Fire tests reveal the possibilities for wooden facades in high-rise buildings

Halfway through the Biofacades:UpHigh project, the short conclusion is: Wooden facades burn well – but it is certainly possible to build bio-based facades.

It’s 10.00 a.m. and the atmosphere in DBI’s facade test hall is tense. The final safety instructions will be given, and in a few minutes it will be clear how the wooden three-storey facade will cope with a fire on the ground floor.

With a WHOOSH that can be felt in the chest 10 metres away, the meticulously built fire of logs is ignited at 10:05 a.m. with a good amount of flammable liquid. Seconds later, the flames from the window opening lick up the facade ,and the radiant heat causes spectators to pull backwards and out to the side.

We are attending the fifth of a total of ten facade fire tests that are part of the Biofacades:UpHigh project. Among other things, the project is aimed at investigating how to build multi-storey buildings with ventilated wooden facades without fire impregnation or sprinklers.

“Together with the project’s partners, we are testing a number of specific facades in order to learn more about what is possible and what is not possible. There are no right or wrong test results in this project, because we experiment and test to learn more,” explains Mia Fossing Frederiksen, who, together with Asmus Haastrup, are DBI’s Project Managers.

Flame deflectors must prevent spreading between floors
To prevent fire spreading upwards, today’s test set-up has been built up with square-shaped flame deflectors in spray-painted steel between the floors. The square steel pipes have also been used vertically as an architectural boundary between the apartments. After ten minutes, the initial fire on the ground floor has fully developed, and the wooden facades of the entire ground floor and the first floor are burning brightly. At the same time, the flames challenge the flame deflector between the first and second floors. If the fire spreads more than one floor up before 60 minutes have elapsed, it means that the specific design of the facade does not meet the specified acceptance criteria.

A quiet murmur spreads among the spectators and they point at the horizontal division structure between the first and second floors. True enough – the fire has now caught hold of the facade on the second floor, and consequently the set-up does not meet the requirements set by the fire safety consultant so that the facade can be passed as acceptable.

Laboratory technician, Kim Bergquist, who ignited the fire 20 minutes and 23 seconds ago, puts on his breathing apparatus again and gestures to the control room behind the glass window that he needs a helping hand with the fire hose.

Then things move fast. In two minutes, both the initial fire and the facade fire are reduced to steaming embers, which simply need to be extinguished. For Mia Fossing Frederiksen, it’s time for reflection:

“It’s obvious that this structure doesn’t last for an hour. I have a suspicion that the vertical steel columns have influenced the result, but we will learn more about this when all the data from the test has been analysed,” says the Project Manager.

Good experiences with robust solutions
As the last embers have been extinguished, it is time for a mid-term status after five facade fire tests:

“We need to note that wooden facades just burn really well, and it is not quite so easy to prevent fire spreading between the floors. We would like to inspire how the challenges of building in a more bio-based way can be met, and we already have a lot of good experience from the project on which types of design are robust and suitable from a purely fire perspective. Interestingly, much of this learning also comes from the facades that have not passed the fire test,” says Mia Fossing Frederiksen.

Read also: Bio-facade lasted for 11½ minutes

Read also: Scaled fire testing leads to successful full-scale bio-facade testing

BioFacades:UpHigh

The goal of the project is to prove that it is possible to build multi-storey buildings with ventilated wooden facades without using impregnated wood or sprinklers if the facade is designed to prevent fire from spreading in the first place. A total of ten tests will be conducted on various wooden facades over the course of the project. All of these tests will be conducted in accordance with a draft of the new European-wide facade testing standard, which is on the horizon.

Besides DBI – the Danish Institute of Fire and Security Technology, the developers NREP, Fælledby and CPH Village are participating in the project, as well as the manufacturer Frøslev Træ. The goal of the project is to generate documented solutions that prevent the spread of fire. The intent is to pave the way for wooden facades on three actual, innovative buildings from the three developers and result in a catalogue of design recommendations for wooden facades on multi-storey buildings.

The project’s total budget is DKK 6.6 million and is supported by Realdania and the Danish Agency for Education and Research via DBI’s performance contract. The project started in November 2022, and will continue until the end of 2024.