Ice on Windows: Causes and Solutions

Ice on Windows Problem Solved

Ice on windows is a common problem during the colder time of the year. If there’s one thing you can count on during the winter months in most of Canada is that it’s going to be cold and snowy. With a good portion of the huge country vulnerable to arctic blasts from the North Pole from early November to late April, Canada is considered one of the coldest countries on Earth.

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If you’re like most Canadians, your home or cottage can be equipped with everything from a wood-burning stove to a high-efficiency furnace to a nice, insulated blanket to keep you warm and comfortable. Unfortunately, that might not be enough to prevent cold air and moisture from penetrating inside.

Ice on windows is not uncommon, but it definitely should be cause for concern. Ice is frozen water so anytime your windows, frames, wallboard and insulation experience prolonged exposure to moisture, you may find both aesthetic and structural problems. Melted frost can discolour the window topcoat, crack paint, rot wood, warp window frames, crack the glass and even cause toxic mold and mildew issues.

As you can see, ice on windows can cause major problems if not addressed. We’ve put together a comprehensive list of causes and solutions to ice on the inside of windows, ice on the outside of windows, ice on the inside of new windows, ice on the outside of new windows, how to stop ice on windows, and how to prevent ice on windows.

It’s time to stop ignoring ice on windows and start protecting your home from potential catastrophe.

Ice Inside of Windows

Ice Inside of Windows

Is it normal to have ice on the inside of your windows?

While ice on the inside of windows may be a common occurrence, it is not normal.


Why do you have ice on your windows?

It forms from an excess of water vapour in the air. Better known as humidity in the summer months, extra moisture gets trapped inside when the outside temperature drops and you close your windows. The moisture is drawn to the window pane, condenses and freezes to form ice crystals.

Ice on the inside of new house windows

Ice Buildup Inside New Windows

Should New windows have condensation on the inside?

The short answer is no. And it’s not your new windows’ fault. The main cause is in the air.

If you’ve got a brand new home with new windows, you probably wouldn’t think you’d have a problem with ice build-up. Today’s top home builders often construct airtight homes building with efficiency in mind. While that may help with heating bills, the lack of ventilation in your home could trap warm, humid air inside, condense on the window panes and freeze up.

Is condensation on windows normal?

While it’s normal to experience condensation on windows, its appearance reminds you of excess moisture in the air and your responsibility is to find the source of it. Check if the exhaust fans run properly when the kitchen and bathrooms are in use, make sure clothes dryer vent goes outside and not blocked by debris.

Ice Outside of Windows

Ice Outside of Windows

While cold air is often thought of as very dry, there are many occasions when there is heavy moisture in the air that can cause condensation and ice on the outside of windows. Just like ice forms on your car windshield, dirt and temperature swings can cause water to freeze and melt on your home’s windows.

Ice on the outside of new house windows

Ice Outside New Windows

While ice on the outside of your new windows may be alarming, exterior window condensation is usually caused when the window is colder than the dew point. There’s no need to panic as it will melt and evaporate once the sun warms the outside of the window.

Ice on the Window Frame

Ice on Window Frame

Air leaks from poorly installed or aging windows can reduce the surface temperature of your window frames and create the perfect condition for ice to form. Often double-hung, single-hung, and horizontal slider windows are at greater risk for air leaks and ice formation. There are several simple ways to find air leaks in your windows. Before hiring a contractor, run the hand test or the candle test to find air leaks. On a cold day with the Heat ON inside your home, use your hand or a lit candle to move around the window frame. If you feel the cold air on your hand or, in case you use the candle, you see the flame dances around then you found the air leak.

Frost on inside of double pane windows

Frost inside of double pane windows

Frost build-up between window panes is an indicator that you’ve probably lost the window seal and moisture is building up inside the two panes of glass. This usually happens in older windows. You may be able to replace the glass units but generally, you should consider replacing the entire window to gain added benefits of energy-efficient Low-E glass coatings, Argon gas or Krypton gas fills, durable vinyl frames, and air-tight construction.

Preventative Maintenance Checklist

Preventative checklist

How can you stop your house windows from icing on the inside?

