PSI - Issue 11

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

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Figure 7 depicts the heat gains from the inner surfaces of the building’s envelope components for option 3. The greater heat gains continue to be produced mainly through the roofs followed by the external walls, but the mean peak heat gains decreased 61 W/m 2 for the roof and 25W/m 2 for the walls (a decrease of 82% and 76%, respectively). However, both walls and roofs present positive values of heat transfer during all day, hence, they do not collaborate with heat losses at any time. Regarding the internal heat gains, the influence of solar gains through glazing areas have decreased an average of 18% ( Figure 8 ). Figure 9 depicts the behaviour of the building during the hottest day for the option 3. The never is lower than the , as happened in the buildin g’s original state during night time. As the solar radiation increases the also increases showing its link to the diurnal path of solar radiation ( ∆ = 11.6°C), however, and operative temperature remain almost constant ( ∆ = 2.1°C and ∆ = 1.6°C). The peak occurs at 2 pm while the peak is at 5 pm, being the overall time shift of the building of 3 hours (see Figure 10 ). Thus, it is demonstrated that improving the thermal inertia of the envelope components, the building manages to keep its indoor temperature almost constant, storing the heat until the time that nocturnal natural ventilation is activated delaying the heat wave release. Figure 10 shows the thermal wave and thermal inertia factors in the original state of the building (left) and with the improvements designed for the option 3 (right), where can be seen the peak temperatures and the thermal amplitudes decreased. The values depicted are referred to average values for the envelope of the building considered as a whole.

Internal Gains

Heat transfer

Hottest day 4/Jan

20 25 30 35 40 45

0 1 2 3 4 5

12 15

10 20 30

0 3 6 9

-30 -20 -10 0

Temperature °C

Solar Radiation kW/m2

Heat Balance (W/m2)

Internal Gains (kW/m2) Day Lighting

Outside Temp Ext. Surf. Temp Glob. Solar Rad.

Inside Surf. Temp Operative Temp

Equip.

Day

Hours

Walls Glazing

Ceilings Floors

Occupancy

Solar Gains

Fig. 7. Heat transfer - Hottest week – Op. 3.

Fig. 8. Internal heat gains – Op. 3.

Fig. 9. Simulations results for the hottest day – Op. 3.

Original State Building's envelope

Option 3

Building's envelope

20 25 30 35 40 45 50 55 Temperature °C ∆ Outside

∆ ൌ 2°

20 25 30 35 40 45 50 55 Temperature °C Outside

ൌ 12°

51,2°C

∆ ൌ 23°

∆ ൌ 14°

43,4°C

41,4°C

29,8°C

29,8°C

29,4°C

28,1°C

27,7°C

Inside

Hours ൌ 0 ℎ

Inside

ൌ 3 ℎ

Hours

External Surface Temperature

Inside Surface Temperature

External Surface Temperature

Inside Surface Temperature

Fig. 10. Thermal wave and thermal inertia factors for the hottest day

In summary, the building in its original state has a very low thermal performance during the period simulated. Among the improved options, option 3 delivered the best results, but in general, the three options have significantly improved the thermal performance. Considering its heritage value, the option 1 could be considered as the less invasive, but some heritage buildings have all the external facades protected. The residential heritage building under study have inner surfaces without any patrimonial element to be preserved, so, option 2 and 3 can be applied. With the changes proposed, the thermal parameters of the building’s envelope components have improved, impacting positively on the thermal performance of the building. To achieve this, the thermal mass of the building has been increased on average 65%, giving it the capacity to store the heat until the time when nocturnal natural ventilation is activated, which interacts with the heat flux released by the envelope components towards the indoor environment of the building, attenuating the indoor temperatures during the heat discharge. This kind of measures is effective due to the high thermal amplitude of the outside temperatures, having lower temperatures during the night which enable opening the building to improve the natural ventilation rates.