Beyond the Gust: Understanding CWCT Cyclic Wind Testing for Rainscreens

What is CWCT Wind Testing?

These tests involve fixing a full-scale mock-up of the rainscreen system onto a pressure chamber.  A typical CWCT “Sequence B” testing sequence includes the following wind tests:

• Serviceability Testing: Understanding how the system performs under peak loads and ensuring it returns to its original state after a significant load.

• Safety Testing: Pushing the system to 1.5x the design wind pressure to ensure no components fail catastrophically.

But a rainscreen test sequence, shouldn’t be just about whether the panels stay on during a once in 50-year wind event; it also needs to consider the risk of fatigue.

While standard wind resistance tests often focus on an "ultimate" load, Cyclic Wind Testing evaluates how a system behaves under repeated stress, by subjecting the system to thousands of cycles of positive and negative pressure.

What Does Cyclic Wind Testing Actually Simulate?

In the real world, wind doesn't just blow steadily. It gusts, swirls, and creates vortices. As wind hits a building, it creates positive pressure on the windward face and negative pressure (suction) on the corners and leeward sides.

Cyclic testing simulates:

• The "Pumping" Effect: The constant dynamic movement of rainscreen panels as they are pushed toward and pulled away from the structure.

• Component Fatigue: The repetitive loading on the fixing points, screws, rivets and brackets that hold the system together.

Why Is This Critical for Rainscreen Systems?

"Invisible" failures can occur over time, due to repeat loading cycles:

• Fastener Hole Enlargement: Repeated movement or vibration can cause fasteners to enlarge the holes in the cladding panels & rails, leading to rattles or, in extreme cases, panel detachment.

• Work Hardening: Aluminium components become more brittle due to repeated bending. This reduced ductility makes the material more prone to failing during a high wind event.

• Micro-Cracking: Components can develop micro-fractures from metal fatigue. If, overs thousands of cycles a crack grows, it can result in a component no longer being able to carry the load imposed upon it resulting in a potential failure.

1. Protecting Design Integrity and Performance Guarantees

Architects and façade designers rely on system performance to uphold the intent of their designs. A façade that distorts, rattles, or prematurely degrades due to cyclic loading undermines both the aesthetic and functional requirements of a project.

By insisting on cyclic-tested systems, specifiers help ensure that:

• Repeated loading does not cause long-term deformation or loosening of panels.

• Components return to their original position after wind events, preserving clean alignment lines and intended visual effect.

• The façade performs predictably throughout its life, supporting warranties and compliance documentation.

Cyclic testing rainscreen support systems gives specifiers confidence that the façade will behave as designed under real conditions — not just when subjected to the peak loads.

2. Reducing Contractor Risk and Protecting Programme

For specialist façade contractors, the consequence of post-completion defects is significant. Rainscreen issues linked to fatigue are notoriously difficult to diagnose and even more difficult and expensive to rectify once the building is occupied.

Cyclic wind testing helps contractors protect themselves by demonstrating, before installation, that the facade support system can:

• Handle repeated pressure and suction loads

• Doesn’t fail structurally as a result of fastener and bracket fatigue or hole enlargement issues

When a system has passed cyclic testing, contractors can install with confidence, knowing the support brackets, rails, and fixings have already been verified under realistic, long‑term load patterns. This reduces the likelihood of callbacks, disputes, warranty claims, and reputational damage.

3. Demonstrating Technical Competence and Best Practice

In a market where clients and insurers are increasingly demanding evidence of robust system performance, insisting on cyclic-tested support systems helps façade contractors and specifiers demonstrate:

• Adoption of recognised industry best practice

• Compliance with evolving risk expectations

• A proactive approach to minimising latent defect exposure

• Credible justification for chosen system and materials

This positions the project team as forward‑thinking and technically rigorous, strengthening client trust and enhancing competitive differentiation.

4. Ensuring Long-Term Client Value and Reduced Lifecycle Costs

Clients increasingly evaluate façades not only on upfront cost but also on the total cost of ownership. Systems that have undergone cyclic wind testing provide building owners with greater confidence that they can withstand decades of fluctuating pressures without components loosening, failing, or requiring premature replacement.

For specifiers and contractors, this translates into:

• Clearer alignment with client quality expectations

• Stronger supporting evidence for specification choices

• Reduced lifecycle risk

By advocating for cyclic-tested systems, the façade team helps protect the client from escalating maintenance costs and potential safety risks — delivering a better building and a more durable asset.

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