The "mass timber" movement is a growing worldwide effort to build high-rises and other buildings out of wood composites rather than steel and concrete, for environmental reasons.

Why it matters: Lightweight, attractive and sturdy, mass timber buildings are considered carbon-friendly alternatives to conventional ones — and some people prefer their warmth, character and texture.

How it works: Mass — or "massive" — timber is "wood that is glued and pressed in special ways to make it similar in strength to concrete and steel and thus capable of replacing those building materials even for skyscrapers and other massive edifices," per the WSJ.

Driving the news: While Europe has embraced the mass timber movement, the U.S. is starting to catch up.

What they're saying: Advocates say mass timber "creates less waste, leaves a lighter carbon footprint (because wood sequesters carbon), and can be quicker and quieter than other construction modes," per BD+C.

The other side: Detractors question "whether the logging and manufacturing required to produce the new material outweigh any benefits," journalist Jim Robbins writes for the Yale School of the Environment.

Tallest so far: The 18-story Mjøstårnet — or Mjösa Tower — opened in 2019 and includes office space, apartments and a 72-room hotel.

What's next: Expect to see lots of mass timber buildings rising in cities across the U.S. — apartment towers and office complexes — and marketed as "green."