**6. Air conditioned spaces**

This work looks at the thermal performance of the specific areas within the air conditioned buildings which have the potential to be naturally ventilated for parts of the year: the office cells of the laboratories and the working spaces of the main office building. The assessment of the air conditioned and mixed-mode spaces followed the main procedures described for the analysis of the naturally ventilated environments, with the inclusion of some specific studies:

Environmental Design in Contemporary Brazilian Architecture:

The Research Centre of the National Petroleum Company, CENPES, in Rio de Janeiro 47

c. mrt (mean radiant temperature) = dbt, since the envelopes are shadowed and/or

d. va < 0.25 m/s for light or sedentary activities during summer, if to < 26 oC (ISO 7730;

In summary, the recommended air-conditioning settings considered dbt = 26 oC, rh = 65% and va = 0,1m/s, complying with ISO 7730 and the Brazilian national regulations, what resulted in higher air temperatures than those frequently adopted by the current Brazilian

A mixed-mode strategy, alternating natural ventilation and active cooling was suggested for the office cells of the laboratory buildings and the specific areas of the main office building, where a minimum of 30%3 of the occupation time was found to be within thermal comfort conditions in the free-running mode. The parameters adopted in this assessment for the

a. window opening at tbs=20 oC, with a gradual increase in the natural ventilation rate; b. window closing and air-conditioning activation at tbs>26 oC, keeping an indoor tbs of 26 oC ou 24 oC (according to the comfort criteria established for each occupation area);

c. window closing when external wind velocity va≥ 5.0m/s, as found in the ventilation

A comparative analysis of thermal performance and energy efficiency of the various

a. the periods of comfort during the free running mode were determined by the adaptive comfort model [22, 23], for a dissatisfaction index of 10% and 20%; the percentage of hours of "comfort", "warm" or "cold" was calculated for each thermal zone during the

b. the maximum thermal load was established by the highest load of the design reference day, and it was provided to inform the sizing of the air-conditioning system; only the internal loads were considered (regardless of the air exchange loads in the coil). It is worth to notice that the thermal loads' values of the annual assessments which exceed the simulations of the reference day are never superior to 5% of the occupation period; therefore, the recommendations for the sizing of the air-conditioning system follow the

c. a profile of annual loads created based on the frequency of occurrence (both

d. a profile of cooling loads of the selected spaces was also created for the reference day.

3 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 [30]. Although the figure of 30% was taken as a reference, it could not be a benchmark, since economic criteria including air-conditioning running costs as well as the associated costs of

accumulated and by intervals) of thermal loads during the year; and

assessments as the threshold for acceptable internal air velocities.

solutions was carried out according to the following criteria:

ASHRAE 55). Above 26 oC, air velocity should be under 0.8 m/s.

insulated. Therefore (ISO 7726) to = tbs; and

practice.

and

mixed-mode strategy were:

occupied time;

reference day recommendations;

operable façades have to be considered in the definition of such a target.


With respects to the thermal comfort parameters for air conditioned spaces, air conditioning settings were established based on the international standard ISO 7730 [24] and the correlated regulations ISO 7726 [25], ISO 8996 [26] and ISO 9920 [27], and compared with the Brazilian national regulations.

ISO 7730 estimates the predicted percentage of dissatisfied people (PPD) in a given thermal environment and recommends a PPD value inferior to 10%. However, such design parameters are limited to the following conditions: dbt between 10 oC and 30 oC, rh between 30% and 70% and air velocity under 1 m/s. Within the context of the national standards, as previously presented for the naturally ventilated buildings at the time of the project there were two buildings' regulations concerning the internal environmental conditions in general working spaces, NR- 15 [20] and NR 17 [21]. For the air conditioned spaces, there were two other national standards: NBR 6401 [28] and the *Orientação Técnica sobre Padrões Referenciais de Qualidade do Ar Interior* (Technical Orientation on Air Quality Standards) by the National Sanitary Supervision Agency, ANVISA [29]. In both cases, the recommended ranges for dry bulb temperature (dbt) and relative humidity (rh) are: dbt = 23–26oC and rh = 40–65%; dbtmax = 26.5–27 oC and rhmax = 65%; dbtmax = 28 oC and rh = 70% (for access areas); and considering air velocity at 1.5 m (va.1,5m) = 0,025- 0,25m/s. Based on the previous references, exploratory studies considered combinations of dbt, rh and va for a PPD inferior to 10%, assuming:


c. mrt (mean radiant temperature) = dbt, since the envelopes are shadowed and/or insulated. Therefore (ISO 7726) to = tbs; and

