Classical Vinyl: Foam-backed vinyl siding accessories help match traditional trim details.

The trim completes the look,” says Brad Pompilli of Tri-State Home Improvement in Branford, Conn., referring to the accessories he uses with foam-backed vinyl siding. For Pompilli, upscale vinyl products — namely Crane Siding's CraneBoard and Royal Building Products' DuraPlank — have been a popular upsell along the coast of Long Island Sound where traditional Colonial and Greek Revival architecture set the tone. It's not a market that tolerates covering up the woodwork and slapping on narrow corner posts.

Foam Advantages Foam-backed vinyl has made strong inroads in high-end markets in recent years. The material consists of rigid vinyl panels glued over foam inserts. The adhesive is fairly gummy and stays flexible, but provides enough tack to bond the pieces together and improve the tensile strength of the unit. Most foam-backed products use expanded polystyrene foam inserts that have a coefficient of expansion that's nearly identical to the vinyl, so the dissimilar materials move as one.

Manufacturers have gone one step further by offering wide lineals, band boards, and corner posts as well as crown and fluted trim stock that allow replacement contractors to match original trim details of traditional homes (above). Like any vinyl siding, panels must be detailed to accommodate this movement by stepping back the nail hem at joints, nailing the panels loosely to the wall, and providing a gap between the end of a course and the adjacent trim. The foam inserts, however, are configured to fit tightly together when the panels are installed. This provides continuous support and a coherent thermal layer. When the panels expand, the foam simply compresses to accommodate the movement, explains Pat Culpepper, president of Progressive Foam Technologies, which makes inserts for Alside, CertainTeed, Crane, Norandex, and other companies offering premium vinyl siding.

Although the foam backing provides a modest boost in wall R-value and reduces sound transmission, the key selling point is appearance, Pompilli says. “It lays nice and flat on the wall, and the backing keeps the seams from opening up.”

Foam-backed vinyl siding panels (like the one shown here) measure from 1 1/8 to 1¼ inches thick, requiring heavier starter strip and J-channel. Over time, standard vinyl siding is pushed around by wind pressure. Underlapping panels often bend in or overlaps get pulled out, creating voids that draw attention to the seams. Standard vinyl is also prone to impact damage from flying objects such as hail. Corner posts are especially vulnerable to lawn mower and snow blower collisions, but the foam backing provides a 300% improvement in impact-resistance. It's the difference that can ensure a house continues to look good after the first season, Culpepper says.

Trim Details The foam increases the depth of the panels, so the job requires slightly different accessories. A special starter strip with an extended leg is needed to accommodate the added panel thickness. Some ordinary accessories, such as corner posts and J-channel, can be used but require foam shims. A variety of inserts and different thickness foam shims are readily available from distributors.

The added depth works well with modern flanged windows, but can present a challenge with existing ¾-inch casing. Bringing the deep J-channel to the edge means the existing trim will be recessed — a look that doesn't always fly in an upscale market.

For Pompilli, this isn't always a big concern. Many of the homeowners are willing to pay to strip the wall clean and install 3½- or 5-inch–wide window lineals. These come complete with sloped sills and crown molding across the head. “Crane offers a pretty complete system that's easy to install,” Pompilli says. “Of course, these accessories add to the price of the job [compared to coil stock], but most customers at this level are willing to pay more for a maintenance-free exterior with a historic look.”