Wind loads in coastal areas of Spain

Coastal winds aren’t just a gentle sea breeze; they place significant strain on window structures. The Levantine wind in Alicante, the Tramontana wind in northern Catalonia, and the Poniente wind in Andalusia create pressure on windows that is several times greater than what’s expected in central regions. Incorrectly selected or installed windows become drafty, rattle, warp, and last significantly less than their stated lifespan.

What is wind load?

Wind load is the pressure of airflow on the window surface. The stronger the wind and the larger the glazing area, the greater the strain on the profile, glass, and fasteners.

Unit of measurement: pascals (Pa) or kilograms per square meter (kg/m²). A wind pressure of 1000 Pa means a load of 100 kg per square meter of window surface. A 3x2 meter panoramic window experiences a pressure of 600 kg in such a wind—the equivalent of 8-10 people pressing on it.

Wind speed and pressure are related by a quadratic law. A wind of 50 km/h creates a pressure of 200 Pa, 100 km/h creates 800 Pa, and 150 km/h creates 1800 Pa. Doubling the wind speed quadruples the load.

Pulsating loads occur during gusty winds. Sudden pressure changes loosen sash fastenings, damage seals, and create vibration. A constant, steady wind is less dangerous than a gusty wind of the same average speed.

Wind zones in Spain

Spain is divided into wind zones according to the CTE (Código Técnico de la Edificación) building code. The classification takes into account average wind speed, building height, and terrain.

Zone A – inland areas with low wind loads. Base wind pressure is 400-600 Pa. This includes most of central Spain, protected by mountains from sea winds—Madrid, Castile, and the interior of Andalusia.

Zone B — moderate wind load of 600-800 Pa. Transitional areas between the coast and the center, as well as elevated areas—parts of Aragon, Navarre, and the interior of Catalonia.

Zone C — coastal areas with high wind loads of 800-1200 Pa. The entire Mediterranean coast, the Atlantic coast of Galicia, Asturias, and the Basque Country. Reinforced windows are required here.

Special zones — areas known for extreme winds. Empordà in Catalonia (Tramuntana up to 150 km/h), Ebro in Aragon (Cierzo), Gibraltar (Levante and Poniente). The design pressure exceeds 1200-1400 Pa.

Building height increases wind load. On the ground floor of a coastal building, the pressure is 900 Pa, on the fifth floor, it’s 1100 Pa, and on the tenth floor, it’s 1300 Pa. Wind increases with height due to the lack of obstacles.

Window Wind Resistance Classes

The European standard EN 12210 defines window wind resistance classes from 1 to 5, plus additional classes A, B, and C.

Class 1 — pressure up to 400 Pa. Minimum wind resistance for inland regions. These windows are not suitable for coastal locations.

Class 2 — up to 800 Pa. Standard for most residential buildings in temperate climates. On the coast, it’s only sufficient for ground floors protected from the wind by buildings or trees.

Class 3 — up to 1200 Pa. Recommended for all coastal areas of Spain. Withstands typical coastal winds, including storms occurring 2-3 times a year.

Class 4 — up to 1600 Pa. For high-rise buildings on the coast and in areas with extreme winds. Mandatory for buildings over 5 stories in coastal areas and in areas exposed to the Tramontana and Levantine winds.

Class 5 — up to 2000 Pa and above. For skyscrapers and extreme conditions. Rarely used, primarily in commercial buildings.

Additional classes A, B, and C indicate the degree of sash deflection under load. Class A is minimal deflection (rigid construction), while Class C is permissible deflection up to the safety limit.

What happens to windows with insufficient wind resistance

Drafting is the primary problem with weak windows. Wind creates a pressure difference between the outside and inside the room. If the locking system does not provide sufficient sash clamping, air enters through gaps in the seals. Drafts, whistling, and wind noise appear in the house.

Profile deformation occurs when the structure is too weak to withstand wind loads. Plastic profiles with little or no reinforcement sag under pressure. Sashes no longer close tightly, and gaps appear.

Insulating glass failure occurs under extreme loads. Glass not designed to withstand high pressure can crack or shatter. This is especially dangerous for large glazing areas, such as panoramic windows and patio doors.

Hardware failure accelerates under constant wind loads. Hinges become loose, locking mechanisms become deformed, and handles jam. Hardware designed for Class 2 conditions fails in 3-5 years under Class 4 conditions instead of 15-20 years.

