Ideally, you can add new insulation to your existing insulation. However, some circumstances require you to remove old insulation before adding any new insulation: 

• If the insulation is over 15 years old

• If the insulation is wet or moldy

• If it is vermiculite insulation

• If you see signs of pest infestation

Removing old insulation is best left to a pro who can safely dispose of potential moldy or asbestos-ridden insulation.

On average, insulating an attic costs about $2,500, with a typical range of $1,500 to $3,500. The final price often depends on the attic's size, with costs generally falling between $1 to $3 per square foot. For example, insulating a 1,800-square-foot attic would likely cost between $1,800 and $5,400.

If the project involves removing old insulation, this can add an average of $900 to the total cost, bringing a full removal and reinsulation project to around $3,000.

Several factors influence the overall cost:

• Insulation Type: Prices per square foot vary significantly by material.

• Reflective: $0.50–$1.50

• Blown-in: $1–$4

• Batt: $2–$4

• Loose-fill: $2–$5

• Spray foam: $2–$5

• Structural insulated panels (SIPs): $4–$7

• Project Complexity: Factors like sealing air leaks, poor attic accessibility, and required inspections can add to the cost.

• Removal Issues: The discovery of mold, asbestos, or pests during the removal of old insulation can substantially increase the price.

Insulating windows with plastic works, but it can be time-consuming, and the end results can—and often do—end up lacking in aesthetics. Window film and caulking your windows to make sure there are no drafts are two options that increase the energy efficiency of your home in a low-cost way. Plastic can be a good strategy while you consider alternatives.

Monolithic slabs don’t require insulation, but many homeowners choose to have their contractors install insulation under the slab during construction. This can help improve home efficiency even more and keep indoor temperatures more stable. Slab foundations are more energy-efficient than uninsulated crawl spaces and basements, and insulated slab foundations are more energy-efficient than insulated crawl spaces and basements.