How to Properly Insulate an Attic

Proper insulation of an attic is one of the most efficient ways to cut down on your heating and cooling costs. Insulation will affect the way that your attic breathes the air that passes through it, however. So make sure that you take steps to ensure proper ventilation when you add insulation.

Things You'll Need

• Plywood flooring
• 24-gauge sheet metal flooring
• Caulk
• Utility knife
• Expanding foam insulation

Instructions

1. Lay down a framework of temporary plywood flooring over attic joists to allow you to work more efficiently. Not having to balance yourself on the joists provides more stability and lets you do the work more effectively.

2. Begin by sealing up air bypasses in the attic. Use caulking to seal off gaps around pipes and ducts. Install 24-gauge sheet metal flashing around the chimney and caulk to seal where the flashing connects to the chimney. Sealing up air bypasses keeps heat from escaping through the attic and thereby reducing the efficiency of the insulation.

3. Cut batt insulation to length. Set the top of batt into place and use your utility knife to cut against the bottom of the batt. Leave an extra half an inch of length to create a tighter fit. Push batts in between the beams so that they fit snugly.

4. Split the batts to make them fit around electrical cables. You can do this simply by tearing the batt in half, working from the bottom to the top. Insert one-half of the batt behind the electrical cable and place the other half over the top.

5. Trim the insulation to make it fit around an electrical box. Run the blade of your knife against the outside the electrical box to help guide your cutting. Don't cut too deeply to avoid accidentally cutting one of the wires.

6. Place the insulation behind plumbing pipes on outside wall. Leave the side that faces the interior uncovered by insulation to make sure that the pipes can remain warm.

7. Apply a bead of expanding foam insulation around the perimeter of a window. Allow at least an hour for this type of insulation to cure. Size up and cut a thin piece of batt insulation that can be stuffed into any space that remains open. Refrain from compressing this insulation into the space to avoid hampering proper operation of the window.

8. Preserve are least 1 inch of air space between the insulation and the roof sheathing. This space should extend from eaves to ridge to help flush out the accumulation of moisture. In colder climates, this 1 inch space also helps in the prevention of ice dams.

Tips & Warnings

• Hedge shears are better than utility knives for cutting through insulation batts because shears don't spread the insulation.

References

• Energy Savers: Attic Insulation
• Madison Gas and Electric Co.: How to Insulate Your Attic
• Energy Star: Air Sealing and Insulating an Attic