London high-rise fire: facade cladding identified as fire accelerant
Since the London high-rise fire, the fire hazard of insulation materials has once again been on everyone's lips. In fact, however, these building materials play only a minor role in fires. This has now also been shown by the preliminary results of the first phase of the investigation into the London high-rise fire, which are still ongoing and became known to experts in mid-October 2018: The weatherboard cladding burned down completely and led to the rapid spread of the fire.
When experts talked about the high-rise fire in London, see box, you assumed that the much greater danger to life and limb of residents is not the burning interior, but insulation materials on the outside of the building. But that's only one side of the problem, because these materials only catch fire in five to ten cases a year, according to researchers.
Residential fires: What role does insulation play?
In Germany, an average of over 500 apartment fires break out every day. So the facade is involved in only one in 20,000 fires. As in the London case, most fires originate in the interiors of residential buildings. The number one source of fire is the kitchen. This is where most apartment fires occur due to the large number of electrical appliances.
In addition to technical defects and negligence, arson also plays a role in causing fires. Negligence in smoking or burning candles are also frequent causes of fire. Facade insulation is not one of the causes of fire.
If a fire has started, the first thing to burn is the interior furnishings of the apartment, such as tables, chairs, shelves, cupboards or beds, before the fire causes windows to break, spreads upwards through the floors and in turn attacks the interior furnishings there. Only now is the building insulation in principle in danger. However, since most insulation materials burn extremely poorly, the materials can withstand a fire for a long time. In many cases, mineral materials such as glass or rock wool are used as insulation materials, which cannot burn at all.
In addition to natural insulating materials with appropriate additives, organic materials such as plastic foams are also suitable as insulating materials. For cost reasons, insulation boards made of polystyrene, also known as EPS insulation boards (EPS for expanded polystyrene), are mainly used. In recent years, they have repeatedly been associated with fire incidents and have thus increasingly come under criticism. The material polystyrene is basically combustible.
However, during production of the insulation boards, manufacturers add flame retardants that make the boards flame retardant. "Composite thermal insulation systems made of polystyrene that have been approved in Germany have long been thoroughly tested for their fire behavior in a facade fire test and are sufficiently safe," says Markus Weissert of the Fachverband der Stuckateure für Ausbau und Fassade Baden-Württemberg. "Numerous furnishing components in private households often burn much more easily than building insulation." Above all textiles, furniture as well as PVC floors fall victim to the flames fast - they burn besides inside and not outside at the facade and cause in case of emergency for the inhabitants poisonous smoke gases.
However, even polystyrene can burn and drip after some time at high temperature. In order to minimize the risk of fire in composite thermal insulation systems made of EPS, fire protection is mandatory in multi-family buildings. It prevents the fire from spreading through the insulation to other floors. Homeowners can choose between a lintel protection or a fire protection bar:
In the case of lintel protection, non-combustible insulating material, often rock or mineral wool, is placed above and next to the windows on the outside. With the alternative fire bar, a bar made of non-combustible insulating materials is placed over the windows on every second floor. Fall protection has been required by building law since 1998/1999, the alternative fire bar since 2006/2007.
Fires in finished facade insulation
The intensity and frequency of discussions about burning insulation contrast with the facts. Burning insulation occurs in only 0.005 percent of all residential fires in Germany each year. The cases in which insulation catches fire are mostly facades that are still under construction. Even if the fire starts outside the property, for example from a burning car, fire in a trash container or accumulations of ignited yellow bags, the insulation is in danger earlier than the building interior.
"Homeowners should also make sure when insulating using composite thermal insulation systems that they are systems approved by the building authorities" says Frank Hettler of Zukunft Altbau. "They must also be installed professionally." For even more safety, the choice of a non-combustible facade insulation and the mandatory placement of trash containers or yellow bags at least three meters away from the building. Building energy consultants also help: They provide neutral information about the properties of individual insulation materials and help select a suitable insulation material.
Greenfell Tower: The insulation did not burn
Most of the insulation boards remained intact
After the fire in the "Grenfell Tower" high-rise building in London, it was suspected that the insulation had greatly accelerated the spread of the flames. However, this was not the case at all. Experts such as Werner Eicke-Hennig, an expert at the Energy Institute of Hesse, point this out. Completely burned down is the weather protection from aluminum plastic completely outside at the front. The insulating layer of rigid polyurethane foam (PU) underneath was only slightly burned. The part behind it, about 90 percent, remained intact. (Source: Haustech.de).