There are a number of things you can do around your home or cottage to help reduce the ice on windows:

  1. Check for damaged gas appliances. Your gas furnace and hot water heater may be malfunctioning and expelling excess water vapour into the air. Safety Tip: Make sure you have a functioning carbon monoxide alarm to alert you to any life-threatening leaks inside your home.
  2. Look for plumbing leaks. Everything from a leaky faucet to a major break under the sink can add water vapour to the air.
  3. Stop air-drying clothes inside. While it may be tempting to hang delicate clothing on a line to dry instead of using a clothes dryer, doing so will add more moisture to the air. If necessary, spin dry the clothes first or damp dry to take out most of the water.
  4. Don’t over-water plants. Live plants look great inside and have the added benefit of producing oxygen. However, the soil they’re planted in retains moisture and overwatering them will have a negative effect on the amount of excess liquid in the air.
  5. Keep firewood outside. It’s convenient to keep wood inside for fireplaces and wood-burning stoves, but it naturally retains moisture that will evaporate in the warm room air.
  6. Absorb condensation. Keep a towel on the window sill to wick away any extra water that drips off the window. This will stop ice from forming on the glass. Replace the wet towel with a dry one each night.
  7. Turn up the thermostat. Today’s energy-efficient thermostats often lower room temperatures at night to save energy. Bump up the room temperature by a degree or two or use a space heater at night to stop ice on windows.


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How to Avoid Frost/Ice on Windows

How to stop ice formation

There are two main causes of frost and ice on windows—excess humidity and air leaks. There are several things you can do to fix the problem once and for all.

Reduce Humidity:

  • Get a humidifier, make sure you adjust the settings based on the outdoor air temperature. National Resources Canada recommends the following:Table of Recommended Indoor Relative Humidity Levels
    Outside Air Temp (°C / °F)Maximum Indoor Relative
    Humidity At 20°C (68°F)
    -30°C / (-22°F) or below15%
    -30°C to -24°C / (-22°F to -11.2°F)20%
    -24°C to -18°C / (-11.2°F to 0°F)25%
    -18°C to -12°C / (0°F to 10.4°F)35%
    -12°C to 0°C / (10.4°F to 32°F)40%
  • Use a dehumidifier instead of a humidifier to draw excess moisture from the air. Just as you do during summer months to reduce musty odours in your basement, you can do the same thing in the winter. Use a hygrometer to keep some humidity in the air or you’ll be getting shocks from everything you touch.
  • Run exhaust fans or open windows occasionally to improve ventilation when cooking or showering. Make sure your exhaust fans and clothes dryer vent to the outside, not just to the attic. Otherwise, when warm, humid air accumulates and condenses under your home’s roof, the frost will start forming. If you ever wondered “Why Is There Frost In Your Attic?” you need to reduce relative humidity levels.
  • Add an HRV system (heat recovery ventilator) to bring in the fresh air and recirculate the inside air. This may be helpful for airtight new homes to reduce condensation buildup and help you save on energy bills.
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Reduce Air Leaks:

    • Apply insulating window film to your leaky windows. Energy Star research indicates that sealing windows can not only reduce condensation buildup, it can also cut your utility bills up to 20 percent.
    • Use foam gaskets behind electrical outlets and switch plates to prevent air leaks. Inexpensive kits are pre-cut to fit tightly around wiring boxes. Focus on outside walls near windows for the most effective results.
    • Caulk around windows to seal cracks and gaps. Larger openings can be filled with foam sealant. 
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  • Replace windows with high-performance, Energy Star-certified windows. Consider casement style made from vinyl or wood for the best insulating values. Replace damaged single-pane windows with double- or triple-pane window models to obtain the best thermo-insulation value.
  • Make sure to include Low-Emissive (Low-E) coatings and/or Argon gas between glass panes to provide the most insulation against heat loss and air leaks.

Ice on Windows—Make it Stop

It’s important to stop the buildup of ice on windows in its tracks. Whether it’s your bedroom or your window reading nook, you’ll need to identify the problem. Is there too much humidity in your home? Are there air leaks that are adding to the issue? Are your windows old or damaged and in need of replacement?

Now is the best time to address these issues to protect your home from damage, save on energy bills, and provide the best living conditions for you and your family.