A.This is a million-dollar question without (unfortunately) a million-dollar answer. Effective rodent management is based on exclusion — you have to keep them out. Killing rodents once they have entered the structure doesn't solve the problem, because there are always more rodents to take their places. Also, killing rodents with poison bait inside insulation causes other problems: When they die, they decay and smell really bad! Plus, they attract insects and other decomposers.

Keeping mice out is a big challenge. They can enter a gap that's only 1/4 inch in diameter. But control is not hopeless. Mice begin to enter homes in search of food and shelter during the early fall when the weather turns colder. Establishing an active trapping effort around the outside of the home during this time will pay big dividends. Tight construction is also essential. Mice can climb well, so be especially careful to identify and seal all gaps in the construction within 3 feet of grade. Don't ignore gaps in the roof construction, either. Look specifically for plumbing and electrical penetrations, spaces under doors, basement floor drains, and other construction gaps. Fill all gaps with inedible materials like sheet metal, hardware cloth, wire mesh, cement, or plaster. Mice can easily chew through most construction foams and caulks.

It's important to make the area around the house unattractive to nesting mice as well. Remove thick vegetation, piles of junk or clutter, bird-feeder droppings (and other mouse food), and any debris from the area surrounding the home. With a little luck and effort, you should be able to keep your rodent roommates to a bare minimum.

Paul Fisette is director of Building Materials and Wood Technology at the University of Massachusetts at Amherst and a JLC contributing editor.