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Fires become deadlier on homes with vinyl siding, study shows

Seventeen people in Texas have died in fires so far this year, according to the US Fire Administration. But there's one thing you may not have thought about that may make the difference between life and death if your home catches fire -- what your home is made of.

A 2008 Loudon County, Virginia fire was a textbook case of what can go wrong if your home is built with vinyl siding. Seven firefighters were hurt -- four of them seriously burned -- after they were trapped on the second floor during flashover.

“The emergency responders are looking at a fire that grows much more rapidly than traditional fires,” said Jeffrey Shapiro, a fire protection engineer with Lake Travis Fire Rescue. “Firefighters have learned through experience that fires that involve more combustible exterior materials are growing much more rapidly than they used to.”

That’s exactly what investigators looking into the Loudon County fire found. A cigarette on the back deck started the fire. When the flames ignited the home’s vinyl siding, they traveled quickly into the attic.

“You can have an attic fire in less than 2 minutes from ignition,” said Steve Kerber, with the Underwriters Laboratories Firefighter Safety Research Institute. He conducted a landmark study for UL, comparing how quickly homes constructed from different materials ignited and the flames spread.

“Used to have 17 minutes to get out of your house,” he said. The materials that went up in flames the fastest were vinyl siding over a foam insulation. “Seventeen minutes is down to three, and if you're asleep, three minutes is not a lot of time to get out of your home,” he said.

That's alarming to central Texas firefighters, who have seen it on the job. “The vinyl catches fire much more rapidly, because it is a plastic product, “said Lake Travis Fire Rescue Asst. Chief Rick Tess. He’s been fighting fires for four decades. Even though some statistics say fires that begin on a home's exterior make up just ten percent of fires nationally, wildfires, like the Hidden Pines Fire in Bastrop County a little over a year ago, are a real concern around Austin. “Because of flying embers, if it doesn't start at the grass or shrubbery right next to the house and catch the vinyl,” Asst. Chief Tess said.

The Underwriters Laboratories study was aimed at firefighters. Shapiro says not a lot of homeowners realize how fast their homes could go up in flames. “With all the synthetic materials and the speed in which those materials burn, new homes are not safer than older homes.”

Old or new, what you want is an exterior that does not catch fire easily. “You want a noncombustible material, such as a brick or a stucco,” Shapiro said.

CBS Austin reached out to some local homebuilders to get their take on vinyl siding and fire prevention during home construction. We either received no response or requests for an interview were declined.

Note to CBS Austin viewers/readers: Our sister station, WJLA in Washington D.C., also produced a story about this same Underwriters Laboratory study about vinyl siding. Below is a statement that was sent from the Vinyl Siding Institute to WJLA regarding questions about the UL report:

Statement from Jeffrey Smith, Communications Director, Vinyl Siding Institute:

Thank you for the opportunity to help you present a balanced story on fire safety to your viewers. Below are our answers and additional background information. We hope you will be examining entire exterior wall assemblies, not just the cladding, and will look at the big picture and shift the story to where it really should be: preventing fires in the first place. On that topic, we are working closely with fire service members, UL, and other material stakeholders on three areas:

Regulation of combustible mulch: Consumers need to be aware of the hazard that combustible mulch poses, especially with Spring approaching and mulch being applied. Mulch can serve as an initial point of ignition and fire spread for fires started by discarded cigarettes or other external fire sources. Numerous jurisdictions in Virginia and North Carolina and other states have adopted regulations that prohibit the use of mulch within a certain distance to the structure; in many cases about 18 inches. Chief Keith Brower of Loudon County, VA, is an expert on this topic and would be a good resource for you.

Changes in smokers’ habits: Discarded smoking materials are often the source of ignition with combustible mulch. With more smokers moving from inside to outside, smokers need to be educated on extinguishing their cigarettes outside safely, which would cut down the risk of fire immediately.

Protection of soffits: For fires that do occur even after causes of ignition have been addressed, we and other the interested parties are working on methods that will prevent or inhibit the entry of fire into the building through the attic by providing greater fire resistance at the eave or soffit area. This will reduce fire severity and provide more time for the fire service to arrive and fight the fire.

That said, residential fires that start outside of the structure, regardless of the ignition source, are extremely rare (only four percent, in fact). And fewer than two percent of house fires originate with the exterior wall surface. This is important context.

1. Sensational video of a tragic 9 year old fire in Loudoun County that lays blame on vinyl siding to recklessly create fear and unnecessary concern over vinyl siding safety.

A 210-page report issued by the local fire chief found that a number of factors were to blame for the tragic results of the fire. (A summary can be found here.) SBG outlets have concealed this critical fact from viewers, and opted instead to show footage of the burning home while misleading viewers to believe vinyl siding may have been the cause – a flawed assumption not supported by the report or other studies.

2. Interview local fire officials.

With all due respect and admiration for firefighters, most cannot speak with authority on the complex chemistry and physics involved in how building materials behave in residential fires.

3. Steve Kerber defending a 2 year old UL study that six associations concluded was flawed.

The technical deficiencies in the UL study were so egregious that representatives of the Vinyl Siding Institute (VSI), the National Association of Home Builders (NAHB), the Extruded Polystyrene Foam Association (XPSA), the Expanded Polystyrene (EPS) Industry Alliance, the Exterior Insulation and Finish System (EIFS) Industry Members Association, and the Vinyl Institute (VI) signed a joint letter in February 2016 requesting that UL promptly remove the report and related wall assembly training videos from the UL website, UL’s YouTube channel and other UL forums.

