Scientists in Norway have assessed how BIPV façades may react to fire accidents following a typical fire test for building façades. They found that flame propagation in the wall cavity is possible, despite the very limited amounts of combustible material, and that flames may propagate on the entire façade very quickly.
Image: Rise Fire Research, Fire Safety Journal, Creative Commons License CC BY 4.0
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Fire safety building standards present a significant challenge and have acted as a barrier to the development of the building-integrated photovoltaic (BIPV) market. This creates a complex landscape where it becomes vital for manufacturers and suppliers of BIPV products to understand and adhere to a multitude of standards in different markets, and to recognize that the fire safety testing of conventional PV products is already deficient.
With this in mind, a group of scientists at the Norwegian institute Rise Fire Research has developed a fire test for both small and large-scale BIPV façades. “Large-scale system tests of BIPV systems are lacking and this should be requested from more BIPV projects,” Rise researcher, ReidarStølen, told pv magazine. “More experiments in realistic scales would be very interesting to see. So if anyone can share information from other tests of complete systems, this can be a way forward to see which parameters are crucial to designing truly fire-safe BIPV façades.”
In the study “Large- and small-scale fire test of a building integrated photovoltaic (BIPV) façade system,” published in the Fire Safety Journal, Stølen and his colleagues conducted the so-called SP FIRE 105 fire test, which is a large-scale façade test method referenced in the building regulations in Sweden, Norway, and Denmark, on BIPV façade. This test evaluates the fire properties of a façade system regarding flame spread, falling parts, temperature at the eaves, and radiation toward the floor above the burning apartment.
The test was conducted on a photovoltaic façade measuring 4 m × 6 mm based on mounting structures and frames made of aluminum. The scientists used “common” custom-sized BIPB modules with a glass front and a polymer backsheet. Each module was based on a plastic junction box made from polyphenylene ether and polystyrene measuring 116 mm × 110 mm × 22 mm with connecting leads and connectors. “The mass of the modules ranged from 14.1 kg to 5.6 kg including junction box and connecting cables,” the scientists explained. “Most of this mass was glass and aluminum, but approximately 12 % was made from different plastic materials.”
Test configuration with BIPV-system installed on the SP FIRE 105 large-scale façade test rig.
Image: Rise Fire Research, Fire Safety Journal, Creative Commons License CC BY 4.0
The façade BIPV system was deployed on a timber frame wall with combustible wood fiber insulation covered with gypsum boards. “The distances between the modules were 20 mm horizontally and 40 mm vertically,” the academics specified. “The vertical gaps between the modules were sealed with an aluminum profile, and the horizontal gaps were open.”
The research group developed a fire on the system in three stages. First, they preheated the fire room and façade before the flashover. They then exposed the two lower rows of modules to large heptane flames and then the flames were propagated in the cavity from the third row to the top of the façade.
The experiment showed that the large heptane fire from the fire room below the façade caused severe damage to the two lowest rows of modules causing all the modules to collapse in a short time. “The highest measured temperatures reached 850 C in the cavity during this stage,” the academics explained. “After the heptane fire had burnt out, the fire was able to propagate self-sustained past the cavity barrier and to the top of the façade causing additional modules to fall down.”
The experiment also demonstrated that flame propagation in the cavity is possible, despite the very limited amounts of combustible material, and that fire was also able to considerably damage glass, glue and aluminum construction. “Sealing the cavity with fire barriers can be challenging if the fire resistance of the surrounding components is compromised,” the researchers said.
The scientists concluded that the test results showed the importance of details in mounting BIPV façades and proper documentation from relevant fire tests of such systems. “Despite complying to IEC EN 61730 and EN 13501-1, the complete façade system failed to prevent modules from falling from the façade and vertically propagating fire in the cavity,” Stølen explained. “The cone calorimeter tests also show that the amount of combustible materials is limited in the modules, but that it ignites quite easily and burns with a high heat release rate.”
In another recent work, RISE researchers conducted a series of experiments indicating that the distance between solar modules and rooftop surfaces could be a crucial factor in PV system fires. A similar study, published by the University of Edinburgh and the Technical University of Denmark, showed similar results. The scientists analyzed fire dynamics and flame spread on the substrate beneath panels. They concluded that the shorter the distance between the panels and rooftop, the higher the probability of larger and more destructive fires.
