When I talk about humidity in the home, I am talking about moisture contained in the air caused by the things we do everyday such as,

  • daily showering & bathing
  • cooking
  • breathing & perspiration
  • washing & hanging wet laundry to dry
  • indoor plants
  • the wood stored indoors for the fireplace
  • open aquariums

Other common causes are,

  • inadequate ventilation with outdoor air
  • inadequate heating in parts of a home re: closed doors to seldom used rooms
  • unheated crawlspaces

All of the above can & does add significantly to the humidity in our homes.


How much humidity you ask?  

2,000 to 10,000 litres of moisture can be added to your home over a typical heating season, (house being closed up).  A cord of wood stored in a home can add up to 500 litres of moisture.  That’s a lot of water to deal with!


What I am not talking about, is moisture entering the home via leaks from the exterior, such as,

  • water leaking through cracks in the foundation
  • poorly installed/maintained flashing details on the exterior of the building
  • leaky roof & poorly installed or maintained roof flashings
  • moisture rising into the house from a dirt or concrete floor in a crawlspace

All of these examples can & do add humidity to your indoor air & can have detrimental effects on your home & your health.  They need to be corrected before any resolution of high humidity levels from our day to day living can be made.  I will add, that these types of issues need to be dealt with independently of any other problems in your home.


Humidity & Dew Point

Before answering the question, How high is too high, we need to define the word humidity.  The simple answer is humidity is the amount of moisture in the air, stated as Absolute Humidity.  But that’s not good enough.  Most of the humidity levels we need to know about are measured in Relative Humidity (RH).  Relative Humidity is the percentage of moisture in the air at a given temperature.  Warmer air can hold more moisture.  Given a sample of air, the RH(%) lowers when the sample temperature rises & the RH(%) rises when the sample cools.  In other words, RH is a function of what the maximum amount of moisture the air can contain at a certain temperature.

Dew Point is the temperature at which the air can no longer hold on to all of the moisture it contains.  Condensation on a glass containing a cold drink is caused by the air close to the surface of the glass has cooled enough to reach its Dew Point.


Humidity in the Home – How high is too high? – Part 2  will address such issues as,

  • What are considered reasonable humidity (RH) levels
  • You & your families health concerns related to excessive humidity & the resulting conditions
  • Practical solutions

As always, I am available to answer any questions you may have relating to this article, home inspections or houses in general.  

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