Insulating your attic

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Insulating your attic is an excellent way to save on energy usage and ease the strain on your pocketbook. It sounds simple enough: Add insulation and the savings roll in. However, an insulation project is much more complex than just blowing some insulation into the attic. Modern homes are elaborate, interactive systems. A large amount of thought and planning should go into an insulation project.

When installed correctly, insulation reduces heat loss and increases the comfort level of your home. Once insulation is in place, no ongoing maintenance is necessary. However, when installed incorrectly, the improper insulation will cause you to waste money and might even cause serious moisture damage to your home.

Stop heat flow

To prevent heat from flowing outdoors, you must fix air leaks and systems that cause air to be sucked out of a home, or enclose the home in a “thermal boundary.”

Insulation stops the convective flow of air and, consequently, halts the flow of heat. Fill the attic space above the ceiling with fiberglass or cellulose insulation—the two types of insulation most commonly used in retrofitting a home during remodeling.

The insulation halts heat movement into the cold attic, but is a poor barrier when air is moving under even slight pressure, such as through the gaps around a light fixture. Seal any gaps that allow air to move from heated spaces into the attic. There are literally hundreds of holes in the thermal barrier, including electrical wiring, light fixtures, plumbing and the chimney. These openings must be sealed, caulked or foamed, or blocked by metal, wood or drywall.

See your home as a system

When evaluating your home’s thermal envelope, check the attic first. The insulation level must match your climate. For a cold climate, you need a level of approximately R-38, or about 12-15 inches of insulation. R-values measure how effective insulation is.

Survey the attic for potential air leaks. Common culprits include the areas around chimneys, plumbing vents and wire penetrations. The trap door or stairway into the attic can be a major air channel. “Can” lights that penetrate the insulation also create big problems. You may need to hire a professional to help address these leaks.

To find an air bypass into the attic, lift the fiber insulation around the hatch door or near plumbing or electrical wiring. If you see darkened insulation, you have just found an air leak into the attic. The fiber insulation is black because it is filtering out dirt as air passes into the attic.

Air leaks and heat loss can occur in another area you may not think of: above the underside of an architectural feature, or above dropped soffits, such as those above kitchen cabinets. Often, these areas are not insulated or sealed. Areas above stairways, and around chimneys or major plumbing also are big offenders. Also, route all kitchen and bath exhaust fans to the outside, instead of into the attic.

did you know?

You can add insulation on top of existing insulation, but avoid creating any air gaps. The insulation should fit tightly onto the lower layer of existing insulation. If the space between ceiling joists (horizontal pieces that support the floor or ceiling) is filled with insulation, you can add batts parallel or perpendicular to the framing. If existing insulation is below the framing, fill in the voids, and blowing insulation over the top may be the best bet.

maintain or add ventilation

Part of adding insulation to the attic is maintaining, or improving, adequate attic ventilation above the insulation. The ventilation should be divided between the overhangs and the ridge of the roof. When insulation is added, it is very important to keep the areas above soffit vents clear for air movement. If you block these areas with insulation, you can create moisture problems. In older homes, these areas should be checked, because often they are blocked with insulation.

call a pro

It’s a good idea to have a professional evaluate the condition of your home and perform much of this work. If you are considering blowing in insulation or addressing can lights that penetrate the thermal barrier, you would benefit enormously from hiring a professional.