Abstract
COST Action FP1404, fire safe use of bio-based building products, is aiming to improve knowledge on the fire safe use of bio-based building products. The subject includes e.g. wood-based structural panels and beams, and non-structural insulating products. One of the tasks of Working Group 3 of FP1404 is to compare regulatory approaches in different countries. Concerning load-bearing structures, maximum number of storeys where bio-based products (such as wood) can be used according to prescriptive regulations varies from two storeys to ‘no limit defined’ without specific protection needs. In some countries, there are additional requirements based on fire separation, on coverings or on protective layers. When performance-based regulations are applied, there is theoretically no limit for number of storeys. External claddings of D class may be used from maximum two storeys to 30 m in height (or even more) and internal wall and ceiling linings of class D can be used in most countries in buildings with three or more storeys.
Introduction
Bio-based building products have a very long history, e.g. as timber in structural members and wooden interior linings or external claddings. Combustibility has been the main reason why bio-based building materials have been banned from many applications or many restrictions for use of these materials have been given. When performance-based design (PBD) became possible, many building regulations opened the market for bio-based building products. However, large differences between regulations in countries currently exist and the use of combustible building products is still very limited especially in buildings with more than two floors.
Fire safety engineering (FSE) may be a tool to address high fire safety levels for combustible building products, and in recent years FSE has found large acceptance in many countries. FSE allows a PBD with customised building solutions. FSE can be defined as the application of scientific and engineering principles to manage the effects of fire in order to ensure safety of life and to reduce property losses. However, the available techniques are often applicable only to non-combustible materials.
COST Action FP1404 offers a networking platform for fire safety engineers, structural engineers and material scientists. Thirty European countries are involved in this activity and work within FP1404 is organised into four Working Groups:
WG1 Contribution of bio-based materials to the fire development WG2 Structural elements made of bio-based building materials and detailing WG3 Regulations for the fire safety of bio-based building materials WG4 Dissemination.
Comparison of fire safety regulations in Europe
One of the tasks of WG3, regulations and standards for fire safety of bio-based building materials, is to compare regulatory approaches in different countries for identifying unresolved topics/obstacles for use of bio-based materials in buildings. As a starting point for this activity, FP1404 members were asked to provide state of the art information for the meeting in Barcelona (April 2015). After that meeting, a questionnaire was sent to all members asking additional data on national requirements and the use of FSE in design of buildings.
aNotations: Allowed (+) and not allowed (−).
bInstead of sprinklers fire detection is required.
cWith sprinklers.
dApplicable for dwellings; more than four storeys requires compliance with French façade test.
Concerning the load-bearing structures, bio-based products (fulfilling at least D level reaction to fire performance, such as wood) can be used according to national fire safety regulations as follows:
According to prescriptive regulations maximum number of storeys (or height) allowed is:
From two storeys to ‘no limit defined’ without specific protection measures, or In some countries, there are additional requirements based on fire separation rating (EI), or coverings (K210/K230/K260 of A2 materials) or B-s1, d0 class protective layers. When sprinklers are used, increased number of storeys are allowed in some countries.
According to performance-based regulations:
No limit for number of storeys (theoretically) In many countries performance-based approach is allowed, but it is not frequently used.
As external claddings, D class products can be used especially in low rise buildings. Limitations can be described in more detail as follows:
With no sprinklers: Maximum number of storeys allowed is from two storeys to 30 m in height or even more (specific conditions may apply) With sprinklers: Increased number of storeys is allowed in some countries.
As internal wall and ceiling linings, D class products can be used in most countries (even without sprinklers) in buildings with three or more storeys. However, in escape routes D class wall and ceiling linings are allowed only in some countries and only if additional protective measures (e.g. sprinklers or fire detection) are taken.
DFL class floorings are accepted in apartments in all countries and also in escape routes in most of the countries listed in Table 1.
Discussion and conclusions
The questionnaire answers showed that the use of FSE methods is not very common when using bio-based building products in buildings. When FSE methods are used, general principles are applied because no specific national methods concerning bio-based products seem to exist. Austria, Finland, Germany, Italy, Norway, Slovakia, Slovenia, Sweden and Switzerland have some guidance available to facilitate implementation of the FSE option.
In general, some aspects of fire safety regulations are difficult to compare in different countries. Despite of the existence in the European Union of the Construction Products Regulation and the development of Eurocodes, there is a broad variety of criteria and requirements for buildings in the various European countries because fire safety in buildings is governed by national legislation. These national legislations are based on historical experience and quite often on prejudice about the use of bio-based building products in the absence of scientific knowledge on the fire safety of these products.
As a conclusion, it is clearly seen that, if the national regulations allow only prescriptive solutions, there are major limitations in using bio-based building products across Europe. These and other possible limitations arise mainly on categorising materials and products as non-combustible (at least A2 reaction to fire class is a commonly used limit) and combustible (which are not allowed at all in defined applications). Performance-based regulations (or performance-based options in regulations) are more flexible, because they do not define acceptable fire performance based on the type of materials used in the building. In PB approach the overall fire performance of the building (structures, linings, passive and active means of fire protection and layout) defines the safety level.
Design flexibility in buildings regarding fire safety is possible e.g. by using sprinklers. Nevertheless, at present, the use of sprinklers does not seem to play a decisive role in Europe. The survey showed that in most countries there are no significant benefits for bio-based product when using sprinklers.
Finally, to be able to influence future national regulations, there is a need to disseminate commonly accepted scientific proof on acceptable fire performance levels of bio-based building products as well as on related assessment principles, calculation methods and acceptance criteria.
Footnotes
Acknowledgements
FP 1404 partners are thanked for their contribution to collecting data on fire safety requirements relevant for bio-based building products. Raido Jalas, Danny Hopkin, Birgit Östman and Maria Pilar Giraldo are specially thanked for their active role in collecting, compiling and making available data from various sources.