**4. Daylighting**

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

(metal screen with local shading)

clothing.

the air speed.

**Table 7.** Thermal comfort at the rooftop area of the central building

Month cold comfort hot January 12,6% 72,7% 14,7% February 13,6% 69,5% 16,9% March 12,8% 73,6% 13,6% April 12,9% 72,1% 14,9% May 15,2% 72,7% 12,1% June 16,2% 80,2% 3,6% July 6,9% 80,5% 12,6% August 12,8% 75,2% 12,0% September 23,2% 70,9% 5,9% October 24,1% 70,0% 5,9% November 16,5% 78,1% 5,4% December 18,2% 71,4% 10,4% Year 15,4% 73,9% 10,7%

Without barriers in the rooftop area, and since the wind speed at 10m is higher than at the ground, the wind speed in rooftop areas is more significant. Nevertheless, the cold discomfort periods caused by the wind could be reduced by adopting local wind breaks in the more affected areas of the rooftop. Moreover, given the hot-humid climatic conditions throughout the year in Rio de Janeiro, theoretical discomfort for "cold" can be challenged by real-life practice and be simply solved considering occupants adaption through

At first sight, comparing the insulated sandwich metal roof solution and the metal screen one, without other designing strategies, both present similar thermal comfort performance. But the metal screen solution has a higher potential to increase thermal comfort conditions, since local shading devices and wind brakes (if required) proved to increase comfort hours significantly. On the other hand, in the case of the insulated sandwich metal roof, in which almost all the situations of discomfort are hot ones, local solutions are not possible, since all solar irradiance is already blocked and it is difficult to induce, yet locally, an increment in

Due to the possibilities of local solutions, the choice of metal screen provides a great diversity of environmental conditions, with different local figures of thermal radiation and air speed, which affect the thermal comfort sensation in open spaces. Providing environmental diversity, with areas of thermal sensation varying between slightly hotter to slightly colder, it is known that people can satisfy their comfort needs by choosing wherever they want to be, increasing even more the percentage of thermal comfort satisfaction. Nevertheless, in real practice, the possibility of creating a semi-open space protected from In response to the design brief, daylighting should be prioritized and maximized in all interior spaces where there is no functional restrictions, in order to provide visual comfort with energy efficiency [1]. Given the specific warm-humid climate of Rio de Janeiro and the major impact of solar irradiation on buildings thermal performance, coupled with the typical partially cloudy and bright local sky conditions, the major challenge of taking maximum benefit of daylight was related to the need for solar protection and avoidance of glare. For this purpose, the building form, together with roof's and facades' components were designed and sized with precision to shade the direct sun, whilst capturing and redirecting daylight to the deeper parts of the interior spaces (see figures 13 and 14).

The design and assessment processes of daylighting focused on the three main building typologies of the research centre, where buildings' orientation and form had a significant impact on the daylighting performance: the linear north and south rows of laboratories, the

Environmental Design in Contemporary Brazilian Architecture:

The Research Centre of the National Petroleum Company, CENPES, in Rio de Janeiro 37

multi-storey west and east facing office building, and the typical factory-like typology, in which the conflicts between natural ventilation, solar protection and penetration of daylight had a determining role in the design of the roofs. A number of in-depth simulation parametric studies were used to analyze architectural design possibilities for solar

In order to estimate internal daylight performance, Brazilian Standard NBR 15215 -3 calculation method was adopted [13]. Quantitative reference parameters in lux, from Brazilian Standard NBR 5413 [14], were complemented by Germany Standards DIN 5034, Daylight in interiors [15], DIN 5035, Artificial lighting of interiors [16] and LEED guidelines

d. Daylight Factor and illuminance Levels should be reached on 75% of work plane areas,

e. Glass transmittance: 0.89 (general); 0.69(main office building and factory sheds).

