**5. Naturally ventilated buildings**

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

**Figure 18.** Laboratories: distribution of daylight in the typical north facing rooms.

In summary, the outcomes of daylight uniformity were:

d. North oriented laboratories: 0.94; e. South oriented laboratories: 0.94.

a. Main office building, 3rd floor rooms, west orientation : 0.82 – 0.88; b. Main office building, 2nd floor rooms, east orientation: 0.82 – 0.88; c. Main office building, 2nd floor rooms, west orientation: 0.35 – 0.75;

around the room.

reading rooms (300 lx), prescribed by the Brazilian Standard NBR 5413, it does not comply with the requirements for office activities, where the advised nominal illuminance is 500 lx [14]. Nevertheless, 500 lx could be considered to be high in the context of contemporary offices and the related work conditions, harming the visibility of computer screens. Adjusting Brazilian Standards guidelines and visual task needs, the complementary artificial lighting was adopted, placing supplementary luminaries over restrict areas controlled by the user. This strategy allows estimated energy savings of approximately 40% to 45% of artificial lighting, taking into account the Research Centre usual working hours between 7 am to 4 pm, during 5 days a week [12]. Almost all main office areas and laboratory rooms presented well balanced daylight distribution. Yet, the uniformity below 0.66 was identified in some places, such as in the office building second floor of the west facing wing of the main office building, where uniformity resulted in 0.35, indicating the need for supplementary artificial lighting, to adjust lighting levels to the task requirements

The main natural ventilated buildings in the extension of the Research Centre were two: *Operational Support Building* and *Utilities Centre.* In addition, both the main office building and the laboratory buildings have spaces optimized to be naturally ventilated for a percentage of the year *(*see topic: *Air conditioned buildings, in the sequence).* The assessment of the naturally ventilated internal spaces involved a set of analytical work developed with the support of advanced computer simulations of thermal and computer fluid dynamics, according to the following procedures [19]:



Environmental Design in Contemporary Brazilian Architecture:

The Research Centre of the National Petroleum Company, CENPES, in Rio de Janeiro 43

For naturally ventilated internal spaces, dry bulb temperature, relative humidity and mean radiant temperature extracted from the simulations' results are used to calculate TE\* for each hour, which is assessed in relation to the comfort zone. Comparing the TE\* figures calculated for each hour of the reference year with the limits of the adaptive comfort zone created for the climate of Rio de Janeiro, one can observe that 50% of occupation time are in accordance with the acceptable thermal comfort conditions [19]. In other words, in a hypothetical scenario where the internal conditions are equivalent to the calculated TE\*(for the external climatic conditions), comfort would be obtained for 50% of the occupied hours, which was then considered as a reference for the performance of the naturally ventilated environments.

The thermal performance of buildings and the potential for natural ventilation were determined by advanced thermal dynamics' computer simulations with the software TAS. The simulated environment was divided in a number of thermal zones, in which the influence of neighboring rooms is taken into account. In that way, several thermal phenomena can be evaluated in terms of simultaneity, location and interaction. Building modeling was carried out in two stages: geometry characteristics, and materials specification

Preliminary analytical studies showed that the sawtooth roofs of the factory-type buildings facing southeast in order to get the minimum direct sun to the maximum diffuse light, incurred in negative impacts on the natural ventilation of the internal environments, as the southeast coincides with the direction of prevailing winds. For this reason, the shed elements of the sawtooth roofs were re-designed changing the position of the opening for ventilation and including a solar and wind protection device (see figures 20 and 21). Without changing the original orientation of the roof (the best one to minimize solar gains), the new solution prevented the unfavourable effect of the prevailing wind on the air outlet of the stack effect, simultaneously taking advantage of the negative pressure generated to maximize the exhaustion of the internal air flow. In addition, thermal insulation was proved to be beneficial in the buildings' envelop and external solar protection was included on the windows and roof openings of all main buildings. The specification of materials and

The factory-type building form played a decisive role in the success of the passive strategies, since the double and triple floor to ceiling heights and the sawtooth roof favoured natural ventilation through stack effect, whilst bringing diffuse daylight into the deeper parts of the floor plan with protection against solar radiation. Shading and ventilation were fundamental strategies for the achievement of satisfactory thermal comfort conditions in the naturally ventilated buildings, followed by external insulation coupled with internal thermal inertia of the buildings' envelop. In the case of interior environments with higher internal heat gains, mechanical ventilation had to be introduced, especially in the hot periods of the year (from December to February). This was the case of the changing rooms in the*Operational Support Building*, where the mechanical ventilation had to provide up to 15 air changes per hour. The mechanical ventilation proved to have a positive impact also in the distribution of air flow

building components used in the thermal simulations are shown in Table 8.

within the environments, reaching with more homogeneity the occupied zone.

and occupation schedules.

