Trees and plants in urban areas are known to improve the surrounding environment, absorbing noise and removing pollution from the air. When incorporated into buildings, trees and plants can boost the health and well-being of occupants. But pull back this foliage and you’ll see that any building is arguably not truly green if it hasn’t been constructed using sustainable methods or materials.
The building sector accounts for 38% of all CO2 emissions globally, including those contributed by the construction industry. In order to reach net zero by 2050, it has been estimated that direct building CO2 emissions need to be halved by 2030. This means the sector’s emissions will have to fall roughly 6% a year between now and the end of this decade.
The Global Alliance for Buildings and Construction has found that the rate of annual improvement in the sector’s energy efficiency has been slowing over the past few years. Despite this, there are opportunities for future growth. The green buildings market is expected to grow at a compound annual rate of 14.3% between 2020 and 2027.
Alternatives to concrete
For engineers, increased investment in green buildings will mean having to work with sustainable materials. Concrete has long been the de facto material of choice owing to its structural properties, thermal ability and long lifecycle. But the production of cement is damaging to the environment – concrete is responsible for around 8% of global CO2 emissions.
Eco-friendly alternatives to concrete that are produced from waste or residual materials, such as coal ash, have been put forward. However, these are often concepts that never make it out of the laboratory.
Recycled steel is becoming a more popular and effective option. Steel can be fabricated into different shaped structures and provides long-term durability.
Prospects for wood
Wood is also being championed as the future of building materials, namely in the form of innovative cross-laminated timber or CLT. Not only does using CLT lower the amount of CO2 that a building produces but, crucially, wood can capture carbon from the atmosphere. This means builders and designers can construct with ambitious CO2 reduction targets in mind.
Although engineered CLT has been used in the UK since the early 2000s, uptake within the industry trails behind other countries owing to regulations. Changes to the International Building Code mean mass timber constructions up to 270ft (roughly 80m or 18 storeys) are permitted around the world. Meanwhile, in the UK, the government’s ban on combustible materials in exterior walls introduced in 2018 following the Grenfell Tower disaster has inhibited the use of CLT.
Wood is probably the most efficient material in terms of carbon and energy but, no matter how innovative CLT or any other material is, if the goal is to construct a building that minimises emissions, every element of a building’s construction should follow the same approach.
The concept of cradle-to-cradle means engineers need to be mindful of the sustainability of their operations and thinking about how a building’s materials can be reused or repurposed at the end of its life. This includes processes used to fabricate a building’s structure offsite and how it is transported to a site.
Cradle-to-cradle is more than just a tangible concept that shows the construction industry is committed to reducing its emissions. If infrastructure is to be sustainable in the long term, then the change needs to come from the top down. This means those at board level need to set environmental goals and pledge to meet net-zero targets.
If those at the top are leading the way, then engineers will be encouraged to develop a circular economy mindset. In time, this will breed further innovation.
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Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.