In the main office building, the terraces (designed to hold social and working activities) showed areas with daylighting levels higher than 300 lx, nearly corresponding to a Daylight Factor (DF) of 2%. In the working environments close to the east facade facing the bay, the predominant DF identified was over 2%, despite the shading device, allowing appropriate levels up to the point of circulation between working stations, of approximately 2.50 meters deep. Further than this point, DF was below 2%, revealing the need for supplementary artificial lighting. In the west façade, facing the first phase of the Research Centre, the figures for the DF were over 2% in almost the whole area close to the openings, of about 5.5 meters deep. On the other hand, in the deeper plan areas (between 5,50 and 13.00 meters from the facade), the values of DF were predicted to be over 2% in 20% of the floor area (at

2 In parallel to the development of this project, ISO and CIE launched the Standard General Sky, presenting 15 sky relative luminance distribution types, including CIE Standard Clear Sky and CIE Standard Overcast Sky. Unfortunately, there was not enough measurement data to feature Brazilian sky in accordance with ISO/CIE 15 types. Hence, CIE Standard Overcast Sky was adopted to calculate values of DF. However, unobstructed external horizontal illuminance was established taking into account Brazilian climate conditions. The unobstructed external horizontal illuminance parameter (13.250 lx) adopted on computer simulations, reports 80% of annual occurrence. Increasing the unobstructed external horizontal illuminance parameter, the annual occurrence decreases, and the autonomy of

protection and penetration of daylight in all three cases [12].

c. Illuminance Levels related to work planes: above 265 lx;

Computer simulation parameters for daylight assessment:

c. Floor, wall and ceiling reflectance: 0.35; 0.60; 0.85;

b. Unobstructed external horizontal plane illuminance: 13.250 lx2;

d. Work plane height: 0.70m (offices); 1.00m (utility buildings);

working height) and 1.5% in 30% (see figures 13, 15 and 16).

[17], adopting performance criteria as follows:

a. CIE overcast sky luminance distribution;

a. Uniformity: above 66%; b. Daylight Factor: above 2%;

at least.

daylight can be estimated.

**Figure 13.** Central Building: design of the building's east facade to provide total solar protection to the working stations.

**Figure 14.** Typical north facing wing of laboratories: design of the shading device for the high-level window aiming to cut the direct solar radiation and redirect it as diffuse light to the deeper parts of the working areas.

multi-storey west and east facing office building, and the typical factory-like typology, in which the conflicts between natural ventilation, solar protection and penetration of daylight had a determining role in the design of the roofs. A number of in-depth simulation parametric studies were used to analyze architectural design possibilities for solar protection and penetration of daylight in all three cases [12].

In order to estimate internal daylight performance, Brazilian Standard NBR 15215 -3 calculation method was adopted [13]. Quantitative reference parameters in lux, from Brazilian Standard NBR 5413 [14], were complemented by Germany Standards DIN 5034, Daylight in interiors [15], DIN 5035, Artificial lighting of interiors [16] and LEED guidelines [17], adopting performance criteria as follows:

a. Uniformity: above 66%;

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

**Figure 13.** Central Building: design of the building's east facade to provide total solar protection to the

**Figure 14.** Typical north facing wing of laboratories: design of the shading device for the high-level window aiming to cut the direct solar radiation and redirect it as diffuse light to the deeper parts of the

working stations.

working areas.


Computer simulation parameters for daylight assessment:


In the main office building, the terraces (designed to hold social and working activities) showed areas with daylighting levels higher than 300 lx, nearly corresponding to a Daylight Factor (DF) of 2%. In the working environments close to the east facade facing the bay, the predominant DF identified was over 2%, despite the shading device, allowing appropriate levels up to the point of circulation between working stations, of approximately 2.50 meters deep. Further than this point, DF was below 2%, revealing the need for supplementary artificial lighting. In the west façade, facing the first phase of the Research Centre, the figures for the DF were over 2% in almost the whole area close to the openings, of about 5.5 meters deep. On the other hand, in the deeper plan areas (between 5,50 and 13.00 meters from the facade), the values of DF were predicted to be over 2% in 20% of the floor area (at working height) and 1.5% in 30% (see figures 13, 15 and 16).

