This fall, when parents dropped off their children at De Leertrommel, a school about 10 miles northwest of Brussels, the young pupils began their studies as they had for many years before.

But while the U-shaped, seven-room school constructed in the 1960s looked much like any other, it represents a major leap forward in sustainable construction: it had been completely renovated in a €2 million (USD $1.9 million) project to become the first Flemish school to ever be built with hemp.

“The project was to build well-ventilated classrooms where pupils can be comfortable and healthy throughout the year,” says Charlotte De Bellefroid, a spokesperson for IsoHemp, the Belgian company that fabricated the school’s hemp-based construction materials.

IsoHemp’s blocks, and alternatives made by many others, are made of hempcrete, a mix of hemp fibers, water, and lime or clay, which acts as a binder.