Kathryn Larsen on why seaweed is the building material of the future

Bio-based designer and architectural technologist Kathryn Larsen is looking to the pass to create a greener future.Larsen looked to an ancient method from the Middle Ages used to thatch roofs out of seaweed and brought it back to the present.Kathryn Larsen’s project, Seaweed Thatch Re-imagined, looks to the old seaweed thatching method of the Danish island of Læsø. During the Middle Ages women used to create roof thatches made from eelgrass that washed up on the shores of the island. The women treated the thatching process like the spinning of wool and completely dominated the construction industry on the island at the time.The material was rot resistant, could withstand any weather condition and also served as an insulating material. The island had a thriving seaweed export industry. However, during the 1930s there was a global wasting disease that nearly destroyed the eelgrass beds of Denmark. As a result the people of Læsø had to turn to traditional thatching materials and methods. Today eelgrass is seen as a waste material. According to Larsen 22 000 tons of eelgrass are thrown out annually. Larsen believes that if we change our perspectives on the material we can begin to harvest it again and create a more eco-friendly building material. She thus came up with the concept to bring seaweed thatch to the modern building industry by creating fabricated thatch panels. “I envision that these panels could be used on facade and roof and act as supplementary insulation and at the same time act as a kind of green roof,” says Larsen.Adding: “I firmly believe that from learning from our past we can build for a better and greener future”.