Listen and Read 93 - Sustainable Construction

 Thẩm Tâm Vy LISTEN AND READ 93 – 13-02-2021 
LISTEN AND READ 93 
Sustainable Construction 
Urban growth 
The AAAS hears about cities made of wooden buildings 
 MORE THAN half the world’s population dwell in cities, and by 2050 the UN 
expects that proportion to reach 68%. This means more homes, roads and other 
infrastructure. In India alone, the equivalent of a city the size of Chicago will 
have to be developed every year to meet demand for housing. Such a 
construction boom does, though, 
bode ill for tackling climate change, 
because making steel and concrete, 
two of the most common building 
materials, generates around 8% of 
the world’s anthropogenic carbon-
dioxide emissions. If cities are to 
expand and become greener at the 
same time, they will have to be 
made from something else. 
 As it happens, Chicago might 
become part of the answer. In recent 
years, as architects have become 
increasingly interested in modern 
timber-construction methods, 
wooden buildings have been getting 
steadily taller. The current record is 
held by the 85-metre-tall Mjostarnet 
building in Norway (see picture), 
completed in 2019. But this would 
be dwarfed by the River Beech 
Tower, a 228-metre edifice 
proposed for a site beside the 
Chicago river. 
 As the AAAS meeting heard this week, wood is one of the most promising 
sustainable alternatives to steel and concrete. It is not, however, everyday 
lumber, chipboard or plywood that is attracting the interest of architects. Rather, 
it is a material called engineered timber. This is a composite of different layers, 
each designed to meet the requirements of specific components such as floors, 
panels, cross-braces and beams. Besides engineering the shape of a component, 
designers can align the grains in the layers to provide levels of strength that rival 
steel, in a product that is up to 80% lighter. Engineered timber is, moreover, 
usually prefabricated into large sections of a building in a factory. That cuts 
down on the number of deliveries that have to be made to a construction site. 
 All this makes a big difference to carbon-dioxide emissions. Michael Ramage 
of the University of Cambridge told the meeting of a 300-square-metre four-
storey wooden building constructed in that city. Erecting this generated 126 
tonnes of CO2. Had it been made with concrete the tally would have risen to 310 
tonnes. If steel had been used, emissions would have topped 498 tonnes. Indeed, 
from one point of view, this building might actually be viewed as “carbon 
negative”. When trees grow they lock carbon up in their wood—in this case the 
equivalent of 540 tonnes of CO2. Preserved in Cambridge rather than recycled 
by beetles, fungi and bacteria, that carbon represents a long-term subtraction of 
CO2 from the atmosphere. 
 If building with wood takes off, it does raise concern about there being enough 
trees to go round. But with sustainably managed forests that should not be a 
problem, says Dr Ramage. A family-sized apartment requires about 30 cubic 
metres of timber, and he estimates Europe’s sustainable forests alone grow that 
amount every seven seconds. Nor is fire a risk, for engineered timber does not 
burn easily. According to a report by the Potsdam Institute for Climate Impact 
Research, in Germany, large structural timbers are fire resistant because their 
inner cores are protected by a charring layer if burnt. It is therefore hard for a 
fire to destroy them. 
 And, for extra incombustibility, fireproofing layers can be added to the timber. All in 
all, then, it looks as if wood as a building material may get a new lease of life. 
 Notes: 
 - anthropogenic carbon-dioxide: CO2 tác động bởi con người 
 - cross-braces: thanh xiên giao nhau (xây dựng) 
 - to take off = to succeed 
 - to get a new lease of life: hồi sinh trở lại 
 - AAAS: American Association for the Advancement of Science