The postwar building boom changed that. Using assembly-line construction techniques he had developed to build war workers’ homes, William Levitt built thousands of inexpensive houses on Long Island, in New Jersey, and in Pennsylvania for returning veterans. To save time and money, Levitt designed his houses with interiors of paper-wrapped gypsum wallboard, a linear descendant of Sackett’s invention. And therein lies the problem.
Gypsum is a common mineral, made of calcium, sulfur, and water. Manufacturers can’t use it to make drywall or plaster, however, until they remove its water molecules. They do this by placing the crushed gypsum in a gas-fired kettle at 300 degrees Fahrenheit for up to three hours. This removes the water, but it also produces copious amounts of CO2 and water vapor, both greenhouse gases.
To make wallboard, manufacturers mix the dried gypsum into a water-based slurry, which they then pour into molds and wrap between thick sheets of paper. (What? They remove the water from gypsum and then add water right back? Yes: There is an enormous chemical difference between “gypsum with attached water molecules” and “dehydrated gypsum floating in water.”) The paper-slurry sandwich is fed into a drying station, which is yet another gas fire, producing more CO2 and water vapor. Because of these manufacturing techniques, designed when energy was cheap and pollution was free, nearly one-eighth of the man-made CO2 in our atmosphere comes from the creation of building materials like cement, glass, concrete, and drywall.