Open Cell Foam for Outdoor Furniture

Open-Cell Foam

• Foam is made from petroleum-based products suffused with small air bubbles. If the air bubbles are wholly enclosed, with each bubble totally independent from all the other bubbles, then the product is closed-cell foam. It is a highly rigid product most commonly used as home insulation. If the air bubbles break and join adjacent bubbles, then the product is open-cell foam. It is flexible, compressible and, in one of many variations, is the foam used in furniture construction and as cushion filler.

Qualities

• The durability and firmness of open-cell foam is measured in weight per cubic foot as density, and the number of pounds of pressure required to squish the foam as "compression." The size of the foam's holes affects both of those ratings, and the size of the holes also affects the foam's suitability for outdoor furniture. More holes and smaller holes usually means more dense and firmer foam. Outdoor foam must have more holes and larger holes in order for water to pass through the foam. Open-cell foam has been the traditional filler for outdoor furniture for many years, but developments have produced two products that far surpass open-cell foam as the product to use in outdoor furniture.

Recycled Plastic Batting

• Plastic bottles are recycled into fibers and spun to create an outdoor furniture product similar to thick quilt batting. Water passes through the product, inhibiting mildew growth. Available 1 or 2 inches thick, it is stacked to the required depth, can be cut easily with scissors and is available online and in large do-it-yourself home decor stores.

Instant Dry

• Thick polyethylene fibers are spun into a sheet that is typically 2 or 3 inches thick to create a product that is firm, does not support mildew growth and can be cut into shapes easily. Water passes through the material quickly and does not accumulate; water evaporates and does not damage the product if trapped by the cover. It is about twice as expensive as foam, but some varieties are guaranteed for at least five years of outdoor use. It is available through upholsters and drapery workrooms. 

Other Considerations

• The fabric used to cover outdoor furniture foam requires consideration as well. Good-quality outdoor fabric resists sun-bleaching and allows moisture to pass. Standing moisture promotes growth of mold, including mildew. If the filler is wrapped with a batting, it should allow water to pass through and resist the formation of mildew.