Blanket insulation, the most common type of insulation, comes in sheets or rolls. While it has traditionally been made of fiberglass, it can now be found in plastic or natural fibers. It’s sized to fit nicely between the standard spacing of studs on unfinished walls, and the joists and rafters of floors and ceilings. It’s also relatively inexpensive, and DIY types can find it in home improvement stores.
Blown-in insulation consists of recycled fiberglass, newspaper (cellulose) or other material that is blown into a space. Because of its loose nature, this type of insulation conforms to fit an existing area without disturbing the surrounding structure and is well-suited to renovations.
Spray foam, a mix of chemicals, expands into liquid foam that becomes rigid after it cures. It acts both as insulation and an air sealant. This type of installation requires more experienced installers, and tends to cost more (though the Department of Energy says that because it has a higher R-value and acts as an air sealant, it may ultimately save money by eliminating the need for other home weatherization tasks).