Contoured Foam Underlayment Product description

Contoured foam underlayment (CFU) is a drop-in rigid foam insu­lation product that is custom made to fit snugly behind different styles of vinyl siding. This new product is intended to improve the rigidity of vinyl siding as well as its resistance to denting and warping. CFU typically is made from XPS foam that provides an li­vable of 2.8 to 3.3 per inch and has a permeance rating of 5 (it is not a vapor barrier). Installation is relatively simple because the CFU is placed behind the siding and cut to size as necessary. The siding is snapped into its final position and nailed to the structure in accordance with the siding manufacturer’s recommendations.

CFU is also available from some manufacturers as an integrat­ed, fused vinyl siding and foam product. The installation is similar to conventional siding except that two courses go up at once and special accessories are used for corner and trim details.