One of the biggest areas of heat loss (or gain, in the summer) is from the ceiling to the attic. Adding insulation to the ceiling is a great way to stop this heat loss. Modern building codes require insulation in ceilings, but there is usually room for improvement from spray foam.
Ceilings are full of holes for light fixtures, vents, and other items. Every one of these holes is a route for heat to escape. Spray foam is the best choice for sealing these holes. While other kinds of insulation can come up to the edge of fixtures or vents, they don’t really address the actual holes. Spray foam does address the holes, by swelling up and filling them.
Ceilings are usually easier to insulate floors because you can stand up and walk around in the attic. While you are up there, make sure to step on ceiling joists only. You can’t walk on a drywall ceiling, and bad things will happen if you try.
When you get to the attic, installing spray foam for the ceiling starts the same way as for the floor – by moving things out of the way and covering things you can’t move. There should be less to cover with a ceiling application because you are spraying down, not up.
Once everything is covered, start spraying. Keep the coating even and get every bit of the ceiling, especially around lights and vents. The foam will fill all the voids and cracks and seal your ceiling against drafts.