The invention described herein generally pertains to the use of low boiling point, low vapor pressure blowing agents with froth polyurethane or polyisocyanurate foams to fill hollow cavities (particularly window lineals) and which have lowered exotherms, which prevent deformation of the hollow cavity (e.g., window lineal) and additional achieve filling of longer lengths of window lineals by increasing the foaming and gel times of the reaction.