With the world’s population growing apace, the need for new building materials that are cost effective, safe, widely available and carbon neutral is growing. Engineered timber is an exciting new development that allows skyscrapers to be built primarily from wood.
To meet the rising demand for urban housing, more homes, infrastructure and services will need to be developed. India will require new buildings to fit the footprint of Chicago each year to house its growing urban population. Despite a positive outlook for construction, the challenges this boom brings in tackling climate change and environmental encroachment are considerable. Steel and concrete, the two most prolific building materials, are also some of the most polluting to create, responsible for over 8% of global carbon emissions. The cities of the future will need to find other materials if these challenges are to be overcome.
Chicago, as it turns out, is a testing ground for new solutions to the building material problem. Architects in the American city have been focusing on timber construction technology broadly termed ‘engineered timber’. Through this discipline, building constructed primarily of wood have been getting steadily taller. Norway’s 85-metre Mjostarnet building, a structure unveiled in 2019. currently holds the record. But Chicago’s plan for the River Beech Tower will more than double it. The 228 metres skyscraper will rise above the Chicago river, and will undoubtedly be the tallest wooden edifice ever created for human habitation.
At a recent American Association for the Advancement of Science (AAAS) meeting, experts testified to the potential for engineered timber to become the leading alternative to concrete and steel. Engineered timber is not the everyday construction lumber sourced from your local hardware. Instead, it is a composite of multiple layers of different types of wood, constructed with a clear end result in mind. Components like flooring, paneling, braces and beams are considered first from the perspective of the engineering problem, and then purpose built to solve the problem.
Beyond the shape of the object, designers have multiple avenues of innovation, from density and grain to flexibility and durability of the various types of wood. Aligned and laminated in different configurations, engineered timber delivers strength that rivals steel, in a substrate that is up to 80% lighter. There are other advantages too. Rather than constructing the towers from the raw material on site, the building is mostly undertaken within factories in large prefabricated sections, reducing the number of deliveries and ensuring a greater level of quality in the manufacturing process.
The reduction this delivers in carbon-dioxide emissions is significant and exciting. University of Cambridge’s Michael Ramage testified at the meeting that a 300 square metre, four-storey wooden building constructed in his university town resulted in a 126 tonnes of gross CO2 emissions. Had the same structure been built with concrete, the emissions would resulted in 310 tonnes. Had structural steel had been utilised, the resulting carbon footprint would have been just shy of 500 tonnes.
Looked at differently however, the wooden structure could be viewed as carbon negative. By their nature, trees lock atmospheric carbon away within the wood. When not broken down in the composting process, such as in engineered timber, the wood represents a long-term reduction in atmospheric carbon. In the case of the Cambridge building, the equivalent is a CO2 reduction of 540 tonnes, offsetting an entire concrete version of itself.
Should engineered timber become a growing trend, the question of whether enough timber could be produced to sustain it. As Dr Ramage pointed out, this is unlikely to become a problem, provided the timber is sourced through sustainably managed forestry. A standard four person apartment needs inputs of approximately 30 cubic metres of engineered wood. Europe’s sustainable forests alone are estimated to produce that amount every seven seconds. Fire is also not the risk on might imagine, said Ramage, as engineered timber does not burn easily even when untreated. A report by Germany’s Potsdam Institute for Climate Impact Research showed the the large structural timbers at the heart of engineer timber structures are naturally fire resistant due to a charring layer that protects their thick inner cores, even at high temperatures. Combined with the fireproofing layers added to the timber, they compare favourably with the traditional materials many hope they will replace. All things considered, engineered timber may well see a resurgence to meet the challenges of tomorrow.
Evergreen Forestry is a vertically integrated, sustainably focused forestry company managing seven plantations across the KZN Midlands. Evergreen Forestry grows its own trees for pulp and sawmilling, with an increasing focus on the sawmilling value chain.
58
Permanent staff
4900ha
Hectares under management
200,000m³