46 Energy Efficiency – The Innovative Ways for Smart Energy, the Future Towards Modern Utilities

This work looks at the thermal performance of the specific areas within the air conditioned buildings which have the potential to be naturally ventilated for parts of the year: the office cells of the laboratories and the working spaces of the main office building. The assessment of the air conditioned and mixed-mode spaces followed the main procedures described for the analysis of the naturally ventilated environments, with the inclusion of some specific

a. in addition to the annual performance assessment, specific studies were developed for the critical summer month of the weather file (February 2003), aiming to analyze the

b. comfort parameters different from the ones used for the natural ventilated buildings

c. thermal dynamic simulations: were first carried out with the software TAS without the air conditioning mode, in order to determine the potential number of hours in comfort; d. subsequently, the loads for the air conditioning and mixed-mode strategies were

e. finally, the results were analysed and changes were proposed in the architectural design, materials and criteria of operation of buildings in order to increase the naturally ventilated hours and improve comfort conditions, where possible, and reduce cooling loads where air conditioning was necessary either for part or the total time of the year.

With respects to the thermal comfort parameters for air conditioned spaces, air conditioning settings were established based on the international standard ISO 7730 [24] and the correlated regulations ISO 7726 [25], ISO 8996 [26] and ISO 9920 [27], and compared with the

ISO 7730 estimates the predicted percentage of dissatisfied people (PPD) in a given thermal environment and recommends a PPD value inferior to 10%. However, such design parameters are limited to the following conditions: dbt between 10 oC and 30 oC, rh between 30% and 70% and air velocity under 1 m/s. Within the context of the national standards, as previously presented for the naturally ventilated buildings at the time of the project there were two buildings' regulations concerning the internal environmental conditions in general working spaces, NR- 15 [20] and NR 17 [21]. For the air conditioned spaces, there were two other national standards: NBR 6401 [28] and the *Orientação Técnica sobre Padrões Referenciais de Qualidade do Ar Interior* (Technical Orientation on Air Quality Standards) by the National Sanitary Supervision Agency, ANVISA [29]. In both cases, the recommended ranges for dry bulb temperature (dbt) and relative humidity (rh) are: dbt = 23–26oC and rh = 40–65%; dbtmax = 26.5–27 oC and rhmax = 65%; dbtmax = 28 oC and rh = 70% (for access areas); and considering air velocity at 1.5 m (va.1,5m) = 0,025- 0,25m/s. Based on the previous references, exploratory studies considered combinations of dbt, rh and va for a PPD inferior to 10%, assuming:

a. Metabolic rate (M) for sedentary activity (ISO 8996) M = 70 W/m2 (1.2 met);

trousers, underwear, socks and shoes);

b. Clothing thermal resistance Iclo (ISO 9920) of 0.5 clo (shirt with short sleeves, light

maximum thermal loads and the heat flows through the building envelop;

were established for the air conditioned spaces;

**6. Air conditioned spaces** 

studies:

simulated;

Brazilian national regulations.

d. va < 0.25 m/s for light or sedentary activities during summer, if to < 26 oC (ISO 7730; ASHRAE 55). Above 26 oC, air velocity should be under 0.8 m/s.

In summary, the recommended air-conditioning settings considered dbt = 26 oC, rh = 65% and va = 0,1m/s, complying with ISO 7730 and the Brazilian national regulations, what resulted in higher air temperatures than those frequently adopted by the current Brazilian practice.

A mixed-mode strategy, alternating natural ventilation and active cooling was suggested for the office cells of the laboratory buildings and the specific areas of the main office building, where a minimum of 30%3 of the occupation time was found to be within thermal comfort conditions in the free-running mode. The parameters adopted in this assessment for the mixed-mode strategy were:


A comparative analysis of thermal performance and energy efficiency of the various solutions was carried out according to the following criteria:


<sup>3</sup> 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 [30]. Although the figure of 30% was taken as a reference, it could not be a benchmark, since economic criteria including air-conditioning running costs as well as the associated costs of operable façades have to be considered in the definition of such a target.

