If your sofa lacks a luxurious feel, or has turned lumpy, bumpy or slouchy from years of use, don't get rid of it; stuff its cushions with new, quality material. The filling you should choose for your sofa cushions depends on the level of luxury and comfort you're after, as well as the type of cushions you have.
Do a Little Foam Work
All foams are not created equally, so it pays to do some homework before selecting a filling. Look at different types of cushion or upholstery foam to find one you prefer. If you prefer firm support, you may want to select a firm, high-density foam -- one that has a high indentation force deflection number -- for the sofa's seat and back. For a more cushy couch experience, go with a medium-density product. As long as you use durable, quality, high-resiliency foam designed for such a project, you can expect to get several years of wear out of it.
That's a Wrap
Foam or foam-clad inner springs are only the core of a topnotch sofa's cushions. What the foam is wrapped in or padded with, such as thick cotton batting or down, makes the seating even more extravagant:
If you appreciate down-filled pillows, comforters or featherbeds, consider padding the sofa cushions' foam with soft feathers in a quill-controlling fabric envelope -- sort of like a readymade down comforter constructed in cushion-wrapping size. Or, you might prefer a down alternative, such as hypoallergenic, softly spun polyester fiberfill.
All the Way Down
For more lavishness, opt for 25/75 down -- 25 percent down and 75 percent feather -- inside pillowcase-like forms designed to help hold air and retain loft. Or, you can choose an all-down-alternative filling. Either way, without any foam in them, the cushions require regular fluffing or patting to discourage settling and break up clumps.
How-to Replace Furniture Stuffing
Unzip zippered cushions and forms, or pick open the seams of zipperless ones -- if needed -- using a seam ripper.
Insert new material into the cushion covers, forms or any channels. Pack them until full, but not overstuffed, to avoid bursting.
Zip or sew the covers closed.