The wrong humidity in your home leads to poor Indoor Air Quality

Humidity and Air Quality

Winters in Canada tend to be very cold and very dry from a relative humidity standpoint. Low outdoor relative humidity can lead to dry indoor air quality or low indoor relative humidity. Relative humidity indoors that is either too low or too high can lead to poor indoor air quality.

Ideally, the indoor relative humidity for maximum occupant comfort is usually in the 55%-60% range. This is where we feel most comfortable year-round and at this level our sinuses and respiratory system, even our skin is properly supported. This is considered good indoor air quality from a relative humidity perspective.

However, this level of humidity is not sustainable in our climate. In the summertime, our outdoor humidity in the Toronto area is usually 65%-85%. If we use air conditioning or dehumidifiers then usually indoor relative humidity in our homes, apartments even at work tend to fall into the 55%-65% range without much effort. On certain hot and humid days that Toronto and the GTA are susceptible to, the indoor humidity levels might increase a little higher for a short time.  

In the winter, outdoor relative humidity can range in the low 20%-30%. So for us to achieve proper indoor relative humidity we either need to have a portable or central humidifier or we naturally have a house that does not ventilate very well and keeps the humidity high naturally. There is a huge problem with this though. In winter, our outer wall surfaces in any building are cold. Windows are also cold. So having relative humidity at the comfort zone of 55% or higher will mean that you will get condensation on these colder surfaces. Excessive condensation will lead to mould growth on walls, inside walls, inside cold closets, cold room, and on windows and doors. Mould growth obviously affects the occupant's health and is not considered good indoor air quality.

So in the wintertime we should be careful to keep the indoor relative humidity dependent on the outdoor temperature. If it’s fairly warm and above zero degrees outside then we can keep the indoor relative humidity in the high 40% range. Your windows will tell you if it’s still too high when you see condensation. If the outdoor temperature dips well below freezing then you may need to lower the indoor air quality to the low 40% range or even high 30% if it gets really cold.

Health effect of Low Relative Humidity Indoors in Winter:

• Colds and flu’s since some of these bacteria and viruses thrive in low humidity
• Sinus irritation
• Respiratory issues
• Coughing
• Dry skin

Health effect of High Relative Humidity Indoors in Winter:

• Health effects from mould growth

The best way to monitor your relative humidity is to purchase a relative humidity meter and adjust your air quality accordingly. We also can perform a detailed indoor air quality testing toronto and determine what your air quality and humidity levels are throughout the house. Alternatively, we also offer indoor air quality monitoring where you would be alerted through your smartphone if there are any relative humidity issues.