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Problems of humidity and air quality (second part)

Problems of humidity and air quality (second part)

Diminish the sources of moisture in the house

It is advised to eliminate excessive moisture at the source before intensively using the various systems of ventilation. Ventilation eliminates excessive moisture, but it also evacuates heat.


Here are some easy ways to reduce the sources of moisture:

- avoid drying the laundry inside;

- evacuate the air of the steam drier to the outside;

- clog the leaks in the foundations;

- make sure that the ventilators evacuate the air to the outside.

Add insulator on cold surfaces

Places which are not insulated or only little, like external corners and foundation walls, can be improved by the addition of insulator. This improvement is less expensive when it coincides with work of restoration.


To note: install an air shield / a steam shield (generally made of polyethylene) on the hot side of the insulator to avoid condensation hidden behind the latter.

Reduce uncontrolled escapes of air

In the higher part of your house or of the building, the air which flees towards the outside transports with it water steam, which accumulates in the attic and in the hollow parts of the walls, causing long-term deterioration. In the lower part, infiltrations of air can cool the window frames and the thresholds of doors, causing the formation of white frost on these places.

Install effective systems of ventilation

If the level of interior moisture is high and if the sources of steam cannot be more reduced, increase the rates of ventilation. The maintenance of an adequate mechanical ventilation is particularly important if you increase the air tightness of your house. Ventilation offers the advantage of improving the quality of the air inside your house.

If you must change or install a system of ventilation, choose a balanced system with a ventilator-recuperator of heat (VRC). A VRC ensures continuous ventilation without causing enormous loss of energy, since it uses the heat of the air extracted to heat the fresh air.

Clean and maintain the mechanical appliances

Moulds can be formed in the humidifiers, in the dehumidifiers, in the air-conditioners and in the apparatuses of filtration. A regular cleaning offers moreover the advantage of improving the output of the appliances.

Improve or replace the windows

Windows are generally the first places where condensation is noticed since they constitute the coldest surfaces of the house. Windows of more recent technology present an increased insulating value and can much reduce condensation.

If you envisage to replace damaged windows, consider the purchase of high-output windows which have special coatings with low loss of heat and which are filled with inert gas such as argon and krypton. The additional cost is generally lower than 10% and energy savings are considerable.


If the windows are still in good condition, consider the installation of an interior ready-to-assemble unit on all the windows and its framing during the heating season. The sets with thin and retractable plastic film, sold in any hardware store, are also useful but they must be replaced every year. Other systems, made of rigid plastic panels, are available for purchase and can be re-used for several years.

If condensation occurs between the panes of unsealed older windows, try to install wind-cuts around the interior window. If condensation occurs between the panes of a window with sealed double glazing, you will possibly have to replace it.

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Québec Landlords Association (1)

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