When you specify a curtain wall glazing system, you need to know it's fit for purpose. That means more than checking the glass specification or taking the manufacturer's word for it.
A curtain wall is exposed to all kinds of stresses during its lifetime. There's wind pressure, driving rain, temperature changes and the possibility of accidental impacts. In some buildings, it may also need to provide fire resistance.
That's why glazing systems undergo rigorous testing.
At Wrightstyle, we supply
steel curtain wall systems for a wide range of applications, including projects with specialist
fire,
ballistic and
blast-resistance requirements.
In this guide, we take you behind the scenes of curtain wall testing. We'll explore the main curtain wall testing standards, how the tests work and what the results mean for architects and specifiers.
How are curtain walls tested?
Curtain wall testing generally takes place in specialised laboratories using full-size or representative sections of a glazing system.
The test specimen is assembled with the relevant components, including glass, frames, seals, gaskets and fixings. It's then mounted onto a test rig designed to reproduce particular conditions.
For example, a laboratory might use air pressure to simulate wind loads or spray water against the facade to assess its resistance to driving rain.
These are physical tests, not computer simulations. However, they're carried out under carefully controlled and repeatable conditions. That's important because the results need to be comparable.
The main European product standard for curtain walling is
BS EN 13830. It establishes a framework for assessing and declaring relevant performance characteristics.
Other standards specify the individual test methods and classifications.
Let's look at five of the most important.
1. Air permeability testing
Air permeability measures how much air passes through a curtain wall under a pressure difference.
Even a small amount of unwanted air leakage can affect a building's thermal efficiency and occupant comfort.
That's why airtightness is an important consideration when specifying large glazed facades.
The relevant curtain wall standards include:
- BS EN 12152: performance requirements and classification
- BS EN 12153: the test method
During testing, the specimen is mounted in a sealed chamber.
Air pressure is applied to create a difference between the two sides of the curtain wall, and the amount of air passing through the assembly is measured.
The test considers positive and negative pressure, representing air being pushed through or drawn through the system.
The results are used to establish an air permeability classification.
For architects, this provides evidence of how well the proposed glazing system limits unwanted air leakage.
2. Watertightness testing
Rain is another major challenge for external glazing systems.
A curtain wall must prevent unwanted water from entering the building, even when strong winds drive rain against the facade. Watertightness testing investigates how effectively the system achieves this.
Three important standards are:
- BS EN 12154: watertightness performance requirements and classification
- BS EN 12155: laboratory testing under static air pressure
- BS EN 13050: additional testing under dynamic air pressure and water spray
In a static-pressure test, water is sprayed against the outside of the curtain wall while a pressure difference is applied. The pressure is increased in controlled stages, allowing technicians to observe whether water penetrates the system.
Dynamic testing introduces moving air and water spray to reproduce more variable wind-driven rain conditions.
These tests help identify weaknesses in seals, joints, drainage paths and other details.
For specifiers, the important question isn't simply whether a system is described as weatherproof. It's
what level of watertightness has actually been demonstrated.
3. Wind resistance testing
Curtain walls are non-loadbearing external walls, but that doesn't mean they can be structurally weak. They must support their own weight and transfer wind loads safely to the building structure.
Wind resistance is particularly important for tall buildings, exposed sites and large-span glazing systems.
The relevant standards include:
- BS EN 13116: wind-load performance requirements
- BS EN 12179: the laboratory test method
During testing, positive and negative air pressures are applied to the curtain wall. This reproduces forces pushing against the facade and pulling it away from the building.
Technicians measure how much the system deflects under load and whether it returns satisfactorily towards its original position afterwards.
Tests can also include higher pressures to assess safety under more demanding conditions.
In some test programmes, air permeability and watertightness are checked again after structural loading. This helps establish whether the stresses have affected the system's weather performance.
4. Impact resistance testing
A curtain wall might also be subjected to accidental impacts. These could come from people, objects or equipment, depending on the building's location and use.
Impact resistance is assessed under
BS EN 14019, which sets out performance requirements for curtain walling.
Testing generally involves striking a representative assembly with a controlled impactor. The purpose is to assess how the curtain wall responds to impact, including whether components become damaged or create a safety hazard.
The appropriate test conditions depend on the intended application.
There's also a related standard for the glass itself.
BS EN 12600 classifies flat glass according to its response to pendulum impact testing, including how it breaks.
This distinction is important. A glass pane may meet a particular safety classification, but that doesn't automatically establish the impact performance of the complete curtain wall.
The frame, fixings and surrounding components also need to be suitable.
5. Fire resistance testing
Some curtain walls need to provide fire resistance.
This is especially important where the facade forms part of a fire-resisting construction or needs to help prevent fire spreading between areas of a building.
Fire testing works differently from weather and structural testing. The glazing assembly is exposed to a controlled heating regime in a specialised furnace.
Depending on the required classification, technicians assess whether the system maintains integrity and limits heat transfer for the specified period.
The relevant standards include:
- BS EN 1364-3: fire-resistance testing of complete curtain wall configurations
- BS EN 1364-4: fire-resistance testing of parts of curtain walling
- BS EN 13501-2: classification of fire-resistance performance
For example, an EI60 classification means the tested system achieved at least 60 minutes of integrity and insulation under the relevant test conditions.
It's important to remember that fire ratings apply to tested or appropriately assessed system configurations. In other words, using fire-resistant glass in an unsuitable frame doesn't automatically produce a fire-resistant curtain wall.
What do the EN numbers mean for specifiers?
The EN numbers identify different European standards, many of which have been adopted as British Standards.
Some describe
how a test is performed. Others establish
performance requirements or classifications.
That's an important distinction.
For example, BS EN 12153 explains how to test air permeability, while BS EN 12152 establishes the corresponding performance classification.
So, a test report should tell you more than which standard was used. It should also explain the achieved result and the configuration tested.
When reviewing curtain wall test evidence, check:
- Whether the evidence relates to the proposed glazing system
- The dimensions and configuration of the tested assembly
- The performance levels achieved
- Any limitations on the application of the results
- Whether the proposed glass, framing and fixings are covered by the evidence
A tested product is useful, but the evidence still needs to be relevant to your project.
Why physical testing matters
Computer modelling is useful for predicting how a curtain wall might perform.
However, physical testing lets you assess real components working together. It can reveal problems that aren't obvious from individual material specifications, including unexpected air leakage, water penetration or excessive deflection.
Testing also provides standardised performance data that architects and contractors can use when comparing systems.
Of course, testing doesn't eliminate the importance of correct installation. A well-tested curtain wall can still perform poorly if the site workmanship or supporting structure is unsuitable.
That's why the strongest specification combines appropriate test evidence with careful design and installation.
How Wrightstyle can help
At Wrightstyle, we develop
steel curtain wall glazing systems with performance and quality assurance in mind.
We provide specialist systems for demanding applications, including fire-resistant, ballistic-resistant and blast-resistant glazing.
We also publish technical information about our systems' performance and can advise on the test evidence relevant to a particular specification.
If you're selecting a curtain wall for a new building or refurbishment project, our technical team can help you understand the available options and choose an appropriate system.
Contact Wrightstyle today for comprehensive product advice and specification support.
