Controlling Winter Humidity

We all know that keeping humidity in our home during the winter is important for our skin, throat and overall health, but did you also know that it’s vital to the health of our home? If humidity level dip too low our furniture and house will deteriorate and certain germs will thrive

We need to understand that every home is different, humidity levels can be affected by many factors. The number of people living in the home, the number of showers taken, the amount of laundry done and even a wood burning fireplace contributes to humidity levels if you keep firewood inside to dry out. The number of times a day an exterior door is opened and even cooking all affect your comfort level.

Humidity Levels Are Too Low
During the winter humidity levels drop because cold air holds less moisture than warm air. Homes that utilize forced air heating have an exacerbated problem because furnaces use combustion to create hot air, thus burning out most of the water vapor that existed in the first place. To make matters worse, when humidity levels dip the ambient air feels cooler than more humid environments, and we turn up the heat to compensate.

Low humidity causes static electricity, dry skin and hair, increased susceptibility to colds and respiratory illness, and can allow viruses and germs to thrive. Wood floors, furniture and millwork will split and crack, paint will chip, and electronics can be damaged because of low humidity levels. Adding a humidifier to your home will remedy these problems

Humidity Levels Are Too High
It is possible for homes to have too much humidity, which will create its own set of problems, particularly the issue of condensation. This does not typically occur in older homes, but new, tightly constructed buildings will retain more heat and moisture, which is when mechanical ventilation is important. During the winter you will first notice this at windows: when warm, moist air comes in contact with a cold window, air temperature drops and it can no longer hold the water vapor and condensation results. If a home does not have the proper mechanical and natural ventilation, excess water vapor can travel through walls and ceilings, causing wet insulation, peeling paint, and mold on walls and rot in woodwork. Try these steps to lower humidity in your home:

• Turn down or off humidifier, and use a dehumidifier when necessary – particularly in basements and during the summer.
• Use exhaust fans while cooking and bathing or open a window to exchange fresh, drier air.
• Reduce the amount of water introduced into the home by cooking with covered pots; taking cooler, shorter showers; venting clothes dryers directly to the outside; and reduce the number of plants in the home.
• In tightly constructed homes, use an energy recovery ventilator.

How to Gauge Indoor Humidity Levels:

• Fogging and condensation accumulating on windows, moisture and mold occurring on walls and ceilings is an indication of too much humidity.
• Increased instances of static electricity, dried and cracking millwork and paint indicate low humidity levels.
• Use a digital or analog hygrometer to measure humidity levels.
• If you use a whole house humidification system, use a humidistat to control and monitor humidity levels.

Here are some good guidelines to consider:

The Canadian Lung Association recommends the following:

• That a RH of 30 - 50% maximum for most of the year, because too much humidity can

   promote mould growth.

• If you notice condensation on your windows, consider replacing them with double pane 

  windows, and getting an energy analysis of your home.

• Meanwhile, use the window condensation as an indicator that the humidifier needs to be

  turned down, or that your home needs more fresh air ventilation

While this information is reasonably good, it is directed more towards existing homes and does not fully reflect the trend towards tighter homes that have HRV’s and ERV’s and the move away from leaky homes that need humidifiers.

CMHC recommends that humidity be kept low enough that window condensation does not occur. In order to limit window condensation, you need to lower your relative indoor humidity. But what relative humidity level is needed to avoid condensation and frosting on cold surfaces in your home?

If you look at this chart produced by National Resources Canada, a simple double pane thermal pane window will form condensation on it when indoor humidity exceeds the listed minimum's for each outdoor temperature, condensation being a result of high humidities and low temperatures. If you can't raise the temperature, then you have to reduce the humidity. Even at zero, you need to drop your humidity to 40% to prevent that condensation. Dehumidifiers cannot drop that humidity below about 50 - 55%, as you found out, and you have to pay the electricity bill to operate these machines as well.

 Source: CMCH