Insulating your exterior walls with closed cell spray foam insulation will stop drafts and air leaks. Closed cell spray foam insulation has the highest r value 6.2 pr inch of all insulation. Closed cell seals by filling in nooks and crannies that other insulation can not fill. It also forms a moisture barrier which prevents mold and mildew from growing in walls. This is important in our humid hot Houston summers. Closed cell also prevents termites from damaging our homes.