-- Detailed examples of technical deficiencies pointed out in the UL report included:

Wall assemblies used: A majority of the test assemblies (18 of 32, or 56%) incorporated vinyl siding, yet according to statistics included in the report 23% of new homes use brick veneer, 23% use stucco, and 18% use fiber cement siding. Baseline tests of individual wall materials were not conducted, rather wall assemblies with select combinations of siding, sheathing and insulation were chosen to be tested for fire performance. The report then proceeds to inappropriately draw conclusions about the “most hazardous” wall assemblies, without addressing the other commonly used wall assemblies.

Test fire methodology: The fire burner used as an ignition source did not comply with any established ASTM or UL standard. Further, in several tests a gas grill was placed directly against a wall assembly to evaluate wall performance when exposed to a grill fire. Such direct contact is unlikely to occur in reality as it would be impossible to open the cover of a typical gas grill pushed that close to the wall.

Improper, non-representative choice of sheathing made: Plywood was improperly selected as the representative sheathing, yet significantly more buildings are sheathed with oriented strand board (OSB) than plywood. It is well documented in testing that plywood has a significantly different fire response than OSB under similar conditions, and the report failed to control for or recognize this distinction.

Incomplete test observations reported: Test notes frequently fail to report significant developments in fire progression and the relative contribution of siding and sheathing. This gives a misleading impression of the dynamics of fire growth.

Unfounded conclusions and disparaging characterizations offered: The “Most Hazardous Wall Assemblies” section attempts to draw value-laden generalizations about specific building materials and wall assemblies, and applies a disparaging label to them. These conclusions are, at best, premature, as they are based on a flawed methodology, cited in part above. Furthermore, they fail to put these assemblies into an overall context of the fire risk associated with single-family residential (Type V) construction, and erroneously imply that these specific assemblies are uniquely hazardous while other wall assemblies are less hazardous.

In addition to these issues, the attached report also highlights statistics and information related to exterior fire and fire spread, which is a large part of the study’s focus. Many statements in the UL study are contrary to the trends and characteristics of the fire statistics which are collected under the National Fire Incident Reporting System (NFIRS) program run by the United State Fire Administration (USFA). Ironically, USFA is part of the same the same agency that provided grant funding for the UL report.

4. Comments from representatives of building materials associations or companies.

-- Here are quotes attributable to Kate Offringa, President and CEO of the Vinyl Siding Institute:

Protecting homeowners: “VSI continues to work closely with fire service members, and other material stakeholders to study recent trends in suburban fires. Our focus has been on working cooperatively to identify appropriate actions that can be taken to accurately and effectively address correctable fire safety issues, such as the use of combustible mulch and smoker habits, and on ways to limit fire spread into the building interior. We have met on a regular basis and expect to continue seeking effective methods for reducing property damage and risks to building occupants and firefighters.”

UL study: “The UL research product has been discredited and cannot be trusted. At least six trade associations have expressed concerns about the non-standardized methodology, bad science, and unrealistic scenarios, such as using a high-energy ignition source similar to a gas grill being pushed directly up against a house. UL designed test conditions to emphasize characteristics it wanted to highlight, rather than objectively assess the performance of each building material. In addition, UL failed to conduct a true hazard analysis to determine the actual mechanisms by which fire severity is increased, before passing judgment on what they considered the “most hazardous” combustible wall materials.”

5. Fire safety characteristics of vinyl siding

Vinyl starts with two simple building blocks: chlorine (57%) from common salt and ethylene (43%) from natural gas. While all organic materials (that is, anything containing carbon) will ignite if exposed to a high enough temperature, vinyl siding is more difficult than many other building materials to ignite due to its chlorine base. This means vinyl siding won’t ignite, even from another flame, until it reaches about 730F (387C), and will not self-ignite until 850F (454C). Those ignition temperatures are significantly higher than common framing lumber and wood exterior wall covering, which ignites from a flame at 500F (260C) and self-ignites at 770F (410C).

Even if ignited, vinyl siding burns more slowly than wood. (A detailed explanation on ASTM E84 test methods and results can be found here.)

Tests show that vinyl siding needs unusually high amounts of oxygen to burn and stay burning. It will not independently sustain combustion in air with a normal concentration of oxygen (about 21 percent) — so it extinguishes relatively easily.

6. Residential construction considerations

All combustible materials will burn, especially wood; the difference is only a matter of degree, and it is often not as great a difference as one might suppose.

As we stated above, claddings of any type are rarely a factor in residential fires. According to the National Fire Protection Association, only 4 percent of all residential fires start on the outside of the structure, but do not necessarily originate with the exterior cladding. Fewer than 2 percent of house fires originate with the exterior wall surface, and fewer than 3 percent of all fires go beyond the structure of origin. The most common areas that produce fires are the kitchen, bedroom, and living room, and most fires (69 percent) never leave the room of origin.

Because house fires can and do happen, a focus of residential construction needs to be limiting the spread of fire to critical areas, such as eaves, which may allow fire to spread from the exterior wall to the attic.

One approach would be to “harden” the interface between the exterior wall and the attic so that fire cannot spread so readily into the attic. This would be consistent with the overall fire protection strategy for combustible buildings, which is to compartmentalize fire so that it cannot readily spread to different areas of the building, while still providing necessary functions such as ventilation.

The 2015 International Building Code allows vinyl siding to be a part of a prescriptive fire rated assembly approach because vinyl siding does not contribute to the growth of the fire.

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