Watch as 6 becomes greater than 8 while installing Invinsa® Roof Board from Johns Manville. At comparable thicknesses Invinsa and Invinsa FR are one-third the weight of traditional gypsum cover board materials, allowing a crew of 6 to install 60 squares of Invinsa 27 percent faster than a crew of 8 can install 60 squares of gypsum cover boards.