If you’ve always lived in regions with extremely cold temperatures in winter, the frost-on-window issue is probably something you’ve already had to deal with multiple times. On the other hand, if you’ve just moved to a cold climate area or it’s been unusually cold where you live, this problem may come as a surprise. We’re here to explain what causes it, how you can prevent it, and if frost can damage your windows.
Key Takeaways
- Frost on windows forms due to condensation caused by warm, humid indoor air meeting the cold glass surface, particularly when indoor humidity exceeds 50%.
- Key prevention strategies include controlling indoor humidity, maintaining a steady indoor temperature, sealing air leaks around windows, and upgrading to energy-efficient, double or triple-pane windows.
- Frost on windows can cause structural damage, leading to issues like wood decay and mold growth.
Why Does Frost Form on Windows?
Frost typically forms on windows during the winter and early spring when there’s a significant difference in temperatures between the indoors and outdoors. It’s exactly what happens with your car in the morning (when you’re late for work and that windshield gets inconveniently decorated with frost!), except that on cars, the frost usually forms on the outside surface first (see below).
This process begins with condensation. The warm, moist air inside your home carries water vapor. When this warm air touches the cold window panes, the water vapor condenses into liquid droplets. The colder it is outside, the higher the chances of condensation becoming frost, although this isn’t the only factor contributing to it.
Indoor temperatures and humidity levels also play a role in this process. For example, high humidity (check below for adequate levels) is often the culprit of excessive frost on and around windows. Some homeowners have also reported that indoor temperatures lower than 20°C (68°F) also contributed to more ice on windows. When they increased the temperature to approximately 20-22°C (68-71.6°F), they noticed that there wasn’t as much ice as before.
Frost On the Inside vs Frost on the Outside Glass Surface
You may have also noticed that sometimes frost forms on the outside glass surface. So, is there a difference between these processes? In essence, the same things are involved – cold temperatures and high humidity. But there are two major differences:
- Frost that appears on the outside glass surface is caused by high outdoor humidity levels, whereas frost that appears on the inside glass surface is linked to high indoor humidity.
- Frost appears on the outside glass surface usually on cold nights and early mornings when temperatures are very low and the humidity is high. Frost on the inside glass surface can appear anytime as long as indoor conditions allow it.
Seeing frost on the outside of your windows is actually a good thing – it means your windows are well-insulated. They don’t allow the warm indoor air to escape through windows, so the exterior glass surface stays cold, and frost appears when it gets cold enough (below freezing).
However, for outside frost to be a sign that your windows are energy efficient there should be no frost on the inside – except when the temperatures are lower than -30°C (-22°F); even the most energy efficient windows may have some frost on the inside when it’s this cold.
Common Causes of Window Frost
Although we often tend to blame the harsh weather conditions for having frost on windows, which is indeed the main culprit if the temperatures go below -30°C (-22°F), sometimes other things can worsen the problem, and here are some of them.
Excess Humidity and Low Indoor Temperatures
When indoor humidity levels exceed adequate levels, the risk of frost developing on interior windows increases significantly. Kitchens and bathrooms are particularly prone to high humidity because of cooking and showering. In the bedroom, humidity levels can increase during the night just because people are breathing in that room.
Here are some recommendations regarding indoor humidity levels based on the outside temperature:
- If the outside temperature is -30°C (-22°F) or below, keep indoor humidity at 15% and temperature at 20°C (68°F), but make sure that the dry air doesn’t cause any health issues and discomfort.
- If the outside temperature is -30 to -24°C (-22 to -11.2°F) or below, keep indoor humidity at 20% and temperature at 20°C (68°F).
- If the outside temperature is -24 to -18°C (-11.2 to -0.4°F) or below, keep indoor humidity at 25% and temperature at 20°C (68°F).
- If the outside temperature is -18 to -12°C (-0.4 to 10.4°F) or below, keep indoor humidity at 35% and temperature at 20°C (68°F).
- If the outside temperature is -12 to 0°C (10.4 to 32°F) or below, keep indoor humidity at 40% and temperature at 20°C (68°F).
Additionally, the colder the inside air, the more likely the window surface will cool down, increasing the chances of condensation and frost. So it’s always best to keep your thermostat at 20°C (68°F) or higher.
Air Leaks and Window Quality
Cold air can enter through windows through the tiniest cracks or gaps. This can happen even if the windows are new – if they’re low-quality and have been installed and insulated incorrectly, air leaks are almost always guaranteed. When that cold air enters your home and meets the moisture in the air, condensation and ice crystals appear.
Moreover, you may have also noticed that frost often appears at the corners of your windows – this tends to happen with windows that don’t have their corners welded, hence being at a higher risk of air infiltration.
Furthermore, frost is much more common on windows with fewer glass panes – single-pane windows being the riskiest. In extremely cold regions, even double-pane windows can have ice on them. Many people who live in regions where winter temperatures drop below -30°C (-22°F) confirmed that installing triple-pane windows significantly improved the frost issue.
Additionally, the window type can also influence how much frost you get – sliding and hung windows aren’t as tightly sealed as casement and awning windows, for example.
