Insulation under siding

Q: Is it a good idea to add insulation under new siding on my 30-year-old home? I get conflicting advice from different sales reps. One says it makes financial sense to insulate, another says it's a waste of money.

A: Any house built to 30-year old standards would fall short of the code requirements for insulation now. So if it makes sense to have ample insulation in the walls of new homes, it seems logical that an older house would benefit in the same way. What you're probably encountering is actually a sales rep who doesn't have the workers capable of installing exterior insulation, yet doesn't want to lose a sale. Another thing to consider is the hidden advantage of applying rigid foam sheets to exterior walls. Unlike insulating batts installed between wall studs, continuous foam offers an uninterrupted thermal barrier. It's highly effective, though not easy to install well. The addition of an inch or two of foam means that door and window openings need to be extended out past the new surface of the outer walls. The trick is finding someone capable of doing a neat and weatherproof job. As you plan the work, consider using a foam product called Wallmate. It's a rigid foam board with grooves milled into the edges. These grooves accept strips of wood that hold anchor screws driven into the underlying wall surface. These wooden strips also form a nailing surface for the siding that comes later.