Insulboard is a 1-inch thick piece of foamboard covered with vinyl on the exposed side and wrapped with a vinyl J. It is attached to the bottom of the seat board to increase the “R” value of the unit.
The standard insulboard spans the length of the unit. It is 17″ wide for retro units, 18.375″ for new construction.
On a fully insulated seat, the insulboard will be 17″ wide plus the jamb width.
A double insulated seat board simply uses two foam boards instead of one.
Posted in: Series 2050 Garden Window