Q. A lot of us with older homes (100 years) are getting energy audits with recommendations to blow in cellulose into the empty exterior wall cavities. I have read that without a vapor barrier moisture can be trapped in the walls, leading to mold and wood decay. Do you have an opinion on this? JIM, in Belmont

A. I think that what you have heard is mostly an old wives tale. Thousands of houses have had insulation blown in without incident, mostly because old houses are so leaky that there is little or no chance for water vapor to build up to cause the insulation to take on water. Even vinyl- and aluminum-sided houses don’t have the problem.