The National Gypsum Company is upgrading its plant in Oxford. According to a company spokeswoman, the second largest producer of drywall boards in the U.S. is upgrading the plant to reduce operational costs and increase energy efficiency. Improvements include replacing a 52 year old boiler and adding new machinery. According to the company’s website, National Gypsum operates more than 30 plants across the U.S. The Oxford plant produces the paper used in drywall manufacturing.