Heather writes from Charlottesville, Virginia: "We have a saltbox house that was built in the 1920's. We had insulation blown into the non-storage attic, but it still feels chilly upstairs. Can we lay insulation over this? Will it make a difference?"

Answer: Yes, you can add rolled insulation on top of loosefill insulation. If the existing blown-in insulation fills the floor joists, we recommend running the new unfaced insulation perpendicular to the direction of the floor joists. If the existing insulation does not fill the joists, place the new insulation between the joists.

Whether you will notice a difference depends on how much insulation is in the attic now. The U.S. Department of Energy recommends R-49 in most parts of the country including yours, which is about 15-1/2 inches of fiberglass insulation.

You may be doing this already but you should make sure you are following good thermal management practices, such as opening curtains and blinds upstairs on sunny days allow sunlight in, closing the curtains and blinds on overcast days or at night when it is cold. Caulking around windows can also help.