Civil Engineering Reference
In-Depth Information
Table 3 Estimated embodied energy values for selected materials and components used in the
case studies
Material/system
Embodied energy
Service life (Yrs)
Polystyrene insulation
88 MJ/kg (24.4 kWh/kg)
50
Solar water heating system (5 m
2
)
6,000 kWh
20
Solar water heating system (10 m
2
)
10,000 kWh
20
PV installation, per m
2
1,700 kWh
25
Double-glazed windows, per m
2
300 kWh
30
Triple-glazed windows, per m
2
400 kWh 30
Mechanical ventilation heat recovery system 9,000 kWh 50
Includes annual replacement of filters and of the ventilation unit every 20 years
Table 4 AEE for components for each case of building refurbishment options (kWh/year), for
the case study house (96 m
2
)
Additional envelope
insulation
Triple
glazing
Solar water
heating
MVHR
PV
Total
AEE
(kWh/
year)
1 (existing)
0
0.0
0
0
0
0
Option 2
159
0.0
300
0
0
459
Option 3
284
73
300
0
0
657
Option 4
381
73
300
0
0
754
Option 5
450
73
300
0
0
824
Option 6
450
73
300
180
0
1,004
Option 7
450
73
500
180
0
1,204
Option 8
450
73
500
180
408
1,612
Option 9
450
73
500
180
816
2,020
Option 10
450
73
500
180
1,224
2,428
2004
; Hernandez and Kenny
2012
) and for PV systems (Pacca et al.
2007
; Nawaz
and Tiwari
2006
; Raugei et al.
2007
; Richards and Watt
2007
).
Data displayed in Table
3
have been chosen according to those sources by the
authors as best estimates for Ireland for some selected building components and
also the estimated service life for each of the products. As an Irish database or a
consistent methodology for embodied energy calculation does not exist at present,
it needs to be emphasized that these estimates are limited exclusively to illustrate
the proposed methodology and there is a high degree of uncertainty, particularly
regarding the lifetime of the products and embodied energy values for the
installations.
Comments on sensitivity of the results are made in a later section (Table
4
).
Dividing the total AEE by the building area, the results can be integrated with
the annual energy performance calculation, as it is presented in the Fig.
6
.
It can be observed that for the first refurbishment Option 2, the AEE represents
a very small portion of the total life cycle energy use, so the achieved energy
