The fire in which at least 9 people died (10 fatalities were previously reported) in the Spanish city of Valencia completely destroyed the residential building where it originated. And he did it in just a few hours.
The incident occurred in a building in the Campanar neighborhood of this coastal town, the third largest city in Spain.
Local authorities said several people are still missing and the death toll could rise.
The fire started on the eighth floor and spread quickly, fanned by the wind blowing in the area. At the time, Valencia was experiencing wind gusts of up to 60 kilometers per hour, according to the national meteorological office Aemet.
Experts said the building was covered with a highly flammable polyurethane coating, which could explain the rapid spread.
But there is another reason that experts already point out as the cause: the chimney effect.
“The ventilated facade that was used at the time when the building that burned down in Valencia was built has created a ‘chimney effect’ and has helped spread the fire,” explained the president of the Official College of Architects of Valencia (COAV), Luis Sendra, to the media. in the place.
This already happened in a similar way with the famous tower fire that consumed the Grenfell Tower apartment building, in west London, in June 2017 and where 72 people died.
A facade to acclimatize
The building began construction in 2005. “It is an apparently well-made building,” added Sendra.
However, at the time, in Spain there were no restrictions on the products that were placed on facades, furniture or terraces, he said. It was not until 2011 when regulations came into force to regulate fire-fighting materials.
One of the things that was done in the building was to put a ventilated façade, that is, “a chamber between the façade [del edificio] and the coating for improve thermal conditions of cold/heat,” Sendra explained.
“The flames went up there, creating a chimney effect.”
The structure of a ventilated façade consists of the construction of a double façade. That is, after the interior layer of the building, an insulating façade and a non-watertight exterior façade are placed, so that there is a small distance between the two. This creates a slight air gap in the entire wall of the building.
This small air chamber constitutes a kind of chimney that goes up throughout the building.
This type of façade is efficient in summer to reduce heat input, something very convenient at that time, since it results in less heat absorption, but It is also a condition that helps the spread of fire.
And this is how what is known as the chimney effect occurs.
What does it consist of
It all has to do with the air density according to its temperature.
Hot air is less dense than cold air. This causes hot air to rise and cold air to fall.
For example, if you try to heat a room with high ceilings by installing a heater, the first thing that will happen is that the hot air will rise to the ceiling and at floor level the air will remain cold.
The same thing happens with the chimney effect.
In this case, it occurs in the space between the façade and the unsealed coating, as well as in smoke ducts and other channels where there may be air buoyancy.
That is to say, in those unsealed places where hot air, coming from the fire, and air from outside, with a lower temperature and density, come together.
The larger the temperature difference, the greater the effect.
What is usually a natural driver of ventilation is also a natural driver of fires, dragging flames up the building if there are no fire barriers in the way.
The height of the “chimney” where the exchange of air of different temperatures occurs also contributes to the expansion.
The building has 14 floors.
The higher the height of this duct and the higher the temperature of the air and gases inside, the more pressure there will be.
Already more pressurethe faster the hot air will have to rise and, in this case, expand.
This effect does not only occur on the ventilated façade. Inside any building there are other points, such as the space left at the top of the building for elevators or stairwells.
The way to stop it is with special interior partitions and fire-fighting floors and partitions.
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