s materials proposed in the detailing phase of thearchitectural design. The first one was the incorporation of gypsumpanels in the interior cladding on the offices’ external walls. Thesecond was concerned with the specification of the glass: all glasspanels, both clear and green, would be 8 mm thick instead of 7 mm,as specified in the intermediate environmental report for theoptimum acoustic performance, however, for structural reasons(see Table). The changes in specification proved not to impact inthe thermal performance of the offices in comparison with theprevious assessments. These changes were tested for the samestrategies for control of the thermal environments, being themixed-mode approach to the east room and the fully air-conditioned environments on the west, therefore, the conclusionsremain the same from the previous simulation studies.

4.2.5. Design parameters for the air-conditioning system

On the Central Building, the air-conditioning concept for theworking spaces is via under floor, which is an unusual solution forcommercial local buildings. According to the mechanical andelectrical consultants, some key aspects of the architectural designdirected the approach to the under floor solution: the shallow planand the building’s envelop protected from the direct solar radiationand well insulated, as these features had a major impact inreducing heat gains. The designed air temperature was set to 24 8C(�1 8C) and, as established for the Laboratories, there is no directhumidity control of the internal environmental conditions, for thepurpose of maximizing the energy efficiency of the system. In order toachieve the design temperature of 24 8C, the inlet air temperature of14 8C was identified to remove the necessary humidity to achievecomfort conditions, maintaining the relative humidity levels between50% and 55%.

Despite the fact that the recommendations for the designparameters from the environmental assessments were notcompletely incorporated in the final design of the air-conditioningsystems, the adoption of the under floor inlet system, together withthe strategy of not controlling directly the relative humidity willcertainly result in positive impacts in the energy consumption forthe environmental control of the working spaces. In terms of intakeair, the air-conditioning system provides 30% of fresh air connectedto a CO2 monitoring control, according to local standards.


The internal open circulation, which gives access to the workingspaces through the central part of the building, was treated as aunique space, with a system of mechanical air supply at 20 8C,reaching the occupants usable height, without any specific controlof the thermal conditions. The result is the creation of a transitionalzone, where there is no direct incidence of solar radiation, betweenthe exposed external environment and the air-conditioned interiorspaces.

5. Final considerations

This experience of developing this consultant and researchproject represented an innovative approach towards the assessmentof thermal performance during the design of buildings in theBrazilianpractice.Addedtothat, italsobroughttothediscussionnewproposals for building’s components and parameters of artificiallycontrolled environmental conditions that which should be dis-seminated throughout the national practice. Interaction betweenenvironmental strategies and the main architectural principlesbegan at the conceptual stage, whilst more detailed designenvironmental requirements from the occupation parameters wereintroduced later in the design process, as a decision from the users.

The final thermal performance of the air-conditioning buildingsof the new research centre of the Brazilian Petroleum Company isdefinitely better than that of conventional office buildings in thecity. In parallel to that, the lack of benchmarks, standards andregulations for energy efficiency in buildings in Brazil, imply in amajor lack of interest for more initiatives for better buildings’environmental performance.

Regarding to the methodological approach, this work bringstwo innovative steps, given the current Brazilian building’s designpractice. The first one is the application of the adaptive comfortindex, which was officially published by ASRHAE, in 2004, shortlyafter the beginning of this project. The choice for advanced thermaldynamic simulations was another innovative position for thestudies of the environmental design, which was equally adequateto the overall purposes of this project, despite its limitations for thesimulation of the mixed-mode strategies.

With special concerns to the Central Building, although thearchitectural design was technically supported by the environ-mental assessments in order to maximize the passive strategies,the architectural quality of the working spaces seen in the finaldesign became similar to those from the commercial local goodpractice, defined by raised floors and false ceilings, due to users’references of the conventional culture of the office environment. Asopposed to that, the major environmental asset of the building’sdesign is on the facades, with regards to the window wall ratio(WWR) and solar protection devices, which were detailed aimingfor the best energy performance. Looking at the laboratories’ officecells, its spatial small dimensions and relatively small internalloads, together with the internal thermal mass in the floor madepossible the achievement of relatively better outcomes in terms ofthe introduction of natural ventilation.

With respects to the technology of the buildings’ air-condition-ing system, to improve the energy efficiency and, moreover, toreduce its environmental impact, absorption chillers wererequested by Petrobras, however, electrical chillers were alsointroduced as a back up system. Nevertheless, based on theexperience of the local consultants on mechanical and electricalengineer, the technology of absorption chillers has no economicadvantages in the current national building sector and, for thisreason, it is not commonly used in Brazil. Still about the technicalaspects of the air condition and the attitude towards energyefficiency, the strategy of heat recovery, which is largely used inEuropean buildings, was not considered for economic reasons.

