Marie writes from North Brunswick, New Jersey: "I have a two family rental property. Is it beneficial to put insulation between the ceiling of the first floor and the floor of the 2nd story? Will I save on heating bills?"

Answer: Probably not. Since both spaces are conditioned (heated and possibly cooled) I wouldn't expect there to be much thermal movement from one floor to the next. Depending on the structure, there may be some acoustic or sound control benefits but I question how you would install the insulation if the building already exists. If the exterior walls are not insulated, you could expect some thermal benefit if you can insulate them. I recommend using a contractor for that job because existing walls need to be insulated very carefully to do a thorough job and avoid damage. The easiest and most effective first step is to make sure the attic has adequate insulation. For your area, the U.S. Department of Energy recommends R-49, which is about 15-1/2 inches of fiberglass insulation.