Insulated vinyl siding refers to siding that’s been reinforced with a foam insulated backing. The foam insulation fills in the natural indentations of the siding’s profile then hardens, making the profile smooth and solid.
This creates siding that’s more resilient against warping and movement than its uninsulated counterpart.
Just like its standard counterpart, insulated vinyl siding has an outer skin of polyvinyl chloride, or PVC. Under that is a layer of expanded polystyrene (EPS) which is form-fitted to the stepped indentations in the vinyl. The insulation itself can be up to 1 1/4 inches at its thickest point, but due to its uneven profile, this thickness is not consistent and much of the insulation is thinner.
Uninsulated vinyl is sometimes called “hollow vinyl,” after the hollow spaces behind the skin. The flimsy material can easily warp against imperfections in a wall, or rattle during storms and winds.
Therefore, one advantage to having insulated vinyl siding is that these unstable conditions are greatly reduced or eliminated altogether. Smoothing over indentations gives the siding—as well as the corner trim and edging materials—a solidity that standard vinyl lacks.
R-value refers to the ability to prevent “thermal bridging,” more colloquially known in this context as “a draft.” While insulation does add some R-value to a wall, it’s only a modest amount on what functions on an additive scale.
Therefore, there is little evidence to support claims made by manufacturers that homes with insulated vinyl siding see significantly reduced draftiness. One might ask then, if vinyl sidings don’t offer an appreciable improvement in R-value, is there still a point in having them?
Yes. Namely, the aforementioned advantage presented by firmer siding.
In fact, the only true con of insulated vinyl siding is the cost which can range anywhere from between 20 to 50 percent higher than conventional siding. This is due to the skill required by whoever performs your installation, as reaping the benefits of insulated vinyl depends upon precise installation to eliminate any gaps in the insulation backing.
For installation, the bottom edge of the insulation is cut carefully to fit the siding’s top edge, and installed with nails (like with standard vinyl), and the flat backside of the insulation glued to the home’s exterior. Improper installation devalues the insulation’s finished look and quality.
So, for homeowners and businesses, your takeaway is to make choosing an insulation expert priority one.