The adjustment/clarification of the CWFT table will become reality in a few months and is causing a lot of stress among manufacturers of wooden cladding. One earthquake has only just passed and another is already approaching. For example, EN 16755 will probably be amended. This European standard concerns the technical durability of fire-retardant treatments. Below you will find the necessary explanation about this adjustment.

Fire safety with (wooden) facade cladding is gaining momentum.
A large amount of scientific research is done and fortunately the knowledge is also shared.
This provides new insights, but also attempts to close previous mistakes and/or gaps.

In the Netherlands I often hear the phrase 'Prove it'.
This possible adjustment of the European standard is interesting to look at in detail.

We summarize what is likely to change:

What exactly is EN 16755?

The EN 16755 stands for the "Technical durability of performance with regard to fire behavior - Classification of wood products treated with fire retardants for indoor and outdoor applications".

It is therefore the standard that indicates how a fire retardant should determine its quality over time and then act accordingly.
For example, the manufacturer can indicate what form of maintenance is required, what maintenance interval, when the treatment must be repeated, which products (possibly additional) must be used, etc.

How is this currently tested?

Fire retardants can map their sustainability in two different ways.

The first way is to do this with the regular SBI test (EN 13823).
You do a fire test in END USE and do an identical fire test after a certain, long-term exposure.
The standard indicates that this is the recommended test, as it naturally identifies more variables.

The second way is to test via the Cone Calorimeter (ISO 5660-1).
This involves testing a small piece of wood before and after long-term or accelerated aging.
This is a commonly used test method, but unfortunately it takes little account of other variables such as profiling, mounting direction, etc.

What might be adjusted?

The standard currently already indicates that EN 13823 is the recommended method.
The possible adjustment therefore means that EN 13823 may become the only way.

The ISO 5660-1 (Cone Calorimeter) may therefore be removed from the standard and will then no longer be valid as proof of sustainability.

Is this correct?

Adjustments to European standards are almost never made unlawfully.
Scientific research indicated that ISO 5660-1 was not always representative for determining the durability of a fire retardant.

If I put my general, down-to-earth logic to it, it's a very logical decision.
The construction world has realized for several years that END USE testing is important to prevent fire infernos.
A small and/or slow leaching of a fire-retardant treatment can therefore have major consequences.

Shouldn't it be the intention to create a tower with fire reaction class B that will again have fire reaction class D after a few years?
And what if it dropped even further...?

Is adapting the test method more difficult?

The ISO 5660-1 was a cheaper and easier way to prove something.
At the same time, it was not fully representative, as it did not take enough into account surrounding variables such as profiling, etc. when building END USE.

The remaining test method also gives more restrictions to the tested setups.
For example, the test will probably only apply to what has been tested (mounting direction, plank width, etc.).

Is every fire-retardant treatment not representative?

Of course we don't say that.
Presumably several parties have already tested their durability in accordance with EN 16755 via EN 13823.

Fortunately, the fire-retardant parties that do rely on this principle still have time to research their product better and avoid problems.
The possible adjustment states that the ISO 5660-1 is not representative for determining the durability of the fire retardant.

The intention of this blog text is to warn colleagues of possible adjustments so as not to hit a wall.
Hopefully colleagues will start their research on time and this challenge can be easily overcome.

Does this European standard also apply to other products that are not treated with fire retardant?

Many products are used in the construction world that achieve untreated fire reaction class B.
Although this standard only applies to fire-retardant treated products, it is of course very interesting to also test the other materials.

Reality says that weather influences such as sun, wind and rainwater have an impact on all materials.
If you have a product that is very close to the limit value, it is of course not an unnecessary luxury to map this out.

Why did I investigate this?

For years I have heard it said that one product leaches and another does not.
I do not want and cannot judge other products myself, so I trust their professionalism and knowledge.

A few months ago I heard a colleague proclaim that "their fire retardant leaches out, but very slowly, leaving you in fire reaction class B".
This cryptic sentence has made me think repeatedly and in combination with my own advanced knowledge, this was logically impossible.

The construction world is moving at an accelerated pace towards END USE testing, where the complete structure is important.
Details such as plank width, mounting direction, etc. all influence the result.
If I make a fire test that is 1% of the limit, each leaching ensures that a different fire reaction class is achieved.
Slow leaching in the same fire reaction class is possible, but certainly not in all cases.

What about untreated wood?

The Forestlines facade and louver system does not use fire-retardant treatments.
In principle, EN 16755 does not apply to our facade cladding.

That being said, Peutz in the Netherlands has had our untreated cladding outside for several months.
Although we don't have to, we want to know what our materials do.

Our own and independent research has now shown which wood building materials have an impact on the flammability of wood.
The suspicion is that no major differences are to be expected with untreated wood.

After all, knowledge is essential to innovate.