Preliminary parametric investigations were carried out for a typical office cell of one of the laboratory buildings to provide an overview of the possibilities and limitations of a mixedmode approach in such spaces (see figure 22). The test-room was in the most exposed side of the laboratory buildings, with one exposed façade towards the west, however with openings shaded, opaque surfaces with light colour finishing and with a maximum occupancy of two people. Simulation parameters included north and south orientated offices, and the possibility of users' control of both windows for natural ventilation and the air-conditioning system. The specification of materials applied in these simulations are described in table 11.

Environmental Design in Contemporary Brazilian Architecture:

The Research Centre of the National Petroleum Company, CENPES, in Rio de Janeiro 49

The results of the preliminary assessment indicated a potential annual period of natural ventilation ranging from 13% to 30%, higher values were found with the inclusion of thermal mass, adding thermal inertia to the internal spaces and considering the entire window as a ventilation aperture, opened for 24hrs during the days of thermal comfort conditions [3]. Excluding the hottest period of the year (from December to February), the performance of natural ventilation increases to 50% of the occupied hours. Based on such results, the mixed-mode strategy has proved to be a positive approach, especially for environments with low internal gains. Furthermore, regarding the set points of the air-conditioning system, the exploratory simulations showed a total reduction in thermal loads of 22% for set point conditions of 26 oC and 60% rh, compared to the scenario of 24 oC and 60% rh, therefore showing the significant impact of comfort standards on building energy efficiency, in the specific case of the Petrobras Research

More in-depth spaces of comparing different environmental control settings of the air conditioning system showed a even more significant impact in the final cooling demand of the spaces, apart from allow a longer period of natural ventilation. Looking at the the case of the east-facing working areas in the main office building, a change in the operation parameters from 26 oC and 65% rh to 24 oC and 50% rh reflected in 28% increase in the room's total annual loads. A higher impact was found for the laboratories' offices, marking 42%, and resulting in a decrease of one month in the natural ventilation potential period. However, the final simulations for annual loads considered the environmental scenario of 24 oC and 50%, as determined in the engineering design as an operation parameter for the cooling system, whereas the settings for the sizing of the cooling systems were 22 oC and

As a consequence of introducing hours of natural ventilation, in the case of the south-facing laboratories, the mixed-mode strategy led to a reduction of 10% in the total annual loads in comparison with the full air-conditioning mode, and a 50% decrease was found considering the maximum thermal loads. For the working areas in the main office building, the mixedmode strategy was only not possible in the west-wing offices natural ventilation was not recommended due to acoustic issues related to the motorway that separates phase one and

Regarding the specification of windows, transparent laminated double glazing windows with air filling (10+28+6 mm) were tested against transparent laminated 8mm single glazing. The double glazing has not presented significant benefits for the thermal performance of the offices of the laboratories, due to the periods of natural ventilation. Similar findings occurred for the east-facing rooms of the main office building. As opposed to that, in the

4 Natural ventilation in such spaces was only possible through the openings on the internal façade, adjacent to the central corridor, which proved to be insufficient, so that the west-wing offices were designed from the outset to

Centre [3].

50%.

phase two of the Research Center4.

operate on the air-conditioning mode [19].

**Figure 22.** Location of the laboratory used as the first base-case for the thermal assessment.


**Table 11.** Materials and building components applied in the thermal dynamic simulations of the typical office space of the Laboratories' office cells.

The results of the preliminary assessment indicated a potential annual period of natural ventilation ranging from 13% to 30%, higher values were found with the inclusion of thermal mass, adding thermal inertia to the internal spaces and considering the entire window as a ventilation aperture, opened for 24hrs during the days of thermal comfort conditions [3]. Excluding the hottest period of the year (from December to February), the performance of natural ventilation increases to 50% of the occupied hours. Based on such results, the mixed-mode strategy has proved to be a positive approach, especially for environments with low internal gains. Furthermore, regarding the set points of the air-conditioning system, the exploratory simulations showed a total reduction in thermal loads of 22% for set point conditions of 26 oC and 60% rh, compared to the scenario of 24 oC and 60% rh, therefore showing the significant impact of comfort standards on building energy efficiency, in the specific case of the Petrobras Research Centre [3].