<sup>2</sup> In parallel to the development of this project, ISO and CIE launched the Standard General Sky, presenting 15 sky relative luminance distribution types, including CIE Standard Clear Sky and CIE Standard Overcast Sky. Unfortunately, there was not enough measurement data to feature Brazilian sky in accordance with ISO/CIE 15 types. Hence, CIE Standard Overcast Sky was adopted to calculate values of DF. However, unobstructed external horizontal illuminance was established taking into account Brazilian climate conditions. The unobstructed external horizontal illuminance parameter (13.250 lx) adopted on computer simulations, reports 80% of annual occurrence. Increasing the unobstructed external horizontal illuminance parameter, the annual occurrence decreases, and the autonomy of daylight can be estimated.


Environmental Design in Contemporary Brazilian Architecture:

The Research Centre of the National Petroleum Company, CENPES, in Rio de Janeiro 39

In the laboratory buildings of north and south orientations, the performance of daylight in the two main working areas: the main (and bigger) working space and the contiguous office cell, showed minimum values of DF of approximate 2% in 75% of the main working plan of the south facing laboratories and 70% in the case of the north orientation. In the office cells the result was the same in both cases, being 50% (see figures 14, 17 and 18). The overhangs placed over the high level windows of the north facing laboratory buildings to block the direct solar radiation didn't compromise daylight performance, as it incorporates horizontal louvers which redirect diffuse light into the deeper areas of the main working laboratory room. In the south facing laboratories, the high-level window was kept with the maximum view of the sky to maximize daylight penetration, being shaded only on the side vertical

plans against the early morning and late afternoon sun.

**Figure 17.** Laboratories: distribution of daylight in the typical south facing rooms.

daylight (and the risk of glare), but also to cut down critical thermal loads.

In the sawtooth roof buildings (the factory type), characterized by top daylight, the minimum illuminance levels established by the national standard [14] were satisfied. However, changes in the design of the shed component in one of the buildings were needed to decrease the initially predicted illuminance levels. For that purpose, a decrease in the height of the shed and the reduction of over 50% of the sheds were tested, not just to reduce

Considering the adopted criteria, the illuminance level 265 lx is achieved with the Daylight Factor of 2%, found as a minimum value in most of the working plans in the laboratories and in the main office building. Although this value is close to the recommendation for

**Figure 15.** Central Building: daylight distribution on the 2nd floor of the east facing offices (relatively narrower plan in relation to the west facing offices).

**Figure 16.** Central Building: daylight distribution on the 2nd floor of the west facing offices (the deepest plan area of the building).

In the laboratory buildings of north and south orientations, the performance of daylight in the two main working areas: the main (and bigger) working space and the contiguous office cell, showed minimum values of DF of approximate 2% in 75% of the main working plan of the south facing laboratories and 70% in the case of the north orientation. In the office cells the result was the same in both cases, being 50% (see figures 14, 17 and 18). The overhangs placed over the high level windows of the north facing laboratory buildings to block the direct solar radiation didn't compromise daylight performance, as it incorporates horizontal louvers which redirect diffuse light into the deeper areas of the main working laboratory room. In the south facing laboratories, the high-level window was kept with the maximum view of the sky to maximize daylight penetration, being shaded only on the side vertical plans against the early morning and late afternoon sun.

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

**Figure 15.** Central Building: daylight distribution on the 2nd floor of the east facing offices (relatively

**Figure 16.** Central Building: daylight distribution on the 2nd floor of the west facing offices (the deepest

narrower plan in relation to the west facing offices).

plan area of the building).

