Foam Board Behind Vinyl Siding

In a typical situation.

Foam board behind vinyl siding.

It also serves as an air barrier. This detail is used with both new construction and also with renovation work. The by the book answer to your question is that vinyl siding manufacturers require a flat solid supportive surface and limit foam installed under their siding to a maximum of 1 in. Installing foam board insulation under vinyl siding today more than ever before homes are being built with foam board insulation installed on the outside of the sheathing and under the siding.

This is most common with vinyl siding. And even though some manufacturers call it rigid foam insulation for the purpose of vinyl siding it basically has the same insulating value as a piece of plywood. In reality rigid foam board which sometimes comes in fanfold usually only has an insulating factor of r 1 and does not add any appreciable insulation effect to your home. 1 2 polystyrine foam board insulation this is typically used to go over the existing siding in order to create an even surface to keep the siding plum during installation.