Spray polyurethane foam insulation offers great thermal performance when compared to fibrous insulation materials.
The benefits of foam insulation can offset the increased upfront cost when climate offers high Delta-T's (temperature difference between outdoors and indoors).
- Depending on location you can expect that foam insulation would be two to three times more expensive than cellulose or BIBS (dense-packed fiberglass).
- Since you are south of Atlanta I would suspect that the Delta T's are lower than more northern or southern states. It would be difficult to justify a recommendation for spray-applied foam insulation.
As an effective alternative you might want to air seal all ceiling penetrations with fire-rated foam sealant before installing cellulose (recycled newspaper).
- Cellulose is also dense enough to reduce convective loops in the walls in your climate zone.
- If you use damp cellulose in your walls make sure it doesn't get covered with drywall until the moisture content is below manufacturer's recommendation.
- Any wood to concrete joints in the wall/floor structure and lumber joints should be sealed to prevent air penetration before insulating the walls.
Blown in blanket
An alternative to to cellulose would be a blown in blanket system. The installer installs netting over the wall studs before blowing fiberglass insulation at a density required to meet the R-value you contracted.
- My recommendation would be R-15 for a 2x 4 wall assembly.
- Certainteed Insul-Safe III is an effective insulation when installed at 2-pounds per cubic foot.
The secret to performance success is to install a material that is dense enough to reduce convection in the wall cavity. Fiberglass and other fibrous blanket material is not an ideal substitute.