At present, we do not have a harmonised European standard governing the testing of façade systems.
However, an analysis by the European Commission studied the various national test standards to suggest a large-scale fire test that can be used throughout Europe. Based on this, they restricted the analysis to the BS8414 test series as a large-scale test and DIN 4102-20 as a medium-scale test.
Regarding the BS8414 test, it is a large-scale test published in 2015 by BSI to evaluate the behaviour of façade systems in the event of fire. The test structure of this test is an L-shaped formation with a 2.6 m main wall and a 1.5 m secondary wall. The height of the system is a minimum of 8 m. The fire load in the system consists of a 400 kg wood pile placed in a chamber that can create a heat flow of 45 to 90 KW/m2, with a constant heat flow of 75 KW/m2 for a period of 20 minutes.
This test lasts 60 minutes. During the first 30 the pile burns, at the end of this period, around when it is largely consumed, it is extinguished and flame propagation is monitored during the remaining 30 minutes. The propagation towards the top of the sample is noted.
In terms of instrumentation, the sample is equipped at two levels (2.5m and 5m) above the chamber. Thermocouples on the first level are mainly used to indicate when the stack is fully ignited. When they reach 200°C, time counting begins. The temperature recorded at level 2 is used to analyse the fire behaviour of the system. Therefore, at this level, thermocouples are not only placed on the outer surface but also in the centre of cavities, insulation and any layer thicker than 12mm.
Currently, the BS8414 test series has no failure criteria other than safety and flame spread to the top of the structure. For this reason, a standard has been drawn up in the UK to indicate how a test can be considered passed or failed.
Failure is determined according to these criteria:
- A temperature of 600°C above ambient temperature for at least 30 seconds at level 2 within the first 15 minutes after the start of the test (i.e. after 200 degrees is recorded at level 1);
- A temperature of more than 600°C above ambient temperature for at least 30 seconds anywhere inside Level 2 within the first 15 minutes after the start of the test;
- A sustained flame for at least 60 seconds on an unexposed surface at a height of 0.5m (or more) above the chamber in an inner layer within 15 minutes of the start of the test (integrity failure).
These results are interpreted as failures.