Editor’s Note: Call to Earth is a CNN editorial series dedicated to reporting on our planet’s environmental challenges and solutions. Rolex’s Perpetual Planet Initiative partners with CNN to raise awareness and education on key sustainability issues and inspire positive action.

CNN
—

The US city of Milwaukee already has the world’s tallest wooden tower, but the skyline could be enhanced by another, even taller wooden skyscraper designed by Vancouver-based studio Michael Green Architects (MGA).

The company recently released plans for the project, which includes a 55-story tower made primarily of mass timber – thick, compressed, multi-layered solid wood panels. If built, it would surpass the current world champion, Korb + Associates Architects’ 25-story Ascent Tower, to become the tallest building in the state of Wisconsin.

MGA, a company specialising in timber architecture, hopes the project will set a “new global benchmark for mass timber construction”.

The project is part of the redesign of the Marcus Performing Arts Center, which opened in 1969 and won the Honor Award for Excellence in Architectural Design from the American Institute of Architects in 1970. Led by Neutral, which describes itself as a “regenerative development company,” the remodeling is expected to transform the center’s current concrete parking lot into a space with residential units, offices, restaurants, cafes, grocery stores and public plazas. According to the MGA, construction costs are estimated at $700 million. The plan is currently going through the city’s approval process, during which it is expected to move forward.

Although the use of mass timber is steadily increasing worldwide due to changes in building regulations and changing attitudes towards the material, it cannot yet match the sheer height of buildings made of concrete and steel – although a number of high-rise timber buildings have been proposed in recent years. According to the MGA, its tower design would be around 182 metres high – more than twice the height of the 87-metre Ascent Tower.

“The race for height is important,” said Michael Green, architect and founder of MGA. “It’s not about showing off, it’s about showing the public what’s possible.”

He argued that the reason wooden skyscrapers have not yet become mainstream is because climate change is not at the center of the discussion. “We didn’t really need to challenge the status quo of steel and concrete,” he said. “But because these materials have such a big impact on the climate, we needed to find another way to build towers and tall buildings in general.”

Currently, the construction sector is responsible for 37% of global emissions, largely due to the production and use of materials such as concrete and steel, which generate huge carbon emissions. Trees are the opposite: they absorb carbon throughout their lifetime. When these trees are processed into mass timber and used for construction, that carbon is “locked in” or sequestered for as long as the building stands. “By building with carbon, we are actually building with a carbon sink,” Green argued.

However, he acknowledges that sourcing enough sustainable wood in the quantities needed to build our cities could be a challenge. In fact, some studies warn that increased demand for mass timber could increase pressure on land use.

To achieve the claimed carbon savings, the trees must grow over a longer period of time to sequester carbon and be replanted after being cut down. Green said MGA uses wood from responsibly managed forests in North America.

In the long term, he believes architects need to think beyond wood to address supply shortages. MGA is currently working on developing other plant-based building materials, he adds. But he believes if we are to phase out concrete and steel, mass timber is “the best option today.”

Other obstacles to the use of solid wood were costs and strict building regulations. But in recent years this has changed, explained Green. In many regions, solid wood is now price-competitive with concrete and steel. “There are more manufacturers than before: we now have a large competitive market that is still growing,” he said.

Building codes have also evolved. Some European countries have mandated the use of wood construction as part of their climate goals. In the US, the International Building Code 2021 updated its guidelines for mass wood and now allows mass wood buildings with more than six stories.

The city of Milwaukee is particularly forward-thinking, Green said, encouraging development downtown but also willing to experiment with new materials. While the proposed tower will continue to use concrete foundations and steel components for the elevator cores, he estimates that wood will make up about 90 percent of the building materials.

“It is America’s second-tier cities that are producing groundbreaking innovations that will help address climate change,” he said.

He hopes that the Milwaukee Tower will help drive innovation in climate-friendly architecture and stimulate people’s imagination for building with wood.

“We need breakthrough moments, and this is a breakthrough moment,” Green said.