Civil Engineering Reference
In-Depth Information
36
34
1-STANDARD GLAZING OLD BUILDING
32
2-STANDARD GLAZING
30
3-LOW-E
28
26
4-GRANULAR AEROGEL
24
5-GRANULAR AEROGEL
22
6-MONOLITHIC AEROGEL
20
18
7-TRIPLE GLAZING
16
14
12
10
8
6
4
2
0
BEIJING
COOLING
HELSINKI
COOLING
LONDON
COOLING
MOSCOW
COOLING
OTTAWA
COOLING
ROME COOLING
Fig. 22 South exposure: annual energy demand for cooling for the six cities and for seven
different kinds of glazing
(Type 6), which has a low thermal transmittance (0.5 W/m
2
K) and a high global
solar factor (75 %). Nevertheless, in summer, it has the worst behaviour, because
of the high solar factor: in summer nights, the indoor air temperature is higher, due
to the low thermal transmittance (0.5 W/m
2
K). The energy demand for cooling is
minimum for the granular aerogel glazing system (Type 5) of 40 mm thickness
due to the low solar factor (0.25). Low thermal transmittance of windows is a good
choice since it decreases the heating demand, but low g-values have a great impact
on the cooling demand. Granular aerogel glazing n.5 saves more energy than the
other window solutions: the cooling energy saved is 25 % (7 kWh/m
2
per year) for
Beijing and 38 % for Ottawa (about 5 kWh/m
2
per year) with respect to the
standard glazing type 2.
Overall, the monolithic aerogel glazing is the best solution for all the cities
except for Rome; this system allows for Ottawa an annual energy demand decrease
of about 22-27 % with regard to the standard glazing type 2 (Fig.
23
). It is not the
best solution for Rome because it does not perform well in summer, and Rome is a
mild-climate city in winter.
The annual energy demands per conditioned building area are not very different
for low-e glazing system and windows with granular aerogel in interspace, above
all for Helsinki and Moscow.
Finally, innovative glazing systems with silica aerogels in interspace are the
best solutions in cold climates, especially the monolithic systems. This type of
window is a good choice during the winter period, but in summer, it does not
