Page 5 - Condensation Guide
P. 5

FAIRVIEW CONDENSATION GUIDE








                  TAKING A CLOSER
                  LOOK.                                               HUMIDITY & DEW POINT








                                    Thanks to science, we can use     form of vapour, and it has to let the water
                                    measurements to pinpoint the exact time   go. If it touches a cooler surface, the water
                                    when condensation will appear. The two   vapour appears as condensation. This often
                                    common terms we use are ‘relative humidity’   means water appears on windows, mirrors
                                    and ‘dew point’.                  and walls, as well as disappearing into the
                                                                      furnishings and carpet.
                                    RELATIVE HUMIDITY
                                                                      KNOWING THE NUMBERS
                                    Relative humidity (RH) is how we measure
                                    moisture in the air. For example, a room   If you’d like to know when conditions are
                                    humidity of 80% RH means the ability of the   right for condensation to start forming
                                    air to hold water is 80% loaded. 100%    in your home, head to a website like
                                    is saturation point. The higher the   www.decatur.de, which has an online
                                    temperature, the greater the amount of   dew point calculator.
                                    moisture the air can hold as water vapour.
                                                                      All you need to know is your room
                                    The lower the temperature, the less the
                                                                      temperature and indoor humidity.
                                    amount of moisture the air can hold. So the
                                    moisture is released at a temperature we call   To find this out, you’ll need a thermometer
                                    the dew point.                    and a hygrometer. Thermometers with
                                                                      accuracy as close as 1%, and electronic
                                    DEW POINT                         hygrometers with accuracy as close
                                    Dew point is the temperature at which the   as 5% are available from hardware or
                                    air becomes cool enough that the moisture   electronic stores – just check the accuracy
                                    in the air is released. The air can only hold   specifications before buying. When you can
                                    a certain amount of moisture. The cooler   measure humidity, it becomes much easier
                                    the air gets, the less it can hold water in the   to start managing it.










                                                        Average NZ home       Standard double glazing
                                                                              Single glazing
                                               +20
                      PREDICTED   CONDENSATION  Outside temperature  +10 0  Condensation forms  Low E double glazing
                                                        air humidity 70%
                                               +15


                                                +8
                                                +5
                                                       Condensation forms
                                                +4
                                                                             25
                                                                        20
                                                                                  30
                                                        5
                                                                                        35
                                                                  15
                                                             10
                                                       Condensation forms
                                               –4
                                                –5
                                                                      Home inside temperature 0C
                                               –10




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