Resolving humidity problems in a home

Significant humidity problems are often accompanied by unpleasant odours.

Before increasing ventilation in winter or installing a dehumidifier in summer, it is essential to identify the cause of the problem and correct it.

In summer, humidity can result from condensation of warm, moist air on cooler basement surfaces.

If cold-water pipes sweat after use, the lower portion of the foundation walls may also be affected.

A poor-quality or improperly installed vapour barrier allows water vapour from warm indoor air to migrate through walls—particularly around electrical boxes or window frames.

When concrete under wood flooring or carpet has not been protected by a waterproof membrane, odours may come from decaying wood or persistent moisture trapped in the carpet.

Water infiltration through cracks can cause humidity and odour problems inside a home.

Damp soil around a building is more prone to freezing and can lead to cracks in foundations and concrete walls.

The following situations increase the risk of excessive humidity around a home:

• Negative ground slope near the foundations;
• Gutters draining into a weeping tile or clogged with leaves;
• Window wells blocked by organic debris;
• Weeping tile clogged with sand or tree roots.

When heating is on, moisture problems may seem to disappear. However, once warmed, the indoor air can actually hold even more moisture. As soon as the temperature drops again, this moisture condenses on cold surfaces and the cycle repeats, adding more water to porous materials.

While waiting to identify the exact source of the problem and make the necessary repairs, clean any mould deposits or black stains using a bleach solution (one part bleach to three parts water). Keep the solution in contact with the affected area for at least 20 minutes. Wearing a mask and gloves is essential.

If the outdoor relative humidity exceeds 70 % in summer, use a dehumidifier. Admitting outdoor air at that time would only raise the basement’s humidity level. In winter, you can ventilate by opening two windows for two to three minutes, depending on the outdoor temperature.

Once preventive measures have been taken and the sources of humidity have been clearly identified, corrective action must be carried out. The assistance of a specialist will be necessary if major work is required.

A weeping tile can sometimes be unclogged using specialized equipment. If this is unsuccessful, excavation around the perimeter and weeping tile replacement may be required. This is also an ideal opportunity to insulate the foundation wall from the outside, particularly if the wall is made of concrete blocks or stone.

The largest cracks in a concrete wall are usually repaired from the outside. However, for cracks of varying size, specialists can also perform guaranteed interior repairs.