analysis of the influences of solar radiation and façade glazing ...

3.4 Testing of a building indoor environment during the warm period 87
As seen in Fig. 3.38 and Fig. 3.39, a reduction of the glazing area in an optimal variant
leads to a decrease in the operate temperature and raises thermal comfort conditions. We
can observe these effects in apartments OG1 and OG2. In the calculation of the optimal
value of WWR it is assumed that the south facing windows area in apartments OG3 and
OG4 were increased to the maximum. As it turned out, this assumption does not
significantly influence the thermal comfort in this part of the building. So, we can conclude
that the optimal window-to-wall ratio, which was determined to achieve energy savings in
heating periods, provides a better quality of thermal environment during a warm season.
In order to reduce the internal air temperature we can use intensive mechanical ventilation
when the outdoor temperature is lower than the air temperature in the rooms. The next
series of calculations were performed to investigate how a variable air volume system
influences the thermal environment in living spaces. The typical work schedule of a
ventilation system with intensive night cooling in OG1 apartment for the last week of July
is shown in Fig. 3.40. The total volume of outside air varied approximately between 60 and
210 m 3 /h. The maximum value of the flow rate appeared very often from 10 p.m. to 7 a.m.
Practical results of a one-week operation of a VAV system and the comparison with
constant air flow ventilation are demonstrated in Fig. 3.41. We observed that the amplitude
between day and night internal air temperatures was significantly higher for the apartment
with a variable air volume system. Due to this effect we could relatively quickly reduce
and stabilize the air temperature inside the living spaces on a lower level.
As shown in Fig. 3.42 the difference between the operate temperature in an apartment with
the constant air volume system and with a night cooling system using the variable air
volume flow grew from April to first half of June. This value stayed at approximately the
same level equal to about 3.5°C on the next period of warm season. The maximum value
differed from 4.1°C for apartment OG2 to 4.4°C for apartment OG1 and the mean value
differed from 2.7°C to 3.0°C, respectively.
As it turned out, cooling by ambient air can be an energy saving solution. This ventilation
system, coupled with external shading devices, is sufficient to prevent living spaces from
excessive overheating during warm seasons.