Civil Engineering Reference
In-Depth Information
Table 5
NER for successive improvements
Annual energy savings (-DAEU)
(kWh/m2 year)
DAEE
(kWh/m2 year)
NER
(-DAEU/DAEE)
Existing ? Option 2
143.9
4.8
30.1
Option 2 ? Option 3
17.5
2.1
8.5
Option 3 ? Option 4
11.7
1.0
11.7
Option 4 ? Option 5
1.5
0.7
2.1
Option 5 ? Option 6
9.6
1.9
5.1
Option 6 ? Option 7
5.1
2.1
2.4
Option 7 ? Option 8
19.0
4.3
4.5
Option 8 ? Option 9
19.0
4.3
4.5
Option 9 ? Option 10
19.0
4.3
4.5
obtained to just above 2. This result emphasizes the large life cycle energy savings
that can be achieved by insulating buildings where there are high transmission
losses or by the installation of a small domestic solar hot water system as are the
issues considered in Option 2. However, an increase in polystyrene insulation to an
already well-insulated building, as described in the proposed improvement
between Option 4 and Option 5, only yields an NER of 2.1. In such cases with very
high insulation levels, the use of insulation products with lower embodied energy
content, such as products based on rapidly renewable materials, which can achieve
similar savings compared to conventional materials with little associated embodied
energy, could achieve a much higher NER.
Regarding the further options looking for a further decrease in energy use
towards zero energy, the measure changing to Option 6 which considers instal-
lation of MVHR gives a value above 5, which means that there is a potential, in
life cycle energy terms, for the installation of this technology in this case study.
Considering a further increase in solar thermal collection area as it is the change to
Option 7 shows an NER of 2.4, relatively low which shows that solar heating in
this climate with low winter solar access is perhaps not the most adequate measure.
For Option 8 onwards, which considers the addition of PV, the calculated NER is
4.5. These values for building integrated renewable energies are relatively small
when compared with some off-site renewable energy. For example, off-site
renewable energy production from wind energy can have NER values in the range
of 10-30 (Kubiszewski et al.
2010
; Crawford
2009
).
5 Uncertainty and Sensitivity Analysis
The presented methodology for life cycle energy performance evaluation is
affected by both factors linked to building energy performance in the use phase and
factors linked to the assessment of embodied energy of the products.
