Is condensation on the inside of windows a problem?

Yes, condensation on the inside of windows is definitely a problem that indicates excess humidity and poor ventilation in your home. While occasional light condensation during extreme temperature differences is normal, persistent interior condensation can lead to mold growth, wood rot, and structural damage.

Interior window condensation occurs when warm, humid indoor air meets the cold glass surface, causing water vapor to condense into droplets. This is most common during Ottawa's cold winter months when the temperature difference between inside and outside is greatest. The condensation typically appears first on the coldest part of the window - usually the bottom of the glass or around the frame edges.

The root causes are usually excess humidity combined with poor air circulation. Common humidity sources include cooking, showering, houseplants, aquariums, and even breathing. In tightly sealed homes, this moisture has nowhere to go. Single-pane windows and older double-pane windows with poor insulation values are particularly prone to condensation because their interior glass surface stays much colder.

In Ottawa's climate, persistent interior condensation often signals that your windows have poor energy efficiency. Windows with U-factors above 0.30 (common in older windows) create cold interior surfaces that encourage condensation. Modern triple-pane windows with Low-E coatings maintain warmer interior glass temperatures, significantly reducing condensation risk while improving energy efficiency.

To address the problem, start by reducing indoor humidity to 30-40% during winter months using exhaust fans, dehumidifiers, and proper ventilation. However, if condensation persists even with controlled humidity, your windows likely need replacement. Modern ENERGY STAR certified windows designed for Ottawa's Climate Zone 6 will eliminate most condensation issues while reducing your heating costs.

For an assessment of the windows and the humidity behind the problem, request a free quote through Ottawa Window Pros - an installer can say whether replacement is really the fix.

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