In the typical warm-humid climate of Rio de Janeiro, the thermal performance of naturally ventilated buildings is dependent on the provision of efficient shadowing strategies, alongside enhanced cross ventilation and possibly external thermal insulation (to be tested on a case by case scenario). However, the ultimate success of naturally ventilated spaces will depend on the definition of the comfort band and its acceptable conditions.

At the time of the project (2004-2005) there were two national buildings' standards related to the general internal environmental conditions of working spaces: NR- 15 [20] and NR 17 [21]. The first one refers mainly to extremely hot environments, such as factories, and recommends resting periods related to people's exposure to above certain indoor temperatures, whereas the second one says that the environment must be adequate to the psycho-physiological characteristics of the workers and to the nature of the task. For working spaces in which intellectual demand and constant attention are required, NR-17 recommends the following design parameters: effective temperature between 20oC and 23oC; air relative humidity not inferior to 40%; air speed not superior than 0.75 m/s. Even though NR-17 applied theoretically to all environments of interest in this work, its parameters were impossible to be attained in a free running mode, in any time of the reference year, given its narrow limits.

Aiming to maximize natural ventilation, the adaptive comfort model adopted by ASHRAE [22] and created by De Dear [23] was adopted here. It brings an empirical model which includes acclimatization, clothing options, behavior patterns and tolerance to climatic variability (based on the New Effective Temperature (TE\*), seen in *Thermal comfort in open spaces)* (see figure 19).

**Figure 19.** Comfort zone for the climate of Rio de Janeiro, created after De Dear's adaptive model [23].

For naturally ventilated internal spaces, dry bulb temperature, relative humidity and mean radiant temperature extracted from the simulations' results are used to calculate TE\* for each hour, which is assessed in relation to the comfort zone. Comparing the TE\* figures calculated for each hour of the reference year with the limits of the adaptive comfort zone created for the climate of Rio de Janeiro, one can observe that 50% of occupation time are in accordance with the acceptable thermal comfort conditions [19]. In other words, in a hypothetical scenario where the internal conditions are equivalent to the calculated TE\*(for the external climatic conditions), comfort would be obtained for 50% of the occupied hours, which was then considered as a reference for the performance of the naturally ventilated environments.

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

depend on the definition of the comfort band and its acceptable conditions.

h. elaboration of design guidelines for a better environmental and energy performance of

In the typical warm-humid climate of Rio de Janeiro, the thermal performance of naturally ventilated buildings is dependent on the provision of efficient shadowing strategies, alongside enhanced cross ventilation and possibly external thermal insulation (to be tested on a case by case scenario). However, the ultimate success of naturally ventilated spaces will

At the time of the project (2004-2005) there were two national buildings' standards related to the general internal environmental conditions of working spaces: NR- 15 [20] and NR 17 [21]. The first one refers mainly to extremely hot environments, such as factories, and recommends resting periods related to people's exposure to above certain indoor temperatures, whereas the second one says that the environment must be adequate to the psycho-physiological characteristics of the workers and to the nature of the task. For working spaces in which intellectual demand and constant attention are required, NR-17 recommends the following design parameters: effective temperature between 20oC and 23oC; air relative humidity not inferior to 40%; air speed not superior than 0.75 m/s. Even though NR-17 applied theoretically to all environments of interest in this work, its parameters were impossible to be attained in a free running mode, in any time of the

Aiming to maximize natural ventilation, the adaptive comfort model adopted by ASHRAE [22] and created by De Dear [23] was adopted here. It brings an empirical model which includes acclimatization, clothing options, behavior patterns and tolerance to climatic variability (based on the New Effective Temperature (TE\*), seen in *Thermal comfort in open* 

**Figure 19.** Comfort zone for the climate of Rio de Janeiro, created after De Dear's adaptive model [23].

g. quantification of thermal loads for air-conditioned spaces;

buildings.

reference year, given its narrow limits.

