Behind a draft coming from a window there is much more than a simple inconvenience: this issue can reveal a lot about how well windows protect your home. Air permeability and wind resistance are not just technical parameters, but the foundations of a house that stays warm, dry and quiet even when outdoor conditions change quickly.
What is the meaning of window air permeability?
By definition, air permeability describes a window’s ability to seal the gap between the sash and the frame. When a traditional window or patio door does not seal this contact point properly, air can pass through even when it is closed: even a very small gap is enough for wind to enter the home, bringing cold air, noise and humidity with it.
More specifically, window standards such as UNI EN 1026 define how much air passes through a window when it is subjected to controlled pressure conditions. The higher the air passage, the more noticeable window drafts become: not only as a cold airflow on the skin, but also as energy losses that affect comfort and household energy consumption..
What is the meaning of window wind resistance?
Wind resistance describes a window’s ability to maintain its performance as air pressure increases. Beyond preventing frame deformation, an efficient window does not vibrate, whistle, or allow drafts or moisture to enter during strong gusts.
Wind applies variable pressure to the window frame. When the structure is not sufficiently robust or properly designed to distribute air loads, the profile can flex just enough to create micro-defects in the seals. This is when the most common issues appear: noise, vibrations, whistling sounds, air infiltration or condensation.
Wind resistance is tested according to UNI EN 12210 and UNI EN 12211 standards. These regulations ensure that the window remains stable, quiet and watertight even under high pressure conditions, equivalent to winds that can exceed 100 km/h.
Drafts, noise and condensation: when windows no longer seal properly
A window that effectively seals against weather conditions makes the home more comfortable and quieter. Air permeability and wind resistance are among the factors that most influence everyday indoor comfort. When these performances are insufficient, drafts and infiltrations quickly become noticeable, compromising comfort and overall living quality.
Here are the most common signs that indicate insufficient performances in terms of air sealing and wind resistance:
- Constant window drafts: a window with low window air permeability performance allows wind and cold air to enter continuously, even when the sashes are fully closed.
- Noise or vibrations: when the window does not adequately withstand wind and air pressure, even a light gust can cause vibrations or whistling sounds.
- Water or moisture: poor air sealing can also increase indoor humidity; for example, during a storm it is possible to notice condensation droplets forming.
- Higher energy bills and low efficiency: the more air penetrates the home, the more energy is required to maintain the desired indoor temperature and limit heat loss.
- Reduced window durability: constant drafts and pressure stress seals, hardware and joints more quickly, shortening the overall lifespan of the window system.
Window air permeability classes: reference standards
UNI EN 1026 defines how to measure the amount of air passing through a closed window subjected to a pressure difference, while UNI EN 12207 provides the window classification, dividing windows into four performance classes (from 1 to 4), plus a class 0 for insufficient performances.
Class | Air permeability limit | Maximum test pressure | Sealing level |
|---|---|---|---|
0 | Performance not determined | – | Very poor |
1 | 50 m³/h·m² | 150 Pa (≈ 50 km/h wind) | Low |
2 | 27 m³/h·m² | 300 Pa | Medium-low |
3 | 9 m³/h·m² | 600 Pa | Good |
4 | 3 m³/h·m² | 600 Pa (≈ 110 km/h wind) | Maximum |
As mentioned earlier, wind resistance refers to a window’s ability to withstand positive and negative wind pressures without compromising safety or undergoing excessive deformation.
UNI EN 12211 defines the laboratory test procedures, while UNI EN 12210 establishes the resistance class. This classification is based on two parameters: the pressure the window can withstand (classes 1 to 5, plus special E), the level of frame deformation (A, B, C).
Class | Test pressure (Pa) | Performance indication |
|---|---|---|
1 | 400 Pa | Basic resistance |
2 | 800 Pa | Improved stability |
3 | 1200 Pa | High performance |
4 | 1600 Pa | Very good resistance |
5 | 2000 Pa | Very high performance |
E ≥ | Higher than Class 5 (e.g. E2200, E3000) | For exposed areas or extreme conditions |
Letter | Description |
|---|---|
A | Higher deformation allowed |
B | Reduced deformation |
C | Best behaviour (highest class) |
What does all this mean when choosing new windows?
- Windows with high air permeability classes (3-4): fewer window drafts, less external noise, reduced thermal and energy losses.
- Windows with high wind resistance classes (4-5 and/or E): greater structural stability, no whistling or vibrations, improved protection during strong gusts and storms.
These classifications provide a concrete reference for understanding which windows will perform reliably over time. When combined, high air permeability and wind resistance ratings ensure a window that does not deform and does not allow air or condensation to pass through, even under increasingly extreme weather conditions.
DQG: high-quality Made in Italy windows and professional installation
At DQG, we believe that the quality of a door or window is never just about the product itself, but the result of the right combination of construction materials and professional installation.
As PosaClima-certified installers, we integrate every window system using advanced installation procedures, carefully managing joints, seals, alignments and airtight sealing. This approach allows windows to maintain their expected performance over time, preventing window drafts and leaks.
Material research is another core element of DQG window profiles, available in uPVC and uPVC/Aluminium. Stable frames, durable gaskets and engineered insulated glazing units ensure consistent air permeability and wind resistance, even during strong gusts. Each window is a complete solution, designed to protect the home from weather exposure.
Discover our range of Made in Italy doors and windows and contact us to learn more.
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