The use of wooden facade claddings and bio-based insulation materials in external walls are increasing because of esthetical and sustainability reasons. The introduction of performance-based building codes has generally facilitated the wider use of these materials and products in multi-storey buildings, but the use of visible woodas exterior facade claddings is still limited.

Key initiating events of facade fires are a) interior fire spreading to external wall system via external openings,b) exterior fire directly adjacent external wall system igniting the wall due to radiant heat and/or flame impingement,and c) exterior fire spatially separated from external wall system resulting from radiant heat.

Contribution of bio-based façade claddings and insulation materials to fire development and spread can beprevented by using protective methods. Examples of these are protection of insulation products by coverings or layers made of materials with good reaction to fire performance and/or with a sufficient protection capacity and/or prevention of facade cladding fires by hindering flames from a flashover room fire by using fire rated windows, automatic window shutters or sprinklers. Fire stops in ventilation cavities or in order to interrupt acombustible insulation are also effective means of fire protection.

Several wooden facade systems do fulfil at least the European reaction to fire class D-s2, d0. Based on fullscale test results some conclusions and recommendations have been made concerning proper criteria and possible area limits of wooden facades.

Fire retardant treated wood may be used, but the durability of the fire retardant treatments at exterior weather conditions need to be demonstrated in addition to the fire behaviour. The new European standard EN 16755for testing and classification of fire retardant treated timber products durability is suitable for this purpose.

This Guidance document on fire safety of bio-based facades is the result of work within several Task Groupsof the COST Action FP1404 “Fire Safe Use of Bio-Based Building Products” and aims at a common understanding of issues related to the description, design and fire testing facades