Understanding Dew Point: Inside vs. Outside Your Windows
- cathiest-germain
- Apr 27
- 2 min read
:The dew point is the temperature at which the air becomes fully saturated with moisture, causing the water vapor it holds to turn into liquid droplets. When warm, humid air comes into contact with a surface colder than this critical temperature, condensation forms.
In a home, this often happens on windows. However, it's important to distinguish between condensation on the outside and condensation on the inside of your windows.
Condensation on the Outside of Windows
When you see fine droplets on the outside of your glass, especially early in the morning, it is actually a good sign. It means your windows are highly energy-efficient: they are effectively keeping the indoor heat inside and not warming the exterior glass surface. As a result, the outer pane remains cooler and may reach the outside dew point, leading to condensation.
In short:✅ It's normal.✅ It's even a sign of excellent thermal performance.
Condensation on the Inside of Windows
On the other hand, when condensation appears inside the window, it usually indicates a problem.
Possible causes include:
Excessive indoor humidity (e.g., drying clothes indoors, frequent showers without ventilation, cooking without a proper range hood)
Poor window insulation, where the inner glass surface cannot retain enough heat.
When the dew point is reached indoors, moisture in the air condenses on the cold window surface. Over time, this can lead to:
Mold growth
Damage to window frames
A decline in indoor air quality
How to Manage It
Ensure proper ventilation (air exchangers, bathroom fans, kitchen hoods).
Reduce indoor humidity during winter, ideally maintaining it between 30% and 40%.
Invest in high-performance windows with excellent thermal insulation suited to your climate.
At VST Doors and Windows, we guide you in choosing products that combine thermal performance, durability, and comfort — helping you maintain a healthy, energy-efficient home. 🏡✨
Have questions about your windows or need personalized advice? Contact us — our team will be happy to assist you!
