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Do You Need More Attic Insulation?

In the battle against winter cold and sky-high home energy costs, the first line of defense is attic insulation. According to the Environmental Protection Agency’s estimates, homeowners can save an average of 15% on heating and cooling costs by sealing up air leaks and adding insulation to their attics. And that’s just the average. If you live in the northern part of the United States, your savings may be even greater because the climate is more severe and energy for heating can be more expensive.

cross section of energy efficient houseJaddingt / Shutterstock.com

A fully insulated attic can dramatically reduce energy loss in a home.

The really good news is that adding insulation is an improvement that qualifies for tax credits and is excellent at returning value on your investment.

For up-to-date information about available tax incentive programs, see EnergyStar.gov. You can check on whether additional programs are available in your state at http://www.dsireusa.org/.


When it comes to value, Remodeling Magazine’s 2016 Cost vs. Value study determined that the addition of fiberglass insulation to an attic offers a better return on investment than any of the other 30 projects studied in this year’s report. Their cost source, RemodelMAX, estimated the average nationwide cost of insulating an attic to be $1,268. Real estate professionals who responded to their survey projected that, within a year of insulating, this improvement would increase the average home’s sales price by $1,482, resulting in a 116.9% return on the investment.

An Insulation Primer

Basic home building materials used for siding and roofing are great at providing shelter but readily allow the conduction of heat. The result is heat loss in the winter or heat gain in the summer. Insulation materials, typically made of fiberglass, cellulose or foam, have an open-cell structure that resists heat transfer—so when these materials are added to attics, walls and floors, they reduce energy loss. Just how effectively they do their job depends on the particular material and quality of installation.

An insulation material’s ability to resist heat transfer through conduction is measured and rated by an R-value: the higher the R-value, the better the insulation.

The R-values to target in your home depend primarily upon your climate and secondarily upon the part of the house being insulated. It’s most important to insulate the attic because that’s where the majority of a home’s heat is lost.

Fiberglass blanket insulation provides an R-value of from 2.9 to 3.8 per inch of thickness. Loose-fill cellulose insulation can vary from about 3.2 to 3.8, depending on how thoroughly it is installed. Sprayed polyurethane foam can be rated as high as 6.0 to 7.3 per inch. Air pockets, shallow coverage or compressed insulation cause diminished effectiveness.

For a more in-depth comparison of different kinds of insulation, see Energy.gov.

How Much Insulation Is Right?

EnergyGuide.org offers complete information on figuring the right amounts of insulation for your home. Note that the lowest recommended amount is R-30, which is the equivalent of about 10 inches of fiberglass or 8 inches of cellulose. For very cold climates, R-60 is recommended.

measuring attic insulation©Don Vandervort, HomeTips

Use a ruler or measuring tape to measure depth of existing insulation in the attic.

If your attic already has some insulation, you’ll need to measure its thickness to figure the amount you should add. When in the attic, be sure to stand or kneel only on fully supported planks or joists—if you step between the joists, you’re likely to fall through the ceiling below.

Before insulating an attic, it should be air sealed, especially in cold climates where warm air that rises into the attic can cause heat loss and create moisture problems. Air sealing is the practice of using expanding foam to seal up cracks, crevices and connections where walls, plumbing stacks, electrical wires and chimneys penetrate the attic. This keeps the rooms below from leaking expensively heated air into the attic. Though some do-it-yourselfers can tackle this, it’s generally best to have it done by a professional.

Basic Insulating Practices

If you’re adding more to existing insulation, it isn’t necessary to use the same material. It’s okay to blow loose-fill insulation on top of fiberglass batts or to place fiberglass batts over loose-fill.

If you intend to install batt or blanket fiberglass insulation, note that you can buy it with or without an attached foil or paper facing (vapor barrier). When you’re insulating a previously un-insulated attic, buy the type with a facing and position this facing toward the warm-in-winter side (against the ceiling below). When you’re adding more to existing insulation, however, buy un-faced insulation or use loose-fill insulation, which doesn’t have a vapor barrier.

In an unfinished attic, insulation is installed between the ceiling joists of the room beneath the attic (the attic’s “floor” joists). When adding more batt or blanket insulation to an attic with existing insulation, the conventional wisdom is to orient the new batts perpendicular to the joists.

Be aware, however, that doing this will make it much harder to identify where you can safely stand or kneel because you won’t be able to see the joists once they are covered. So start at the outer perimeter and work your way toward the attic hatch. Place and fasten planks or plywood, supported by joists at both ends, where needed for safely accessing and working in the attic.

Do not install insulation over the eaves vents—this will interrupt proper attic ventilation. Also, to avoid causing a fire hazard, never place insulation over recessed light fixtures unless the fixtures have an IC (Insulated Ceiling) rating. Use wire mesh to hold back insulation if necessary. Last but not least, insulate and seal the attic access panel.

recessed light with insulationJohns Manville

Hold back insulation from recessed lights in the ceiling beneath the attic floor.

This article, written by HomeTips’s Don Vandervort, was originally posted at USNews.com


About Don Vandervort
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Don Vandervort has developed his expertise for more than 30 years, as Building Editor for Sunset Books, Senior Editor at Home Magazine, author of more than 30 home improvement books, and writer of countless magazine articles. He appeared for 3 seasons on HGTV’s “The Fix,” and served as MSN’s home expert for several years. Don founded HomeTips in 1996.

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