Perimeter Curtain Wall Revised 1

Saving Lives and PropertyThrough Fire and Smoke Containment ©2004 IFC

Perimeter Curtain Wall Fire Protection


• Brief history

• Dynamics of fire

• What do the codes say?

• How are they tested?

• How testing is affecting design

Topics for Discussion


Curtain Walls &

the Perimeter Joint


A Brief History of Fires -Where Curtain Wall or

Safing Issues Have Been Cited…


• Summerland, Isle of Man, British Isles. Fire spread through safing slot. 50 people killed.

• Hilton Hotel, Las Vegas, NV. Fire spread from 8th to 13th floor in 25 minutes. 8 fatalities.

• First Interstate Bank, Los Angeles, CA. Flames spread from 13th to 16th floor via perimeter joint. One death.

• One Meridian Plaza, Philadelphia, PA. Fire spread from 22nd to 30th floor through unprotected openings including slab edge.

Unsealed or Improperly sealed perimeter joints cost lives and huge liability losses…


What are the dynamics of vertical spread in a high-rise

building?


Rated Floor Assembly and non-rated Curtain Wall System

Vision Glass

Fire begins on a lower floor, products of combustion

accumulate at ceiling level, and positive pressure builds


The fire follows the flow of air currents…

Vision Glass Rated Floor Assembly and non-rated Curtain Wall System

If the void between the floor and curtain wall is not properly sealed, flames will spread vertically…

and compartmentation

is breached!


Vision Glass

Rated Floor Assembly and

non-rated Curtain Wall System

Elevated temp. and pressure breaks lower vision glassFlames may erupt through

the windows. Oxygen fuels the fire.

Fire attacks the curtain wall structure from both sides causing a premature failure of the wall structure and potentially the vision glass above!


Firestop Coating or Sealant over mineral wool safing

Rated Floor Assembly and non-rated Curtain Wall System

A properly designed & tested Perimeter Fire Barrier Systemnot only protects the perimeter

joint but critical wall framing and support elements as well!

Properly installed & supported mineral wool

spandrel insulation


How do the codes address the

protection at the perimeter?


• All Model Codes call for the rating of the floor to extend to the exterior wall

• All Model Codes require minimum spandrel height

• All Model Codes allow spandrel height exceptions in certain sprinklered conditions

What do the codes say?


Extending the Rated Floor to the Wall...

In rated construction, all floors are rated

The perimeter joint must be sealed with an approved material or system that extends

this rating to the exterior wall surface

MANDATORY!


Code Compliance

Firestopping the perimeter joint is mandatory.

Meeting the Letter of the Law...

1. Designing the wall to keep the firestop system in place for the rated period of the floor is an obvious necessity.

PROTECTING THE PERIMETER JOINT:

2. Designing and installing the firestop correctly is the final step!


The Leap Frog Effect…


Fire may break out of a window and leap back to the floor above!

That being the case… Why bother to protect the perimeter???

The Leap Frog effect…


Sprinklers are an exception to window separation requirements…

But not to requirements for protection of safing slot!



Sprinkler advocates are lobbying to reduce these requirements…

After all… The fire may jump around the protection!



The Leap Frog affect…

The fact is, depending on window spacing and other factors, the fire may jump!

So what exactly does a Perimeter Fire Barrier System do?


Slows the process down. Of course it depends on window spacing and other construction factors…

As well as the nature and severity of the fire…

The Perimeter Fire Barrier System…


Along with sealing the slot area, a well engineered system provides structural protection and maximizes the integrity of the wall system…

Keeping the wall and window system above intact longer!



• Extends the rating of the floor to the wall.• Forces the fire to exit the building in order to

propagate to upper floors.• Protects structural elements and helps prevent

catastrophic failure of the spandrel system.• Maximizes fire protection afforded by the

non-rated wall.



• Prevents the migration of flame, hot gases and smoke through to floors above.

• Buys time for occupants to escape.• Buys time for first responders to secure the

building• Provides additional protection in the event of

a sprinkler or detection failure.




Provides energy savings through increased thermal efficiencies throughout the life of the building…

When considered this way, the life safety benefits are free!


How Are Perimeter Fire

Barrier Systems Tested?


ASTM E2307

Standard Test Method for Determining Fire

Resistance of Perimeter Fire Barriers Using

Intermediate-Scale, Multi-Story Test Apparatus


How Are Perimeter Fire Barrier Systems Tested?

