You wake up one morning in January and you see water dripping from your windows in the kitchen. Perhaps, it is the corner of one pane or entire sill that is wet. In either case, the next thing on your mind is whether it can be fixed or if you have to replace your windows.
Well, the honest answer to this is – it depends on where condensation is occurring. That’s the one detail that makes all the difference. Sometimes condensation is benign and can be completely corrected without any cost. Other types are a clear indication that your windows are no longer working and there is no way of fixing them yourself.
Here, we will explain the difference between them and help you make the right decision for your home.
Why Condensation Happens in Toronto Homes
It’s condensation: Warm, moist air hitting a cold surface – and Toronto winter windows are one of the coldest surfaces in the house. The warm air cools down, which causes it to lose its moisture holding capacity and it condenses water on the glass.
Most Canadian cities do not make it worse than Toronto. Summer doesn’t completely freeze over, and releases moisture continuously into the ambient air mass. The average outdoor winter humidity in the GTA is around 70-75%, which is much higher than the average for inland cities. This moisture belongs in your home and it needs to be absorbed by your home as you change the air. Many times it clears up on your window.
That’s physics. However, where the condensation occurs (interior surface, exterior surface, or between the panes) gives you a completely different clue as to what is actually wrong.
The 3 Types of Window Condensation (And What Each One Means)
Type 1: Condensation on the Inside Surface of Your Window
It’s the most typical one, and in most instances, it’s not a window issue; instead, it’s a humidity issue.
If the humidity level is too high and the window glass is cool, water droplets form on the inside surface. This is more prevalent in basements, bathrooms and kitchens. It may also occur in the entire house when the house is not properly ventilated.
This type of condensation will typically be reduced or eliminated without replacement windows. Begin here first.
Type 2: Condensation on the Outside Surface of Your Window
When water condensation occurs on the outside surface of the glass, it is considered a good sign. It’s when your windows are so effective at keeping the cold in that on some mornings, the moisture from the outside air briefly condenses on the window glass.
This is most commonly observed in the spring and early fall on modern low-E windows. Usually burns down in an hour or less after it first appears in sunlight and does not need to be treated.
Type 3: Condensation Between the Glass Panes (Foggy or Cloudy Look)
This is the one that indicates your window has gone bad.
Modern windows are sealed units that are two or three panes of glass with an insulating gas (typically Argon) between the panes. At the break of the seal, the air in the cavity is drawn in from the outside. That air contains moisture that falls between the panes and gives it a foggy, hazy or milky look that doesn’t rub off on either side.
The seal is irreparable if it is broken. The gas is gone. The insulation value has become quite low. The only long-term cure is replacement.
How to Fix Type 1 Condensation (Interior Surface): 6 Practical Steps
When condensation is occurring on the inside surface of the glass, before you call anyone, here are a few things to try:
- Lower your indoor humidity. In the winter, the target is 30-45% relative humidity for a Toronto home. A hygrometer (under $20) will let you know where you are. Above 45% in winter is when condensation problems typically begin.
- Run your bathroom and kitchen exhaust fans longer. Run them while cooking and bathing, and for 15–20 minutes after. These are the two biggest sources of moisture generation in any home.
- Check your HRV (Heat Recovery Ventilator). It has been a feature at the center of most new homes constructed in Ontario since 2012. Your home is like a sealed container collecting water by the breath and shower if it is turned down to minimum or if it has never been serviced in the last several years. Run it in a proper manner and turn it on.
- Don’t dry clothes indoors. One load of laundry in the dryer inside your house can release a few litres of water vapor into the air. Dry using the dryer or outdoors, if possible.
- Move houseplants away from windows. Transpiration is a continuous process by which plants give out water. A patch of foliage within a window pan can greatly increase the humidity in the vicinity.
- Use a portable dehumidifier in problem areas. This is particularly beneficial for basements. Water seeping up from an untreated basement spreads throughout the house.
All of the above, and if condensation remains throughout a complete winter, the window itself might be faulty, especially if it is a single-pane or early double-pane window that can no longer keep the interior surface warm enough.
When Fixing Isn’t Enough: Clear Signs You Need Replacement
In some cases, no amount of humidity management can resolve the issue. When to stop fixing, and start replacing:
Condensation is between the panes. As stated above, this indicates a seal failure. The window has been de-argoned and the R-value has been decreased. You’re shelling out cash to warm the air outside.
You can feel cold radiating from the window frame, not just the glass. If the frame is cold to the touch, then the thermal break is not working or has failed. Single-aluminium-panes from the 1970s – 90s are a bad culprit for this.
