Insulation choices to consider when what's in the walls isn't up to par

If you're looking to take advantage of a renovation to add or replace insulation, you've got a lot of choices - fiberglass, shredded paper, even plastics, denim scraps, and wool - in several forms. Which material is best for you?
Things to consider: site conditions, your budget, the material's efficiency (expressed as an R-value that measures resistance to heat transfer), and the skill level needed for the installation; insulating with rolls or batts, for example, can be a do-it-yourself project, while filling walls with spray foam is a job for the pros. To get a handle on some of the options that may best suit your renovation, read on.
Rolls or batts
They are fluffy blankets in long strips or precut pads that fit between studs. These are most commonly made of fiberglass, but you can also find ones made from cotton, mineral wool, and real sheep's wool. It is best used in walls gutted down to the studs or in attics. This is a job you can handle
Loose fill
These are dry bits of insulation that get blown into attics. The material is also injected into wall cavities through holes about 2 inches wide. It goes in either from the exterior, which requires prying up siding and drilling through the sheathing - adding to the cost of professional installation - or from the interior walls, which require patching holes. There are three main types: fiberglass, either treated with formaldehyde or untreated; cellulose, which is about 80 percent ground-up newsprint and 20 percent borate, a mineral added as a fire retardant; and mineral wool. It is best used to beef up attic-floor insulation, or inside existing walls when the budget is tight. If you decide to do it yourself, you can rent a blower from a home center.
Expanding foam
This is made of either open-cell or closed-cell polyurethane, or a special cement, this insulation goes on as a soft foam or foaming liquids, filling all spaces, then stiffening in place. Applied only by professionals, it's more costly than other options but is the best at plugging air leaks. Open-cell polyurethane is a low-density, spongy foam. It's sprayed between exposed studs and expands to 100 times its volume in seconds. For finished walls, installers pour a tamer version through small holes; it expands over minutes to 60 times its volume. Closed-cell polyurethane foams to 30 times its volume and dries to a very hard shell. Cementitious foam, which goes on like shaving cream but hardens over days into a meringue-like consistency, requires mesh across the studs to contain it. This is best used when you can look beyond initial cost to long-term comfort. You should most likely let the professionals do it.