Damaged Glass and Window Frame
Even the tiniest crack in the glass can cause condensation and frost on your windows. Therefore, it’s of utmost importance to replace the glass or the entire window unit to prevent further damage.
The same goes for the window frame – if it’s visibly damaged, your windows aren’t energy-efficient anymore, so they’re not insulating well. Frost will inevitably form when outside temperatures drop too much.
How to Prevent Frost on Windows
Preventing frost on windows requires a combination of strategies:
- Seal air leaks around windows with caulking or weatherstripping.
- Make sure that indoor humidity and temperature are always steady. You can use dehumidifiers and exhaust fans to promote air circulation and lower humidity levels.
- Keep the lids on when cooking.
- Ventilate the house after taking a shower.
- Keep some windows open when you’re having guests.
- Keep the curtains, blinds, or other window coverings open as much as possible.
- Wipe the windows several times a day to remove any condensation.
- Use insulating kits to improve the windows’ insulating capabilities.
- Place a towel on your window sills to absorb the melting water, so it doesn’t get into the window frames and the wall.
- Avoid air drying your clothes – if this is absolutely necessary, get a dehumidifier with a dryer setting.
- Keep fewer plants in your house, as they increase humidity.
- Check if the exhaust vents are working properly.
- Inspect your windows regularly to check for damage and lubricate the hardware when needed.
Here’s another tip – don’t try to melt the frost using a hair dryer. This can damage your windows.
Upgrading to Energy-Efficient Windows
While this is not something you can do overnight – after all, replacing windows takes time and requires quite an investment – it’s definitely worth considering long-term. First, frost on windows isn’t just a visual problem. It can damage your windows beyond repair, so the issue will only worsen over time.
Even if your windows are new and don’t look damaged, they may not be suitable for your region’s climate. At Magic, for example, we never manufacture and sell windows before assessing the climate of our clients’ houses. This is the only way we can fully personalize the windows based on how hot and cold it gets in various regions.
Therefore, if frost on windows is a constant in your house during the winter, it may be time to consider replacing the windows. If you need guidance, you can book a free consultation with Magic anytime!
Potential Damage from Frosted Windows
Extended exposure to frost can cause serious problems with your house windows and not only. One of the most significant problems is wood decay, which can occur when moisture from frost penetrates window frames and other wooden structures. This decay can lead to costly repairs and even compromise the integrity of your home’s structure.
Frost also creates conditions that promote mold and mildew growth, particularly when moisture seeps into drywall and window frames.
Choosing Energy-Efficient Replacement Windows
Window replacement can significantly improve the overall thermal performance of your home. Here’s what to look for when choosing energy-efficient windows:
- Look for window manufacturers that can add more inert gas between glass panes, which improves insulation. Opt for double-paned window technology or even triple-paned windows if it gets extremely cold in your region.
- Install windows with energy-efficient frames that do not warp or crack in extreme weather conditions. Magic’s Hybrid Fusion Frame, for example, is a combination of vinyl, steel, and aluminum, which makes it incredibly sturdy and able to withstand the harshest winters.
- Look for windows with welded corners and high-quality insulating materials.
- Install casement or awning windows. They form a tight seal when closed. Sliding windows and double-hung windows are more prone to condensation and frost because of their opening mechanism.
- Check the windows’ energy ratings: U-factor, Solar Heat Gain Coefficient, Air Leakage, and Visible Transmittance.
- Look for a window company like Magic that can personalize your windows based on the climate of your region. This way, you buy exactly what you need, not a one-size-fits-all window.
Ready to Take Energy Efficiency To a New Level? Contact Magic!
At Magic, we prioritize customizability. This means that, upon booking a free consultation with us, one of our experts will assess your current windows, your house, the climate of your region, and your design preferences.
After this, we’ll come up with a solution that meets all the requirements, thus providing you with fully personalized windows that will serve your home for years to come.
Our windows are built to last 40 years even in the harshest weather conditions, and one of the reasons we can make this happen is by bringing glass production in-house.
Contact us today!
Frequently Asked Questions
Is it normal to have frost on the inside of my windows?
Frost forms on the inside of your windows because warm, humid air inside your home comes into contact with the cold window surfaces, leading to condensation and frost. This can be caused by high indoor humidity, low indoor temperatures, and poorly insulated windows or windows that aren’t suitable for the climate in your region (single-pane windows or sliding windows).
How to stop windows from frosting up?
The most straightforward way to stop windows from frosting up is by reducing indoor humidity and increasing indoor temperatures to at least 20°C (68°F). The best solution, however, is to have your windows assessed for leaks and damage and upgrade to energy-efficient windows suitable for your region’s climate.
Can frost damage your windows?
Frost can definitely damage your windows. When it melts, the water can infiltrate into your window frames and surrounding walls. This can eventually lead to warped windows and mold growth.
How can I identify air leaks around my windows?
To identify air leaks around your windows, inspect for cracks and gaps in the frames and assess for drafts. You can also light a match and go around your windows – it will show you where the air is coming from.
Why is it important to maintain my windows regularly?
Maintaining your windows regularly is crucial to prevent condensation and frost, which can lead to damage over time. This proactive approach ensures your windows remain functional and visually appealing.