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Why Is Water Condensation Forming on My Windows? An Explanation for Homeowners

Why Is Water Condensation Forming on My Brand New Windows: An Explanation for Concerned Homeowners

As a seasoned window installer, I'm well-acquainted with the occasional concerned calls from clients that are noticing condensation forming either inside or outside. This unexpected sight can rightly catch homeowners off guard and prompt them to reach out with questions. While it might seem counterintuitive, new windows are not immune to this phenomenon. In fact, their high efficiency can sometimes contribute to the formation of surface condensation.

The Paradox of Insulation

New windows are designed with advanced insulation properties to maintain a comfortable indoor environment by preventing heat transfer between the inside and outside. While this insulation is excellent for energy efficiency, it creates an interesting paradox when it comes to condensation. The tightly sealed nature of high efficiency windows traps both warm air and moisture inside the house, setting the stage for possible surface condensation to occur. However, there's an intriguing twist to this tale – the presence of condensation on your freshly installed windows should hardly send you into a panic. In reality, it's a reassuring indicator that your windows are performing splendidly and diligently carrying out their intended role.

Rest assured, there's no cause for concern. In this article, we’ll delve into the elements that lead to water condensation on new windows, especially as they navigate the fluctuating temperatures of both warmer and cooler months. And here's the important part – I've got a lineup of practical tips ready to ensure that you can keep condensation in check.

Temperature Variation and Dew Point

Condensation occurs when warm, moist air comes into contact with a colder surface, causing the air to release its moisture in the form of water droplets. The temperature at which this occurs is known as the dew point. New windows, with their effective insulation, can create a sharp contrast between the warm indoor air and the cold exterior surface of the window, causing condensation to form when the dew point is reached.

Winter Condensation : An Inside Affair

Imagine a cozy winter evening, snuggled up by the fire, when suddenly, you spot water droplets forming on the inside of your new windows. What's the deal? Let's break it down. Those sleek, energy-efficient windows you've invested in? They're actually doing their job splendidly. Their advanced design and insulation properties keep your indoor space warm by trapping heat inside. But, and here's where it gets interesting, they're also keeping the warm, moist air your daily activities generate. When this indoor humidity meets the cooler glass, it's like a playful tango of temperatures. Cue the condensation – those little water droplets are simply your windows showing off their efficiency.

Summer Condensation: An Outdoor Affair

Now, fast-forward to summer. As the heat kicks in, you might observe water droplets forming on the outside of your windows. When it's hot and humid outside, your air conditioning swoops in to keep the indoors cool. This means your windows become cooler than the outdoor air. So, when the humid outside air meets your refreshingly cool windows, it's like a cool breeze on a sweltering day – hello, condensation! But guess what? This is another pat on the back for your high-performing windows. They're working tirelessly to keep your indoor haven cooler than the great outdoors.

But I've Never Experienced Condensation Before!

The unexpected presence of condensation on your new windows might leave you perplexed, particularly if you never experienced this phenomenon with your previous older windows. However, it's crucial to take into account that the design of older windows often featured lower energy efficiency, and their age might have led to air infiltration. As a result, the contrast in temperature between the glass and the exterior wasn't as prominent as it currently is with your upgraded, airtight, and well-insulated new windows.

Pro Tips To Keep Condensation In Check

Now let's talk solutions. Whether you're cuddled up indoors during winter or enjoying the summer sun, here are some friendly strategies to keep condensation in check:

1. Mastering Humidity Control

When it comes to battling condensation, the key player in the game is indoor humidity. Throughout the year, everyday activities such as cooking, showering, and even the simple act of breathing release moisture into the air. The crucial strategy to counter this moisture buildup is twofold: first, employing dehumidifiers to actively extract excess moisture, and second, ensuring a continuous circulation of fresh air. By mastering the art of indoor humidity regulation, you hold the reins to a condensation-free environment within your home.

Below is the humidity level recommended to best control condensation during winter months

Outside temperature

in degrees Celcius

Maximum relative humidity level desirable

for an indoor temperature of 21°C

-28 °C or less


-28 °C to -23°C


-22 °C to -17°C


-16 °C to -12°C


-11 °C to -6°C


-5 °C to +4°C


(Source: APCHQ)

2. Embrace Open Doors

Leaving interior doors open during the day promotes air circulation and prevents the confinement of humid air within specific areas. This simple step allows moisture to disperse throughout your home, reducing the likelihood of condensation forming on windows.

3. Summer Air Conditioning

Summer days call for a smart air conditioning move. Bump up the temperature setting a tad. This bridges the gap between indoor air and your window glass, leaving less room for condensation to make an appearance.

4. Letting Fresh Air In

Periodically opening your windows lets fresh air in and allows stale, humid air to escape. This exchange of air helps maintain a balanced humidity level indoors, making it less conducive for condensation to occur.

5. Use Curtains Wisely

Regularly opening blinds or curtains, especially during the day, promotes air circulation near the windows. This measure prevents the surfaces from becoming too cold and reduces the chances of condensation forming. Opening curtains during the day allows warm indoor air to circulate near the window, preventing the surface from becoming too cold and minimizing the potential for condensation.

6. Harness the Power of Dehumidifiers

Investing in a dehumidifier can be a game-changer in controlling indoor humidity. These devices actively remove excess moisture from the air, creating an environment where condensation struggles to take hold. Placing a dehumidifier in particularly humid areas can yield remarkable results.

7. Air Exchangers at Work

If your home is equipped with an air exchanger, be sure to follow the manufacturer's recommendations for usage. Air exchangers help maintain a balanced airflow while preventing the buildup of excess humidity.

8. Extractor Hoods in Action

When cooking, turning on the extractor hood helps to channel steam and moisture out of the kitchen. This proactive step prevents excess moisture from accumulating in the air, reducing the overall humidity levels in your home.


The next time you spot those water droplets, keep in mind that they're not a reason to worry; instead, they're a testament to the effectiveness of your windows. Whether it's winter or summer, grasping the science behind condensation empowers you to manage your indoor environment effectively. By embracing these approachable strategies, you will be fully prepared to sustain a condensation-free living space.

- Rudy Moskun

Owner & Installer

514 402-5656


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Contact us

Tel: 514 402-5656

By appointment : 

2113 Boul Saint Régis Suite 240

Dollard-des-Ormeaux, QC H9B 2M9

Specialized in residential windows and doors supply and installation in the Montreal West Island.

RBQ #5627-9706-01

© 2023 Portes et Fenêtres Innovations Générales


Contact us

Tel: 514 402-5656

By appointment : 

2113 Boul Saint Régis Suite 240

Dollard-des-Ormeaux, QC H9B 2M9

Specialized in residential windows and doors supply and installation in the Montreal West Island.

RBQ #5627-9706-01

© 2023 Portes et Fenêtres Innovations Générales

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