Such innovation is everywhere at CAT. I was shown rooms full of heat pumps and clanking biomass boilers; thick-walled, small-windowed homes built in the 1970s as models for sustainability; and a modern lecture hall with walls made of rammed earth, a lower-carbon alternative to concrete (the production of cement, a key ingredient in concrete, contributes to approximately 7% of all greenhouse gas emissions worldwide). Small buildings pepper the grounds as standalone experiments, among them the "Hairy Hut", made from layered thatch and resembling Cousin Itt from the Addams Family.