Re-siding and insulating

Q: Our old farmhouse has 30-year-old vinyl siding installed over wood clapboards. We would like to re-side with vinyl. What is the correct way to re-side? Could I improve the R-value by stripping off the old vinyl and clapboards and installing 1/2-in.- thick foam board plus housewrap before re-siding?

A: Senior editor Daniel S. Morrison replies: To create a flat nailing surface for vinyl siding, 1/2-in.-thick foam board is often installed over clapboards. But it won’t affect your home’s energy performance much. Depending on where you live, 1 in. to 2 in. of foam does a better job. Stopping drafts with exterior foam can save a lot of energy. But you should also consider energy losses due to leaky windows, doors, ceilings, and floors.

The attic is the cheapest place to put insulation that will stop air leakage. Performing this energy upgrade typically provides the biggest payback by limiting heat loss in winter and heat gain in summer.

For a great article about how to install vinyl siding well, see Vinyl Siding Done Right  from Fine Homebuilding Issue #149 (Aug/Sep 2002), pp.82-88.