Materials such as concrete or stone, better against fire

Experts continue studying the causes of the virulent fire in the 14-story building in the Campanar neighborhood in Valencia and analyze what exactly happened for the flames to spread so quickly (beyond the very strong wind that shook the city of Turia that day). There has been much speculation about the façade because it was the claim of the advertisements for this housing development in 2008 when they talked about “innovative cladding.” They are looking for what caused the fire and if any of the materials used in this façade fueled the fire even more. Sigfrido Herrera, dean of the Official College of Architects of Madrid (COAM), recalls that “it is the experts who have to determine what happened, but there have been three key elements: the wind, the chimney effect of the transventilated façade and the presence of surely some combustible material.

The truth is that ventilated facades are common in construction, because they promote energy savings, which is why the experts consulted have doubts about the execution of this one in particular. For José Ygnacio Pastor, professor of Materials Science and Engineering at the Polytechnic University of Madrid, it seems that in this case, “a façade with a hermetically closed air chamber cannot be considered. Since there is air circulation, if you have a fire and the wind comes in from outside, the temperature increases and the chamber acts as a chimney, burning the materials even more, as it seems to have happened.

As for the materials, the presence of aluminum in the coating (which responds poorly to heat) and the insulating layer, which could be anything from polyurethane to rock wool, have been pointed out as possible culprits. However, the composition of the façade is not yet known. Perhaps that is why the National Association of Insulating Materials Manufacturers (Andimat) has asked from the beginning for caution when making statements that relate and mention products or systems used in construction until there is a report. official.

Pending what is ruled, the confusion that the fire has caused is enormous, especially when it has many points in common with the one that occurred in the Grenfeel towers in London in 2017 (it caused 71 deaths). The cladding was of the same type and, in the case of the London one, was done years after the initial construction. This fire was what caused the change in construction standards, so it is worth asking whether it would not have been desirable to review buildings that had structures of the same style. «In the 2019 Technical Code, which is an update of the first one from 2005, some materials were prohibited for certain uses and the need to have a firewall every three floors was added. The regulatory changes have been becoming more and more restrictive and now it could be the case that it has to be updated again as some ask,” says the dean of COAM. For now and to gain peace of mind, the dean affirms that an information office will be opened so that “neighbors or architects who have any concerns can make inquiries and thus be able to study each circumstance and reach conclusions and, if necessary, change facades. All materials must be viewed with care and tranquility,” says Herrera, who also believes that “there must be a kind of ITV for buildings and that the state of the materials, the structure, the safety and the state of conservation be controlled by “If updates need to be made.”

Ecological materials?

Regarding the materials used, some things must be clarified. Aluminum is not a material that responds well to heat (and in this case it also does not seem to be well insulated), so some experts point to other materials that would have been more suitable for use in the coverage, such as ceramic or stone. . One of them is Luis de Garrido, an expert architect in “green architecture”: “In the Valencia building it seems that it was glued to aluminum, which is already an anti-ecological material (because it consumes 200 megajoules per kilo manufactured), another anti-ecological insulator and then there was the air chamber, when the aluminum should have been loose, then the air chamber and then the insulation. If there had been some ecological material, the structure would have burned less. If stone or ceramic had been used…

The architect has made a list of more or less ecological materials in which he analyzes the 75 most used materials in construction and assigns them a score based on 109 indicators that analyze the optimization of resources, energy consumption during the useful life of that material , the energy sources used (some require blast furnaces powered by fossil fuels and others can be manufactured at room temperature), the waste they generate, health, etc. His list says it all: the higher up the chart, the less impact the material has.

Thus it is not surprising that the architect even recommends the use of concrete, a material that is good against fire, and “one of the most ecological, despite the energy consumption during its manufacture.” If it is used in prefabricated parts, you can disassemble them and use them as in some football stadiums. This way, you avoid generating waste and having to make new concrete. The concept of ecology that we have been sold many times is false. The first thing for something to be ecological is that it lasts as long as possible, that it can be repaired and reused and that it does not generate waste. he says.

For this reason, in addition to increasingly common materials in construction such as wood, ceramics, straw or hemp, there is also a lot of research into concrete mixed with all types of waste or plant materials to reduce emissions during its manufacture (it is said that concrete is responsible for 8% of total GHG emissions). «It is what is known as bioconstruction; make concrete by mixing it with other materials such as cane and bamboo or plastic waste. In this way, you reduce emissions and, in some cases, improve concrete, as happens, for example, when it is mixed with plastic waste. In this case, you also address two problems: concrete emissions and plastic waste,” says Garrido, and the architect is one of the first to have experimented with these mixtures in construction.

Pastor's team at the UPM is also working on a European project called CSTO2NE (Biomimicry and carbon-adsorbing ecomaterials for a climate-neutral economy) in which they reuse steel mill waste. «The waste is treated and mixed with captured CO2. Thus, these remains of steel mills are transformed into new cements. Emissions are reduced, because to manufacture a ton of cement, you normally produce a ton of CO2, but in this case not only do you not emit it, but you also capture it and put it into a new product. The curious thing is that the idea arose after observing a natural phenomenon. It was seen that carbonates appeared over time in the waste dumps where these waste had been dumped and from there people began to think about how to imitate nature.

Research is also being carried out on self-healing concrete. Already in 2015 Henk Jonkers, from Delft University of Technology (Netherlands), showed a method for repairing cracks. Capsules containing specific bacteria and nutrients for them are added to the concrete. Bacteria are activated by humidity and, in this way, it repairs itself.

Choose structures to reduce consumption

According to data from the European Construction Sector Observatory (ECSO), buildings represent 40% of the total energy consumed in the euro zone, and produce 35% of emissions. That is why one of the big bets in the EU is to achieve buildings with almost zero energy consumption, in which insulation plays a fundamental role. «It is about reducing losses and to do this you have to insulate windows and walls. The second strategy for these buildings is energy production or self-generation, which can be done with thermal solar panels for hot water and heating systems and with photovoltaic panels for energy production. There are already buildings that have solar facades that produce energy while serving as insulation. Another trend is that green roofs insulate the building and absorb CO2,” says José Ygnacio Pastor of the UPM.