Adding Attic Insulation to a Finished Attic

Attic windows casting squares of light on a finished floor.
What You'll Need
Insulation material
Spray gun
Hand saw
Protective overalls
Working gloves
Gas mask

Proper insulation is an ideal way to keep the house warm and cut energy bills. Before adding attic insulation, inspect the state of the old insulation. Caution: do not work on vermiculite insulation, as it commonly contains asbestos and should only be handled by professionals.

Step 1 – Measure Present Insulation

To determine if there is need for more insulation, use a ruler to measure the width of the insulation present in the attic. Recommended measurements are 3.5 inches for blown-in loose cellulose, 3.2 inches for fiberglass batts, and 2.5 inches for blown-in fiberglass.

Step 2 – Consider Attic Insulation to Use

Add more insulation material if the measurements are below the recommended figures. It is best to add insulation of the same type as what is already there.

Step 3 – Applying Attic Insulation

Fiberglass batts can be easily applied by laying them perpendicularly to joists; this prevents them from compressing the insulation below. For loose-fill fiber glass or cellulose, use a spray gun or blowing machine. Make sure the material is at the correct density. Fill all cracks, seals, and gaps.

Use a hand saw to scrape off excess material once the insulation has set.

A worker installing loose fill insulation in an attic.Learn how to choose between the two main types of blown insulation - fiberglass or cellulose.