Hilti studies façade fires in real life conditions in partnership with UL

With increasing urbanization and changing architectural trends add innumerable buildings and skyscrapers with glass facades to our city skylines, it becomes imperative to understand the challenges posed by such infrastructure. To study the hazard associated with façade fires, Hilti partnered with UL LLC to study the spread of Fire in real life conditions at the Indian Institute of Technology, Gandhinagar.

In India, as per the National Building Code 2016 under clause 3.4.10.2 (b) “All gaps between floor – slabs and façade assembly shall be sealed at all levels by approved fire-resistant sealant material of equal fire rating as that of the floor slab to prevent fire and smoke propagation from one floor to another.”

One of the key questions which can be asked that what kind of test should be done to evaluate the performance of such Firestop systems that ensures to the users that it will work in the Indian scenario too. To do this, UL and IIT Gandhinagar (a very prestigious engineering institute in India) have built a set up to explore through a series of planned test to identify what works and what does not.

The test set up

The test setup consists of 3 storey building constructed of a steel frame structure. Total 3 fire compartments were made at each floor. The deck slab of each floor was made as a concrete steel deck. All the steel columns in the test set up were protected with the traditional practice of protecting the steel with masonry cover.

Fire Load: For fire load, most of the contents were made of realistic furnishings (sofa, bed, carpets, chairs etc.). Some fuel was added later to match the occupancy calorific value close to the residential and commercial occupancies recommended per NBC. This was done by adding a wooden crib.

Test Sequence

For the Fire stop evaluations, multiple research tests were carried out by UL and IIT, Gandhinagar.

Test A: Non-rated fire stop – internal spread

Test B: Tested and Approved Hilti Firestop – internal spread

Test A:

• Fire stop provided in form of 12mm thick plywood planks.
• Initial ventilation provided at GF by opening the external door.
• Ventilation factor increases as fire causes façade material to fail.
• Spandrel was purposefully made by concrete to force the fire to go from inside only and have full impact on Firestop installed.

Test A Observations:

00:00 Ignition

1 Mins Flames begin to impact Wooden (not approved) fire stop area near GF roof.

4 mins Glass panels break due to restraining effect. Max temperature reaches 625 oC.

6 mins Glass panels exhibit outward bending due to restraints and high temperatures. Fire spreads to FF level internally.

13 mins Fully developed fire at GF and FF levels Max temperature reaches 850 oC.

17 mins Fire reaches SF level

Conclusion Test A: In case of non-approved usage of Firestop like wooden plate at the edge of the slab, the fire reached the first floor from the ground floor in 6 mins and finally reached the top floor of the building in 17 mins. Hence the usage of such unapproved systems like (wooden plates, steel plate, etc.) will be a high threat to the life safety of occupants of the building.

Test B:

• UL Approved Fire stop from Hilti was installed.
• Initial ventilation provided at GF by opening the door.
• Ventilation factor increases as fire causes façade material to fail.
• Spandrel was purposefully made by concrete to force the fire to go from inside only and have full impact on firestop installed.

Test B Observations:

00:00 Ignition

50 sec Flames begin to impact Hilti Firestop.

4 mins Glass panels at ground floor break due to restraining effect. Max temperature reaches 400 oC.. No Fire spread on any floor above. Firestop intact.

5 mins Fully developed Fire at GF. The temperature in the ground floor reached 700 oC. No Fire spread on any floor above. Firestop intact.

13 mins The temperature on ground floor reached 820 oC. The max temperature rise on the first floor is 80 oC. No Fire spread on any floor above. Firestop intact.

20 mins Fire still did not breach the Hilti Firestop assembly at the edge of the slab of the façade.

Conclusion from Test A and Test B

In the case of usage of an approved system like ASTM E2307 tested systems, the fire stop systems held its place and contained the fire in the ground floor and also it did not let the heat spread to the upper floors more than 80 oC for the entire duration of the test in such real-life building test scenario. 

The provisions of ASTM E2307 are intended to restrict the interior vertical passage of flame and hot gases from one floor to another. Its use is recommended by many building codes to evaluate the fire resistance rating of the perimeter fire barriers.

International Building Code 2015: “Clause 715.4 Exterior curtain wall/floor intersections: Where fire resistance rated floor or floor/ceiling assemblies are required, voids created at the intersection of the exterior curtain wall assemblies and such floor assemblies shall be sealed with an approved system to prevent the interior spread of fire. Such systems shall be securely installed and tested in accordance with ASTM E2307 to provide an F rating for the time period no less than the fire resistance rating of the floor assembly.”

ASTM E2307 Test in Brief

Test Sequence:

1. Cycling Test – In ASTM test, before subjecting the firestop sample for fire tests, The test method requires joint systems with movement capabilities to be cycled through the intended range of movement prior to the fire test. The movement cycling is intended to demonstrate the compatibility between the individual components of the joint system and the supporting construction.
2. Fire Test: Throughout the fire, test observations are made about the fire and hot gases on the unexposed side of the perimeter fire barrier or any adjacent supporting construction.

Conclusion

We believe such exploratory study along with UL LLC’s and IIT Gandhinagar’s supervision will be able to guide the industry to use only tested systems which perform and save lives:

• Movement capable Fire Rated Perimeter Firestop systems tested per ASTM E 2307 standard

Avoiding or compromising the edge of the slab opening with no systems or untested system means compromising with the safety of people. Perimeter fire barriers are one of the required systems from the Building Codes and it’s an effective fire and smoke resistance compartmentation methodology. The test at IIT from Hilti and UL is only an effort to drive scientifically driven and appropriately tested systems in India to ensure safety at the highest level.

For more information, go to www.youtube.com/watch?v=aRvkwBW8rKE