John writes from Phoenix, Arizona: "I have some kind of spray in insulation in my attic. My house is 50 years old and I want to know if I should remove the existing insulation and replace it with new, or should I leave the existing and add to it. If so, what kind of insulation is recommended?"

Answer: Owens Corning doesn't make spray-in insulation so I don't have any specific knowledge about the product you have in the attic. If the current insulation is not causing you any problems, we generally recommend leaving it in place. That saves you a messy job, keeps the material out of the landfill and lets you continue to benefit from whatever insulating value it is providing. You should be able to put more insulation on top of what is there. If you are using fiberglass insulation, it should be unfaced. The U.S. Department of Energy now recommends up to R-60 in attics in many parts of the country. As you probably already know given the climate where you live, insulation helps save energy and money during the cooling season just as it does during the heating season.