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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Fanger PMV Index

Temperatures and Solar radiation

0 1 2 3 4 5 Index

0 1 2 3 4 5

20 25 30 35 40 45

Temperature °C

Day

Solar Radiation kW/m2

Day

Original

O1 O3

O2

O1

O2

O3

Original

Outside Temp

Glob. Solar Rad.

Fig. 2. Fanger PMV index of the building with retrofit measures for the hottest week.

Fig. 3. Operative and outside temperatures coupled with Global solar radiation: building with retrofit measures for the hottest week.

The operative temperature with the improved solutions has improved significantly. The options 1 and 2 deliver again practically the same results, being the exterior cladding with thermal insulation as efficient as the inner cladding with hollow brick. Thus, when is not possible to do an exterior reinforcement of the walls, the option 2 represents an alternative. However, it is required cladding all the walls inner face, and this will decrease the useful indoor area of the building. Option 3 follows the same variation of the previous ones but with values slightly lower, delivering a maximum value of 28.3°C for the in the hottest week, 7.1°C less than in the building original state. Whit the improvements designed also the fluctuations of the throughout the day have decreased, being the mean daily thermal amplitude of 1.6°C (for option 3) against the 5.3°C of the original state of the building. With this retrofit solution, the building gets a better capacity to keep constant its indoor temperature without being too affected by the outside temperature. Analysing the heat transfers through building’s envelope in the original state ( Figure 4 ), it was detected that the heat gains are produced mainly through the roofs followed by the external walls, which is expected considering the poor values of thermal parameters of the roof, which has the lowest values of , , 1 among the buildings’ envelope components. Consequently, the roof is the main responsible for heat gains during daytime but, at night contributes to heat losses. Walls have positive values of heat transfer all day. The ground floor has the capacity to dissipate heat, which is a positive aspect for summer sthe eason. Figure 5 depicts the internal gains produced in the building during the period of simulation, where the solar gains are the most significant, indicating the need to improve the thermal performance of the glazing areas. Aiming to depict more in detail the thermal performance of the building in the original state, Figure 6 shows the simulation results for the hottest day of the week, where can be seen the fluctuation of the operative, outside and external/internal surface temperatures, coupled with the global solar radiation along the day. During the night, the external surface temperature is lower than the internal surface and operative temperature, and as the solar radiation increases, this situation reverses, evidencing the strictly link to the diurnal path of solar radiation. Also, it is highlighted that in this day the peak external surface temperature matches with the peak of internal surface temperature, which occurs at 1 pm, also matching with the peak of global solar radiation value, evidencing the deficient time shift value. The peak operative temperature occurs at 5 pm, four hours later. However, the peak of outside temperature occurs at 3 pm.

Heat transfer

Internal Gains

Hottest day 4/Jan

0 5 10 15 20 Internal Gains (kW/m 2 )

0 1 2 3 4 5

20 25 30 35 40 45 50

-50 -30 -10 10 30 50 70 90 Heat Balance (W/m 2 )

Solar Radiation kW/m 2

Temperature °C

Day

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

Inside Surf. Temp Operative Temp

Hours

Day

Lighting Occupancy

Equip.

Walls Glazing

Roofs Floors

Solar Gains

Fig. 4. Heat transfer through building’s envelope - Original state - Hottest week.

Fig. 5. Internal heat gains – Original State - Hottest week.

Fig. 6. Simulations results of the building’s original state for the hottest day.