The homeowner that Dean Williams called on “was all set on seamless steel. He wouldn't even talk about vinyl,” says Williams, owner of Dean Williams Quality Home Improvement, in LeSeur, Minn., which sells both steel and vinyl siding, seamless steel being a popular cladding product in the upper Midwest. The client ended up buying insulated vinyl siding, a product Williams has carried for more than 10 years.

RANGE OF CHOICES Manufacturers claim many advantages for insulated vinyl siding over conventional vinyl, even over fiber cement. Insulated vinyl, proponents say, resists denting, bowing, and bending; is more breathable; is quieter; and carries three to four times the R-value of conventional vinyl siding. And longer panels introduced during the last several years reduce unsightly seams. But here's the caveat: Insulated vinyl is also more expensive than conventional vinyl siding.

But of all those advantages, energy savings appeals most to homeowners and has helped to drive sales. Jim Ziminski, president of Crane Performance Siding, a manufacturer in Columbus, Ohio, says that the market share of insulated vinyl siding has gone from 3% to 4% of the total cladding market five years ago to 7% or 8% today. He attributes that growth to expanded consumer awareness of cladding choices, via Internet search.

Many home improvement companies now offer not just options in siding materials – cedar vs. vinyl vs. fiber cement vs. steel — but options within the vinyl category, based on panel thickness and whether or not the vinyl is insulated. “We sell the regular, but we promote the insulated,” says Steve Rennekamp, owner of Energy Swing Windows, in Murraysville, Pa., which began carrying siding four years ago. The insulated product differentiates Energy Swing from numerous companies that only carry regular vinyl.

NOT FOR ALL OCCASIONS Not all vinyl siding contractors, however, are sold on insulated vinyl. “I have it, but I don't push it,” says Jeff Petrucci, owner of Bloomfield Construction, in Bloomfield Hills, Mich. He advises homeowners who are re-siding that they can get more energy efficiency by first filling uninsulated wall cavities with blown-in insulation, then installing conventional vinyl. “That way you might get an R-7, whereas with just the foam-backed you might get an R-2.”

Joe Iuvarra, owner of Iuvarra Siding & Windows, in Haddon Heights, N.J., has been in business 38 years. He remains unconvinced about the superiority of insulated vinyl. The housewrap and insulation he installs behind vinyl panels should do the trick. It's all in the quality of the installation, he says. Besides, Iuvarra notes, “a lot of guys don't use it because it's all special order.”