GreenGuard FQ350 Fanfold Underlayment

When every penny counts, you can rely on the performance of one of our most economical fanfold siding underlayments. The 0.3" FQ350 is made of extruded polystyrene foam (XPS). Designed to be used as a “leveling board”, it adds insulation and moisture protection during installation of new vinyl siding over old siding. It is configured in fanfolded bundles 4’ x 48’. It comes with crease-fold hinges and a reflective facer on one side for added energy efficiency.

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