Condensation is pooling on the sill and causing damage. Rotting on a wood sill is caused by chronic wetness. It causes mold growth on drywall. If you notice that the frame is already discoloured, soft around the frame or mold, you are not having a condensation problem and you are having a structural problem.
Interior condensation persists even at 30% indoor humidity. Today’s double and triple glazing windows can keep condensation at a warm enough surface temperature, so that it will not condense at the normal humidity level. If it is still occurring at 30% RH, the window is thermally failing.
Ice is forming on the interior glass surface. This indicates that the R-value of the window is dangerously low. Properly insulated, modern windows should not ice up inside in Toronto winters.
The Real Cost Comparison: Repair vs. Replacement
Many homeowners attempt to stop the fogging from being replaced by redrilling and treating the fogged glass unit, which involves the creation of small holes in the outer pane to extract moisture. This will run about $100-200 per unit and will only clear the glass for a short time.
The issue is that it doesn’t replace the Argon gas or the insulation level. The seal has yet to be found. The thermal performance remains impaired. You’ve paid for cosmetic repairs but still your energy bills are showing a broken window.
The average price for a proper window replacement in Toronto is between $400 and $900 per window installed, depending on the window size, style and the glass package. It has a lifetime guarantee, the insulation properties have been restored and there are no further repair expenses.
For the case of two or more failed sealed units in the same window, replacement is almost always the more cost-effective alternative to on-going repair.
Milano’s Honest Advice: Start With the Right Diagnosis
New windows aren’t the only answer to condensation. If we visit your home for a free consultation, and you have high humidity indoors, we will inform you of this and show you the steps you can take listed above. We’re not in the business of selling windows that people don’t need.
On the other hand, if you have broken seals, your frames are aging, or the glass can get very cold and fog over just about anywhere you are at normal humidity, replacement is the answer. Our windows are made in Canada to endure the climate in Ontario, come with Low-E triple pane glass choices, Argon gas fill and thermal break frames that keep the interior glass surface warm enough there won’t be an issue with condensation.
All installations are warranted for a lifetime, and transferable. But, right now, qualifying installations may be eligible for up to $10,600 in government grants for energy efficiency through available Ontario energy efficiency programs.
The Bottom Line
Are there any condensations inside the glass surface? Take humidity control as a first step; it costs $20 and involves some adjustment of ventilation habits.
Condensation between the panes? That window has been broken. There are no do-it-yourself solutions that can bring back what has been lost.
If you are uncertain of the type, or if the humidity remedies have not been effective or you have used, but still have the issue, schedule a free home assessment with Milano. We will be honest about the problem and let you know if you need new windows or just a dehumidifier and provide a written estimate if replacement is advisable.
Call us at 437-464-2753 or request a free consultation online.
Frequently Asked Questions
Why are my windows sweating on the inside in winter?
High humidity inside is the most common reason for sweating on the inside of windows during the winter months. Household air is warm and moist, and when it comes into contact with the cold glass surface, it deposits moisture. The solution is to lower humidity indoors to 30-45%, increase ventilation and use your HRV. If the condensation continues at normal humidity, it could be that the condensation is caused by a poor thermal performance of the window itself.
Is condensation between window panes fixable without replacing the window?
Not for good. If condensation is visible between the panes, it is likely that the seal has failed and the gas fill has escaped from the sealed unit. Some companies will drill holes to get rid of the moisture that can be seen, but this will not add insulation value. Either the replacement of the glass or the entire window is the only permanent solution.
Does window condensation mean I need new windows?
Not automatically. Interior surface condensation is typically a humidity problem and not a window problem. If condensation between the panes, condensation even at low humidity in the house, ice on the inside of the glass or water on the floor and damaging frames then it’s time to replace the windows.
How do I know if my window seal has failed?
The easiest way to tell is if the fog, haze, or cloudiness is not wiped from one side or the other between the panes. The potential for reduced insulation is also apparent, the room next to that window is much colder.
What indoor humidity level should I maintain in a Toronto home in winter?
Relative humidity between 30% and 45%. Below 30% makes the air dry, above 45% during the winter months greatly increases the risk of condensation. This can be easily measured with a basic hygrometer from any hardware store.
Can new windows cause more condensation than old ones?
Temporarily, yes – and this confuses a lot of homeowners. Older leaky windows allowed moisture to escape through gaps. New, properly sealed windows trap that moisture inside, making pre-existing humidity problems suddenly visible. The solution is improving ventilation and running your HRV, not assuming the new windows are defective.
How much does window replacement cost in Toronto?
Most Toronto homeowners pay between $400 and $900 per window installed, depending on size, style, and glass options. Multi-window projects typically bring the per-unit cost down. Milano offers free in-home consultations with written quotes and 0% financing options.