Frost and Ice on Windows: Why It Happens and How to Prevent It

February 13, 2026 – Frost and ice buildup on windows are common during Canadian winters and can lead to issues over time. Persistent moisture and ice can lead to serious issues if left untreated, ranging from window damage to higher energy bills and even health concerns. Understanding why ice forms and what you can do about it is the first step toward protecting your home. 

Why Does Ice Build Up on the Inside of Windows? 

Ice on interior window surfaces may seem surprising, but several factors contribute to this winter problem—especially in cold climates. 

Water Vapour 

Water vapour is one of the primary causes of ice buildup. When outdoor temperatures drop below freezing, warm, moisture laden air inside your home is drawn toward the cold window glass. If the surface temperature of the glass is low enough, that moisture condenses into water droplets that freeze to your windowpane. 

Indoor Humidity 

Elevated humidity levels inside your home significantly increase the likelihood of condensation forming on windows. When there’s a large temperature difference between the warm interior and the cold outdoor air, condensation—and eventually frost—becomes much more likely. 

Air Leakage and Poorly Performing Windows 

Windows are meant to act as a barrier against the cold. However, older windows, damaged seals, or poor installation can allow cold air to leak inside. This cools the interior glass surface enough for condensation to freeze. Over time, underperforming windows will only worsen this issue. 

What Happens If Ice Isn’t Removed? 

Ignoring frost and ice buildup can lead to more than just foggy views. 

As ice melts and refreezes, the resulting moisture can damage window frames—especially wood frames. Water can seep into the material, leading to cracking, warping, and rot. This not only affects the appearance of your windows but also reduces their energy efficiency. 

When frost melts, lingering moisture around windows creates a perfect environment for mold and mildew. Mold is a known health hazard and can trigger allergies and respiratory issues. If left unchecked, it can spread into walls and significantly degrade indoor air quality. 

Frequent ice buildup reduces a window’s insulating performance. As heat escapes, your heating system must work harder to maintain a comfortable indoor temperature. If you notice rising energy bills or find yourself constantly adjusting the thermostat, underperforming windows could be the culprit. 

How to Prevent Frost and Ice on Windows 

Preventing window ice often comes down to managing moisture, airflow, and insulation. 

Upgrade to Triple Pane Windows 

Having triple pane or glazed windows greatly improves energy efficiency and reduces condensation.  

Seal Gaps and Cracks with Caulking 

Small cracks around windows allow cold air to leak in, encouraging condensation. Applying caulking around seams and edges to improve insulation and keep frost at bay. 

Install Plastic Window Insulation Film 

Shrink film window insulation kits are a temporary fix that adds an extra protective layer and helps reduce condensation.  

Turn On Exhaust Fans 

Cooking, showering, and using appliances like dryers release moisture into the air. Always use kitchen and bathroom exhaust fans during these activities, and make sure they vent outdoors rather than back into your home. 

Use a Dehumidifier 

Running one helps remove excess moisture from the air—one of the main causes of window condensation and frost. 

Open Curtains and Blinds During the Day 

Keeping window coverings open improves air circulation and helps prevent moisture from becoming trapped between the fabric and the glass. Better airflow keeps windows warmer and drier. 

Avoid Drying Clothes Indoors 

Airdrying clothes indoors releases a large amount of moisture into the home. If indoor drying is unavoidable, use the dryer first to remove as much moisture as possible and ensure the space is well ventilated. 

Maintain a Consistent Indoor Temperature 

A steady indoor temperature helps keep window surfaces warm enough to prevent frost. If some rooms run colder than others, a space heater can help balance temperatures. 

Consider a Heat Recovery Ventilator (HRV) 

An HRV system exchanges humid indoor air with fresh, filtered outdoor air. This helps control indoor humidity and reduces condensation. HRVs are especially useful in airtight homes or those with ongoing moisture issues. 

How to Safely Remove Ice from Windows 

If ice has already formed, remove it gently to avoid damaging the glass. 

• Let warm room air naturally melt the ice. 
• Use lukewarm water to melt ice—never hot water, as it can cause glass to crack. 
• Spray a mixture of 1 part water and 2 parts rubbing alcohol, then wipe clean. 
• Use a solution of 1 part water and 3 parts vinegar, spray, wipe, and dry. 
• Use a hairdryer on the lowest heat setting, maintaining a safe distance from the glass. 

If your windows keep icing up it might be time to upgrade to some new high performing windows, contact us today to talk to one of dedicated sales representatives to see how Ply Gem Canada windows can help you.