*spaces)* (see figure 19).

The thermal performance of buildings and the potential for natural ventilation were determined by advanced thermal dynamics' computer simulations with the software TAS. The simulated environment was divided in a number of thermal zones, in which the influence of neighboring rooms is taken into account. In that way, several thermal phenomena can be evaluated in terms of simultaneity, location and interaction. Building modeling was carried out in two stages: geometry characteristics, and materials specification and occupation schedules.

Preliminary analytical studies showed that the sawtooth roofs of the factory-type buildings facing southeast in order to get the minimum direct sun to the maximum diffuse light, incurred in negative impacts on the natural ventilation of the internal environments, as the southeast coincides with the direction of prevailing winds. For this reason, the shed elements of the sawtooth roofs were re-designed changing the position of the opening for ventilation and including a solar and wind protection device (see figures 20 and 21). Without changing the original orientation of the roof (the best one to minimize solar gains), the new solution prevented the unfavourable effect of the prevailing wind on the air outlet of the stack effect, simultaneously taking advantage of the negative pressure generated to maximize the exhaustion of the internal air flow. In addition, thermal insulation was proved to be beneficial in the buildings' envelop and external solar protection was included on the windows and roof openings of all main buildings. The specification of materials and building components used in the thermal simulations are shown in Table 8.

The factory-type building form played a decisive role in the success of the passive strategies, since the double and triple floor to ceiling heights and the sawtooth roof favoured natural ventilation through stack effect, whilst bringing diffuse daylight into the deeper parts of the floor plan with protection against solar radiation. Shading and ventilation were fundamental strategies for the achievement of satisfactory thermal comfort conditions in the naturally ventilated buildings, followed by external insulation coupled with internal thermal inertia of the buildings' envelop. In the case of interior environments with higher internal heat gains, mechanical ventilation had to be introduced, especially in the hot periods of the year (from December to February). This was the case of the changing rooms in the*Operational Support Building*, where the mechanical ventilation had to provide up to 15 air changes per hour. The mechanical ventilation proved to have a positive impact also in the distribution of air flow within the environments, reaching with more homogeneity the occupied zone.

Environmental Design in Contemporary Brazilian Architecture:

The Research Centre of the National Petroleum Company, CENPES, in Rio de Janeiro 45

Looking at the yearly percentage of comfort hours in the naturally ventilated environments, the highest performance was found in the changing rooms in the Operational Support Building, featuring approximately 60% of the yearly occupation hours within comfort conditions (considering the hours found in "cold" conditions are insignificant) (see table 9). In addition, it was estimated that the addition of the mechanical system would increment the number of air changes per hour could raise the hours in comfort to 75% (an increase of 65% comparatively to its performance before the implementation of the initial architectural modifications) [19]. On the other hand, the lowest performance was in the kitchen of the same building marking 51% of hours in comfort (see table 10). In conclusion, it can be said that the results of the thermal performance of the naturally ventilated internal environments (seen in number of hours within the comfort zone) shows the adequacy of the architectural

response to the specific warm-humid conditions of the climate of Rio de Janeiro.

**Daily occupation 5am-7pm Month PDD = 20% PDD = 10% Cold Comfort Hot Cold Comfort Hot**  January 0.0% 32.8% 67.2% 0.0% 20.6% 79.4% February 0.0% 32.3% 67.7% 0.0% 24.7% 75.3% March 0.0% 47.9% 52.1% 0.0% 34.2% 65.8% April 0.0% 47.9% 52.1% 0.0% 34.2% 65.8% May 0.0% 49.5% 50.5% 0.0% 38.1% 61.9% June 2.0% 87.0% 11.0% 8.1% 65.8% 26.1% July 1.6% 76.2% 22.2% 3.8% 59.4% 36.8% August 7.3% 76.7% 16.1% 15.5% 56.4% 28.2% September 0.3% 76.3% 23.3% 4.0% 57.0% 39.0% October 0.0% 60.3% 39.7% 0.3% 42.9% 56.8% November 0.0% 47.6% 52.4% 0.6% 31.5% 67.9% December 0.0% 44.4% 55.6% 0.0% 29.5% 70.5% **Year 1.1% 58.5% 40.4% 3.2% 42.6% 54.2%** 

