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Controlling indoor humidity

A matter of comfort, health and energy savings

Just as the temperature shown on your thermostat, the relative humidity level in your home has a direct impact on the air quality and the comfort of occupants.

Relative humidity is often underestimated: too much or not enough humidity can cause health problems, and even damage to your home or luxurious goods, in periods of heating as well as cooling. Not to mention some discomfort, despite maintaining a normal average temperature.

 

How to measure relative humidity

The relative humidity (RH) of a house should be set at about 40%, ideally around 50% during cooling periods and 30% during heating. The most effective way of measuring the percentage is by using an analog or digital hygrometer, an inexpensive device easily found in hardware or large surface stores.

Many signs of inadequate humidity levels may still often occur such as these most common:

Too much humidity

  • Condensation on windows in winter
  • Moisture stains on walls
  • Musty smell

Not enough humidity

  • Itchy eyes, nose and skin
  • Dry skin and chapped lips
  • Static

 

How does the humidity level affects our comfort level?

Humidity is a factor that greatly influences our body perception of temperature. The evaporation of oceans, rivers and streams, affects the amount of moisture in the air. The hotter the air temperature, the more moisture it can hold. In Canada, meteorologists use humidex to determine what the temperatures feels like at given degrees and the percentage of moisture present in the air.

When it’s warm, the human body perspires to maintain its temperature around 37 ° C. When it evaporates, it cools the body. When the moisture level in the air is very high, the sweat will not evaporate. As a result we feel much hotter and uncomfortable.

When the air is at 60% relative humidity, it is certain that people will experience some discomfort. For example, if the temperafture reading is at 27 ° C on the thermometer and RH at 60%, the temperature felt increases by 6 degrees, i.e. at 33 ° C. The table below shows how humidex influences our comfort level.


Humidex from Temperature and Relative Humidity Readings
 

How to restore an appropriate humidity level

Our daily routine (laundry, showers, baths, meal preparation, etc.) generates from 5 to 10 liters of moisture. However, there are natural ways to maintain or restore a balanced humidity level, such as, for example, at the end of heating season, opening windows on beautiful spring days to encourage fresh air circulation and evacuate excess moisture. Simple changes to our lifestyle can also lead to significant improvements, either by controlling moisture sources (showers, laundry, etc.), by ensuring a proper ventilation or by using a dehumidifier.

During the hot, sticky days of summer, if the humidity level is too high, using an air conditioner or heat pump will help to dehumidify the air and to reduce relative humidity inside the home. 

 

What about energy savings?

An appropriate control of the humidity level during heating mode makes it possible to save energy. On the other hand, in cooling mode, the unit must remove excess moisture to achieve the desired comfort level: which translates inevitably into an electricity expense.

However, it is possible to control and even lower our heating costs, by maintaining the recommended HR level.

 

Apparent temperature (AT) from temperature and relative humidity - after Steadman 1994

 

Take this example:

It is mid-February, and your thermostat is set at 22 ° C. Despite this, you are still feeling cold and uncomfortable. You see that the relative humidity of the house is at 15%. It is quite normal to have this sensation of cold since the humidity is too low, resulting in a felt temperature of only 19 ° C. Two options are possible: increasing the temperature of the thermostat to 25 ° C to reach the desired temperature, or increasing the humidity to 35 to reach a recommended ambient temperature of 21 ° C. Given the energy costs, we can easily conclude that the best way to ensure your well-being is to control humidity rather than soliciting your heating system!

Controlling indoor humidity


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