Who said its too late to worry about our energy costs
Insulation was installed prior to this project on the sills, but we removed it and replaced it with four inches of closed cell with a R value of close to R 28.
Not only did the owner save money their comfort also increased which allows them to keep the thermostat lower saving even more money.
So before you decide to insulate, air seal all gaps, you can use spray foam in a can, caulking or simply call a company that does this type of work. It is more expensive as professionally installed spray foam runs around $1.50 per board foot and up, but the savings more then pay for the cost in the near future.