**Table 9.** Operational Support Building: Percentage of predicted yearly hours in comfort in changing

**Daily occupation 5am-7pm Month PDD = 20% PDD = 10% Cold Comfort Hot Cold Comfort Hot**  January 0.0% 21.4% 78.6% 0.0% 8.4% 91.6% February 0.0% 25.0% 75.0% 0.0% 9.3% 90.7% March 0.0% 38.8% 61.2% 0.0% 19.1% 80.9% April 0.0% 38.8% 61.2% 0.0% 19.1% 80.9% May 0.0% 45.1% 54.9% 0.0% 21.3% 78.7% June 0.0% 93.3% 6.7% 0.0% 66.4% 33.6% July 0.0% 70.8% 29.2% 0.0% 41.6% 58.4% August 0.0% 81.8% 18.2% 0.0% 56.7% 43.3% September 0.0% 63.3% 36.7% 0.0% 39.3% 60.7% October 0.0% 46.1% 53.9% 0.0% 23.5% 76.5% November 0.0% 32.4% 67.6% 0.0% 16.7% 83.3% December 0.0% 34.6% 65.4% 0.0% 16.8% 83.2% **Year 0.0% 51.3% 48.7% 0.0% 29.8% 70.2%** 

**Table 10.** Operational Support Building: Percentage of predicted yearly hours in comfort in kitchen of

rooms.

the Operational Support Building.

**Figure 20.** The Operational Support Building, one of the factory type buildings featuring triple floor to ceiling heights and shed structures in the roof for daylight and stack ventilation.

**Figure 21.** Design of shed showing the ventilation aperture on the back of the shaded glazed area.


**Table 8.** Materials and building components applied in the thermal dynamic simulations of the naturally ventilated factory type buildings

Looking at the yearly percentage of comfort hours in the naturally ventilated environments, the highest performance was found in the changing rooms in the Operational Support Building, featuring approximately 60% of the yearly occupation hours within comfort conditions (considering the hours found in "cold" conditions are insignificant) (see table 9). In addition, it was estimated that the addition of the mechanical system would increment the number of air changes per hour could raise the hours in comfort to 75% (an increase of 65% comparatively to its performance before the implementation of the initial architectural modifications) [19]. On the other hand, the lowest performance was in the kitchen of the same building marking 51% of hours in comfort (see table 10). In conclusion, it can be said that the results of the thermal performance of the naturally ventilated internal environments (seen in number of hours within the comfort zone) shows the adequacy of the architectural response to the specific warm-humid conditions of the climate of Rio de Janeiro.

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

**Figure 20.** The Operational Support Building, one of the factory type buildings featuring triple floor to

**Figure 21.** Design of shed showing the ventilation aperture on the back of the shaded glazed area.

ceramics + cement + 25mm gypsum +200mm air gap +

Ceramics + cement + 100mm concrete (d=2.500kg/m3)

+ steel +1000mm air gap + 12,5mm gypsum

120mm concrete (d=2.500kg/m3)

U = 1,63 W/m²ºC

U = 0,85 W/m²ºC

U=5,66 W/m²ºC

**Table 8.** Materials and building components applied in the thermal dynamic simulations of the

8mm clear single glazing

ceiling heights and shed structures in the roof for daylight and stack ventilation.

Preliminary solution Final solution

aluminium + 50mm rock wool + aluminium (metallic sandwich panel)

EXTERNAL WALL

U = 1,77 W/m²ºC

12,5mm gypsum U = 0,82 W/m²ºC

6mm clear single glazing

GLAZING

U=5,73W/m²ºC

CEILING/ROOF

U=0,58 W/m²ºC

FLOOR

150mm concrete (d=1,200kg/m3)

Ceramics + cement + 150mm concrete (d=2.200kg/m3) + steel +1000mm air gap +

naturally ventilated factory type buildings


**Table 9.** Operational Support Building: Percentage of predicted yearly hours in comfort in changing rooms.


**Table 10.** Operational Support Building: Percentage of predicted yearly hours in comfort in kitchen of the Operational Support Building.
