Climate change and population growth are intimately related. Together with the population growth the demand for water, food and housing increases. The demands of the human race are transforming the planet.
The urban population has increased exponentially, from 751 million in 1950 to 4,200 million in 2018 and everything indicates that this trend will continue.
According to the UN's 2018 World Urbanization Outlook, by 2050, 68% of the world's population will live in cities, significantly above the current 55%, both due to the displacement of the rural population to cities and population growth. . The result is that 2.5 billion more people will be living in cities by that date.
Outward urban expansion is not optimal. Upward growth is more efficient, taking advantage of existing services (energy, health, transport). And although there are conscious efforts to achieve sustainable urban development, with "green" buildings, the results are not what they seem.
In developed countries, authorities are tightening rules for urban developers, imposing "zero carbon" standards. As of January this year, all public buildings in the European Union must be built according to "near zero energy" or "zero carbon" standards. In near zero energy buildings (NZEB), the energy demand is equivalent to that generated by the building itself through renewable energy and energy efficiency, which leaves net energy consumption at very low or reduced levels. And all new buildings will have to submit to the same standard by January 2021.
Now what`s the downside of all this? The rules apply to the building in operation, without considering its construction. Yet it is estimated that emissions at the construction stage can represent between 30% and 60% of the total over the life of a structure.
Michael Green is a Canadian architect recognized as the "guru" of wooden skyscrapers. He developed a construction system that he named Finding the Forest Through the Trees (FFTT) to use the new laminated wood panels that, in his words, "changed the scale". Wood, according to Green, has magic. "People who enter my wooden buildings have a different reaction," he said in a TED Talk. "I've never seen anyone embrace a column of concrete or steel, but I have seen this in wooden buildings," he said.
As cities grow, he warned, the use of concrete and steel increases. "The materials of the last century; steel and concrete, are good materials. But they're also materials with very high energy and very high greenhouse gas emissions in their process". This last point is a key element: “Steel represents about three percent of man's greenhouse gas emissions, and concrete is over five percent. So if you think about that, eight percent of our contribution to greenhouse gases today comes from those two materials alone. We don't think about it a lot, and unfortunately, we actually don't even think about buildings, I think, as much as we should", he said.
A study by the British think tank Chatham House corroborates that concrete accounts for almost 8% of carbon emissions in the world. More than half of that figure (5%) is explained only by the cement manufacturing process. And steel (half of the steel produced is used in construction) is responsible for another 8% of emissions. The cement industry is making an effort and has reduced its emissions in recent years, but the Chatham House report warns that the development and use of low-carbon cements is too slow.
So, what is Green’s challenge? “I believe that we have an ethic that the Earth grows our food, and we need to move to an ethic in this century that the Earth should grow our homes. Now, how are we going to do that when we're urbanizing at this rate and we think about wood buildings only at four stories?