Wildland–urban interface (WUI) fires are an increasing global challenge, and local knowledge is essential for efficient mitigation. In Norway, as for the rest of Northern Europe, wildfires are expected to increase in frequency and severity, which will also increase WUI vulnerabilities. This study analyzes all registered vegetation fires damaging buildings in Norway from January 2016 to April 2023 (74 fires damaging 102 structures), with a case-by-case review of 18 fires impacting two or more structures. We have identified that spring season fires and direct flame contact are the primary contributors to vegetation fires that damage buildings in Norway. We also provide insights from three wildfire exercises with prescribed burns and a post-fire evaluation, providing fire dynamics data on fires in low vegetation while identifying a need to focus on hazards related to juniper vegetation and unmanaged cultural landscapes. This new knowledge is vital for developing effective and targeted prevention measures for Norwegian communities in WUI areas.

WUI guideline for Norway

Norway is a long country where forests, grass, and heather cover vast areas. Approximately 38% of the country's land area consists of forests, and many structures are located near or surrounded by nature. In these wildland-urban-interface (WUI) areas, a wildfire could damage structures and infrastructure. Norway's tradition of constructing houses and cabins from timber adds an extra layer of vulnerability in WUI areas. As part of the EU-funded research and innovation project TREEADS, Norway's first WUI guideline has been developed to strengthen resilience against wildfires.

The guideline is targeted at citizens in WUI areas, and presents measures that may protect built areas from wildfires. The development of the guide is based on an extensive process, including a literature review of WUI guidelines from countries such as the USA, Canada, and Sweden. This review formed the foundation for a list of relevant topics and recommendations, which were further refined through in-person workshops with stakeholders, surveys, and expert consultations. To ensure relevance for Norwegian conditions, the recommendations were adapted to local building traditions and by using insights from past fire incidents, fieldwork, and laboratory experiments. This process resulted in six main recommendations and five supplementary recommendations).

Norge er et langstrakt land der skog, gress og lyngheier dekker store områder. Omtrent 38 % av landets areal består av skog, og mange bygninger ligger i nærheten av eller er omkranset av natur. I denne randsonen mellom natur og bebyggelse, kjent som Wildland-Urban Interface (WUI), vil en skogbrann eller annen naturbrann kunne gjøre skade på bygninger og infrastruktur. Det at Norge har en tradisjon for å bygge hus og hytter i trematerialer utgjør en ekstra sårbarhet i den norske randsonen.

I det EU-finansierte forsknings- og innovasjonsprosjektet TREEADS er Norges første randsoneveileder utviklet for å styrke motstandsdyktigheten mot naturbranner. Veilederen er rettet mot innbyggere i randsonen mellom natur og bebyggelse og gir konkrete tiltak for hvordan man kan beskytte bebyggelse mot naturbranner.

Utviklingen av veilederen bygger på en omfattende prosess som inkluderer en litteraturgjennomgang av WUI-anbefalinger fra land som USA, Canada og Sverige. Dette dannet grunnlaget for en liste over relevante temaer og anbefalinger, som videre ble utviklet gjennom fysiske arbeidsmøter med interessenter, spørreundersøkelser og ekspertkonsultasjoner. For å sikre relevans for norske forhold ble anbefalingene tilpasset nasjonale byggetradisjoner og erfaringer fra tidligere branner, feltarbeid og laboratorieeksperimenter. Prosessen resulterte i seks hovedanbefalinger og fem tilleggsanbefalinger.

Analysis of fatal fires in Norway in the 2015-2020 period 

 This project is a continuation of the project "Analysis of fatal fires in Norway in the 2005-2014 period" and has collected and analysed data on fatal fires in Norway in the 2015-2020 period. The project is financed by The Norwegian Directorate for Civil Protection (DSB) and Norwegian Building Authority (DiBK) as part of the project portfolio under the research agreement between DSB and RISE Fire Research. The aim of the project has been to analyse fire statistics and other sources to find out who dies in fires and why they die, and the project may also address which targeted measures can be implemented to reduce the number of fire fatalities. In addition, the project has analysed data from fatal fires in Finnmark in the 2005-2014 period which was not part of the report "Analysis of fatal fires in Norway in the 2005-2014 period". The project has focused on fatal fires that have occurred in buildings. Initially, the following research questions were defined: 1. Which risk factors are associated with those who perish in fires in Norway? 2. What are the causes of fatal fires in Norway?

The Scandinavian countries have in later years seen several severe wildfires and is expected to exhibit more severe fire danger. While direct flame spread has been an important topic in wildfire research, there is a need for development and to ensure that experimental methods are relevant for Scandinavian wildfire characteristics. To ensure relevant lab conditions for fire-resilient material development work, large lab-scale (2×4 meters) experiments were conducted on various fuels. Its fire behaviour (such as rate of spread, fireline intensity and flame length) was compared with ongoing wildfire field studies from ongoing field studies in boreal and hemiboreal Sweden. The lab fire experiments show good potential to mimic relevant natural wildfire conditions in the laboratory once a standard design fire exposure for fire resilient materials is developed.

The use of external fire suppression systems can reduce the risk of fire spreading between buildings. This study investigated the effectiveness and efficiency of different externally placed water-based fire suppression systems on façade fire safety. A series of large-scale experiments comprising an SP Fire 105 setup equipped with sprinklers and high-pressure water mist nozzles have been performed. A combustible facade, consisting of 2.5 cm thick oriented strand board (OSB) plates, was installed to provide challenging conditions and allow a visual assessment of the post-fire damage. The temperature profile on the façade surface was measured with 34 thermocouples, while five heat flux gauges and two fast-response plate thermocouples were used to measure the heat flux on the facade surface and emitted to the ambient. The sprinklers and the high-pressure water mist system effectively suppressed the upwards flame migration and reduced the heat flux toward adjacent buildings. It was observed that the sprinklers acted as a water curtain and kept the facade wet during the fire, promoting minor damage (the burnt area is less than 1% of the total area). The temperature and heat flux measurements demonstrated that the sprinkler system was the most effective suppression system. However, the high-pressure water mist systems achieved similar effectiveness but a much higher efficiency concerning water consumption. The sprinkler nozzles used four times as much water as the high-pressure water mist nozzles. 

Understanding of wildfire risk requires an understanding of the natural species' fire dynamics. This study investigates fire characteristics of common wildland species in Norwegian forests – stair-step moss, lingonberry shrub, juniper, bilberry, and heather. Cone calorimetry experiments were conducted after conditioning samples to similar moisture content. Stair-step moss and bilberry stems exhibited longer burning times and lower peak heat release rates, suggesting a slower, more sustained combustion. Heather, despite age differences, showed similar fire behaviours, indicating moisture content's role in wildfire risk. Evergreens displayed the most intense fire development, with juniper potentially acting as a ladder species for vertical fire spread.