The voracious fire in Valencia, which has caused 10 deaths, offers a disturbing conclusion: it leads to a review of building technology in Spain, especially in projects dating from the real estate “boom” (1997-2007), according to some experts consulted by this diary. Everything will depend, however, on the result of the investigation. The Minister of Science, Diana Morant, pointed to this rethinking yesterday, who indicated that in parallel with the investigation “solutions will be sought so that this does not happen again.” And as a result of all this, he added, “we will end up having a new catalog (of solutions) to contribute to the building codes and the possible review of buildings” existing in Spain that may have the same characteristics” as the damaged blocks in Campanar. . The Ministry of Education has commissioned a study from the Eduardo Torroja Institute of Construction Sciences.
Suspicions about the reason for the magnitude of the event point to a cocktail of circumstances in which the flammable material used in the cladding, the exterior aluminum “skin” of the building (high-density polyethylene, possibly) on rock wool ( fireproof) and the chimney effect caused in the ventilation chamber on a day with a strong west wind. It would also remain to be clarified whether the segmentation of the building’s fire sectors was sufficient or new requirements would be necessary to increase them.
Some experts point out that the origin of the event was located in the very thin aluminum sheet (composite), which acts as the first skin of the building. Since this sheet is very thin, in order to have sufficient rigidity, the aluminum coating has a layer of high-intensity polyethylene attached to its inner core that gives it rigidity and can be completed with another layer of lower quality aluminum. From the outside in, these facades have in their external coating a layer of aluminum, the ventilation chamber and the thermal insulating elements (rock wool, polyurethane foam…). Polyethylene is the material used to make plastic supermarket bags; although in this case it is a “high density and rigid element” material.
In this building, the core of this composite was, apparently, high-density polyethylene. And high-density polyethylene burns at high temperature. What is very characteristic is that burning drops fall. “And this causes a very dangerous situation; Well, burning drops are falling. This is what could have happened in this building,” according to Angel Sendarrubias, architect at the Pich Aguilera office, an expert in the construction execution of projects.
Luís Sendra, president of the College of Architects of Valencia, agreed with this possibility. The firefighters who attacked the fire gave the same description: “a fire liquid was falling, everything was very, very fast, everything spread along the façade, everything burned in half an hour, it is not normal.”
Sendarrubias clarifies that not all composites are manufactured with a rigid inner polyethylene core, but rather they can use other plastic elements that are considered almost non-flammable, which require very high temperatures and which immediately go out after removing the heat source. “I sense that a polyethylene core must be much cheaper than the plastics that we call self-extinguishing,” says Sendarrubias.
In Spain, there are not many residential buildings with this type of aluminum composite facade. These finishes have been used above all in office buildings (mainly because the material used is quite expensive) or luxury estates, such as the one in Valencia. “As for doing more inspections, in my opinion I think it wouldn’t hurt. But these inspections should not only be to determine the nature of the material, but rather the solution used for the façade as a whole should be studied,” he adds.
Technical inspections of buildings are done only visually, externally. If, for example, you enter a building to inspect and observe a false ceiling, the inspector only looks at the exterior, visualizing that there are no cracks; but he does not go in to evaluate if there are some beams in poor condition or worm-eaten wood behind it. This verification of the condition of the building “in situ” is only visual, unless the technician detects other factors, such as cracks that make him suspect that there is a hidden problem, a circumstance that he then records in his inspection report to indicate that it is a serious sign that requires a period of time to resolve.
Additionally, inspectors rely on factory certificates for the material, they cannot audit plate by plate, it is not their job. There is a high probability that what happened is that the polyethylene used (or another fuel element) and those “burning drops” together with the wind that was blowing that day, as well as the ventilation chamber, could have made the fire especially voracious and that will spread more quickly. Another factor: when a fire breaks out in the ventilation chamber, if it is not sectored, it acts like a chimney. And it has a brutal print run.
At this point, attention is also drawn to the fact that, once the fire was activated (originating on a balcony halfway up the building), it did not spread from the bottom up, but rather downwards. It is unusual for a fire to occur with a path from top to bottom. This could be due to the flammable material (polyethylene or whatever), and the fall of those droplets of inflamed material. Normally, when lower plants burn it is because the plant has collapsed and the fire breaks the soil and causes it to expand. The building has not collapsed.
All this was not regulated before as it is now. With the new technical building code (June 2008) a new classification of construction materials appeared based on their reaction to fire. It was a more lax classification than the current one; With the new code this classification was much more refined. Building regulations are constantly evolving. The General Directorate of Territorial Planning of the Generalitat is preparing a working group to evaluate whether there are properties like the burned one in Valencia. It is the beginning. The case of the Campanar neighborhood has opened a line of work with unpredictable consequences
