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Ventilation & air quality

How comfortable you feel in your home is determined by a combination of:

Proper ventilation draws out your home’s stale, humid, indoor air and replaces it with fresh, outside air in a controlled way. Air in a well-ventilated home should not be too moist or too dry. A well-ventilated home is generally more comfortable.

In older homes, ventilation can happen when air leaks in and out of gaps around windows, doors, and through the building’s exterior. New homes’ exteriors are more air-tight, so since 2011, builders install heat recovery systems to assist with ventilation and improve air quality.

Heat recovery ventilator

Graphic shows an HRV operation.

Example of a typical operation of an HRV.

Enlarge image: Graphic shows an HRV operation.

A heat recovery ventilator (HRV) provides whole-home ventilation. It lets you control when and how the stale air is drawn out of the house and outside air is brought in. Before the stale air is pushed outside, the HRV recovers and transfers some heat to the incoming outside air during the heating season.

You can turn your HRV on or off using a basic HRV control, but your most efficient option is to install an advanced HRV control. An advanced control offers more options to best set up the HRV to match your home’s ventilation needs. It can reduce your energy bill by matching your ventilation needs with your lifestyle.

Tips for using your HRV

  • Set the unit to run as needed, according to the instruction manual and judging from your comfort level.
  • An HRV that is running all the time could result in increased heating/cooling costs and uncomfortable humidity levels.
  • Adjust the humidity control seasonally. Set the control to the highest setting in warmer weather; lower the setting as the weather gets colder. In winter, set the dehumidistat just low enough to prevent condensation on windows.
  • Do not shut off or unplug your HRV. This can result in high humidity levels, which can lead to mould and mildew growth and unhealthy living conditions.

Other ventilation options

  • Ventilating fans are used to remove air from specific areas of your home, as required. These exhaust fans are manually controlled by a switch or timer and are typically located in kitchens, bathrooms, and utility rooms.
  • A central exhaust system removes air from the entire home. These systems are controlled by a switch, dehumidistat, or timer. Air is pushed out of the home; a central exhaust system doesn’t recover any heat from the stale air .

Ask your furnace contractor if an HRV or other changes to your ventilation system may improve the indoor air quality of your home.

Renovations and ventilation

If you renovate or upgrade one area of your home, you can affect another area that may seem unrelated. Renovations that may affect a home’s ventilation:

  • increasing insulation levels;
  • installing new windows and/or doors;
  • caulking/sealing gaps and cracks;
  • installing new weatherstripping around exterior doors;
  • removing or capping off a chimney once used for a furnace or water heater;
  • reducing the number of appliances connected to an existing chimney.

Humidity and condensation

Your home’s humidity level affects the comfort and quality of your indoor air. This chart provides some guidance, but each home operates differently. If you have one, use your HRV to control humidity and improve air quality in your home.

Recommended maximum humidity levels
Outdoor temperature Practical humidity level
−35°C 20%
−30°C 25%
−25°C 30%
−18°C 35%
−10°C 40%
−5°C 45%
0°C 50%
Summer 100% or off

Too much humidity can cause window condensation, icing issues, and mould. If your home is too humid:

  • Turn humidifiers down or off.
  • Don’t hang wet clothes indoors to dry.
  • Always vent exhaust fans and your clothes dryer to the outdoors.
  • If you don’t have exhaust fans, consider installing them or an HRV.
  • Run the exhaust fan during a shower or bath, plus an extra 10 to 15 minutes afterwards. Install a timer switch so you don’t forget to turn it off.

Too little humidity can cause dry, itchy skin and can damage your home’s woodwork and artwork. If your home is too dry:

  • Seal and weatherstrip your home to reduce air leakage.
  • Don’t over-ventilate.
  • Use a humidifier only after all sealing and weatherstripping attempts have been made.