An energy efficient method for making a gypsum cellulose fiberboard comprising adding a first portion of cellulose fiber to gypsum before the gypsum and cellulose fiber are co-calcined in a reactor, adding a second portion of cellulose fiber to the slurry after it leaves the reactor to form a second slurry, depositing the slurry to form a mat, dewatering the mat, rehydrating the mat and then finishing the mat to form a final gypsum cellulose fiberboard. A reduction of up to about 40% to 50% of steam energy used can be achieved when the second portion of added cellulose fiber is 50% or more of the total cellulose fiber used in the final board compared to gypsum cellulose board made with the same ingredients but when all of the fiber is added to the gypsum prior to the reactor.