Trial by fire

The trial gets fully under way as a technician moves a gas-powered flame bar up to the wall assembly mock-up exterior. A fire in an oven has already been moved up to the back of the mock-up, simulating an interior fire.

I’m proud of the fact that PROSOCO R-GUARD Cat 5, our primary air-and-waterproof barrier, keeps water out of structural walls, rigid sheathing and CMU back-up in conditions from a mild Spring day to a category-5 hurricane.

Mild to wild, as we say.

Now we get to add a new bullet point to Cat 5′s resume — fire-resistance.

Here’s the story. They’re anticipating using Cat 5 on an EIFS project in the Caribbean. They get hurricanes and tropical storms there, along with rain almost every day, so Cat 5 is a good choice.

But if your wall assembly has combustible components like this Caribbean project, the International Building Code says it has to be tested according to NFPA 285–Standard Fire Test Method for Evaluation of Fire Propagation Characteristics of Exterior Non-Load-Bearing Wall Assemblies Containing Combustible Components.

NFPA stands for National Fire Protection Association.

Combustible components in this assembly include exterior foam plastic continuous insulation — 2-foot by 4-foot expanded polystyrene panels, 4 inches thick. Cat 5, like all water-resistive barriers on the market is also considered combustible — even though it’s similar to silicon sealants and chemically inert when cured. So the wall assembly needs to be tested.

It’s important to understand that NFPA 285 isn’t a test of Cat 5 — or any individual component in the assembly. It’s a test of the wall assembly itself.

Individual testing under ASTM E 84-12
Tested individually under ASTM E 84-12 Standard Method of Test for Surface Burning Characteristics of Building Materials in April, Cat 5 proved to be a Class A building material under the NFPA’s Life Safety Code.

Class A is defined as “Can withstand severe exposure from fire originating from a source outside the building.” Clay brick is another example of a Class A building material.

On the zero-to-100 Flame Spread Index where zero is fiber-reinforced cement board, grade II; and 100 is red oak flooring, Cat 5 rated 10.6. On the zero-to-100 Smoke Developed Index, Cat 5 tested at 2.6

The test assembly
An independent third-party test facility conducted NFPA 285 on the wall assembly incorporating Cat 5 June 14. Representatives of the manufacturers whose components went into the walls built the mock-up to the same specs as the Caribbean project. Here’s some photos of the test assembly going up.

Shawn Derosier applies CAT 5 primary air & water barrier over Densglass.

Next, the expanded polystyrene continuous foam plastic exterior insulation goes on over the Cat 5.

The EIFS finish coat goes on.

Time for fire
With the mock-up constructed, it’s time for the fire.

NFPA 285 tests the wall assembly — a two-story mock-up with a first floor window — to measure whether or not the fire spreads beyond an acceptable distance either horizontally or vertically on the exterior, or through the core of the wall, where the combustible materials are located.

The 30-minute test scenario is that there’s a fire inside, shooting a fire plume out of the window.

The inside fire is simulated by backing the mock-up against a test oven lit with a roaring fire.

The interior fire is simulated by backing the mock-up to this test oven, which will be filled by real, live flames.

Here’s NFPA 285 under way.

An inspector tears away the burnt surface to see how the foam plastic insulation and Cat 5 beneath it fared.

Here’s the damage revealed. though much of the foam plastic melted and ran during the 30-minute burn, it doesn’t appear to have actually ignited.

Here’s a closer look. It appears that a bit of the Cat 5 was scorched off the window header where the flames made direct contact, but was not impacted elsewhere.

Along with dimensions written on the side of the test panel, the mock-up also contained thermocouples for measuring heat. I’m told they indicated 1600 degrees — more than double the melting point of lead.

Result of the testing? The wall assembly, including Cat 5, faced trial by fire — and passed.

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