In the past 50 years, the economics of home construction has changed dramatically. When vinyl siding and synthetic insulation materials were introduced in the 1960s as a substitute for traditional brick and wood, tract homebuilders found their costs were reduced dramatically. In recent years, it is estimated by trade associations that homes wrapped in vinyl siding and synthetic insulation are purchased by 33 percent of new home buyers.
This increase in the use of synthetic materials has been profitable for home builders, especially those who construct “starter” homes. Unfortunately, there are deadly consequences for homeowners and firefighters when these homes catch fire.
Underwriters Laboratories Weighs in on Vinyl Siding Fires
According to a landmark project conducted by a division of the well-known Underwriters Laboratories (UL) – the UL Firefighter Research Institute – when vinyl siding is combined with newer insulation materials, firefighters sent to extinguish fires in these structures face unique challenges, and the consequences for homeowners who become trapped in these fast-moving infernos can be tragic.
In a 587-page report, the UL fire experts – led by Stephen Kerber – analyzed the speed of the spread of the flames over various building materials including vinyl, wood, aluminum, and several other synthetic materials. Since it is impossible to ignite brick and stone, these materials were not included in the testing. The results, while controversial among the vinyl siding industry, were conclusive.
The objectives of the research were to determine the time it takes for a fire to spread through a home and to help firefighters approach an exterior fire more efficiently. The quicker an exterior fire spreads through a house and into the attic, the less likely a fire fighting unit can extinguish it. Even when the time is calculated in minutes, the speed at which an exterior fire speeds can mean the difference between life and death of the residents.
The report noted that the shortest ignition time was in the combustible materials such as vinyl, polypropylene shingle and wood lap. The aluminum siding delayed ignition significantly until it melted away after 04:52 minutes of exposure. The speed at which the fire reaches the top of the wall is important because once it is there, the highly-combustible attic space becomes vulnerable.
According to the report, “This indicates that regardless of the siding material, once the polystyrene became involved, rapid flame spread occurred.”
How Exterior Wall Fires Start
In its recommendation to professional firefighters, the UL report continued, “Changes in residential wall construction methods are playing an important role in how exterior fires are initiated, as well as how they spread and extend. The potential to respond to an exterior fire that has extended into the house increases as home design and construction techniques continue to evolve. In the past, a small outside fire or rubbish fire adjacent to a house spread slowly, if at all. Now, the same fire may quickly involve the entire side of a house and rapidly extend into the eaves and attic or to adjacent structures.
“Older homes commonly have brick, wood clapboard or stucco on the exterior of the structure’s walls. Construction materials and the techniques used to construct homes have evolved over time and will continue to evolve. Vinyl siding was introduced in the 1960s and has gained popularity since the 1970s. Today, the wood siding and vapor barrier that was once in place underneath the vinyl has been replaced with a rigid foam sheathing to increase energy efficiency in homes. The fire service must understand the potential impact these changes have on fire ground operations and safety and evolve as well.”
Brick Construction is Safer
Winds and the lack of moisture can lead to fires. These can be caused by mulch fires, garbage fires, automobile-related ignitions and grass fires started by cigarettes and matches. Wildfires are a real concern and the flames from these types of fires are the most serious ignition sources for exterior fires.
“Brick structures don’t ignite from an exterior fire source. " Jay said. "Where a simple grass fire can envelop a home built of wood and wrapped in vinyl siding in seconds, brick structures maintain their integrity against these fires.
“Some insurance companies have also noticed the advantage of brick. Insurance rates for homes constructed of brick and stone are generally lower than those of other materials because the potential for fires is considerably less,” he said.
Where There’s Smoke, There’s Fire
Nonetheless, the evidence of the danger of vinyl siding and synthetic insulation is compelling. A report published by Fire Engineering pointed to a National Institute of Standards and Technology (NIST) study by Dan Madryzkowski, which compared the combustibility of three siding materials: aluminum siding, T-111 (plywood), and vinyl siding. Again, brick was not studied because it is not combustible.
“The results were interesting. A small focused area of the aluminum siding melted after 10 minutes of flame contact, at which point a smoldering fire developed inside the wall, but there was no vertical flame spread. The T-111 allowed burning and flame spread 200 seconds after ignition, and it took an average of 80 seconds to burn to the soffit level. The NIST report describes the test results for vinyl siding: 'Less than 90 seconds after ignition, the flames began to spread upward, and within another 50 seconds, the flames were in the attic space.'”
Hazardous Chemicals are Also a Problem
The rapid spread of exterior fires is not the only challenge firefighters and residents face. Because siding is manufactured from synthetic materials, when it is ignited, those chemicals can become poisonous.
Even the trade publication for the siding industry – Siding Magazine noted, “Vinyl siding is made primarily of polyvinyl chloride, or PVC, a durable and cheap plastic often used in construction. When PVC is heated up or burned, such as in very hot weather or a fire, it will release formaldehyde, hydrogen chloride, and dioxin into the air, all of which are gases that may cause illness and are known carcinogens.
“In case of a fire, it is possible for these gases to kill the occupants of a home before the fire reaches them. In some cases, firefighters have allowed homes to burn to avoid toxic exposure from burning vinyl siding.”
If you are considering building a new home, consider the safety issues. For more information on brick construction, contact Acme Brick.