48 Energy Efficiency – The Innovative Ways for Smart Energy, the Future Towards Modern Utilities

**Figure 22.** Location of the laboratory used as the first base-case for the thermal assessment.

Door Wood (3cm)

Elements Materials U value

Walls Cellular concrete panel (15cm), no coat 0,90

(50cm) + concrete 400 kg/m³ (15cm) in

concrete 400 kg/m³ (15cm) + air cavity (100cm) + sandwich panel (15cm)

Floor Concrete 2000kg/m³ (15cm) + air cavity

Roof Plasterboard (2cm) + air cavity (50cm) +

**Table 11.** Materials and building components applied in the thermal dynamic simulations of the typical

contact with the soil

Windows Aluminum frame (5%) + transparent float glass (one sheet -6 mm)

(W/m²ºC)

5,73

1,10

0,25

described in table 11.

Occupancy parameters

2 people + 15 W/m² equipment load + 12 W/m² lighting

office space of the Laboratories' office cells.

Preliminary parametric investigations were carried out for a typical office cell of one of the laboratory buildings to provide an overview of the possibilities and limitations of a mixedmode approach in such spaces (see figure 22). The test-room was in the most exposed side of the laboratory buildings, with one exposed façade towards the west, however with openings shaded, opaque surfaces with light colour finishing and with a maximum occupancy of two people. Simulation parameters included north and south orientated offices, and the possibility of users' control of both windows for natural ventilation and the air-conditioning system. The specification of materials applied in these simulations are

> More in-depth spaces of comparing different environmental control settings of the air conditioning system showed a even more significant impact in the final cooling demand of the spaces, apart from allow a longer period of natural ventilation. Looking at the the case of the east-facing working areas in the main office building, a change in the operation parameters from 26 oC and 65% rh to 24 oC and 50% rh reflected in 28% increase in the room's total annual loads. A higher impact was found for the laboratories' offices, marking 42%, and resulting in a decrease of one month in the natural ventilation potential period. However, the final simulations for annual loads considered the environmental scenario of 24 oC and 50%, as determined in the engineering design as an operation parameter for the cooling system, whereas the settings for the sizing of the cooling systems were 22 oC and 50%.

> As a consequence of introducing hours of natural ventilation, in the case of the south-facing laboratories, the mixed-mode strategy led to a reduction of 10% in the total annual loads in comparison with the full air-conditioning mode, and a 50% decrease was found considering the maximum thermal loads. For the working areas in the main office building, the mixedmode strategy was only not possible in the west-wing offices natural ventilation was not recommended due to acoustic issues related to the motorway that separates phase one and phase two of the Research Center4.

> Regarding the specification of windows, transparent laminated double glazing windows with air filling (10+28+6 mm) were tested against transparent laminated 8mm single glazing. The double glazing has not presented significant benefits for the thermal performance of the offices of the laboratories, due to the periods of natural ventilation. Similar findings occurred for the east-facing rooms of the main office building. As opposed to that, in the

<sup>4</sup> Natural ventilation in such spaces was only possible through the openings on the internal façade, adjacent to the central corridor, which proved to be insufficient, so that the west-wing offices were designed from the outset to operate on the air-conditioning mode [19].

case of the west-wing offices, which present fixed façades, as already mentioned, transparent double glazing was recommended for both façades in order to increase the efficiency of the air-conditioning system.

Environmental Design in Contemporary Brazilian Architecture:

25mm gypsum + 50mm rock wool +200mm


Composition: perforated metal panel (40% void)+ metalic sandwich panel + 8mm green

120mm celular concrete d=2.500kg/m3 +

200mm aereted concrete d=2.500kg/ m3 + impermeabilization + cement + ceramics

12,5mm gypsum +1530mm air gap + metallic

The Research Centre of the National Petroleum Company, CENPES, in Rio de Janeiro 51

air gap + aluminium U = 0,43 W/m²ºC

single glazing+ shed

plasterboard U = 1,07 W/m²ºC

U = 1,52 W/m²ºC

U=5,66 W/m²ºC

sandwich panel U=0,39 W/m²ºC

**Table 14.** Materials and building components tested in the thermal dynamic simulations of the office

8mm clear single glazing

raised carpet floor (metal+120mm concrete d=2.200kg/m3 + 375mm air gap + metal + carpet)

**Table 13.** Materials and building components applied in the thermal dynamic simulations of the main

Preliminary solution Final solution

25mm gypsum +50mm glass wool +25mm

51mm metallic sandwich panel (EPS filling)