Sash separation is a critical situation during hurricane-force winds. Incorrectly secured or installed windows can break off their hinges. This is dangerous not only for property but also for human life.

Reinforced Profiles for Coastal Areas

Profile reinforcement determines its rigidity and wind resistance. The standard reinforcement for PVC windows is a 1.5 mm thick steel profile inside a plastic chamber.

For coastal areas, a minimum of 2 mm reinforcement is required, while high-rise buildings and areas with extreme winds require 3 mm. Thicker steel prevents profile deflection under load.

Closed reinforcement is essential for high wind loads. The U-shaped reinforcement used in inexpensive windows is not rigid enough. A closed steel contour acts like a box, distributing the load evenly.

Profile width affects the rigidity of the structure. Narrow 60 mm profiles are only suitable for small windows and low wind loads. For coastal areas, choose profiles with a minimum installation width of 70 mm, and preferably 80-90 mm.

Aluminum profiles are inherently stiffer than plastic profiles due to the properties of the material. Aluminum with a thickness of 1.5-2 mm provides Class 4 wind resistance without additional reinforcement. This makes aluminum the optimal choice for large glazed surfaces on the coast.

Aluminum systems with thermal breaks withstand wind loads of up to 2000 Pa, even with sash dimensions of 3x3 meters. PVC profiles of this size sag under their own weight even without wind.

Double-glazed windows for wind loads

Glass thickness is critical for large glazing areas. Standard 4 mm glass is suitable for windows up to 1.5 m² under normal conditions. For coastal areas and larger windows, 6-8 mm glass is required.

Glass thickness calculations take into account the sash area, wind zone, and building floor. A 2x2 meter panoramic window on the coast requires a minimum of 6 mm glass. Above the fifth floor, 8 mm glass is required.

Tempered glass is 5-7 times stronger than standard glass of the same thickness. The tempering process creates internal stresses that increase resistance to bending and impact. If broken, tempered glass shatters into small, blunt shards, which is safer.

For windows above the third floor on the coast, tempered glass is recommended, at least in the outer layer of the insulating glass unit. This protects against breakage in extreme winds and impacts from flying objects.

Laminated glass (triplex) is made from two or three layers of glass bonded with a polymer film. If broken, the shards remain on the film and do not fall out. This provides maximum safety for large windows at heights.

Triplex is 40-60% more expensive than tempered glass, but provides additional sound insulation and burglary protection. For ground floors on the coast, this protection not only protects against wind but also against burglars.

Asymmetrical insulating glass units (AIG) – the outer glass is thicker than the inner glass. The formula is 6-16-4 instead of the standard 4-16-4. The outer glass bears the brunt of the wind load, while the inner glass provides thermal insulation.

The asymmetrical design also improves sound insulation—the different glass thicknesses dampen sound waves at different frequencies. This is beneficial on the coast, where wind and wave noise can disrupt sleep.

Hardware for High Wind Loads

The number of locking points determines the tightness of the sash clamping around the perimeter. Standard hardware has 3 locking points—sufficient for normal conditions.

For coastal areas, a minimum of 5 locking points is required for a tilt-and-turn sash 1.5 meters high. For sashes taller than 2 meters, 7-9 locking points are required. More locking points ensure uniform clamping around the entire perimeter and prevent drafts.

RC2 class burglar-resistant hardware not only provides protection against burglary but also increases strength under wind loads. Reinforced hinges and mushroom-shaped locking pins withstand heavy lifting loads.

Three-dimensionally adjustable hinges allow for precise sash positioning. Over time, sashes shift slightly due to wind and their own weight. Adjustable hinges compensate for these changes without the need for a professional.

For heavy, large sashes, use concealed hinges. They can withstand up to 200 kg, compared to 130 kg for standard hinges, and distribute the load more evenly.

Opening limiters are required on upper floors. A strong gust of wind can yank the handle out of your hand and force the sash open, damaging the hardware. A limiter prevents the sash from opening beyond the set angle.

Window Installation in Coastal Areas

Even the strongest windows will fail to withstand wind loads if installed incorrectly.

The frame fastening to the opening must withstand pull-out forces. Standard fastenings are anchors or self-tapping screws spaced 70 cm apart around the perimeter. For coastal areas, the spacing is reduced to 50 cm, using larger diameter anchors.

In aerated concrete and porous materials, standard anchors do not hold well. Use special anchors for lightweight concrete or through-fastenings through the frame to the full depth of the wall.

