Today I will try to share with you as much as I know about CLT technology.
I can't write neatly about any subject, but I will try to present it as concisely as possible. I will try to divide the whole article into four parts :
★ What is CLT?
★ What are its advantages or disadvantages?
★ This is why it is important to think in terms of environmental science.
★ What are the limitations of CLT technology?
First of all, what is the CLT thing?
The full form of CLT is Cross Laminated Timber. It is a special kind of material used to make houses and buildings, which is made of wood. Scientists and engineers are constantly trying to figure out if CLT technology can be used as an alternative to the most common material we use to build houses and buildings (concrete). Building a house with wood is nothing new. People have been building houses out of wood for hundreds of years. However, there are some differences between ordinary wooden house / building and house made of CLT.
CLT panels are basically made up of several wooden planks 1-1.5 inches thick and 4-5 inches wide arranged side by side with another layer horizontally at a 90 degree angle, thus three layers, five layers, seven layers (in odd number of layers). The panels are made by attaching pairs with strong glue arranged in layers. These specially made panels are much stronger than ordinary wood and do not burn easily in fire. These specially made panels are then cut according to the specifications of the building to be constructed in the factory. And these pre-fabricated panels are tracked to the building site and the building made of CLT panels is made by attaching them with nut-screws with the help of a crane.
Then what are the advantages or disadvantages of CLT technology?
To understand why CLT technology is superior, we need to compare CLT with concrete,
First of all, with carbon dioxide emissions, the main components of the buildings Rocks, rod, cement, brick and sand . The reaction of making Rod is to burn coal with iron ore (we who have studied science at school level, we all know about this reaction). This process of making steel is responsible for 5% of the total global carbon emissions. Then comes the cement, where a lot of gas is burned. The process of making cement emits an additional 6% of carbon dioxide. Bangladeshis do not have to be told anew how much plants, coal and gas are burned to make bricks, another component of concrete. According to WorldGBC, the building construction sector accounts for 39% of total global carbon emissions. In contrast, CLT technology does not emit that amount of carbon, but rather absorbs more carbon (carbon negative). And this is the biggest advantage of CLT technology.
The heat isolation capacity of wood is much higher than that of concrete, which means that buildings made of CLT will require less energy for heating and cooling (carbon saving here as well).
Being pre-fabricated, the building takes much less time to build and also has a lot of flexibility in design.
Engineers have tested the engineering specification to show that CLT panels can withstand a fire for a maximum of 2 hours, because if a fire breaks out in a building made of CLT, the top layer of wood burns to form a special layer of fire resistant coal. And prevents the inner part from burning. As a result, these buildings do not collapse easily even if they are on fire for a long time, where concrete buildings can collapse easily at high temperatures.
Concrete structures are usually not very beautiful to look at, and we cover the concrete with plaster so that it does not look bad, on the other hand CLT panels made of wood are naturally beautiful to look at.
When a building loses its usefulness for any reason, it is demolished and the concrete dust is useless in that sense. On the other hand, when a building made of CLT has lost its usefulness, it can be easily opened in the form of parts and re-built in another place or wood materials can be easily recycled. Which is not possible in the case of concrete buildings.
In strong earthquakes where concrete buildings easily collapse due to cracks, almost nothing happens to buildings made of CLT. Due to the natural flexibility of the wood, it can stand up straight again by moving a little.
Then why is CLT important in terms of environmental science?
If we think that it would take a lot of wood to make CLT panels, there is very little forest in the world at present, and if we could supply wood for CLT, the forest would be deforested. If many trees are cut down, then CLT is definitely harmful to the environment. But if we think a little differently, there is a huge supply chain for the most popular building material concrete of today. Some are producing bricks, some are producing cement. Some are making rods, others are extracting ore, sand and stones from the rods. That is a huge ecosystem but it has been built slowly. As such, the amount of ecosystem required for CLT is still almost zero. When CLT technology becomes popular, there will be a huge demand for timber and trees. The big companies can then be seen starting commercial timber production. The uncultivated lands will be transformed into fast-growing tree forests. Regularly, big trees will be cut down and seedlings will be planted again. Cutting down a single tree and turning it into timber means removing huge amounts of carbon dioxide from the atmosphere. At present, planting trees and growing them is not very economically viable. But if CLT technology becomes popular, then gradually everyone will lean towards it. In contrast to where a large amount of carbon dioxide is currently emitted in the construction of a single concrete building, the construction of a single building with CLT technology means the removal of a large amount of CO2 from the atmosphere. Which will undoubtedly play a very positive role for the environment.
The last point of our discussion is what are the limitations of CLT technology?
If we compare it with concrete in the beginning, then CLT technology is still in its infancy compared to concrete. We have long mastered the knowledge of how to build durable skyscrapers with concrete materials. The material properties of concrete are fully known to us. We also know which climate will perform it. Much more about CLT than that is still beyond our knowledge. This is constantly being researched. But even then the adaptation rate of new technology is always much slower. Also, like any new technology, the cost of CLT is still very high. Moreover, CLT technology will only make sense if the trees used for CLT are produced locally. Every region of the world has a different climate. The type and nature of the plants there is also different. Large-scale research is still needed on these issues. And most importantly, the ecosystem / supply-chain needed for CLT building materials has not yet been developed. It also requires a lot of time, investment, and research. Maybe tomorrow we won't see everyone start building wooden (CLT) houses with the exception of rod, brick, cement. However, we can only hope that research and investment will increase.
So far today, I have tried to attach a reference link to the information I have used to write this article. Even then, one or two missed information may come to mind. If you find any inconsistencies in this article, please let me know. Love and best wishes from the bottom of my heart to all those who read the article with difficulty, wasting your precious time.
References :
https://bellona.org/news/ccs/2019-03-is-steel-stealing-our-future
https://www.worldgbc.org/news-media/WorldGBC-embodied-carbon-report-published