Preliminary solution Final solution

office building: preliminary vs. final solution

25mm gypsum +50mm glass wool +25mm

110mm concrete d=2.200kg/m3 + 700mm air gap + 150mm concrete, d=2.800kg/m3

gypsum +400mm air gap +110mm concrete,

cells of the Laboratories: preliminary vs. final solution

EXTERNAL WALL

U = 0,85 W/m²ºC

U=5,73W/m²ºC

U=4,76 W/m²ºC

EXTERNAL WALL

concrete, d=2.200kg/m3 U = 0,66 W/m²ºC

U = 1,38 W/m²ºC

U=5,73W/m²ºC

CEILING/ROOF

d=2.200kg/m3 U=1,82 W/m²ºC

6mm clear single glazing

GLAZING

FLOOR

FLOOR

GLAZING

CANOPY

concrete, d=2.200kg/m3 U = 0,66 W/m²ºC

6mm clear single glazing

Regarding the specification of windows, transparent laminated double glazing windows with air filling (10+28+6 mm) were tested against transparent laminated single glazing (8mm). The double glazing has not presented significant benefits for the thermal performance of the offices of the laboratories, due to the periods of natural ventilation. Similar findings occurred for the east-facing rooms of the main office building (see table 12). As opposed to that, in the case of the west-wing offices, which ended up with fixed windows, transparent double glazing was recommended for both façades in order to increase the efficiency of the air-conditioning system.


**Table 12.** Total annual loads for the east and west office rooms, with different glazing types and airconditioning settings.

The thermal performance of the working spaces of the main office building was strongly influenced by the big roof, a fundamental element of the design of such building, covering the terraces and the office floors. Different design solutions were tested for the roof, aiming to find a balance between daylighting and the thermal conditions of both the offices and the open spaces of the terraces (as seen in the *Thermal comfort in open spaces*). In comparison to the original design based on a metallic screen, permeable to air and light, the final solution of the insulated sandwich metal panels showed reduction of 20% in the cooling loads of the office areas located at the top floors o, mainly due to a reduction in the solar heat gains through the open corridor between the two office wings (see Table 13).

With special concerns to the main office building, in spite of the environmental and energy assessment carried out, some architectural aspects, such as raised floors and insulated ceilings, resulted in internal environments similar to those from the commercial international standards (see Table 13). Alternatively, the working spaces of the laboratories, with reduced dimensions and relatively low thermal loads, additionally to internal thermal mass use, presented a comparatively higher performance, mainly due to the natural ventilation (see Table 14).

efficiency of the air-conditioning system.

office / room

conditioning settings.

ventilation (see Table 14).

13).

increase the efficiency of the air-conditioning system.

total annual load (MWh)

east (mixed-mode) 58,8 57,0 79,1

west (full a/c) 62,9 61,8 81,3

case of the west-wing offices, which present fixed façades, as already mentioned, transparent double glazing was recommended for both façades in order to increase the

Regarding the specification of windows, transparent laminated double glazing windows with air filling (10+28+6 mm) were tested against transparent laminated single glazing (8mm). The double glazing has not presented significant benefits for the thermal performance of the offices of the laboratories, due to the periods of natural ventilation. Similar findings occurred for the east-facing rooms of the main office building (see table 12). As opposed to that, in the case of the west-wing offices, which ended up with fixed windows, transparent double glazing was recommended for both façades in order to

clear single glazing clear + green single glazing

**Table 12.** Total annual loads for the east and west office rooms, with different glazing types and air-

The thermal performance of the working spaces of the main office building was strongly influenced by the big roof, a fundamental element of the design of such building, covering the terraces and the office floors. Different design solutions were tested for the roof, aiming to find a balance between daylighting and the thermal conditions of both the offices and the open spaces of the terraces (as seen in the *Thermal comfort in open spaces*). In comparison to the original design based on a metallic screen, permeable to air and light, the final solution of the insulated sandwich metal panels showed reduction of 20% in the cooling loads of the office areas located at the top floors o, mainly due to a reduction in the solar heat gains through the open corridor between the two office wings (see Table

With special concerns to the main office building, in spite of the environmental and energy assessment carried out, some architectural aspects, such as raised floors and insulated ceilings, resulted in internal environments similar to those from the commercial international standards (see Table 13). Alternatively, the working spaces of the laboratories, with reduced dimensions and relatively low thermal loads, additionally to internal thermal mass use, presented a comparatively higher performance, mainly due to the natural