Foam secures the frame in the opening and provides thermal insulation, but is not a load-bearing element. Foam does not withstand pull-out forces; the window must be secured mechanically.

Use professional-quality foam with a low expansion coefficient. Highly expanding foam will deform the profile, which is critical for geometric accuracy.

Waterproofing and vapor barriers around the joint are essential on the coast. Wind and rain drive water into any cracks. Without protection, the foam becomes damp, loses its thermal insulation properties, and deteriorates.

On the exterior, use a vapor-permeable waterproofing tape—it draws moisture out of the joint but keeps water from entering. On the interior, use a vapor barrier tape to prevent moisture from entering the joint.

Drip flashings should be secured not only to the frame but also to the wall. Wind creates uplift, which can tear loose drip flashings. Use screws every 30-40 cm, plus sealant around the perimeter.

Apply compression tape or sealant under the drip flashing to prevent leaks under the drip flashing during slanting rain and wind.

Features for Different Window Types

Sliding systems are less resistant to wind loads than tilt-and-turn systems. The roller sash does not press as tightly against the frame, which can lead to drafts in strong winds.

For coastal areas, choose lift-and-slide systems (PSK or HST). When closing, the sash lowers and is pressed tightly against the frame by rubber seals around the entire perimeter. The seal is comparable to that of casement windows.

Panoramic floor-to-ceiling windows experience maximum wind loads due to their large surface area. For coastal areas, use only aluminum or combination systems with a reinforced profile.

Separate large areas with mullions—vertical or horizontal crossbars. This increases the rigidity of the structure and reduces the load on each individual element.

Roof windows in coastal areas require a wind resistance class one higher than vertical ones. A tilted position increases the wind load. All roof windows for coastal areas must be at least Class 4.

French balconies (full-height panoramic doors) require reinforced hinges and multi-point locking. A tall sash acts like a sail—even moderate winds create significant torque on the hinges.

Regional Features

Costa Brava and Empordà (northern Catalonia) — the Tramontana zone. This northerly wind reaches speeds of 120-150 km/h, blowing for several days in a row. Here, Class 4 windows are required; for houses in open spaces, Class 5.

Costa Blanca (Alicante, Valencia) — the Levant wind from the southeast can reach speeds of up to 100 km/h. Class 3 is sufficient for most houses, and Class 4 for high-rises and open spaces.

Costa del Sol (Málaga) and Gibraltar — Levante (easterly) and Poniente (westerly) winds create turbulence in the Strait of Gibraltar. Class 4 winds are mandatory for the entire region.

Galicia and the Basque Country — Atlantic storms from the west. Sustained winds of 60-80 km/h with gusts up to 120 km/h during storms. Class 3 minimum, Class 4 for the coastal area.

Canary Islands — Trade winds blow year-round at 30-50 km/h, up to 100 km/h in storms. Class 3 is sufficient, but given the salty air, enhanced corrosion protection for fittings is required.

Checking the Wind Resistance of Existing Windows

Blow Test - Close the window and hold a lit candle or lighter to the perimeter of the sash. If the flame flickers, there is a blower. Check in windy conditions.

Tightness Test - Close the sash on a sheet of paper and try to pull it out. If it comes out easily, the tightness is insufficient. The sheet should be difficult to pull out or tear.

Visual Inspection - Profile deformation, gaps between the sash and frame, or damaged seals indicate that the window is not handling wind loads.

Noise and Vibration - Rattling glass, whistling in cracks, or humming in strong winds indicate sealing issues or insufficient structural rigidity.

If the windows fail these tests, the hardware needs to be adjusted or the seals replaced. If problems persist after maintenance, the windows are not suitable for the wind zone and need to be replaced.

Cost of Wind-Resistant Windows

Reinforced windows for coastal areas cost 20-40% more than standard windows.

Class 3 PVC windows with reinforced reinforcement and multi-point hardware start at €350 per square meter, including installation.

Class 4 aluminum systems start at €520 per square meter.

The additional cost of tempered glass is an additional €40-60 per square meter, while laminated glass adds €80-120 per square meter.

Saving on wind resistance class means windows need to be replaced after 5-7 years instead of 20-25 years. Additionally, there are ongoing heating and air conditioning costs due to drafts, hardware repairs, and adjustments. Properly selected windows are more expensive to purchase but cheaper to operate.