Humidex
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What is the dew point?
The dew point is one of the three environmental variables that are important when discussing the
conditions in your home. Understanding the dew point will help you understand how the HCS unit
operates and how it will help to reduce the relative humidity (RH%) level infiltrating your home and
eliminate excess humidity, while providing energy efficient ventilation for your home. The dew point
is defined as the temperature at which the water vapor contained in a given volume of air will condense
into water. This is best illustrated by an example:
Assume the following measurements are taken by the unit:
Temperature = 68
⁰
F
Relative Humidity = 60%
Using the temperature and RH% values measured, we would calculate that the dew point in your
home is 54
⁰
F. As the temperature of surfaces in your dwelling (these tend to reflect the floor
temperature, which is generally cooler than the ceiling air temperature) approaches the value of the
dew point, you risk having condensation on those colder surfaces (as well as un-insulated water pipes).
This condensation can lead to problem situations that might produce unhealthy living conditions in
your home (odors, molds, etc.)
New Installations in the Summer
The late spring and early/mid-summertime temperature in most basements remains at approximately 59° to
66° F (15° to 19° C) whereas the air entering the basement from the upstairs of the house will generally be in
the range of 75° to 85° F (24° to 29° C) with a relative humidity of 70 to 75%. This air will have a dew point
(the temperature of surfaces on which it will condense, including basement surfaces) in the range of 64° to 76°
F (18° to 24°).
When a Humidex is installed in these conditions, condensation may result, as the air from the upstairs comes
in contact with cold surfaces (i.e. concrete walls, floors, etc). The Humidex ventilation effect will over time
increase the basement temperature and help prevent this condition, however, during the initial operating season;
a small amount of heat may have to be added temporarily to the basement to increase its temperature. If this
condition occurs also reduce speed exhaust to medium.
If an air conditioner is present in the house, close all AC vents/leads/ducts to the basement.
COLD SURFACE FACTS – IMPORTANT
It is recommended that any exposed cold water pipes and A/C ducts should be insulated to reduce
condensation on these cold surfaces before a humidex is installed.