26°C / 65% 26°C / 65% 24°C / 50%


**Table 14.** Materials and building components tested in the thermal dynamic simulations of the office cells of the Laboratories: preliminary vs. final solution

Regarding the thermal performance of building components, it was verified that, in general, U values close to 1,00 W/m2 ºC and higher for the walls of both naturally ventilated and air conditioned spaces and modes, coupled with light external colours, give a good balance between heat losses and heat gains in the specific climatic conditions of Rio de Janeiro. On the other hand, the roofs had to be more insulated, given the intensity of solar radiation throughout the year, with U values between 0,25 W/m2 ºC and close to 0,50 W/m2 ºC in the great majority of the buildings, reinforcing the validity of the initial hypothesis of double roofs with extra shading and insulation for a better thermal performance of the internal spaces.

Environmental Design in Contemporary Brazilian Architecture:

The Research Centre of the National Petroleum Company, CENPES, in Rio de Janeiro 53

informal feedback has confirmed the satisfaction of the occupants with the environmental quality of both naturally ventilated and air conditioned buildings, translated into internal visual communication and access to daylight, views towards the outside from all working spaces, physiological cooling through natural ventilation and inviting shaded transitional

Possibly, the positive response of the occupants about their working environments will maximize the use of natural ventilation in the working spaces where environmental quality can induce a better performance than the predicted in the simulations, since a more flexible and adaptable notion of comfort could be put in practice by the occupants as a consequence of the overall quality of the spaces. This could be the case of the office cells in the laboratories, for instance, where the relatively small internal loads, coupled with the internal thermal mass and operable windows facing the gardens could spontaneously lead to the

Overall, the environmental quality and performance potential achieved in the design of the extension of the Petrobras Research Centre in Rio de Janeiro define a new reference for future environmentally responsive buildings in Rio de Janeiro, exploring environmental attributes from outside the boundaries (and often limited) of energy performance

*1Laboratório de Conforto Ambiental e Eficiência Energética (LABAUT), Departamento de Tecnologia* 

*Laboratório de Conforto Ambiental e Eficiência Energética (LABAUT), Departamento de Tecnologia* 

Thanks to: Anésia Frota, Anna Miana, Alessandra Shimomura, Bruna Luz, Cecília Muller, Gisele de Benedetto, Jose Cremonesi, Jose Ovidio, Luciana Ferreira, Marcia Alucci, Rafael

*da Arquitetura (AUT), Faculdade de Arquitetura e Urbanismo, Universidade de São Paulo* 

*da Arquitetura (AUT), Faculdade de Arquitetura e Urbanismo, Universidade de São Paulo* 

*Departamento de Tecnologia da Arquitetura (AUT), Faculdade de Arquitetura e Urbanismo,* 

Denise Duarte, Leonardo Marques Monteiro and Mônica Pereira Marcondes

*2Environment & Energy Studies Programme Architectural Association School of Architecture,* 

preference for natural ventilation rather than the air conditioning system.

spaces.

standards.

**Author details** 

Joana Carla Soares Gonçalves1,2,\*

*(FAUUSP), São Paulo, Brasil* 

*(FAUUSP), São Paulo, Brasil* 

**Acknowledgement** 

Corresponding Author

 \*

Norberto Corrêa da Silva Moura

*Universidade de São Paulo (FAUUSP), São Paulo, Brasil* 

*London, Great Britain* 

It must be noticed that the mixed-mode approach to the control of the internal thermal environments is a new concept in Brazil, where most air-conditioned buildings are sealed boxes with raised floors and insulated ceilings. Nevertheless, in the context of this project it is considered that the mixed-mode approach can bring economic and environmental benefits, introducing periods of natural ventilation and allowing for fluctuations in the internal environmental conditions within the limits of a given comfort zone, whilst also reducing the thermal loads of the air-conditioning periods. It also increases the user interaction with the exterior, fact which has proved to have positive psychological effects in the occupation of buildings [31].

Despite the technical reasoning that would support the use of a mixed-mode approach to internal environmental control, in the final design of buildings and systems, all environments in which air-conditioning should be necessary for any period of the year became fully air-conditioned main due to a established design culture. Notwithstanding, the specification of operable windows, coupled with an air distribution zoning in the office environments in both in the laboratories and in the working areas of the main office building (one fan-coil for each unity), granted the occupant with the possibility of choosing for periods of natural ventilation, if technically possible and desirable.
