The voracious fire in Valencia, which has caused 10 deaths, offers a disturbing conclusion: it calls for a review of building technology in Spain, especially in the case of projects dated during the real estate boom (1997-2007), according to some experts consulted by this newspaper Everything will depend, however, on the outcome of the investigation.
The Minister of Science and Universities, Diana Morant, pointed to this rethinking yesterday, who indicated that, in parallel with the investigation, “solutions will be sought so that it does not happen again”. And, as a result of all this, he added, “we will have a new catalog (of solutions) to contribute them to the building codes and to the possible revision of the buildings” that exist in Spain that may have the same characteristics as the Damaged blocks in Campanar. His ministry commissioned a study at the Eduardo Torroja Institute of Construction Sciences.
Suspicions about the reason for the magnitude of the disaster point to a cocktail of circumstances in which the flammable material used in the cladding, the aluminum outer skin of the building (high-density polyethylene, possibly) converged on wool rock (fire retardant), and the chimney effect caused in the ventilation chamber on a day of strong westerly wind. It would also be necessary to clarify whether the segmentation of the sectors of the building’s facade was sufficient or whether new requirements would be necessary to increase it in other properties.
Some experts point to the fact that the origin of the incident was located in the very thin aluminum sheet (composite), which acts as the first skin of the building. Since the sheet is very thin, so that it has enough rigidity, the aluminum coating has a layer of high-intensity polyethylene attached to the inner core that gives it rigidity, and it can be completed with another layer of aluminum of lower quality. From the outside in, these facades have an aluminum layer on the external cladding, the ventilation chamber and the insulating thermal elements (rock wool, polyurethane foam…). Polyethylene is the material used to make supermarket plastic bags, although in this case it is a “high density and rigid element”.
In the burned building, the core of this composite was apparently high-density polyethylene, and high-density polyethylene burns at high temperatures. What is very characteristic is that fiery drops fell. “This causes a very dangerous situation, because drops are falling that burn. This is what happened in this building”, according to Ángel Sendarrubias, architect from the firm Pich Aguilera, an expert in the construction of projects.
Luis Sendra, president of the College of Architects of Valencia, agreed with this possibility. The firefighters who attacked the fire gave the same description: “fire liquid was falling, everything was very, very fast, everything spread through the facade, everything burned in half an hour, it’s not normal”.
Sendarrubias clarifies that not all composites are made with a rigid inner core of polyethylene, but can use other plastic elements that are considered almost non-flammable, that require very high temperatures and that, immediately after removing the heat source, they turn off “I sense that a polyethylene core must be much cheaper than the plastics 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 mainly 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 don’t think it would be excessive. But these inspections should not only be to determine the class of material, but the solution used for the facade as a whole should be studied”, adds the architect.
Technical inspections of buildings are done only visually, externally. If, for example, he enters to inspect a building and notices a false ceiling, the inspector only looks at the outside, sees that there are no cracks, but does not go in to assess whether there are beams in poor condition or a crooked wood This on-site check of the building’s condition is visual only, unless the technician detects other factors such as cracks that make him suspect a hidden problem, which he then notes in the inspection report to point out that it is a serious indication that requires a deadline to solve it.
Also, inspectors rely on material factory certificates, they can’t audit plate by plate, it’s not their job. There is a high probability that what happened is that the polyethylene that had been used (or another combustible element) and the “burning drops”, together with the wind, as well as the ventilation chamber, started the fire especially voracious and spread more quickly. Another factor: when a fire takes place in the ventilation chamber, if it is not sectorized, it acts like a chimney and has a brutal draft.
At this point, attention is also drawn to the fact that, once the fire started (originating on a balcony at mid-height of the building), it did not spread from the bottom upwards, but also downwards. It is unusual for a fire to travel from top to bottom. This could be due to the flammable material (polythene or whatever) and falling droplets of flammable material. Normally, when lower floors burn, it is because the floor has collapsed, but the building in Valencia 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 how they react to fire. It was a looser classification than the current one; with the new code, this classification was much more refined.
Building regulations are constantly evolving. The Generalitat’s General Directorate of Territorial Planning is preparing a working group to assess whether there are properties like the calcined one in Valencia. It’s the beginning. The case of Campanar has opened a line of work with unpredictable consequences.
