More and more often we may observe extreme weather phenomena in Poland that we used to treat as weather anomalies. However, nowadays they constitute fairly regular dangerous climate situations. Gale-force winds do not only tear trees but also inflict significant damage in the building structures: they destroy roofs, they break power lines, putting at risk people’s health and life. Recent events show how damaging the elements can be and how far-reaching results they bring about. Such phenomena emphasize the importance of a stable construction that may protect us against devastating consequences of strong gales and storms.
The intensifying climate change occurs not only at the turn of winter and spring, but it surprise us even in summer, when we observe exceptionally strong and unpredictable weather conditions resulting from clashes of air masses.
Unfortunately, weather forecasts are not encouraging. Weather forecasters claim that as a result of climate change, violent storms and gales will be more and more common. During recent storms the wind blew with the speed of from 112 (Chojnice area) up to 150 (Elbląg area) kilometers per hour - as for pressure, it was in the range of 600 to 1050Pa. With such winds it is worth checking the quality of our windows, and before buying them we need to seriously consider the parameters that really affect the woodwork resistance to wind load, and check if it will be able to protect us against leak of meteoric water. We need to analyze the profile structure, reinforcement, gaskets and properties of woodwork fittings since these elements affect parameters such as: water tightness, air permeability and wind load.
Resistance to wind load and water tightness constitute vital criteria that determine windows’ quality. They are especially important for inhabitant of high floors and owners of houses situated in open areas and at the seaside.
Resistance to wind
A window fitted in a building is exposed to wind load, that is wind pressures and suctions. The window structure must be designed, executed and installed so that excessive air permeability, leak of meteoric water and glass breakage do not occur as a result of wind pressure and suction when the window is used.
Strong wind may cause permanent deformation of the window through the frame deflection even by a few millimeters. This kind of activity leads to permanent unsealing. In order to ensure comfort and protection against adverse weather conditions, we need to, above all, invest in top-quality windows that stand out for high rigidity.
Resistance to wind load, so-called window rigidity, determines its class. The indicator of resistance to wind load shows at what wind speed will occur the maximum permissible deflection of the most deformed window element. It must not exceed 1/300 of the element length. Importantly, the parameter must be chosen depending on the wind force where we live, since windows in a high-rise block should have different wind resistance from a single-story house, which is connected with the structure physics.
„Checking the class of the window wind resistance is executed in testing laboratories. The test consists of applying a specific series of positive and negative test pressures when measures and tests are executed in order to evaluate the relative front deflection and resistance to damage resulting from wind load’’ – says Mirosław Furtan, quality director at DRUTEX S.A.
Resistance to wind load is indicated basing on such tests with symbols from A-1 (the lowest rigidity) to C-5 (the highest). Taking into account our climate conditions, the average building requires a window with resistance to wind load in B-3/B-4 class, in extreme cases, exposed to strong wind, that is heights or open areas - C-3/C-4 class. It means that it will resist wind of 1200-1600 Pa force, i.e. 158-184 km/h.
In other words, if ‘resistance to wind load’ is in B3 class, it means that the window frame will bend at pressure up to 1200 Pa, so it resists 1200 Pa pressure with no damage. This pressure corresponds to wind blowing with 160 km/h speed.
On the other hand, the window with top resistance to wind force classified by C-5 symbol will be resistant to wind blowing over 205 km/h, and the window with the lowest resistance to wind load in A-1 class will yield to wind blowing with 90 km/h speed.
Therefore, before you buy a window, it is highly important to discuss with the window producer where and in what surrounding the building will be located in order to obtain advice what class of the window will be the most proper. In regions more exposed to extreme weather conditions – in areas under influence of sea weather or in the mountains it is better to apply windows in higher class.
„Window testing is a requirement, and each window producer has to provide a product card with the tested parameters and their classes. That’s why before you buy the window you need to check thoroughly what parameters the product provides, i.e. the safety level it offers. Three parameters are vital in this area: wind resistance and, connected with it, water tightness and air permeability. Facing the more and more common weather changes it is worth remembering that window parameters may determine the usage comfort and our satisfaction. Drutex windows resist wind blowing even with 200 km/h speed. The proper window rigidity is ensured by the high-quality profiles made exclusively of prime material, a steel reinforcement, optimum system of chambers with high-quality glass. The optimum combination of such elements constitutes a guarantee of both resistance to wind, as well as water tightness and air permeability’’ – advises Mirosław Furtan from DRUTEX S.A.
Apart from resistance to wind, it is also vital to test the level of woodwork water tightness. Water tightness indicator shows the wind load when water will leak from outside into the window structure during rainfall. In this case the recommended class is E 750 Pa. with this class, water will not leak inside even if the wind blows with ca. 130 km/h speed.
The lowest 1A class means that the window will leak even with no wind. Almost the highest 9A guarantees tightness even with gale of 600 Pa pressure (i.e. 112 km/h).
Modern windows stand out for technological advancement. Cutting-edge solutions often determine their high quality. Therefore, we may find woodwork that is perfectly tailored to our needs and preferences regarding shapes, colors and size of windows. However, we should not forget that resistance to wind load and water tightness remain crucial parameters. That is why we need to check and ask since such knowledge gives us the certainty that we have chosen the right window. We need to ask about certificates, attestations and technical approvals that the producer has obtained. It is also important
to trust reliable partners, companies with traditions, whose credibility is confirmed by perennial experience in the industry.