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7 – Introduction to building thermography
Figure 7.7 A: Temperature in degrees Fahrenheit; B: Maximum amount of water in gr/ft
A
B
86.0
13.30
84.2
12.60
82.4
11.93
80.6
11.29
78.8
10.68
77.0
10.10
75.2
9.54
73.4
9.01
71.6
8.51
69.8
8.03
Example:
7
The relative humidity of a certain volume of air at a temperature of +30°C (+86°F) is
40 % RH. Amount of water in 1 m
= 30.44 × 0.40 = 12.18 g (187.96 gr).
7.3.7.2
Dew point can be regarded as the temperature at which the humidity in a certain
volume of air will condense as liquid water.
Example:
The relative humidity of a certain volume of air at a temperature of +30°C (+86°F) is
40 % RH. Amount of water in 1 m
= 30.44 × 0.40 = 12.18 g (187.96 gr). In the table above, look up the temperature
for which the amount of water in air is closest to 12.18 g. This would be +14.0°C
(+57.2°F), which is the approximate dew point.
52
A
B
68.0
7.58
66.2
7.14
64.4
6.73
62.6
6.34
60.8
5.97
59.0
5.62
57.2
5.29
55.4
4.97
53.6
4.67
51.8
4.39
3
(35.31 ft
Definition of dew point
3
(35.31 ft
A
B
50.0
4.12
48.2
3.86
46.4
3.62
44.6
3.40
42.8
3.18
41.0
2.98
39.2
2.79
37.4
2.61
35.6
2.44
33.8
2.28
3
) of air at +30°C = 30.44 × Rel Humidity
3
) of air at +30°C = 30.44 × Rel Humidity
Publ. No. 1558440 Rev. a156 – ENGLISH (EN) – February 28, 2006
3
(at sea level)
A
B
32.0
2.12
30.2
1.96
28.4
1.81
26.6
1.67
24.8
1.54
23.0.
1.42
21.2
1.31
19.4
1.21
17.6
1.11
15.8
1.02
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