The concern to energy efficiency is also present to the zoning ofthe systems. Having said that, the distribution of the air, which willbe controlled by an automated building management system, iszoned accordingly to the specific needs of the different buildings:Laboratories, Central Building, Convention Centre, Workshops andCentre for Virtual Reality.

Besides all the objectives and achievements on the thermalperformance of buildings, with respect to the issue of energy, ingeneral, the local power plant (part of the research centre’sprogramme), was designed to supply the triple of the demand ofthe total demand from buildings’ complex, for security reasons.The basis of the power plant is equally shared on three sources:electricity, gas and diesel. In terms of clean energy, the area ofphotovoltaic panels over the Laboratories’ roofs showed a verymodest energy generation. In that respect, this technology wasapplied more as a gesture than as an effective strategy.

Acknowledgements

Thanks to Klaus Bode, director, and the PhD engineers AllanHarris and Niel Campbell, from BDSP Partnership in London, for allthe support with respects to the simulation studies. Thanks also toProfessors Marcia Alucci, Anesia Barros Frota and Fulvio Vittorinofor the major collaboration with regards to the methodology andanalysis of the technical data. Finally, thanks to Petrobras, forauthorising the publication of the information presented in thispaper.

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[10] ISO (International Organization Standardization), ISO 9920, Ergonomics of theThermal Environment: Estimation of the Thermal Insulation and EvaporativeResistance of a Clothing Ensemble, ISO, Geneve, 1995.

[11] Nike Baker, M. Standeven, A behavioral approach to thermal comfort assessmentin naturally ventilated buildings, in: CIBSE National Conference. Proceedings. . .,1995, pp. 76–84.

[12] Peter Hoppe, Different aspects of assessing indoor and outdoor thermal comfort,Energy and Buildings 34 (2002) 661–665, Elsevier, 2002.

[13] LABAUT (laboratorio de conforto ambiental e eficiencia energetica do departa-mento de tecnologia da FAUUSP), CENPES-II, Arquitetura e Eco-eficiencia: Clima,Insolacao e Indices de Conforto (Relatorio tecnico de acesso restrito, etapas 2-3/Technical Report, phases 2-3), FAUUSP, Sao Paulo, 2004.

[14] LABAUT (Laboratorio de Conforto Ambiental e Eficiencia Energetica do Departa-mento de Tecnologia da FAUUSP), CENPES-II, Arquitetura e Eco-eficiencia: Con-forto e Desempenho Termico das Edificacoes II (Relatorio tecnico final de acessorestrito, etapas 2–4/Technical Report, phases 2–4), FAUUSP, Sao Paulo, 2004.

Rafael Silva Brandao He was an architect and urbanist from the Federal University

of Minas Gerais, Faculty of Architecture and Urbanism, FAUUMG, Belo Horizonte,

Brazil. He was a PhD student from FAUUSP, researcher and consultant at LABAUT,


the Laboratory of Environment and Energy Studies from the Department of

Technology of FAUUSP.

Monica Pereira Marcondes She was an architect and urbanist from the University

of Sao Paulo, Faculty of Architecture and Urbanism, FAUUSP, Sao Paulo, Brazil. She

was a PhD student from FAUUSP, researcher and consultant at LABAUT, the

Laboratory of Environment and Energy Studies from the Department of Technology

of FAUUSP.

Denise Duarte She was a PhD professor in Architecture and Urbanism from the

University of Sao Paulo, Brazil, Faculty of Architecture and Urbanism (FAUUSP),

Department of Technology. She was a research coordinator at the Laboratory of

Environment and Energy Studies from the Department of Technology of FAUUSP

(LABAUT).

Joana Carla Soares Goncalves She was a PhD professor in Architecture and

Urbanism from the University of Sao Paulo, Faculty of Architecture and Urbanism

(FAUUSP), Department of Technology, Sao Paulo, Brazil. She was a research

coordinator at the Laboratory of Environment and Energy Studies from the

Department of Technology of FAUUSP (LABAUT).

Gisele S. De Benedetto She was an architect and urbanist from the University of Sao

Paulo, Faculty of Architecture and Urbanism, FAUUSP, Sao Paulo, Brazil. She was a

MSc architect in Environmental, Energy and Sustainable Design from the University

of Sao Paulo, Faculty of Architecture and Urbanism, FAUUSP, Sao Paulo, Brazil,

practicing architect at Ipiranga S.A., Rio de Janeiro, Brazil.

Jose Ovidio Ramos He was an architect and urbanist from the University of Mogi

das Cruzis, Faculty of Architecture and Urbanism, FAU-MC, Sao Paulo, Brazil. He was

a MSc architect in Environmental, Energy and Sustainable Design from the

University of Sao Paulo, Faculty of Architecture and Urbanism, FAUUSP, Sao Paulo,

Brazil, researcher and consultant at LABAUT, the Laboratory of Environment and

Energy Studies from the Department of Technology of FAUUSP.

the new research centre of the brazilian petroleum company in rio de janeiro, brazil: the...

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