Facades and Summer Performance of Buildings - Low Energy Cooling for Sustainable Buildings - page 41

Figure 2.14 Measured air change n as a function of temperature difference between fa¸ade air and
room air. The two horizontal lines indicate the minimum hygienic air exchange rate for one and two
persons

and integrated blinds. The air exchange rates were measured in summer 2004 in
the Zeppelin Carre building using a tracer gas system from the Dantec Company.
Concentrations were measured in three locations of the room simultaneously. Both
the shading blind position and the window opening size were varied. The position of
the blinds, which can be tilted to six different angles between closed and fully open,
did not have any influence on the air exchange rate. There is no clear dependency of air
change rate on temperature difference between the fa¸ade and room air. Measurements
on one tilted window showed an air change increase with temperature difference (see
Figure 2.14), whereas with two tilted windows there even a decrease was measured
(see Figure 2.15). The main influence is the opening cross-section of the window:
if only one of the two windows is tilted, the mean air exchange is 0.97 h − 1 ; if both

3.0 0.18

0.16

2.5

0.14

Flow velocities

2.0 0.12

0.10

1.5

0.08

1.0 0.06

0.04

0.5

0.02

0.0 0.00

0.93 1.68 1.91 2.8
Air temperature difference, gap to room / K

Figure 2.15 Measured air change n for two tilted windows