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The report by Emiliano Bellini dated 08.01.2024, on fire tests for BIPV façades in Norway, rightly points out that fire protection standards for buildings represent a major challenge for BIPV façades. Solutions for successful implementation lie in the details and require careful consideration, hence the following comments and corrections to the report. The statement that “large-scale system tests of BIPV systems are lacking” may be true with regard to Norway and perhaps also Scandinavia. There are comparable fire tests in Germany and also in Switzerland, with partly differing results. However, only glass-glass modules that are mandatory for BIPV façades were used in these tests. The glass-laminate modules described for the Norwegian test are not permitted due to their fire properties. The report by E. Bellini describes module junction boxes made of plastic. However, there is a recommendation, especially for high facades, that boxes made of non-combustible material should be used, similar to the cable routing, which should be routed in ducts made of aluminum or even sheet steel. Such measures were apparently not used in the Norwegian test. Furthermore, the cladding of the timber frame wall with 9.5 mm gypsum boards is described. In Germany and Switzerland, however, 2x 15 mm gypsum fiber boards are common for encapsulation in timber construction, as is also required in other areas for fire safety. The question therefore arises as to whether the test system really complied with EN 13501-1 and whether a different result would not have been achieved if all options had been used with regard to the selection of materials. Publications on fire tests in Germany and Switzerland generally report that the risk of independent fire propagation through BIPV modules is low.
Berlin, 17.01.2024, T. Kühn – BAIP, http://www.hz-b.de/baip Counseling center for BIPV at the Helmholtz-Zentrum Berlin für Materialien und Energie GmbH
Dear Thorsten Kühn, thank you for interesting comments and remarks related to our large-scale experiment of a BIPV facade. Particularly, the comments on comparable experiments with glass-glass modules would be of interest to look further into. Could you provide a link to where these reports may be found? We are currently in a stage where we want to understand better which of the relevant design parameters that are most important with respect to fire propagation and any insights in this would be valuable. As stated in the journal paper*, the front face of the module was classified as Euroclass B,s1-d0 according to EN 13501-1. No information on the properties of the back of the module was available. This, and the fact that the insulation material behind the gypsum boards was combustible was the background for the requirement of the large-scale test of the facade according to Norwegian regulation. * https://linkinghub.elsevier.com/retrieve/pii/S037971122300351X
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The report by Emiliano Bellini dated 08.01.2024, on fire tests for BIPV façades in Norway, rightly points out that fire protection standards for buildings represent a major challenge for BIPV façades. Solutions for successful implementation lie in the details and require careful consideration, hence the following comments and corrections to the report.
The statement that “large-scale system tests of BIPV systems are lacking” may be true with regard to Norway and perhaps also Scandinavia. There are comparable fire tests in Germany and also in Switzerland, with partly differing results. However, only glass-glass modules that are mandatory for BIPV façades were used in these tests. The glass-laminate modules described for the Norwegian test are not permitted due to their fire properties. The report by E. Bellini describes module junction boxes made of plastic. However, there is a recommendation, especially for high facades, that boxes made of non-combustible material should be used, similar to the cable routing, which should be routed in ducts made of aluminum or even sheet steel. Such measures were apparently not used in the Norwegian test. Furthermore, the cladding of the timber frame wall with 9.5 mm gypsum boards is described. In Germany and Switzerland, however, 2x 15 mm gypsum fiber boards are common for encapsulation in timber construction, as is also required in other areas for fire safety.
The question therefore arises as to whether the test system really complied with EN 13501-1 and whether a different result would not have been achieved if all options had been used with regard to the selection of materials. Publications on fire tests in Germany and Switzerland generally report that the risk of independent fire propagation through BIPV modules is low.
Berlin, 17.01.2024, T. Kühn – BAIP, http://www.hz-b.de/baip
Counseling center for BIPV at the Helmholtz-Zentrum Berlin für Materialien und Energie GmbH
Dear Thorsten Kühn, thank you for interesting comments and remarks related to our large-scale experiment of a BIPV facade. Particularly, the comments on comparable experiments with glass-glass modules would be of interest to look further into. Could you provide a link to where these reports may be found? We are currently in a stage where we want to understand better which of the relevant design parameters that are most important with respect to fire propagation and any insights in this would be valuable.
As stated in the journal paper*, the front face of the module was classified as Euroclass B,s1-d0 according to EN 13501-1. No information on the properties of the back of the module was available. This, and the fact that the insulation material behind the gypsum boards was combustible was the background for the requirement of the large-scale test of the facade according to Norwegian regulation.
* https://linkinghub.elsevier.com/retrieve/pii/S037971122300351X