The wind zone is one of the most critical factors in the design of structures, especially in rooftop photovoltaic installations. An incorrect calculation can compromise the stability of the system or lead to oversizing of the structure, directly impacting the project cost.
This guide explains how the wind zone is defined according to the Spanish Building Technical Code (CTE) and the Eurocode , and how to apply it correctly in real-world projects, especially for flat roofs with ballasted systems.
What is the wind zone?
The wind zone represents the basic wind speed that can affect a structure depending on its geographical location.
This speed serves as a starting point for calculating:
- Wind pressure
- Suction on deck
- Efforts on solar structures
- Need for ballast or securing
In photovoltaic systems, wind is the most decisive factor along with the system’s own weight.
Wind zone according to the CTE (Spain)
The Technical Building Code (CTE), in its Basic Document SE-AE (Structural Safety – Actions on Buildings), divides Spain into different wind zones based on wind speed.
Classification of wind zones in Spain
The Technical Building Code (CTE), in its DB SE-AE, establishes the wind zoning in Spain.
Classification of wind zones
- Zone A → lower wind speed
- Zone B → average speed
- Zone C → high wind exposure
These zones are based on the basic wind speed (vb) , which usually ranges between 26 and 29 m/s .
Application in solar structures
Depending on the area:
- The ballast is increased or decreased.
- The structural configuration is modified
- The spacing between modules is adjusted.
Wind Zones of Spain – Image taken from https://www.dlubal.com/
Calculation according to Eurocode (EN 1991-1-4)
Eurocode 1 allows for a more detailed calculation of wind actions.
Unlike the CTE, it takes into account:
- Terrain roughness
- Building height
- Orographic effects
- Specific pressure coefficientsRugosidad del terreno
This is especially important in industrial or large-scale projects.
How the wind zone affects ballasted structures
On flat roofs, ballasted solar structures depend directly on wind loads.
Direct impact on design
- Low wind zone (A)
Less ballast, greater optimization - Mid-wind zone (B)
Balance between weight and stability - High wind zone (C)
Significant increase in ballast
Structural optimization at Alusín Solar
At Alusín Solar we design optimized solutions taking into account real wind loads , guaranteeing structural safety, efficiency and cost reduction in each project.
Our calculations guarantee:
- Reducing ballast without compromising safety
- Optimize load distribution. Learn about techniques for reducing loads in industrial photovoltaic installations here.
- Adapt the structure to each roof
- Comply with CTE regulations and Eurocode
Our approach allows for savings in materials and logistics , which is key in large installations.
Factors that influence the situation, in addition to the wind zone
For a realistic calculation, we consider:
- Building height
- Type of environment (urban, industrial, open)
- Roof geometry
- Critical areas (edges and corners)
Two facilities in the same area can have completely different behaviors.
Advantages of a correct wind calculation
- Greater structural safety
- Ballast cost reduction
- Less overload on the roof
- Longer system lifespan
Frequently asked questions about wind zones
Which wind zone is my project in?
It depends on the geographical location according to the CTE (Technical Building Code). We can help you determine it and calculate actual loads.
Is it mandatory to use Eurocode?
The CTE is mandatory in Spain, but the Eurocode is used for more precise calculations.
Is it possible to reduce ballast in high wind areas?
Yes, through structural optimization and aerodynamic design.
Are ballasted structures safe in zone C?
Yes, provided the calculation is done correctly.
Do you need to calculate the wind zone of your project?
At Alusín Solar we help you design the best structural solution for your photovoltaic installation:
- Wind load calculation
- Ballast optimization
- Technical design adapted to regulations
- Support for engineers and installers
Contact our technical team and optimize your project from the design stage.
