[gtojohn]

You still might want to look at your manual j numbers before hand. Closed and insulated might be the best, but in a southern climate the gains aren't much for the trouble. Money and effort could yield you faster returns on other areas vs what only affects me 3000bthuhr during 1-2 months of winter. I really can't measure the difference where my floor is insulated and where it isn't, but its also about outdoor ambient and even wind speed.