The first full-scale facade test in the BioFacades:UpHigh project has just been conducted at DBI. After 11 ½ minutes, the fire reached above the second flame deflector, and the construction failed the test. A further nine tests will follow in the project, which will shorten the path for sustainable facades in multi-storey buildings and result in actual facades being built in Denmark.
It is very difficult to use wood or other bio-based materials on a ventilated facade in multi-storey buildings. Because, even though wood can be impregnated to meet the material requirements, there is doubt as to how exposure to moisture and ageing affect the wood’s fire properties over time. With the BioFacades:UpHigh project, DBI wants to provide the construction industry with knowledge of multi-storey buildings with ventilated wooden facades without fire impregnation or sprinkling.
“In the past, impregnated wood was used, but there is uncertainty about the useful life, and no one is willing run that risk today. In this project, we’re investigating whether facades can be made with bio-based materials that are designed to prevent the spread of fire on the facade. The aim is to be able to build as high as possible with the same level of safety as in traditional construction,” says Asmus Haastrup, Research Consultant at DBI, who is leading the project together with Mia Fossing Frederiksen.
First step towards a bio-based facade solution was taken on 31 August when DBI conducted the first of a total of 10 full-scale facade fire tests of bio-based facades in the project. The construction was an 8 metres high facade designed with steel flame deflectors, and on the inside of the ventilated facade was a fire stop of expanding material to avoid the chimney effect. The test was conducted in accordance with a draft version of the new European facade test standard, and thus constructed with an inner corner. Furthermore, the fire was lit in a wooden bonfire at the bottom of the installation.
“The facade must not be fireproofed or have sprinklers, and the goal is that the fire does not spread by more than one floor. To achieve this, you can, for example, work with non-combustible elements in the facade, projections in the facade, flame deflectors or fire stops,” says Mia Fossing Frederiksen, Project Manager at DBI.
The fire reached the first flame deflector after approx. five minutes and moved up over the second flame deflector after 11 ½ minutes. The fire had thus spread two floors up.
”However, that is okay. There are no right or wrong test results in this project, because we experiment and test to improve our level of knowledge,” says Asmus Haastrup.
Each of the project’s five partners has two of the total of ten facade tests at their disposal and is free to design the facade and try out the solutions or ideas they want.
The first facade test was one of the two tests in the project that DBI itself has at its disposal. During the autumn, four more facades will be tested in the project, while the remaining five tests will take place in the spring.
“The project makes fire safety a design parameter from the start, so that it’s not a necessary evil at the end of the process, but is part of the design. It’s necessary to incorporate fire protection into the design and have elements that have several functions – such as architectural and fire-related properties,” says Mia Fossing Frederiksen.
The three contributing developers all have major innovative buildings in the pipeline, which will push the boundaries of sustainability in the construction industry with features including wood in the structure, bio-based insulation and, of course, bio-based facades.
“The combination of concrete buildings, new experiences and documented fire safety properties for the tested facades should ideally result in the tested facades becoming a reality. It’s not only up to the tests of the spread of fire on the facade, but also depends on the overall fire strategy of the individual building, where factors such as radiant heat and horizontal spread must also be taken into account. But the facades should ideally be out there in a couple of years,” says Asmus Haastrup.
Even though there are high expectations of the upcoming nine tests, the hope is, however, that in the long term the project can in due course result in far more than the three facades. But what is stopping bio-based facades today, including high-level wooden facades, is money. For a wooden facade without fireproofing, there are strict requirements for the project’s certified fire consultant, a requirement for third-party inspection by a certified fire consultant, not to mention any tests to produce sufficient fire safety technology documentation. Because there are no documented and absolutely no pre-accepted solutions in this area, which makes it expensive. Furthermore, facades are traditionally a complex area – architects must make them aesthetic, fire safety consultants must make them safe, and at the same time they must be good for the indoor climate and preferably also for the climate in general.
“This project can have a big impact. There is strong awareness in the construction industry that bio-based materials are the way forward, and that development is achieved through transparency and the sharing of knowledge. During the project, there will be a strong focus on sharing knowledge, both at home and abroad,” says Mia Fossing Frederiksen.
Experiences and results from the first successfully completed test and the subsequent ones will be made available on an ongoing basis to the parties – and everyone else – so that they can be incorporated into subsequent tests. It is also expected that at the end of the project, a number of design principles for wooden facades can be drawn up on the basis of all the tests.
“Architects and planners need a better basis for making the right design choices. Based on this project, we’ll be compiling a catalogue of design recommendations or principles that provide an advantage in terms of fire safety. We hope to be able to describe methods of building at a height of three floors, for example, and that the recommendations will also mean that the number of tests to obtain fire safety technology documentation for a facade will be reduced,” says Asmus Haastrup.
Data from the tests is also to be used in connection with a post-doctoral project in order to predict results of fire tests with simulations.
“Knowledge and results from the project can initially only be used for function-based fire safety, but the project will in due course allow for the development of pre-accepted solutions in this area. The aim is to show that it is possible, if you make fire safety a design parameter, and that in the future there will be less need for testing bio-based facades because you’re standing on the shoulders of the knowledge that this project is creating,” says Mia Fossing Frederiksen.
The tests in BioFacades:UpHigh are being conducted in accordance with a draft version of the new European facade test standard, which is in the pipeline. The tested facade was 8 metres high and, as described in the upcoming standard, was constructed with an inner corner where the fire was lit in a wooden bonfire at the bottom of the installation. This year, four more tests will be conducted in connection with BioFacades:UpHigh, while the project’s remaining five tests will follow next year.
DBI is testing in accordance with the European standard, because that is the future. The only thing that the standard lacks before it is ready for publication is a decision on which criteria are to be used to assess the result.
The project started in November 2022 and will continue until the end of 2024. The purpose is to prove that it is possible to build multi-storey buildings with ventilated wooden facades without fire impregnation or sprinklers, if the facade is designed to prevent the spread of fire.
During the course of the project, 10 facade tests will be conducted on different wood facades. In addition to DBI, the developers Nrep, Fælledby and CPH Village are participating in the project, as well as the manufacturer Frøslev Træ. The project aims to result in documented solutions that prevent the spread of fire. It intends 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 for 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.