© PCE Instruments
23
Eng
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2.4
Wood moisture equilibrium and normal moisture content
Wood is a hygroscopic material and reacts to fluctuations in the air humidity. If the air humidity
drops, the water content in the wood also drops and vice versa. This means that there is a
constant relationship between the air humidity and the wood moisture. This relationship is called
wood moisture equilibrium. The normal moisture content is understood to be the wood moisture
content that occurs in a normal climate with an ambient temperature of 20 °C and a relative
humidity of 65 %.
Further values can be seen in chart 1 below.
Relative
humidity in %
90 %
21.0
21.0
21.0
20.8
20.0
19.8
19.3
85 %
18.1
18.0
18.0
17.9
17.5
17.1
16.9
80 %
16.2
16.0
16.0
15.8
15.5
15.1
14.9
75 %
14.7
14.5
14.3
14.0
13.9
13.5
13.2
70 %
13.2
13.1
13.0
12.8
12.4
12.1
11.8
65 %
12.0
12.0
11.8
11.5
11.2
11.0
10.7
60 %
11.0
10.9
10.8
10.5
10.3
10.0
9.7
55 %
10.1
10.0
9.9
9.7
9.4
9.1
8.8
50 %
9.4
9.0
9.0
8.9
8.6
8.4
8.0
45 %
8.6
8.4
8.3
8.1
7.9
7.5
7.1
40 %
7.8
7.7
7.5
7.3
7.0
6.6
6.3
35 %
7.0
6.9
6.7
6.4
6.2
5.8
5.5
30 %
6.2
6.1
5.9
5.6
5.3
5.0
4.7
25 %
5.4
5.3
5.0
4.8
4.5
4.2
3.8
10 °C
15 °C
20 °C
25 °C
30 °C
35 °C
40 °C
Temperature
in °C
Chart 1: Equilibrium moisture values
