Refurbishment Scenario to Shift Nearly Net ZEBs Toward Net ZEB Target: An Italian Case Study - Nearly Zero Energy Building Refurbishment - page 243

1,500,000

1,000,000

500,000

0

-500,000

-1,000,000

-1,500,000

-2,000,000

Produced
GWP

Avoided
GWP

Net GWP

Baseline scenario 1,144,461 -1,104,166 40,295

Refurbishment scenario 1,019,106 -1,714,447 -695,341

Fig. 11 GWP balance in the two assessed scenarios

the avoided ones during the operational phase, due to the on-site electricity gen-
eration by the PV system (Table 6).
In order to get a deeper description of the energy and environmental perfor-
mance of the retrofit options in the Refurbishment scenario, the following payback
indices were added to the EPD set: the EPT and the EPT.
In detail, the EPT of the building retrofit is defined as the time needed to save as
much energy (valued as primary) by means of the retrofit options as that consumed
during the whole building life cycle:

E P ; T ¼ CED Building
E s ; y

ð 2 Þ

where

• CED Building is calculated with regard to the life cycle of the building in the
Refurbishment scenario (GJ);
• E s, y is the yearly saving of primary energy due to the retrofit actions, which
results 411 GJ/y.

The yearly saving of electricity was converted into primary energy based on the
Italian energy mix for the production of electricity.
The EPT (Em PT ) is the time during which the avoided emissions by the
accomplishment of the Refurbishment scenario are equal to those released during
the building life cycle. The authors decided to calculate the Em PT with regard to
the GWP index to express the environmental pollution.
Then, it was defined as

Em P ; T ¼ GWP Building
GWP a ; y

ð 3 Þ