8 Tips for Insulating Your Attic

by Joseph Truini

It doesn't matter where you live, or whether it's winter or summer — having the correct amount of insulation will help you conserve energy, stay comfortable, and save money all year round. While your entire house should be insulated, there's arguably no more important place to install insulation than in the attic.

During winter, attic insulation keeps heated room air from escaping up into the attic, and in summer, insulation prevents hot attic air from heating up the living spaces below. Simply put, insulating the attic will make your entire home more comfortable and energy-efficient. Here are eight DIY tips for insulating your attic:

Dress Appropriately

When handling any insulation, it's smart to protect your skin, eyes, and lungs from airborne fibers. Be sure to wear pants (not shorts), a long-sleeve shirt, tight-fitting eye goggles, gloves, and a dust mask, or better yet, a dual-cartridge respirator. Consider taping closed the cuffs of your pants and shirts and putting baby powder on the back of your neck to keep out irritating fibers. 

Know How Much More Insulation You Need

Installing too much isn't harmful to your home or family, but it is a waste of money. The map and chart below show the approximate amount of attic insulation you should have based on the zone in which you live. (Alaska is in Zones 7 and 8; Hawaii is in Zone 1.) For more specific information, check with your town's building department.

Chart and Image Source:  Energy Star

Add New Insulation

If your attic has no insulation, install either foil- or Kraft paper-faced fiberglass rolls or batts in between all the attic floor joists (which are also the ceiling joists of the rooms below). Fill the entire depth of the joists with insulation. Be sure to place the faced side — the side with the paper or foil moisture barrier — facing down against the topside of the attic floor. Then, to further increase the attic's insulating value, lay unfaced fiberglass or mineral wool insulation on top, running it perpendicular to the joists.

Increase the energy efficiency of your attic by rolling unfaced
fiberglass insulation right over the top of the existing insulation.

Enhance Existing Insulation

If you currently have insulation between the floor joists in your attic, you can dramatically enhance the energy efficiency of your home by adding more insulation over it. As described above, lay unfaced fiberglass or mineral insulation over the existing insulation. Just remember to run it perpendicular to the joists. You can also top off existing insulation with loose fill fiberglass or cellulose, but fiberglass or mineral wool batts are easier and neater to install.

Leave Room for Air

Air is a great insulator, which is why most insulations are relatively light and fluffy. Keep that in mind when you're insulating your attic. Many people make the mistake of stuffing the insulation into tight spaces, but that squeezes out the air and reduces the insulating value of the insulation. Insulation should be cut to fit snugly, but not compressed so much that it forces out the air trapped within the insulation.

Don't Block the Vents

One of the most common mistakes homeowners make when insulating attics is pushing insulation deep into the narrow spaces where the roof rafters come down to the tops of the exterior walls. The insulation will block the flow of fresh air from entering through the soffit vents, and that can cause moisture and mildew problems. To protect these vents, install a polystyrene attic baffle between each pair of rafters. Position the baffles to block the insulation from covering the vents, then secure each baffle to the underside of the roof sheathing with ¼-inch-long staples.

Place polystyrene baffles between the roof rafters to allow air to flow
up from the soffit vents. Be careful not to cover the vents with insulation.

Seal Ceiling Holes

This step is critical to the overall energy efficiency of your home. It's important to seal up every crack, hole, and opening in the room ceilings directly beneath the attic, including all pathways for cables, ducts, pipes, and wires. While these gaps may seem small, in their totality they're major energy wasters and must be sealed to allow the insulation to deliver optimum energy efficiency. Most cracks and holes can be sealed with high-quality caulk or minimally expanding foam insulation. Be aware that many building codes require the use of fireproof caulk to plug ceiling penetrations.

Watch Out for Recessed Lights

If you have a recessed light fixture protruding into the attic from below, it's important to identify what kind of fixture it is before installing the insulation. Recessed lights produce an enormous amount of heat, which could ignite the insulation and start a house fire. If it's a standard recessed fixture, as indicated by a cylindrical metal "can" projecting into the attic, then you must keep all insulation at least 3 inches away from the fixture. However, if it's an IC-rated fixture (IC stands for Insulation Contact), you can safely lay insulation on top of the light. IC fixtures have large, well-insulated boxes instead of cylindrical cans. If you're not sure which type of recessed fixtures you have, ask a home inspector or licensed electrician.

Use these tips to achieve a well-insulated attic that keeps your home comfortable and energy efficient. With the right materials and knowledge, insulation installation is easy.

About the author:  Joe Truini writes about a variety of topics related to carpentry and plumbing. As a home improvement expert, Joe is also the author of numerous DIY books, including the best-selling Building a Shed. To see a selection of the kinds of insulation you could use to insulate your attic, please click here to go to The Home Depot website.

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