Based on the provided information, which offered several useful techniques, there are a few effective methods for restoring the fluffiness and loft to flattened sofa cushions. The approach you choose will depend on the type of cushion and the degree of deflation.
One of the simplest initial steps is to manually fluff the cushions. If your cushions have a zipper, open them and break up any clumped filling by hand. For all cushion types, you can take them outside and beat them firmly on both sides, much like you would a rug, to help redistribute the filling and reintroduce air. Placing them in direct sunlight for a few hours can also help by drawing out moisture that contributes to compression.
For a more substantial fix, you can add new filling. Many cushion covers have a zipper that allows you to access the inner contents. You can purchase polyester fiberfill, often sold as Poly-Fil, and stuff it around the existing foam core or filling to plump up the cushion and fill out the cover. Another effective technique is to wrap the existing foam block with a layer or two of quilt batting before reinserting it into the cover. This adds a soft, even layer of padding that smooths out lumps and restores a full appearance.
If the internal foam core is significantly compressed and no longer supportive, the most durable solution is to replace it entirely. You can carefully measure the dimensions of the old foam insert and purchase a new, high-density foam block cut to the same size. This provides a long-lasting fix that restores both the cushion's shape and its structural support. While one of the provided sources was a general webpage and did not offer specific guidance, these methods are proven ways to revive your sofa's comfort and appearance.
