Condensation in Buildings - Australian Building Codes Board

Information Handbook: Condensation in Buildings
station location. The record also contains monthly mean dew point temperatures for 9am and
3pm, which indicate the water vapour content of the atmosphere at those times. The charts in
Figure 4.7 and Figure 4.8 compare the average of the dew point values (dotted blue curve) with
the mean minimum temperature in each month. When the mean minimum temperature
(red/purple curve) falls below the dew point, condensation can occur, as highlighted by the blue
filled area between the curves.
As Figure 4.8 shows, the potential need not be limited to the colder months of the year. In some
locations, the critical combinations of temperature and water vapour levels can occur in any
season. In both charts, the yellow mean maximum temperature curve offers some context for
the daytime conditions likely to follow overnight condensation events. It is typical of many
Australian locations that conditions triggering condensation will be followed by warmer daytime
conditions that can assist drying. As a result, the overnight condensation flagged by these
comparisons may be a temporary event with little lasting effect. This possibility is discussed
further in Section 4.6, where the effects of likely indoor water vapour loads for dwellings are also
considered.
Figure 4.8 – Outdoor condensation potential spanning all 12 months
30°C
Mean Maximum
Temperature
25°C
20°C
Average 15°C Outdoor
Dew Point
10°C
5°C
Warrnambool (VIC)
Outdoor condensation
potential in all twelve
months
Mean Minimum
Temperature
DRAFT HANDBOOK
0°C
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Outdoor Condensation Potential
The comparison illustrated in Figure 4.7 and Figure 4.8 can identify the month with the greatest
potential for outdoor condensation and how many months are affected in each year, under
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