Only two labs presently perform testing in accordance with newly developed test methods:

• Underwriters Laboratories Inc. – Northbrook, IL• Omega Point Laboratories – Elmendorf, Texas


UL & OPL Testing

• Perimeter joint curtain wall test is performed in accordance with ASTM E2307

• Other labs, testing per UL 2079 alone, do not adequately capture the dynamics between a rated floor and a non-rated curtain wall assembly, the structural nature of curtain walls, and fire attacking at two planes

• Intermediate-Scale, Multi-Story Test Apparatus (ISMA) was developed for this application


• Two ratings are provided per the ASTM E2307 test:

- “F”-rating, in hours (resistance to fire spread)

- “T”-rating, in hours (temperature on non-fire side)

• UL provide two additional ratings using same test apparatus

- “integrity rating” & “insulation rating”

Question: What Test is used to Evaluate Perimeter Fire Barrier Systems?

Testing Questions…

Answer: ASTM E2307 using the Intermediate- Scale, Multi-Story Test Apparatus (ISMA) is used to determine…


Question: How can this be representative of real life?

Answer: It can’t! The test method indicates whether…

1. The safing method can last as long as the floor.

2. The protection scheme can adequately protect wall framing and attachments.



Question: Then how representative is this test?

Answer: It should be considered broadly representative.

Spandrel width, height, and window spacing are limited because the test is not full scale. Story height is approximately 7 feet.

Wall framing methods, support, and the safing slot itself are well represented and provide excellent engineering data.



Curtain Wall Test Assembly

Pre-Burn

Transom above floor

Transom below floor

Mechanical attachments supporting insulation

Mineral wool insulation at spandrel area

Mullions


AssemblyInterior View

Pre-Burn

Thermocouples measuring temperature rise


Interior Burner Lit - Time: 0:00


Exterior Burner Lit - Time: 0:05


Flames Climbing Exterior

Time: 0:15


Melting of Mullions

& Transoms

Time: 0:45


Vision Glass

Breaks

Time: 2:00


Burner Off at 2 hours


Post Test:

Close up Detail of Mullion and Transom

Damage


Post Test – Interior View


ASTM E2307 Testing has Improved

Perimeter Joint Evaluation…


Vertical Mullions

Transoms

Mechanical Attachment

Mullion Covers

Firestop Coating

Vision Glass

Spandrel Panel

Mineral Wool Safing

StiffbackAngle

SpandrelInsulation


Perimeter Fire Containment - Basic Design Criteria

1. Mechanically Attached Curtain Wall Insulation


1

Mechanically Attached



2. Protect Aluminum Mullions



2Protect Mullions

1





3. Compression-Fit Safing Insulation -as required per tested assembly

Install Safing Impaling Clips -as required per tested assembly

Horizontal fiber orientation

Vertical fiber orientation



2Protect Mullions

1


3

Compression Fit Safing (Direction of Safing

as required per tested assembly)

Safing Clips (as required per tested assembly)


Compression Fit Safing (Direction of

Safing as required per tested assembly)





3. Compression-fit Safing Insulation -as required per tested assembly


4. Provide Backing/Reinforcement Member at Safing Line



2Protect Mullions

1


3




4 Reinforcement Member


75% of fire related deaths are caused by smoke inhalation

What about smoke?




3. Compression-fit Safing Insulation -as required per tested assembly


4. Provide Backing/Reinforcement Member at Safing Line

5. For “Smoke Containment,” Add Firestop Coating



5 Firestop Coating

4 Reinforcement Member

2Protect Mullions

1


3





5Firestop Coating


Question: Why aren’t floor-to-wall (FW) systems acceptable for curtain walls?

Answer: Floor-to-wall systems test fire resistance between a rated floor and rated wall tested per ASTM E1966.

CW systems are specific perimeter tests between a rated floor and non-rated curtain wall using the Intermediate Scale Multi-story Apparatus (ISMA) per ASTM E2307.

Additional Design Questions…


Question: Why are windows spaced so far apart? My windows are closer together…

Answer: ASTM E2307 evaluates the interior passage of fire and hot gases through the perimeter joint only. Increasing the spandrel height reduces the likelihood of the leap frog effect.



Question: What is the function of the firestop coating in these systems?

Answer: The firestop coating performs several important functions.




1. The most obvious role is as a smoke seal.

2. Seals off the path of hot gasses. Makes the safing more effective.

3. “Glues” everything together.

The Role of the Firestop Coating:



Question: Are curtain wall joints static or dynamic?

Answer: This area is referred to as a slot. The word joint suggests movement. Experts tend to agree that a small amount of movement occurs within the slot area. It is up to the design professional to determine the level of movement required for the project.

Some wall designs are subject to a small amount of vertical shear or horizontal sway and some systems incorporate these values.



Question: What if our design isn’t a perfect match for a system?

Answer: We strongly suggest specifying tested systems. However, real world designs are seldom a perfect match!

Find a listing that is reasonably close and contact the manufacturer for an Engineering Judgment to match the design.


Benefits of Specifying A Listed Perimeter Joint System

• Completes the curtain wall package

• Applies pedigreed testing and competent engineering

• Assists the local AHJ

• Standardizes design and cost

• Limits liability

• Provides energy conservation from insulation value

Perimeter Curtain Wall Revised 1

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