If you need to add insulation in your attic, save big by blowing in cellulose insulation yourself. The pros charge $1,500 to $2,000 to do a 1,200-sq.-ft. house. You can do it yourself for about $500. Blowing attic insulation isn’t hard, but it’s dusty, sweaty work.
If you don’t have HVAC and ducts in the attic, spray foam on the roofline isn’t really necessary. I’d blow insulation on the attic floor (after air-sealing, of course). The big disadvantage with spray foam is cost. It’s generally 3 to 4 times what you’ll pay for blown cellulose or fiberglass.
For DIY attic insulation, you've basically got two choices: loose fill or batt (the common term for blanket insulation). Both can be added to uninsulated attics or layered over existing material. Once you've decided which type is best for you, examine the material options and prices to home in on the right product.
1. Fix roof leaks. Water is insulation's enemy. It creates a breeding ground for mold and mildew and ruins the air-trapping pockets that block heat flow. Look for water stains on the roof sheathing or damp or moldy spots on attic joists and existing insulation as a clue to where leaks might be. 2. Box out light fixtures.
Since spray foam is both insulation and air barrier, proper alignment of insulation and air barrier is guaranteed. What's not guaranteed, however, is that all spray foam homes will be efficient and comfortable. I've seen a number of houses with problems even though they're insulated with spray foam.