Development of full-scale façade tests in ISO TC 92

During the 90ies, ISO TC92 SC1 started the development of full-scale tests for facades based upon an international review. The work resulted in two standards namely ISO 13785 part 1 and part 2. The work was performed in WG7 and a substantial input from international experts was given. The paper gives a short historical update on the development but also includes a short overview of the major type of hazards or risks, which can be identified with respect to façades and how they relate to the façade test standards developed. Finally the two methods are summarised and reference to recent work is given.

that the requirement of the total heat flux in the test standard could be fulfilled.The final level of total heat flux was established by international consensus.The standard set-up is explained more in detail in one of the next paragraphs.
Simultaneously a screening method was developed in the same WG7.This action was made as it was felt that large-scale tests are very expensive and there is need from industry to have cheaper product development tools.The standard was based on the results of a number of research project related to wooden façades [16,17].The work was also incorporated in a PhD dissertation [17] showing the link between the intermediate scale test and a large-scale test.The work resulted in an intermediate scale test [18].However it was not checked if the test also correlated with the part 2.
During the development also European actions were undertaken.These actions resulted in a report dealing with the risk related to façades, an overview of a number of national standards and their link to the different risks [19].The risk of façades will also be taken up in this paper in the next paragraph.After the publication of the ISO 13784 part 1 and 2 standards, a number of research publication were published showing comparison of different tests methods and different façade systems [20][21][22][23].More recently work has been done in EOTA with respect to large-scale tests [24].All these studies show the considerable risk associated to façades and the diversity of national and regional standards worldwide [25][26][27][28][29][30][31][32][33].

HAZARD AND RISK DETERMINATIONS
When considering façades and curtain walling systems, different types of hazards/risks can be considered.The risks and hazards considered in this paper are certainly not all types but they include the most important ones.Recent fires and research publications [20,34] have shown that fires involving the exterior of a building should not be neglected.First there is the type of thermal attack or fire source.This thermal attack can be divided in to the following four main types 1. Fire inside the room 2. Fire in a room and outside the window 3. Fire at the exterior of the building close the façade e.g.container fire 4. Fire from another building.
Together with the type of fire source, different cases can be distinguished each addressing a specific hazard or risk.A schematic overview is given of four different hazards/risks below.Each of them has to be covered by a different type of testing set up or regulations and such attempts were made in earlier standardisation work [19].Such work should always be done before introduction of new test methods in regulations.Regulations worldwide can namely address fire safety of façades in different ways.Examples are given in [35] for the Nordic regulation or in [28,29] for insurance applications.Even routes of performance based design [36] and fire safety engineering [37] can be used.However this is considered outside the scope of this article.

Case 1
In this case the fire risk is penetration of the fire through the facade system from one level to another level trough e.g. the joint systems of the façade systems when a fire occurs inside a room.It can be considered that this type of hazard/risk is more linked to the evaluation of the fire resistance of a specific system.Specific attention should be given to the complexity of such system and the possible requirements the fire barrier border should or should not go throughout the façade system.This type of risk can also include spread of a fire from an attic down into the façade system [38].

Case 2
When a fire occurs outside a room through the window there is a risk of penetration of the fire through the façade system or through the glazing to the next floor.This can occur even when appropriate joints are covering the risk in case 1.Also here most of the risk can be covered by a fire resistance test.Else regulation of safety distance can cover this risk (see case 2b, Fig. 3).An example is given in [39].

Case 3
When a fire occurs outside the window or at the exterior of the building (container fire) a considerable risk of fire spread on the façade surface or through the void between façade and building exists.Here the reaction to fire properties of the material used for the façade should be considered and is the main determining factor.However constructional details of windows and voids should not be neglected as well as means how to check fire stoppers inside the construction.

Case 4 Falling parts or debris
When a fire occurs through a window or al the exterior of the building nearby the façade it is important that no parts are falling clown from the façade.This would endanger the work of the rescue teams and also cause problems for evacuation of the building.
Constructional details from the façades are in this case extremely important.Glazing can be included if necessary but can be covered by other tests.

INTERMEDIATE SCALE FAÇADES TEST ISO 13785 PART 1 3.1 Need of screening test
Full-scale tests are expensive and there is need for the industry and for certification of products to reduce the scale of the tests.However it is necessary to explain the difficulties when scaling down the size of full-scale tests.Problems can occur if thermal exposure is not sufficient or not well scaled down.Another problem can be that the size of the specimens is too small so that mechanical behaviour of systems is 01005-p.4 2 nd International Seminar for Fire Safety of Facades, Lund (Sweden), 2016 not covered by the screening test.Screening tests can be used in combination with modelling but here it is important to investigate, verify and validate the models considerably [40].

Description of test method
Part 1 of the ISO standard consist of a test specimen of 1.2 × 2.9 m which is exposed at the bottom by a line burner with a heat release rate of 100 kW.Two draught screens are position perpendicularly to the 01005-p.5

Recent developments
After the research performed with mainly wooden façades no real further investigations have been done on this method.Each systematic review of the standard in ISO resulted in confirmation of the standard.

LARGE SCALE FAÇADES TEST ISO 13785 PART 2 4.1 Description of test method
The method consists of a large-scale set-up built as an L-shaped configuration with two walls with dimensions of minimum 3 × 4 m and 1.2 × 4 m (width × height).The exposure to the façade construction is by flames emerging from a window with dimensions 2 × 1.2 m.The combustion chamber shall be of a regular shape with an internal volume not less than 20 m 3 and not more than 100 m 3 .The recommended heat source is propane but other alternatives are given (wooden cribs and combustible liquids).Measurement of flame spread, temperature on surface and inside the construction as well as total heat fluxes at the surface are performed.An overview of the test set-up is given in Fig. 7 and different characteristics of the test method are listed in Table 1.

Recent developments
After development of the test standard there was little data available on the test method.However during the last 5 years a number national and regional projects were conducted which investigated the suitability of the method and compared it to other façade test standards [41][42][43].During the latest systematic review

CONCLUSIONS
With the increase of high rise buildings and higher demands on thermal insulation, fire safety of external façades has become recently more important.Several hazards/risk can be identified with respect to façades and in order to tackle the flame spread risk on the surface, ISO TC92 SC 1 WG7 developed a large-scale test during the 90ies, which was published in 2001.As façades construction are very complex and are complete systems and not single materials or products, a full assessment by means of full-scale test is necessary.However there is a need for intermediate or screening to reduce testing and developing costs.Therefore an intermediate screening test was also developed by ISO and published in 2001.At the moment a myriad of national and regional test standards are available but the actual ISO test standard provides an internationally accepted alternative.Before introducing test standards into regulations, regulators should identify which risk they want to reduce and choose the appropriate performance criteria or safety levels.With this information, a suitable test method can be chosen or a suitable performance based solution based on fire engineering can be proposed.

Table 1 .
Summary of the test method.
in ISO a request was launched for revision of the standard.At this moment ISO TC 92 SC1 is waiting for a formal request to start revision of the method.