**Figure 17.** Laboratories: distribution of daylight in the typical south facing rooms.

In the sawtooth roof buildings (the factory type), characterized by top daylight, the minimum illuminance levels established by the national standard [14] were satisfied. However, changes in the design of the shed component in one of the buildings were needed to decrease the initially predicted illuminance levels. For that purpose, a decrease in the height of the shed and the reduction of over 50% of the sheds were tested, not just to reduce daylight (and the risk of glare), but also to cut down critical thermal loads.

Considering the adopted criteria, the illuminance level 265 lx is achieved with the Daylight Factor of 2%, found as a minimum value in most of the working plans in the laboratories and in the main office building. Although this value is close to the recommendation for

Environmental Design in Contemporary Brazilian Architecture:

The Research Centre of the National Petroleum Company, CENPES, in Rio de Janeiro 41

Daylight Factor and Uniformity calculations provided artificial lighting design optimization. By means of isolines plotted on work planes, one could map each room and identify natural lighting availability inside the building, detecting zones and establishing the proper strategy for each one [12]. In this sense, artificial light keeps up with natural light variations, adjusting lighting levels and distribution in order to improve luminous environment

The daylighting analysis made use of concept of Daylight Autonomy [12], to predict periods only on account of natural light providing the proper visual task lighting level. Although the minimal value of 2% for the Daylight Factor is adopted by some international standards to consider a well-daylit space, regarding tropical countries, daylight availability can be increased due to high sky luminance conditions, consequently, the minimal Daylight Factor value can be decreased. On this basis, minimal value of 1.5% for DF was considered accepted in the context of this work, whereas the minimal of 2% remained as an initial reference. Being so, by maintaining the same criteria, external illuminance parameter was increased to reach the same internal illuminance value related to DF 1.5% and 2%. In essence, beyond the performance indicators, quality of daylight in most of the working areas, including daylight distribution, views, visual communication and absence of contrast and glare, was achieved with the design of the façade's components in relation to the

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,

a. elaboration of a 5 year weather file (1998 - 2004) with hourly data from the Tom Jobim

b. identification of the critical summer month (February 2003) and a summer reference design day for in-depth assessments of heat flow through the building envelope;

d. definition of base cases including building's thermal zoning, occupation profile,

e. advanced computer simulations of fluid dynamics (carried out with the software CFX 5.7) to determine air flow around buildings, pressure coefficients, air velocity on the

f. thermal dynamic simulations (carried out with the software TAS v.9.0.5) in order to quantify buildings' thermal performance and, consequently, estimate the potential

c. establishment of comfort parameters for naturally ventilated internal spaces;

openings of buildings' envelope and convection exchange coefficients;

quantity and quality, intending good visibility and visual comfort.

orientation and building form.

**5. Naturally ventilated buildings** 

according to the following procedures [19]:

International Airport station [4];

number of hours in comfort;

construction materials and internal thermal loads;

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

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 around the room.

In summary, the outcomes of daylight uniformity were:


Daylight Factor and Uniformity calculations provided artificial lighting design optimization. By means of isolines plotted on work planes, one could map each room and identify natural lighting availability inside the building, detecting zones and establishing the proper strategy for each one [12]. In this sense, artificial light keeps up with natural light variations, adjusting lighting levels and distribution in order to improve luminous environment quantity and quality, intending good visibility and visual comfort.

The daylighting analysis made use of concept of Daylight Autonomy [12], to predict periods only on account of natural light providing the proper visual task lighting level. Although the minimal value of 2% for the Daylight Factor is adopted by some international standards to consider a well-daylit space, regarding tropical countries, daylight availability can be increased due to high sky luminance conditions, consequently, the minimal Daylight Factor value can be decreased. On this basis, minimal value of 1.5% for DF was considered accepted in the context of this work, whereas the minimal of 2% remained as an initial reference. Being so, by maintaining the same criteria, external illuminance parameter was increased to reach the same internal illuminance value related to DF 1.5% and 2%. In essence, beyond the performance indicators, quality of daylight in most of the working areas, including daylight distribution, views, visual communication and absence of contrast and glare, was achieved with the design of the façade's components in relation to the orientation and building form.
