What Is Better Under Vinyl Siding, 1-Inch Styrofoam or 1/2-Inch Styrofoam?

Insulating Value

• The thicker the rigid foam panels, the greater insulation value they will give the house. A product’s R-value indicates how much it reduces the transfer of heat from one side of the product to the other. A standard 1-inch thick layer of rigid foam insulation has an insulation value of R-5, while a 1/2-inch thick layer has an insulation value of R-3. In addition to installing the rigid foam panels over the house boxing, add insulation between wall studs for the best energy savings.

Attaching the Rigid Foam

• The rigid foam panels are lightweight and easy to install, requiring “tacking,” with roofing nails, about every 2 feet apart. The nails used to install the vinyl siding will secure the panels further to the boxing. Although gluing isn't required, if you want to use adhesive between the panels and boxing, make sure it’s suitable for use on rigid foam. Some types of construction adhesive can melt the foam.

Nailing the Siding

• Rigid foam panel thicknesses require the use of a longer nail to install the vinyl siding panels. For the 1-inch panels, use a 2 1/2-inch roofing nail. For the thinner, 1/2-inch panels, use 2-inch roofing nails.

Door and Window Considerations

• Before hanging vinyl siding, you must trim around doors and windows with J-mold, a special trim that conceals the cut ends of the vinyl siding. In standard construction, window and door frames extend about 1/2 inch out from the surface of the boxing. When vinyl siding is installed directly on the boxing, the door and window trim are relatively flush with the finished siding. If you install rigid foam panels, you should also extend the window and door trim the same distance as the thickness of the foam panels for a professional look.

Considerations

• Conserving energy is important for most homeowners, but so is the appearance of their homes. For those who don’t want to extend door and window trim to accommodate the installation of rigid foam insulation, vinyl siding can be installed with custom molded Styrofoam already attached to the back of the panels.