PSI - Issue 11

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Fabiana Silvero et al. / Procedia Structural Integrity 11 (2018) 52–59 Silvero, et al. / Structural Integrity Procedia 00 (2018) 000 – 000

Table 3. Input parameters used for the simulations. For each thermal zone the Occupation density (m 2 /person), the minimum fresh air (l/s-person), the target illuminance (Lux), the internal gains (W/m 2 ) and the occupation schedules are shown

Thermal Zone

Lounge

Circulations

Kitchen & Dining

Bedroom

Bathroom

Occupation Fresh Air Illuminance Heat Gains

53.32

64.50

59.12

43.59

53.37

200 3.9

100 1.57

300

100 3.58

150 1.67

30.28

Weekday Weekend

0,8

0 0,4 0,8 Occupancy Factor

0,4

Schedule

Occupancy Factor

Time of Day

It is considered that the building does not have any heating or cooling systems. However, natural ventilation is considered, being the natural ventilation rate set in 5 air changes per hour. The windows operation schedule defines the operation of natural ventilation. Thus, for summer season windows are open and allow natural ventilation only when the outdoor temperature is lower than indoor temperature, but it is restricted when the outdoor temperature is lower than 20°C. Regarding the window shading (exterior Venetian blinds), it is on when solar radiation on the window reaches the medium solar setpoint of 189 W/m 2 (Wankanapon et al., 2011), aiming to reduce thermal discomfort due to direct solar radiation but taking advantage of natural daylight. All the retrofit options include the glazing area improvement ( G1a ). Furthermore, extra glazing areas to improve natural night ventilation were considered in the simulations, above the existing windows in the lateral and posterior facade. Thus, these windows follow the schedule described above during the day but are fully open from 5 pm to 10 am. The analysis of the outcomes will be made at the building level, and the parameters chosen as evaluation indicators are operative temperature ( ) and Fanger’s PMV index. The internal and external surface temperatures ( and , respectively), internal gains and the heat transfer through building’s envelope will also be analysed to detect the building components with the greatest influence on the thermal performance. The simulations were made during the hottest week of a year with hourly intervals, nevertheless, some daily simulations are also shown in order to do a detailed analysis of the building’s behaviour considering some specific parameters. 3. Dynamic simulations – Results and Discussions Once the input parameters were defined, the dynamic simulation of the building was carried out, and the results are summarised in this section. For the improved options of the roof, the building showed a slightly better thermal performance with the roof R1b, the reason why it was used for the following simulations. The results show that for the hottest week, the Fanger PMV index presents too high values in the building original state ( Figure 2 – orange line ), since the maximum value obtained was 4.37, indicating high levels of discomfort, since the thermal sensation scale ranges from -3 (very cold) to +3 (very hot). Analysing the improved options, the options 1 and 2 deliver almost the same results, being the option 3 the one with the lowest PMV Fanger indexes, and therefore, with the best results for the summer season. With the options 1 and 2, it was observed a decrease of 58% of the maximum value obtained for the index in the building’s original state, while with the option 3 the decrease reaches 70%. Thus, with the Option 3, the building achieves an average Fanger PMV index of +0.8 for the hottest week, which is described as a neutral and comfortable environment. In the original state, also presents very high levels ( Figure 3 – orange line ), with a maximum value of 35.5°C. increases from 5 am (mean − = 27°C) until 1:30 pm (mean − = 49°C), afterwards it starts decreasing until 5 am of the following day. increases from 6 am (mean − = 27°C) until 2 pm (mean − = 42°C), following by a decrease until 6 am of the following day. So, the time differences between the peaks of the temperatures at the outer and inner surface of the building are 30 minutes. This behaviour is attributed to poor thermal parameters of the building’s envelope, which have very low thermal mass causing very low values of thermal shift and internal areal heat capacity.

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