Compare R Values

• Learn the R values, the resistance of insulation to heat. R values range from 11 to 38. The higher the number, the more effective the insulation is against heat loss. The most common R value in house walls is 19, which in fiberglass batts is about 4 inches thick. R values vary with the material and the depth of the insulation. Fiberglass batt and loose fill cellulose, the most common home varieties, have roughly the same R value per inch and about the same cost. Rigid foamboard is thinner for comparable R value but is more expensive.
  
  

Fiberglass Batts

• Fiberglass batts come in long strips or rolls; some types have weatherproof facing on one side to be installed on the inside. Batts are used in walls between the studs; in attics between joists; in basements and under floors. Most batts come with paper facing with strips that are stapled to the studs; batts usually are laid loose between joists in attics. One comparison table shows cost for fiberglass batts at 43 cents per square foot, but prices will vary by year, season, manufacturer and supplier.
  
  

Loose Fill

• Loose fill insulation is usually cellulose, granules formed by processing old newspaper and treating it with a fire retardant. Loose fill also may be fiberglass, rock wool or a material called slag wood. All loose fill is best installed by using a blower which will distribute the insulation into cavities between studs and joists. It is most often used in attics, but can be put in walls during construction; installing loose fill in finished walls requires cutting openings in each cavity. One comparison table shows its cost at 31 cents per square foot.
  
  

Rigid Foamboard

• Rigid foamboard is some type of polystyrene or similar plastic material. Pellets are molded into sheets, which vary in thickness. One-inch rigid foamboard is commonly installed on the exterior of house walls before siding is put on or on roof decks before shingling. Sheets are nailed to studs and joists with roofing-type nails. Some rigid foamboard has weatherproof facing, usually a metallic covering. One comparison table shows costs from $1.14 to $1.82 per square foot, depending on the material.
  
  

Special Types: SIPs and ICFs

• Special types of insulation are used for special types of construction. Structural insulated panels (SIPs) are made of thick rigid foamboard faced on both sides with oriented strand board (OSB). SIPs are used on walls of timber frame or post and beam construction and provide some structural support as well as insulation. Insulating concrete forms (ICFs) are thick fiberglass panels used as forms to make poured concrete walls; they are left in place after the concrete hardens. A comparison table shows costs for SIPs and ICFs range from $4.21 to $5.10 per square foot.
  
  

Costs Will Vary

• All insulation prices will vary with time, location and installation costs. Fiberglass batts are easiest for a homeowner to install. Batts may be added over existing blown-in insulation in attics. Blown-in and special form insulation frequently requires professional assistance or rented equipment. Check local building codes before installing any insulation. There may be regulations about what types may be used in various components.